After the Fukushima nuclear disaster in 2011, large amounts of radioisotopes (mainly Cs-137 and Cs-134) were released into the environment. Various monitoring activities have revealed radiation on the ground both in local and wide areas; however, aerial dose variation in the vertical direction is poorly known. This paper presents the results of airborne gamma-ray spectroscopy of a contamination field in Namie, Fukushima, as measured from 0 m to 150 m above the ground by drone. We found that the gamma-ray dose rate measured at 100 m height is about seven times higher than that expected based on ground measurements, which is caused by two factors: (1) the integrated dose includes contamination of upward scattered 662-keV gamma rays and (2) radiation from Cs-137 is vertically collimated because Cs-137 is buried in the soil. We also propose a novel method to obtain the distribution of radioactive substances in the soil only through aerial mapping.

In order to clarify the impact of air pollution on the formation of sudden and locally distributed heavy rain in urban areas (hereafter UHR = urban-induced heavy rain), we analyzed inorganic ions concentration, dissolved and suspended fraction of trace metals, and stable isotope ratio of water (delta D and delta O-18) in rainwater samples collected from 2008 to 2016 in Tokyo. Acidic substance-derived components (H+, NH4+, NO3-, nss-SO42-) have high concentrations in UHR, and acidic deposition increased locally along with rainfall amount near urban centers when UHR occurs. In addition, UHR has stable isotopes of hydrogen and oxygen smaller than normal rainfall, indicating that the influence of marine-derived water vapor was small. The concentration of air pollutants before the UHR was high, and secondary reaction rapidly progressed just before the UHR. Based on these results, we proposed the following UHR formation mechanism: (1) Air pollutants accumulate from the surrounding area into the area with the low atmospheric pressure due to the development of upflow by urban warming. (2) Due to oxidants formed by photochemical reactions, sulfate and nitrate that are produced secondarily from SO2 and NOx become cloud condensation tuberculosis (CCN). (3) These CCNs generate many small cloud particles using water vapor evaporated from the urban area. (4) When the updraft is further developed, moist sea breezes containing sea salt particles, which are giant cloud condensations, flow in to form large cloud particles, which rapidly grow into raindrops due to collection with small water droplets.

Lightning is an important source of nitrogen oxides (LNOx). The actual global production of LNOx is still largely uncertain. One of the reasons for this uncertainty is the limited available observation data. We measured the concentrations of total reactive nitrogen (NOy), nitric oxide (NO) and nitrogen dioxides (NO2) and then obtained NOx oxidation products (NOz: NOz=NOy - NOx) at a station at the top of Mount Fuji (3776ma.s.l.) during the summer of 2017. Increases in NOy and NO2 were observed on 22 August 2017. These peaks were unaccompanied by increases in CO, which suggested that the observed air mass did not contain emissions from combustion. The backward trajectories of the above air mass indicated that it moved across areas where lightning occurred. The NOy concentration was also calculated by using a chemical transport model, which did not take NOx produced by lightning into account. Therefore, the NOy concentration due to lightning can be inferred by subtracting the calculated NOy from the observed NOy concentrations. The concentration of NOy at 13:00 on 22 August 2017 originating from lightning was estimated to be 1.11 +/- 0.02 ppbv, which comprised 97 +/- 2% of the total NOy concentration. The fractions of NO2 and NOz in the total NOy were 0.54 +/- 0.01 and 0.46 +/- 0.03, respectively. The NO concentration was below the detection limit. We firstly observed increase of concentrations of NOy originating from lightning by ground-based observation and demonstrated the quantitative estimates of LNOx using model-based calculation.

To investigate the impact of mineral/road dust particles on the formation of sudden and locally distributed heavy rain in urban areas (hereafter, urban-induced heavy rain: UHR), we analyzed the trace metal elements and the stable isotope composition of hydrogen and oxygen in rainwater. Rainwater samples, which were collected in Shinjuku (Japan) from April 2014 to December 2015, were analyzed for 12 trace metal elements (Al, V, Cr, Mn, Fe, Ni, Cu, Zn, Cd, Pb, Se, and As) in three fractions: coarse suspended particles (> 1.2 mu m, CSP), acid-insoluble fine suspended particles (0.45-1.2 mu m), and a dissolved/acid-soluble fine suspended fraction. Concentrations and wet deposition fluxes of trace metal elements in CSP were markedly higher in UHR than other types of rainfall, i.e., normal rain, typhoon heavy rain, and frontal heavy rain. There were strong positive correlations between 3180 and the total concentration of trace metal elements in UHR (r = 0.902) and specifically for Fe, Mn, Al, V, and Pb in CSP (r = 0.919, 0.883, 0.823, 0.843, and 0.820, respectively). These findings indicate that mineral/road dust particles were removed by in-cloud scavenging process under the meteorological conditions causing UHR. There is one possibility that they could play important roles as giant cloud condensation nuclei and/or effective ice nuclei for the formation of UHR.

We observed the atmospheric resuspension of radiocaesium, derived from the Fukushima Dai-ichi Nuclear Power Plant accident, at Namie, a heavily contaminated area of Fukushima, since 2012. During the survey periods from 2012 to 2015, the activity concentrations of radiocaesium in air ranged from approximately 10-5 to 10-2 Bq per m3 and were higher in the warm season than in the cold season. Electron microscopy showed that the particles collected on filters in summer were predominantly of biological origin (bioaerosols), with which the observed radiocaesium activity concentration varied. We conducted an additional aerosol analysis based on fluorescent optical microscopic observation and high-throughput DNA sequencing technique to identify bioaerosols at Namie in 2015 summer. The concentrations of bioaerosols fluctuated the order of 106 particles per m3, and the phyla Basidiomycota and Ascomycota (true Fungi) accounted for approximately two-thirds of the bioaerosols. Moreover, the fungal spore concentration in air was positively correlated with the radiocaesium concentration at Namie in summer 2016. The bioaerosol emissions from Japanese mixed forests in the temperate zone predominately included fungal cells, which are known to accumulate radiocaesium, and should be considered an important scientific issue that must be addressed.

© 2017 Elsevier B.V. A multipixel photon counter (MPPC) features excellent photon-counting capability as a radiation detector. In particular, a two-plane Compton camera consisting of Ce:GAGG scintillators coupled with MPPC arrays has significant application potential owing to its compact size and low weight. For example, the camera can be easily mounted on a commercial drone to identify radiation hot spots from the sky. In Fukushima, we demonstrated that a 137Cs distribution within a 100 m diameter can be mapped correctly within a couple of tens of minutes. The advanced use of the Compton camera is also anticipated in the field of proton therapy. We evaluated an image of 511 keV annihilation gamma-rays emitted from a PMMA phantom irradiated by 200 MeV protons to mimic an in-beam monitor for proton therapy. Finally, we developed an ultracompact Compton camera (weight = 580 g), for 3-D multicolor molecular imaging. In order to demonstrate the performance capabilities of the device, 131I (365 keV), 85SrCl2 (514 keV), and 65ZnCl2 (1116 keV) were injected into a living mouse and the data were taken from 12 angles with a total acquisition time of 2 h. We confirmed that all tracers had accumulated on the target organs of the thyroid, bone, and liver, and that the obtained 3-D image was quantitatively correct with an accuracy of ±20%.

© 2018, The Author(s). A large quantity of radionuclides was released by the Fukushima Daiichi Nuclear Power Plant accident in March 2011, and those deposited on ground and vegetation could return to the atmosphere through resuspension processes. Although the resuspension has been proposed to occur with wind blow, biomass burning, ecosystem activities, etc., the dominant process in contaminated areas of Fukushima is not fully understood. We have examined the resuspension process of radiocesium (134,137Cs) based on long-term measurements of the atmospheric concentration of radiocesium activity (the radiocesium concentration) at four sites in the contaminated areas of Fukushima as well as the aerosol characteristic observations by scanning electron microscopy (SEM) and the measurement of the biomass burning tracer, levoglucosan. The radiocesium concentrations at all sites showed a similar seasonal variation: low from winter to early spring and high from late spring to early autumn. In late spring, they showed positive peaks that coincided with the wind speed peaks. However, in summer and autumn, they were correlated positively with atmospheric temperature but negatively with wind speed. These results differed from previous studies based on data at urban sites. The difference of radiocesium concentrations at two sites, which are located within a 1 km range but have different degrees of surface contamination, was large from winter to late spring and small in summer and autumn, indicating that resuspension occurs locally and/or that atmospheric radiocesium was not well mixed in winter/spring, and it was opposite in summer/autumn. These results suggest that the resuspension processes and the host particles of the radiocesium resuspension changed seasonally. The SEM analyses showed that the dominant coarse particles in summer and autumn were organic ones, such as pollen, spores, and microorganisms. Biological activities in forest ecosystems can contribute considerably to the radiocesium resuspension in these seasons. During winter and spring, soil, mineral, and vegetation debris were predominant coarse particles in the atmosphere, and the radiocesium resuspension in these seasons can be attributed to the wind blow of these particles. Any proofs that biomass burning had a significant impact on atmospheric radiocesium were not found in the present study. [Figure not available: see fulltext.].

This work presents diurnal variations of gas and particle-phase dicarbonyls (glyoxal (Gly) and methylglyoxal (Mgly)) in the atmosphere, which are important compounds that contribute to the formation and growth of atmospheric particulate matter. To obtain variations in partitioning, continuous collection of gaseous dicarbonyls was performed using a parallel plate wet denuder, and at the same time, the dicarbonyls in particle were collected using a spray-type particle collector downstream. Hourly samples were analyzed by high performance liquid chromatography-electrospray ionization-tandem mass spectrometry. This method is advantageous to monitor the gaseous and particulate carbonyls separately without loss during sampling. Sampling was performed in summer and winter in a midsize city (Kumamoto, Japan). The concentrations of the dicarbonyls increased in the summer daytime, which suggests that they are mostly formed by secondary production in the local atmosphere. The dicarbonyls and formaldehyde (HCHO) were found in both gas and particle phases, and partitioning to the particle phase was highest for Gly, followed by Mgly and HCHO. It was observed that the compounds moved to the particle phase in the midnight and early morning hours according to the growth of hygroscopic aerosols in summer. The particle/gas ratio also increased in the presence of high PM2.5, which is transported from the Chinese Continent in winter. The dicarbonyls were also observed on Mt. Fuji (3776 m) in the free troposphere. From back trajectory data and information on volatile organic compounds, they were most likely produced from relatively long-lifetime organic compounds from the Chinese Continent and biogenic volatile organic compounds emitted in the Japan Alps mountain range. Higher particle/gas ratios at the Mt. Fuji station indicate that low temperatures and high humidity precede the partition. The estimated effective Henry's law constants for the dicarbonyls, 108 order in mol/kgH(2)O/atm for summer data, were much higher than those for ideal liquid/vapor equilibrium but close to reported results obtained by chamber experiments. In the proposed method, oligomers in particle were also counted as the compounds. The dicarbonyl compounds existed up to submolar levels in real atmospheric aerosols, which suggests they undergo further reactions in the particle phase.

Analytical methods for the detection of NOz have been developed by using a laser-induced fluorescence spectroscopy (LIF) technique and a chemiluminescence (CL) method. NOz (= NOy - NOx) represents NOx oxidation products. The NO2 concentrations are measured by LIF, which has a high sensitivity and no chemical interferences when a conversion technique to NO is applied by such as a CL method. The NO and NOy concentrations are measured by an improved CL method. The NOz concentrations are obtained by subtracting the concentrations of NO and NO2 from NOy. The NOz concentrations in the atmosphere were measured at the top of Mt. Fuji in August, 2017. The average concentration of NOz was 0.28 +/- 0.26 ppb. A back-trajectory analysis suggested that the air mass from the Asian continent showed a high concentration of NOz, and the air mass from the Pacific Ocean showed a low concentration of NOz. The concentrations of NOz and O-3 showed a correlation, and ozone production efficiencies (OPE) were obtained from correlation plots. The obtained OPEs at a mountain site showed that the air mass from the Asian continent was 3 to 10 and from the Pacific Ocean was 18. An analytical method of NOz in the atmosphere at a mountain site was established.

We analyzed the trends in rainfall amounts and the number of heavy rain events with hourly rainfall amounts over 30 mm at the inland section of the 23-ward Tokyo metropolitan area (nine wards and ten sites) in the warm season (July to September) from 1978 to 2008. Heavy rain events in the Nerima Ward occurred nine times during decade I (1978-1987; 0.90 times/yr), 13 times during decade II (1988-1997; 1.3 times/yr), and 23 times during decade III (1998-2008; 2.1 times/yr). The annual average number of heavy rain events was 1.43 times/yr in Nerima from 1978 to 2008, while it was 0.98 times/yr on average at nine locations excluding Nerima. The frequency of extremely strong heavy rain events with hourly rainfall amounts greater than 50 mm during decade III was the highest in Nerima (six times) among ten sites. These data suggest that the frequency of heavy rain events has increased at Nerima during the past 30 years. Bulk precipitation data were collected biweekly by filtration-type collectors at 14 sites around Nerima from 2008 to 2010 to determine the impacts of urban-induced heavy rains (hereafter UHR), defined as a heavy rain event other than typhoons and frontal heavy rains, on the distribution of deposition fluxes of inorganic acidic substances. The NO3- and nss-SO42- concentrations in bulk precipitation were higher during the periods including UHR than those not including UHR. The deposition fluxes of NO3- and SO42- showed clear differences at the center of UHR (NO3-: 231 mu eq/m(2)/d, SO42-: 234 mu eq/m(2)/d) and its surrounding area (NO3-: 76.4 mu eq/m(2)/d, SO42 -: 86.1 mu eq/m(2)/d). Our results suggest that large amounts of inorganic acidic substances are deposited locally by UHR in urban areas in summer.

Stable isotope ratios of hydrogen and oxygen of water are useful tracers of the hydrological cycle. For example, isotopes monitor the evapotranspiration in vegetated areas, local snow ice processes and stream water flow processes. delta O-18 and delta D in rainwater reflect the processes of evaporation, condensation and precipitation. Heavy rains thus modify the stable isotope ratio of ground water, stream water and transpiration water vapor. However, the controlling factors of delta O-18 and delta D are not clear. Here we analyzed the inorganic ion concentration and stable isotope ratio in 38 normal rainwater and 15 heavy rainwater samples were collected in Shinjuku, Tokyo, Japan, during four years from October 2012 to December 2015. Results show a decrease in delta O-18 and delta D values with the total rainfall amount, thus highlighting the amount effect. delta O-18 and delta D volume-weighted mean values in typhoon heavy rain were higher than the values estimated from amount effect, whereas delta O-18 and delta D volume-weighted mean values in urban-induced heavy rain were lower. Typhoon heavy rain has high Na+ ratio and stable isotope ratios, while urban-induced heavy rain has low Na+ ratio and stable isotope ratio.

Considerable amounts of radioactive substances (mainly Cs-137 and Cs-134) were released into the environment after the Japanese nuclear disaster in 2011. Some restrictions on residence areas were lifted in April 2017, owing to the successive and effective decontamination operations. However, the distribution of radioactive substances in vast areas of mountain, forest and satoyama close to the city is still unknown; thus, decontamination operations in such areas are being hampered. In this paper, we report on the first aerial gamma-ray imaging of a schoolyard in Fukushima using a drone that carries a high sensitivity Compton camera. We showthat the distribution of Cs-137 in regions with a diameter of several tens to a hundred meters can be imaged with a typical resolution of 2-5 m within a 10-20 min flights duration. The aerial gamma-ray images taken 10 m and 20 m above the ground are qualitatively consistent with a dose map reconstructed from the ground-based measurements using a survey meter. Although further quantification is needed for the distance and air-absorption corrections to derive in situ dose map, such an aerial drone system can reduce measurement time by a factor of ten and is suitable for place where ground-based measurement are difficult.

In order to make clear the impact of air pollution on the formation of sudden and locally-distributed heavy rain in urban area (hereafter Urban Heavy Rain: UHR), we analyzed inorganic ion concentration and stable isotope ratio of water (delta D and delta O-18) in rainwater. Rainwater samples were collected in Shinjuku, which is a representative downtown of Tokyo, Japan, during four years from October 2012 to December 2015. The concentration and wet deposition fluxes of acidic components (H+, NH4+, NO3-, and nss-SO42-) in UHR were especially higher than those in other types of rain events, i.e. normal rain, typhoon heavy rain, and frontal heavy rain. UHR had distinctly lower stable isotope ratios than those in other urban rains with same rainfall amount and summer precipitation systems. There was a high negative correlation between delta O-18 and the distances from the sampling point to the formation area of UHR within 10 km, while there were high positive correlations between delta O-18 and the concentration of acidic components in UHR. These findings indicate that UHR could effectively scavenge acidic substances within cloud and suggest the use of stable isotope ratios as tracers of an urban heavy rain's water and in-cloud scavenging process.

This is the first paper that describes the atmospheric sulfur dioxide (SO2) and nitric acid (HNO3) monitored with a good time-resolution at the summit (3776 m a. s. l.), which is located in the free troposphere, and southeastern foot (1284 m a.s.l.) of Mt. Fuji. Japan. During the summer of 2012, two analytical systems consisting mainly of a parallel-plate wet denuder and ion chromatograph operated simultaneously at both the sampling sites. All the samples collected at both the sampling sites contained detectable levels of sulfate from gas-phase SO2 while the nitrate from gas-phase HNO3 was detectable in 97.8% of air samples at the southeastern foot and 88.4% at the summit. The average concentrations of SO2 and HNO3 were, respectively, 0.061 +/- 0.071 and 0.031 +/- 0.020 ppbv at the summit (n = 672), and 0.347 +/- 0.425 and 0.146 +/- 0.070 ppbv at the southeastern foot (n = 1344) of Mt. Fuji. Both the acidic gases at the southeastern foot and the HNO3 at the summit showed a diurnal pattern with daytime maxima and nighttime minima. Meanwhile, the SO2 at the summit did not show a distinct shift, which indicates the SO2 concentrations at the summit would be principally controlled by the advection of air parcel in the free troposphere.

In order to clarify the impact of air pollution on the formation of sudden and locally distributed heavy rain in urban areas (hereafter UHR = urban-induced heavy rain), we analyzed inorganic ions in rainwater samples collected on an event basis over 5 years from October 2012 to December 2016 in Shinjuku, Tokyo. Hourly rainfall amounts and wet deposition fluxes of acidic components (the sum of H+, NH4+, NO3-, and nonsea-salt SO42-) in UHR were 13.1 and 17.8 times larger than those in normal rainfall, respectively, indicating that large amount of air pollutants were scavenged and deposited by UHR with large amounts of rainfall. The level of air pollutants, such as NO2, SO2, and potential ozone, in the ambient air increased just before the formation of UHR and decreased sharply at the end of the UHR event. These results indicate that NO2, which was formed secondarily by oxidants, was further oxidized by HO radicals and formed HNO3 just before the formation of UHR, which was subsequently scavenged by UHR.

Radio-Cs concentrations in fresh leaves/needles, litter, surface soil, and stream sand were continuously investigated in a deciduous broadleaf forest and cedar forest in Namie-town, Fukushima prefecture from June 2012 to June 2016, except for snow-cover periods. The result of a car-borne survey from Fukushima city to Minamitsushima showed that the air dose rate declined faster than the physical attenuation due to decontamination, outside of forests. Radio-Cs concentrations (Cs-137 + Cs-134) in litter and surface soil in broadleaf forest were constant at 52.0, 102 kBq kg-dry(-1), respectively from 2014. In a cedar forest, however, the radio-Cs concentrations in fresh needles and litter declined from 2012 to 2015, probably because of washing and leaching by throughfall, and radio-Cs was accumulated in surface soil. In broadleaf forest, the buffer depth of radio-Cs in soil (1.26 cm) which indicates the extent of infiltration into deeper layers was greater than in the cedar forest (1.14 cm) in April 2013. However, the buffer depth in the cedar forest overtook that in the broadleaf forest in December, 2015 (1.5 cm in broadleaf forest and 2.6 cm in cedar forest). The radio-Cs values in the stream bottom sand were concentrated in smaller sand (over 2 mm, 3.04; 0.21-2.0 mm, 10.2; under 0.21 mm, 54.5 kBq kg-dry(-1) in downstream near the broadleaf forest and over 2.0 mm, 2.67, 0.21-2.0 mm, 7.95; under 0.21 mm, 41.3 kBq kg-dry(-1) in the upstream area near the cedar forest). It is concerned that a part of them causes the outflow of radio-Cs as suspended sand. The relative radio-Cs concentration ratio between smaller bottom sand and surface soil, which indicates the outflow of radio-Cs from forest via stream declined (2013: 0.54, 2016: 0.29 in downstream and 2013: 1.4, 2016: 0.31 in the upstream region). However, we found that floating male flowers of cedar containing high radio-Cs (23.8 kBq kg-dry(-1)) could be another transport media in the spring.

In order to clarify the impact of air pollution on the formation of sudden and locally distributed heavy rain in urban areas (hereafter UHR = urban-induced heavy rain), we analyzed inorganic ions in rainwater samples collected on an event basis over 5 years from October 2012 to December 2016 in Shinjuku, Tokyo. Hourly rainfall amounts and wet deposition fluxes of acidic components (the sum of H+, NH4 +, NO3, and nonsea-salt SO4 2-) in UHR were 13.1 and 17.8 times larger than those in normal rainfall, respectively, indicating that large amount of air pollutants were scavenged and deposited by UHR with large amounts of rainfall. The level of air pollutants, such as NO2, SO2, and potential ozone, in the ambient air increased just before the formation of UHR and decreased sharply at the end of the UHR event. These results indicate that NO2, which was formed secondarily by oxidants, was further oxidized by HO radicals and formed HNO3 just before the formation of UHR, which was subsequently scavenged by UHR.

Radio-Cs concentrations in fresh leaves/needles, litter, surface soil, and stream sand were continuously investigated in a deciduous broadleaf forest and cedar forest in Namie-town, Fukushima prefecture from June 2012 to June 2016, except for snow-cover periods. The result of a car-borne survey from Fukushima city to Minamitsushima showed that the air dose rate declined faster than the physical attenuation due to decontamination, outside of forests. Radio-Cs concentrations (137Cs +134Cs) in litter and surface soil in broadleaf forest were constant at 52.0, 102 kBq kg-dry–1, respectively from 2014. In a cedar forest, however, the radio-Cs concentrations in fresh needles and litter declined from 2012 to 2015, probably because of washing and leaching by throughfall, and radio-Cs was accumulated in surface soil. In broadleaf forest, the buffer depth of radio-Cs in soil (1.26 cm) which indicates the extent of infiltration into deeper layers was greater than in the cedar forest (1.14 cm) in April 2013. However, the buffer depth in the cedar forest overtook that in the broadleaf forest in December, 2015 (1.5 cm in broadleaf forest and 2.6 cm in cedar forest). The radio-Cs values in the stream bottom sand were concentrated in smaller sand (over 2 mm, 3.04
0.21-2.0 mm, 10.2
under 0.21 mm, 54.5 kBq kg-dry–1 in downstream near the broadleaf forest and over 2.0 mm, 2.67, 0.21-2.0 mm, 7.95
under 0.21 mm, 41.3 kBq kg-dry–1 in the upstream area near the cedar forest). It is concerned that a part of them causes the outflow of radio-Cs as suspended sand. The relative radio-Cs concentration ratio between smaller bottom sand and surface soil, which indicates the outflow of radio-Cs from forest via stream declined (2013: 0.54, 2016: 0.29 in downstream and 2013: 1.4, 2016: 0.31 in the upstream region). However, we found that floating male flowers of cedar containing high radio-Cs (23.8 kBq kg-dry–1) could be another transport media in the spring.

Atmospheric trace gases CO, O-3, and SO2 were observed at the summit of Mt. Fuji (3776 ma.s.l.) during the summer of 2013. Considerable variations were observed in the concentrations of CO and O-3; however, they were correlated in most cases. Trends analyzed through backward trajectory calculations showed lower concentrations of CO and O-3 transported from the Pacific Ocean and South East Asia directions, while higher concentrations were detected from the direction of the Asian continent. High O-3 and low CO concentrations were observed during some periods; in these air masses, water content of the air was low indicating that the air originated from high altitudes and was influenced by the stratosphere. Gaseous SO2 was mostly lower than the detection limit of the instrument used for measurement (0.06 ppbv), but on August 20-21, high SO2 spikes of about 5 ppbv were observed. Backward and forward trajectory calculations confirmed that volcanic smoke from the Sakurajima volcano was transported to the summit of Mt. Fuji.

In recent years, various gamma-ray visualization techniques, or gamma cameras, have been proposed. These techniques are extremely effective for identifying "hot spots" or regions where radioactive isotopes are accumulated. Examples of such would be nuclear-disaster-affected areas such as Fukushima or the vicinity of nuclear reactors. However, the images acquired with a gamma camera do not include distance information between radioactive isotopes and the camera, and hence are "degenerated" in the direction of the isotopes. Moreover, depth information in the images is lost when the isotopes are embedded in materials, such as water, sand, and concrete. Here, we propose two methods of obtaining depth information of radioactive isotopes embedded in materials by comparing (1) their spectra and (2) images of incident gamma rays scattered by the materials and direct gamma rays. In the first method, the spectra of radioactive isotopes and the ratios of scattered to direct gamma rays are obtained. We verify experimentally that the ratio increases with increasing depth, as predicted by simulations. Although the method using energy spectra has been studied for a long time, an advantage of our method is the use of low-energy (50-150 keV) photons as scattered gamma rays. In the second method, the spatial extent of images obtained for direct and scattered gamma rays is compared. By performing detailed Monte Carlo simulations using Geant4, we verify that the spatial extent of the position where gamma rays are scattered increases with increasing depth. To demonstrate this, we are developing various gamma cameras to compare low-energy (scattered) gamma -ray images with fully photo -absorbed gamma -ray images. We also demonstrate that the 3D reconstruction of isotopes/hotspots is possible with our proposed methods. These methods have potential applications in the medical fields, and in severe environments such as the nuclear-disaster-affected areas in Fukushima. (C) 2016 Elsevier B.V. All rights reserved.

The multi-pixel photon counter (MPPC) is a promising light sensor for various applications, not only in physics experiments but also in nuclear medicine, industry, and even high-energy astrophysics. In this paper, we present the current status and most recent progress of the MPPC-based scintillation detectors, such as (1) a high-precision X-ray and gamma-ray spectral image sensor, (2) next-generation PET detectors with MRI, TOF, and DOI measurement capabilities, and (3) a compact gamma camera for environmental radiation surveys. We first present a new method of fabricating a Ce:GAGG scintillator plate (1 or 2 mm thick) with ultra-fine resolution (0.2 mm/pixel), cut using a dicing saw to create 50 mu m wide micro-grooves. When the plate is optically coupled with a large-area MPPC array, excellent spatial resolution of 0.48 mm (FWHM) and energy resolution of 14% (FWHM) are obtained for 122 keV gamma rays. Hence, the detector can act as a convenient "multi-color" imaging device that can potentially be used for future SPECT and photon-counting CT. We then show a prototype system for a high-resolution MPPC-based PET scanner that can realize similar or equal to 1 mm (FWHM) spatial resolution, even under a strong magnetic field of 4.7 T. We develop a front-end ASIC intended for future TOF-PET scanner with a 16-channel readout that achieves a coincidence time resolution of 489 ps (FWHM). A novel design for a module with DOI-measurement capability for gamma rays is also presented by measuring the pulse height ratio of double-sided MPPCs coupled at both ends of scintillation crystal block. Finally, we present the concept of a two-plane Compton camera consisting of Ce:GAGG scintillator arrays coupled with thin MPPC arrays. As a result of the thin and compact features of the MPPC device, the camera not only achieves a small size (14 x 14 x 15 cm(3)) and light weight (1.9 kg) but also excellent sensitivity, compared to the conventional PMT-based pinhole camera used in Fukushima. Finally, we briefly describe a new product recently developed in conjunction with Hamamatsu Photonics K.K. that offers improved sensitivity and angular resolution of Delta theta similar to 8 degrees (FWHM) at 662 key, by incorporating DOI-segmented scintillator arrays. (C) 2014 Elsevier B.V. All rights reserved.

In fair weather, a clear diurnal variation of atmospheric electric field (AEF), which is distinctly different from the global diurnal variation, i.e., Carnegie curve, was observed during the summer time (July and August) of the year 2010 and 2011 at the summit of Mount Fuji, Japan (3776m in altitude). The variation of the AEF at the summit showed a local time dependent feature, which means that the AEF increased at sunrise and decreased at sunset. This local diurnal variation is known as a mountain variation. The intensity of AEF in the daytime reached 1.5-3 times larger than that in the nighttime. From the multipoint observations of cloud images and AEF, the mountain variation was found to be attributable to the AEF generated by the positively charged top of a horizontally extensive sea of clouds below the summit. Since the sea of clouds grows with the temperature rise, the AEF variation follows local time.

After the nuclear disaster in Fukushima, radiation decontamination has become particularly urgent. To help identify radiation hotspots and ensure effective decontamination operation, we have developed a novel Compton camera based on Ce-doped Gd3Al2Ga3O12 scintillators and multi-pixel photon counter (MPPC) arrays. Even though its sensitivity is several times better than that of other cameras being tested in Fukushima, we introduce a depth-of-interaction (DOI) method to further improve the angular resolution. For gamma rays, the DOI information, in addition to 2-D position, is obtained by measuring the pulse-height ratio of the MPPC arrays coupled to ends of the scintillator. We present the detailed performance and results of various field tests conducted in Fukushima with the prototype 2-D and DOI Compton cameras. Moreover, we demonstrate stereo measurement of gamma rays that enables measurement of not only direction but also approximate distance to radioactive hotspots.

Sizes and compositions of atmospheric aerosol particles can be altered by in-cloud processing by absorption/adsorption of gaseous and particulate materials and drying of aerosol particles that were formerly activated as cloud condensation nuclei. To elucidate differences of aerosol particles before and after in-cloud processing, aerosols were observed along a slope of Mt. Fuji, japan (3776 m a.s.l.) during the summer in 2011 and 2012 using a portable laser particle counter (LPC) and an aerosol sampler. Aerosol samples for analyses of elemental compositions were obtained using a cascade impactor at top-of-cloud, in-cloud, and below-cloud altitudes. To investigate composition changes via in-cloud processing, individual particles (0.5-2 mu m diameter) of samples from five cases (days) collected at different altitudes under similar backward air mass trajectory conditions were analyzed using a transmission electron microscope (TEM) equipped with an energy dispersive X-ray analyzer. For most cases (four cases), most particles at all altitudes mainly comprised sea salts: mainly Na with some S and/or CL Of those, in two cases, sea-salt-containing particles with Cl were found in below-cloud samples, although sea-salt-containing particles in top-of-cloud samples did not contain Cl. This result suggests that Cl in the sea salt was displaced by other cloud components. In the other two cases, sea-salt-containing particles on samples at all altitudes were without CL However, molar ratios of S to Na (S/Na) of the sea-salt-containing particles of top-of-cloud samples were higher than those of below-cloud samples, suggesting that sulfuric acid or sulfate was added to sea-salt-containing particles after complete displacement of Cl by absorption of SO2 or coagulation with sulfate. The additional volume of sulfuric acid in clouds for the two cases was estimated using the observed S/Na values of sea-salt-containing particles. The estimation revealed that size changes by in-cloud processing from below-cloud to top-of-cloud altitudes were less than 6% for sizes of 0.5-2 mu m diameter. The obtained results will be useful to evaluate the aging effect and transition of aerosol particles through in-cloud processing. (C) 2013 Elsevier B.V. All rights reserved.

We propose a rapid preparation method for the simultaneous analysis of gas-phase polycyclic aromatic hydrocarbons (PAHs) and oxygenated polycyclic aromatic hydrocarbons (OPAHs) by an accelerated solvent extractor (ASE) and solid-phase extraction (SPE). We used polyurethane foam (PUF) for collecting gas-phase PAHs and OPAHs. Recovery of selected PAHs and OPAHs from blank PUF ranged from 80 to 100 %, except for low molecular PAHs and OPAHs, such as acenaphthylene, acenaphthene, 1,4-naphthoquinone with a relative standard deviation (R.S.D.) of less than 5 %, while their recoveries from the collected PUF ranged from 80 to 120 %, except for benzanthrone with a R.S.D. from 10 % and 20 %. The proposed preparation method in combination with ASE and SPE could be useful for screening gas-phase PAHs and OPAHs, although there is a problem to some extent concerning the collection efficiencies of low molecular PAHs and OPAHs in the gas-phase. The application of the proposed method to samples collected at Shinjuku in June, 2012 revealed that the concentration of PAHs and OPAHs, mainly presented in the gas-phase, was significantly higher than that of PAHs and OPAHs, mainly presented in the particle phase.

The methylene blue method was troublesome and susceptible to operational error. In our improved method, we use only one vial (50 mL glass centrifuge tube) to determine the concentration of anionic surfactants as methylene blue active substances (MBAS). The combination of hand-shaking 20 times with shaking (1000 rpm) for 5 minutes by a shaker leads to a calibration curve (n = 4) with a high linearity (average r = 0.996) and a high sensitivity (average 1.07 mu M-1) within 0 - 0.12 mu M. In the optimum condition, the recovery of sodium dodecyl sulfate (SDS) was 94.7 +/- 3.3 % (n = 3) for a water extraction solution of blank quartz fiber filter, 92.3 +/- 1.5 % (n = 4) for that of atmospheric aerosol collected on a quartz fiber filter, and 90.8 +/- 3.5 % (n = 3) for the throughfall of Japanese ceder (Cyptomeria japonica), respectively. This improved method revealed that the concentration of anionic surfactants in atmospheric aerosol ranged from 44.9 to 163 pmol m(-3) (84.3 pmol m(-3) on average, n = 8) at Shinjuku, Tokyo in May, 2011.

Rapid and sample preparation using stir bar sorptive extraction (SBSE), followed by highperformance liquid chromatography with fluorescence detection to determine polycyclic aromatic hydrocarbons (PAHs) in atmospheric water was studied. Applying the SBSE method to authentic atmospheric water samples revealed that rainwater in Shinjuku contained a 226 pM concentration of total PAHs, which was 10-times as much as that at Mt. Fuji, especially in a higher concentration of soluble PAHs. There was no seasonal variation of the concentration and composition of PAHs in rainwater at Shinjuku. Comparing the concentration of PAHs in rain, cloud, and dew water collected at the foot of Mt. Fuji, 5- and 6-rings PAHs were enriched in cloud water. This result suggests that cloud droplets could condense PAHs, especially high molecular weight PAHs. © 2013 The Japan Society for Analytical Chemistry.

We propose a rapid preparation method for the simultaneous analysis of gas-phase polycyclic aromatic hydrocarbons (PAHs) and oxygenated polycyclic aromatic hydrocarbons (OPAHs) by an accelerated solvent extractor (ASE) and solid-phase extraction (SPE). We used polyurethane foam (PUF) for collecting gas-phase PAHs and OPAHs. Recovery of selected PAHs and OPAHs from blank PUF ranged from 80 to 100 %, except for low molecular PAHs and OPAHs, such as acenaphthylene, acenaphthene, 1,4-naphthoquinone with a relative standard deviation (R.S.D.) of less than 5 %, while their recoveries from the collected PUF ranged from 80 to 120 %, except for benzanthrone with a R.S.D. from 10 % and 20 %. The proposed preparation method in combination with ASE and SPE could be useful for screening gas-phase PAHs and OPAHs, although there is a problem to some extent concerning the collection efficiencies of low molecular PAHs and OPAHs in the gas-phase. The application of the proposed method to samples collected at Shinjuku in June, 2012 revealed that the concentration of PAHs and OPAHs, mainly presented in the gas-phase, was significantly higher than that of PAHs and OPAHs, mainly presented in the particle phase. © 2013 The Japan Society for Analytical Chemistry.

The methylene blue method was troublesome and susceptible to operational error. In our improved method, we use only one vial (50 mL glass centrifuge tube) to determine the concentration of anionic surfactants as methylene blue active substances (MBAS). The combination of hand-shaking 20 times with shaking (1000 rpm) for 5 minutes by a shaker leads to a calibration curve (n = 4) with a high linearity (average r =0.996) and a high sensitivity (average 1.07 μM&lt
sup&gt
-1&lt
/sup&gt
) within 0 - 0.12 μM. In the optimum condition, the recovery of sodium dodecyl sulfate (SDS) was 94.7±3.3 % (n = 3) for a water extraction solution of blank quartz fiber filter, 92.3± 1.5 % (n = 4) for that of atmospheric aerosol collected on a quartz fiber filter, and 90.8± 3.5 % (n =3) for the throughfall of Japanese ceder (Cyptomeria japonica), respectively. This improved method revealed that the concentration of anionic surfactants in atmospheric aerosol ranged from 44.9 to 163 pmol m&lt
sup&gt
-3&lt
/sup&gt
(84.3 pmol m&lt
sup&gt
-3&lt
/sup&gt
on average, n =8) at Shinjuku, Tokyo in May, 2011. © 2013 The Japan Society for Analytical Chemistry.

We have studied the biogenic volatile organic compounds (BVOCs, namely isoprene, α-pinene, β-pinene, δ-3-caren, and limonene) in the ambient air in a small forest (Tokyo Univ. of Agriculture and Technology Field Museum TAMA Hills, Hachioji City), which is located 33 km from Shinjuku. Simultaneous sampling of the BVOCs was performed at three points, namely, at the top of the canopy of Konara (14 m), under the canopy (1 m at the ground), and in the forest clearing (1 m at the ground) on 20-25 June, 2011. Isoprene showed a clear diurnal variation and was high in the daytime and low in the nighttime at the three points. The maximum concentration of isoprene was 11.1 ppbv at the top of the canopy. Monoterpenes such as α-pinene, β-pinene, and limonene did not show any diurnal variation and their concentrations were higher under the canopy and in the forest clearing than those at the top of the canopy. δ-3-Caren was below its detection limit at the three points. A correlation analysis showed that the sources of isoprene were different from those of the monoterpenes, and among the monoterpenes, the sources of the pinenes were different from the sources of limonene. A positively high correlation coefficient between the concentration of α-pinene and β-pinene showed that they were emitted from identical species. The concentration of the BVOCs in the ambient air at FM TAMA was about 10 times higher than at Shinjuku, indicating that Satoyama (the border zone or area between the mountain foothills and arable flat land) is the important source of the BVOCs.

Simultaneous sampling of 26 AVOCs (anthropogenic volatile organic compounds), namely seventeen chlorinated hydrocarbons (CHs), six monocyclic aromatic hydrocarbons (MAHs), three dicyclic aromatic hydrocarbons (DAHs), in the ambient air and atmospheric water was performed in an urban area (Shinjuku), mountainous area (at the southeastern foot of Mt. Fuji; 1284 m a.s.l.), and the free troposphere (at the top of Mt. Fuji; 3776 m a.s.l.) from 2007 to 2010. The atmospheric concentration of the AVOCs in 2010 was the highest at the top of Mt. Fuji (average in July: 11.6 ppbv, n=5) and then in Shinjuku (average in October, November, and December: 7.9 ppbv, n=52) and at the foot of Mt. Fuji (average in July: 6.8 ppbv, n=9). It was found that the concentrations of the MAHs at the top of Mt. Fuji were extremely high compared to those at Shinjuku and other high altitude sites, suggesting a highly suspicious contamination near the sampling site at the top of Mt. Fuji. The mean concentrations of the total AVOCs in the rainwater (15.8 nM, n=8) at the foot of Mt. Fuji and in cloud water (15.7 nM, n=19) at the top of Mt. Fuji were higher than those in the dew water (5.33 nM, n=15) and rainwater (3.36 nM, n=30) at Shinjuku. These results indicated that the enrichment of AVOCs in the atmospheric water was strongly influenced by factors other than the concentration of the AVOCs in the ambient air, temperature, and hydrophobicity of each AVOC.

Temporal and spatial variations in concentrations of particle-associated polycyclic aromatic hydrocarbons (PAHs) and their nitrated and oxygenated derivatives (nitro-PAHs and oxy-PAHs) were investigated to assess the influence of secondary formation on atmospheric occurrences of oxy-PAHs associated with particulate matter in downtown Tokyo, Japan. The daily variation in concentration of 1,8-naphthalic anhydride (1,8-NA) in summer 2007 was similar to that for 2-nitrofluoranthene (2-NF), a representative secondary formed nitro-PAH, while the variation for benzanthrone (BA) was similar to PAHs. In addition, the concentrations of polycyclic aromatic compounds (PACs) associated with airborne particulate matter decreased in the order of PAHs > BA > 9-fluorenone (9-FO) or 9,10-anthraquinone (9,10-AQ)> 1,8-NA with an increase in distance from the roadside, whereas 2-NF was constant. These results suggest that a considerable fraction of some oxy-PAHs such as 1,8-NA associated with airborne particulate matter in downtown Tokyo originates from atmospheric secondary formation. (C) 2010 Elsevier Ltd. All rights reserved.

A new sampling system of gas- and particle-phase polycyclic aromatic hydrocarbons (PAT-Is) in ambient air is proposed. The system is composed of a commercially available multi-nozzle cascade impact sampler for collecting particles less than 10 mu m and a newlydesigned glass cartridge (35 mm inner diameter) packed with 5.0 g of a styrene-divinylbenzene copolymer resin adsorbent (XAD-2) for collecting gas-phase PAHs at a flow rate of 20 L/min. A rapid sample preparation for the analysis of PAHs in XAD-2 resin by ultrasonic extraction was also studied. The recovery rates of selected PAHs, i.e. phenanthrene (PHEN), antrathene (ANT), fluorantene (FL), pyrene (PY), benzo[a]pyrene (BaP), benzo[k]fluoranthene (BkF), benzo[ghi]perylene (BghiP), and indeno[1,2,3-cd]pyrene (IP) after the pretreatment ranged from 80 to 100%. More than 95% of the PAHs were extracted from XAD-2 by ultrasonication twice for 20 min with dichloromethane. The newlydeveloped cartridge had more than 95% collection efficiencies of the gas-phase PAHs (PHEN, ANT, FL and PY) in both the summer and winter seasons. Storage at 30 C for 4 weeks did not have an adverse effect on the gas-phase PAHs collected with the cartridge. The application of the new sampling system to a field observation at a tower with a height of 12 m in a small forest at Field Museum Tama Hills revealed that the concentrations of the gas-phase PAT-Is at the lower level of the tower were lower than those at the upper level of the tower. However, there were no changes in the concentrations of the particle-phase PAHs between at the upper and lower levels. These results suggested that the forest filter effects for the gas-phase PAT-Is might be higher than those for the particle-phase PAHs.

The optimization of the analysis of volatile organic compounds in atmospheric water samples, such as rainwater and dew water by head space solid-phase microextraction and gas chromatography/mass spectrometry (HS SPME/GC/MS), was studied. The sensitivity of 23 VOCs, i.e. halogenated hydrocarbons and monocyclic aromatic hydrocarbons, was the highest after the extraction of VOCs in 16 mL of samples including 3.5 g of sodium chloride to SPME fiber (100 mu m PDMS) at 40 degrees C during 20 min of incubation. The repeatability of 1 ppb VOCs standard solution was below 10%, except for 1,2-dichloroethane (13%), and their detection limits ranged from 0.02 nM for dichloromethane to 0.30 nM for benzene. The recoveries of 22 VOCs, except for dichloromethane, ranged from 80 to 120% under the condition where 32 mu L of 0.5 ppm VOC standard solution and 5 ppm fluorobenzene as an internal standard was added to 16 mL of atmospheric water samples. The application of the HS SPME/GC/MS method to the determination of VOCs in rainwater and dew water, which was collected in the western part of Tokyo, Hino, revealed that 6 chlorinated hydrocarbons (CHs) and five monocyclic hydrocarbons (MAHs) were detected, and the concentrations of MAHs were higher than those of CHs. Toluene was the dominant VOCs both in rainwater and dew water in Hino, and the volume-weighted concentrations of toluene in rainwater and dew water were 3.31 nM (n = 39) and 5.21 nM (n = 38), respectively. The results of this study made clear that the observed concentrations of VOCs in rainwater and dew water were considerably higher than the estimated concentrations, which were based on Henry's law equilibrium.

The performance of a solar-powered small automatic rainwater collector was investigated, which was developed with an emphasis on small-size, lightweight, and inexpensive for use in a wet deposition monitoring network in a mountainous area. It was studied at Tarobo, which is located at the southeast mountainside (1300 m a.s.l.) on Mt. Fuji, during four years from July 2005 to September 2009. The rainfall amounts estimated by the automatic rainwater collector corresponded to those observed by a rain gauge verified by Japan Meteorological Agency. A comparison of the rainwater chemistry by the automatic rainwater collector with that by a commercially available wet-only sampler indicates that the automatic rainwater collector is available for use in wet deposition monitoring in mountainous areas. The mean annual wet deposition fluxes of H(+), NH(4)(+), NO(3)(-), and SO(4)(2-) at Tarobo were 48.9, 35.0, 38.0 and 69.4 meq/m(2)/y during three years from 2006 to 2008, respectively, and were higher than those at remote sites in Japan, particularly NO(3)(-) deposition. The concentration of acidic substances at Tarobo was nearly equal to those at remote sites in Japan, so it is expected for Tarobo to be in use for a remote site of an acid-deposition monitoring network in Japan because of easy access to Tarobo.

A new sampling system of gas- and particle-phase polycyclic aromatic hydrocarbons (PAHs) in ambient air is proposed. The system is composed of a commercially available multi-nozzle cascade impact sampler for collecting particles less than 10 μm and a newlydesigned glass cartridge (35 mm inner diameter) packed with 5.0 g of a styrene-divinylbenzene copolymer resin adsorbent (XAD-2) for collecting gas-phase PAHs at a flow rate of 20 L/min. A rapid sample preparation for the analysis of PAHs in XAD-2 resin by ultrasonic extraction was also studied. The recovery rates of selected PAHs, i.e. phenanthrene (PHEN), antrathene (ANT), fluorantene (FL), pyrene (PY), benzo[a]pyrene (BaP), benzo[k]fluoranthene (BkF), benzo[ghi]perylene (BghiP), and indeno[1,2,3-cd]pyrene (IP) after the pretreatment ranged from 80 to 100%. More than 95% of the PAHs were extracted from XAD-2 by ultrasonication twice for 20 min with dichloromethane. The newlydeveloped cartridge had more than 95% collection efficiencies of the gasphase PAHs (PHEN, ANT, FL and PY) in both the summer and winter seasons. Storage at -30°C for 4 weeks did not have an adverse effect on the gas-phase PAHs collected with the cartridge. The application of the new sampling system to a field observation at a tower with a height of 12 m in a small forest at Field Museum Tama Hills revealed that the concentrations of the gas-phase PAHs at the lower level of the tower were lower than those at the upper level of the tower. However, there were no changes in the concentrations of the particle-phase PAHs between at the upper and lower levels. These results suggested that the forest filter effects for the gas-phase PAHs might be higher than those for the particle-phase PAHs. © 2010 The Japan Society for Analytical Chemistry.

The effectiveness of the government regulation on tail-pipe emission for diesel vehicles issued in 2003 in Tokyo was evaluated in this study. Variations in annual average concentrations of polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs associated with airborne particulate matter were investigated in connection with the variation in airborne elemental carbon (EC) concentration in downtown Tokyo, Japan in 2006-2007 and in 1997-1998. The annual average concentrations of EC, seven different PAHs, and 1-nitropyrene were found to have decreased significantly from 1997-1998 to 2006-2007. The most prominent decrease in atmospheric concentration was observed for 1-nitropyrene, which is a representative nitro-PAH originating from diesel vehicles. This indicated that the government control has worked to considerably reduce both atmospheric mutagens and airborne particulate matter. In contrast, the concentrations of two nitro-PAHs, 2-nitrofluoranthene and 2-nitropyrene, remained the same. These nitro-PAHs are known to be formed by atmospheric nitration of their parent PAHs, and this result suggested factors other than the concentration of parent PAHs and NO2 affects the degree of atmospheric formation of nitro-PAHs.

Atmospheric polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs and oxy-PAHs are emitted from primary sources. Some nitro-PAHs and oxy-PAHs can also arise from secondary formation in the atmosphere. To assess the relative importance of these sources, the polycyclic aromatic compound (PAC) concentrations were determined at a roadside (Roadside site) and on a rooftop (Urban Background site) in downtown Tokyo Japan. The concentrations of PAHs, 1-nitropyrene and oxy-PAHs at the Roadside site were higher than those at the Urban Background site, while 2-nitrofluoranthene levels were the same at both sites. However, the mean ratios of concentrations at the Urban Background site to the Roadside site were in the order 1,8-naphthalic anhydride9,10-anthraquinonePAHs or 1-nitropyrene or acenaphthenequinone or benzanthrone. This suggests that in addition to vehicle emissions, a considerable fraction of some of the oxy-PAHs studied originates from another source, which might be secondary formation by atmospheric PAH degradation, and this contribution varied among the oxy-PAHs.

Simultaneous sampling of chlorinated hydrocarbons (CHs) and monocyclic aromatic hydrocarbons (MAHs), potentially harmful to humans and/or responsible for the formation of ozone and secondary particles, in dew water and in the ambient air was carried out from August 2004 to July 2005 in Hino City, situated in the western part of Greater Tokyo, Japan. CHs were less contained in dew water than MAHs. Toluene (volume-weighted mean concentration, VWM: 4.77 nM) and m,p-Xylenes (VWM: 5.07 nM) except dichloromethane, which was abnormally high (VWM: 1.14 mu M), were abundant among eleven VOCs determined in dew water. Chloroform, carbon tetrachloride, 1,2-dichloroethane, and benzene were not detected in dew water during the study period. Dew water contained higher amounts of VOCs than would have been expected from the ambient gas-phase concentrations and the temperature-corrected Henry's law constants. Following the determination method of humic substances in river water proposed by Hiraide et al. [Hiraide, M., Shima, T., Kawaguchi, H., 1994. Separation and determination of dissolved and particulate humic substances in river water. Mikrochim. Acta 113, 269-276], the VWM of soluble humic and fulvic acid fractions in dew water was found to be 1.00 mg/L and 0.87 mg/L (n = 20), respectively, while the VWM of particulate humic and fulvic acid fractions was found to be 0.61 mg/L and 0.42 mg/L (n=20), respectively. Surface tension decreased with an increase in dissolved fulvic acid fraction in dew water, indicating that humic-like substances with relatively lower molecular weight, which is soluble in acid solution, could be an effective surface-active species within dew water. The enrichment factors, which were defined as the ratio of the observed VOCs concentration to the estimated, were over 10(2) for MAHs except for benzene and increased as the increment of total humic-like substances (HULIS) concentration (the sum of humic and fulvic acid fractions in both dissolved and particulate form) normalized by total inorganic ion concentration in dew water. Our results indicate that total HULIS in dew water could enhance the dissolution of atmospheric VOCs into dew droplets. (c) 2007 Elsevier B.V. All rights reserved.

2- and 3-Nitrobenzanthrones (NBAs) in airborne particles collected in central Tokyo on a seasonal basis from 1996 to 2001 are quantified and possible sources are investigated. The concentrations of 2- and 3-NBA are found to range from 49 to 831 fmol m-3and 0.5 to 3.5 fmol m-3, while the nitrated polycyclic hydrocarbons 1-nitropyrene and 2-nitrofluoranthene are found at concentrations of 100-492 fmol m-3 and 10-97 fmol m-3. Significant linear correlations are identified between 2-NBA and NO2, a photochemical product, suggesting that 2-NBA is formed by atmospheric reactions of benzanthrone initiated by hydroxyl or nitrate radicals in the presence of NO2. 2-NBA is not correlated with directly emitted compounds such as 1-nitropyrene. The concentration ratio of 2-NBA to 1-nitropyrene is 5 or greater in all samples. Nitrated polycyclic aromatic compounds formed by atmospheric reactions therefore appear to represent a substantial contribution to the mutagenicity of airborne particulate matter.

The wet deposition fluxes of acidic substances were observed on the mountainside (1300 m a.s.l.) of Mt. Fuji from July 2005 to November 2006 by a solar-powered automatic rainwater collector, which was developed with emphasis on its being small-size, lightweight, and inexpensive for use in wet deposition monitoring network in mountainous area. The collector is divided into two parts, namely rainwater collection and solar battery system. The former is composed of a capacitance-type rain sensor, an originally designed automatic switching cover, a polycarbonate filter holder (80 mm in diameter), which is equipped with a 47 mm diameter and 1.2 &mu;m pore size membrane filter, a polyethylene bottle, and a polypropylene tube connecting the holder and the bottle. The latter is composed of a 20 watt solar panel, a solar charge controller, and a 12 V lead acid battery. A comparison of the deposition fluxes, estimated by the automatic rainwater collector with those by a filtering-type rainwater collector, indicated that they were free of the influence of dry deposition without a loss of rainfall in the automatic rainwater collector. Rainfall amounts estimated by the automatic rainwater collector corresponded to those observed by a commercially available rain gauge except for winter. Annual wet deposition fluxes of H⁺, NO₃^&minus;, and SO₄^2&minus; in the mountainside on Mt. Fuji were 58.5, 40.4, and 78.8 meq/m²/y, respectively.<br>

It has been reported that the nitrate concentration in stream water in the mountainside on Mt. Oyama (1252 m a.s.l), which is located at the western part of Kanagawa Prefecture, is higher than that in stream water in other regions, indicating that nitrogen saturation is occurring in the forested ecosystem. However, there has been no report on nitrogen saturation across the Tanzawa mountains, except Mt. Oyama. We investigated the current status of the stream water chemistry and the effect of acid deposition on the stream water chemistry across the East Tanzawa mountains. Thirty-eight samples were collected in nine mountain streams in this region. The mean pH and alkalinity in stream water in this region were 7.315 and 650 mu eq/L, respectively. There was no symptom of stream-water acidification by acid deposition in East Tanzawa, probably because of the high acid buffering capacity by the weathering of carbonate and silicate minerals. Nitrate concentrations in the stream water ranged from 27.6 to 87.8 peq/L and NH4+ was detected. High nitrate concentration in stream water suggests that nitrogen saturation is occurring in the forested ecosystem in East Tanzawa mountains. We divided our sampling sites into southeast (SE), southwest (SW), and north (N) regions by the ridge line of Mt. Tanzawa - Mt. Tonodake - Shindainichi - Mt. Sannoto - Mt. Takenodai - Mt. Oyama - Mt. Mitsumine. The stream water pH was lower and the concentrations of Na+ and NO3 were higher in south regions. There were high correlations between the concentrations of Na+ (r = - 0.854), Cl- (r = - 0.815) and NO3- (r = - 0.922) and the distance from the coast of Odawara City, Oisomachi, and Ninomiyamachi. In addition, a high correlation between the N03 and Cl concentrations (r = 0.741), which is an indicator of atmospheric deposition, in stream water was observed. Our preliminary investigation indicates that the runoff of nitrate, originated from atmospheric deposition, might occur in the forested ecosystem in the southern regions in East Tanzawa.

The wet deposition fluxes of acidic substances were observed on the mountainside (1300 m a.s.l.) of Mt. Fuji from July 2005 to November 2006 by a solar-powered automatic rainwater collector, which was developed with emphasis on its being small-size, lightweight, and inexpensive for use in wet deposition monitoring network in mountainous area. The collector is divided into two parts, namely rainwater collection and solar battery system. The former is composed of a capacitance-type rain sensor, an originally designed automatic switching cover, a polycarbonate filter holder (80 mm in diameter), which is equipped with a 47 mm diameter and 1.2 pm pore size membrane filter, a polyethylene bottle, and a polypropylene tube connecting the holder and the bottle. The latter is composed of a 20 watt solar panel, a solar charge controller, and a 12 V lead acid battery. A comparison of the deposition fluxes, estimated by the automatic rainwater collector with those by a filtering-type rainwater collector, indicated that they were free of the influence of dry deposition without a loss of rainfall in the automatic rainwater collector. Rainfall amounts estimated by the automatic rainwater collector corresponded to those observed by a commercially available rain gauge except for winter. Annual wet deposition fluxes of H+, NO3-, and SO42- in the mountainside on Mt. Fuji were 58.5, 40.4, and 78.8 meq/m(2)/y, respectively.

It has been reported that the nitrate concentration in stream water in the mountainside on Mt. Oyama (1252 m a.s.l), which is located at the western part of Kanagawa Prefecture, is higher than that in stream water in other regions, indicating that nitrogen saturation is occurring in the forested ecosystem. However, there has been no report on nitrogen saturation across the Tanzawa mountains, except Mt. Oyama. We investigated the current status of the stream water chemistry and the effect of acid deposition on the stream water chemistry across the East Tanzawa mountains. Thirty-eight samples were collected in nine mountain streams in this region. The mean pH and alkalinity in stream water in this region were 7.315 and 650 μeq/L, respectively. There was no symptom of stream-water acidification by acid deposition in East Tanzawa, probably because of the high acid buffering capacity by the weathering of carbonate and silicate minerals. Nitrate concentrations in the stream water ranged from 27.6 to 87.8 μeq/L and NH4+ was detected. High nitrate concentration in stream water suggests that nitrogen saturation is occurring in the forested ecosystem in East Tanzawa mountains. We divided our sampling sites into southeast (SE), southwest (SW), and north (N) regions by the ridge line of Mt. Tanzawa-Mt. Tonodake-Shindainichi-Mt. Sannoto-Mt. Takenodai-Mt. Oyama-Mt. Mitsumine. The stream water pH was lower and the concentrations of Na+ and NO3- were higher in south regions. There were high correlations between the concentrations of Na3+ (r = -0.854), Cl- (r = -0.815) and NO3- (r = -0.922) and the distance from the coast of Odawara City, Oisomachi, and Ninomiyamachi. In addition, a high correlation between the NO3- and Cl- concentrations (r = 0.741), which is an indicator of atmospheric deposition, in stream water was observed. Our preliminary investigation indicates that the runoff of nitrate, originated from atmospheric deposition, might occur in the forested ecosystem in the southern regions in East Tanzawa. © 2007 The Japan Society for Analytical Chemistry.

The contaminants adsorbed on the surface of pollen may affect the development of hay fever, because the patients of the fever are larger in areas with much air pollution than in nonpolluted areas and the fine particles and gases are susceptible to deposit on the nasal cavities and eyes by their transfer on the pollen. Since Japanese cedar pollinosis is the most common hay fever in Japan, we analyzed the air pollutants adsorbed on the surface of dispersed Japanese cedar pollen in the urban and mountainous districts. Fine anthropogenic particles were significantly adsorbed and many elements were concentrated on the surface of the pollen in the urban site of Yokohama, while they were not concentrated on the surface of the pollen collected at a mountainous site. The acid gases are also adsorbed and acidify the surface, and their amounts increase with their concentrations in the ambient air. The high adsorption of nitric acid on the pollen determined by an exposure experiment of nitric acid gas suggests that nitric acid is dissolved in the inner part of the pollen. The adsorption amounts of the gases on the pollen were especially greater than those on other natural particles, humic acid and yellow sand. (c) 2006 Elsevier Ltd. All rights reserved.

Hydrophobic volatile organic compounds (VOCs) are usually found in rainwater with higher concentrations than the values determined from Henry's law partitioning. Laboratory experiments demonstrated that dissolved organic compounds, such as humic acids, act as cosolvents to solubilize the VOCs. Wet removal by rainfall is a significant sink of trace VOCs.

Simultaneous sampling of six chlorinated hydrocarbons (CHs) and five monocyclic aromatic hydrocarbons (MAHs) in dew water and in the ambient air was performed from 1998 to 2000 in Yokohama, Japan. Dichloromethane (volume-weighted mean concentration (VWM): 2.43 nM) and trichloroethylene (VWM: 2.91 nM) were abundant among CHs in dew water, while toluene (VWM: 9.69 nM) and p-dichlorobenzene (VWM: 6.06 nM) were abundant among MAHs. The contribution of total measured volatile organic compounds (VOCs) concentration to dissolved organic carbon (DOC) concentration in dew water was only 0.02 wt% on average. The concentrations of VOCs except for dichloromethane and benzene in dew water were several hundred times higher than those in rainwater collected at the same site. In particular more hydrophobic VOCs with higher octanol-water partition coefficient K-OW tended to be concentrated in dew water, indicating that urban dew water has stronger hydrophobicity than rainwater. Dew water contained higher amounts of VOCs than would have been expected from the ambient gas-phase concentrations and Henry's law constants. The enrichment factors, which were defined as the ratio of the observed concentration to the estimated, ranged from 6.98 (for dichloromethane) to 62.7 (for trichloroethylene) on average. Relatively high correlations (r &gt; 0.55) between the enrichment factors of highly hydrophobic VOCs (K-ow&gt; 10(3)) and the ratios of DOC to total inorganic ion concentration (TIC), which could be a potential surrogate of surface tension for urban dew water, indicated that the existence of any dissolved organic compounds, which could reduce the surface tension, in dew water also caused the enrichment of highly hydrophobic VOCs. (c) 200S Elsevier Ltd. All rights reserved.

We continuously collected aerosol samples of PM7 from 1990 to 1997 and of PM10-2 and PM2 from 1998 to 2001 and measured their water-soluble components of pH, conductivity, major ions, dissolved organic carbon (DOC) and total mass (TM) in an urban site, Yokohama (35degrees28'N, 139degrees38'E) and the mountainside (680 m asl) of Mt. Oyama (35degrees28'N, 139degrees46'E, 1252 m asl), Japan, to contrast the aerosol composition between an urban site and a mountain site. In Yokohama, annual mean TM concentration decreased gradually for over 10 years with the decrease of NH4+, Mg2+, Cl-, and SO42- concentrations, and TM concentrations were the highest in winter and the lowest in summer. At Mt. Oyama, there was no significant change in the duration, and TM concentrations were the highest from late spring to early summer, although the seasonal variation was smaller. Equivalent concentration ratio of Cl- to Na+ at Mt. Oyama was lower than that in Yokohama, because Cl loss which occurred was larger for the aerosol collected at Mt. Oyama remote from the sea rather than Yokohama. The conversion ratio of sulfur to sulfate was calculated and the ratio was not affected strongly by the variation of O-x concentration at both sites and was high at Mt. Oyama in summer. NH4+, NO3-, SO42-, and DOC concentrations were higher under weak wind velocity than those under strong wind velocity regardless of the wind direction in both the sites. (C) 2004 Elsevier Ltd. All rights reserved.

By simultaneous sequential sampling of gas and rainwater from 1999 to 2000 in the campus of Kanagawa University in Yokohama, Japan, we investigated the wet-scavenging process of volatile organic compounds, some chlorinated hydrocarbons (CHs) and monocyclic aromatic hydrocarbons (MAHs), via rain droplets. Their volume-weighted mean concentrations in 125 rainwater were 4.98 nM for dichloromethane, 3.71 nM for toluene, 2.00 nM for benzene, 0.93 nM for 1,2-dichloroethane, 0.62 nM for o-xylene, 0.57 nM for m,p-xylene, 0.51 nM for p-dichloro benzene, and 0.35 nM for trichloromethylene. Their rainwater concentrations did not depend on the rainfall intensity, and the temporal variation of their concentrations was similar to that of gas-phase concentrations. The dissolution of CHs and MAHs into rainwater, however, was larger than expected from their gas-phase concentrations at the ground and their temperature-corrected Henry's law constants. A simple below-cloud scavenging model, which was developed by Levine and Schwartz (Atmos. Environ. 16 (1982) 1725) Could explain the independence of the rainfall intensity but not explain their enhanced dissolution in rainwater. The results of this study indicate the estimated concentrations, which were based on the Henry's law equilibrium, considerably underestimate the wet-deposition fluxes of CHs and MAHs onto the ground. (C) 2004 Elsevier Ltd. All rights reserved.

Dew water characteristics are not as acidic as those of rainwater and fog water, and they are abundant in weak acid components. The dew water components are dominated by the coarse-mode aerosol rather than the fine-mode aerosol, and calcium carbonate, the component of soil, is the important chemical species raising the pH of the dew water. Carbon dioxide is deposited as calcium carbonate into dew water and is the only major component released from dew water. The total concentration of carbon dioxide increased with an increase in the dew water pH, while the degassing rate increased with the decrease in dew water pH. In the low-pH region, the pepsilon values in dew water are lower than those in rainwater, and the dew water is in a reductive state. The concentration of the representative oxidant, hydrogen peroxide, was much lower in the dew water than in the rainwater in Yokohama (dew water, 0.4 muM; rainwater, 13.1 muM in 1998). The representative conjugate base ions of a weak acid, sulfite and hydrogen sulfite ions, are easily oxidized by hydrogen peroxide, and the lower concentration of hydrogen peroxide in dew water may cause the higher concentration of sulfite ion in dew water than in rainwater. The dew water pH is higher than the rainwater and fog water pH, and a weak acid is easily dissolved into the dew water. Therefore these weak acid ions are more abundant in dew water than in rainwater and fog water.

In neutralization dialysis, the salt solution is desalinated continuously. The cations in desalination compartment are exchanged with protons in the acid compartment across a cation-exchange membrane and the anions are exchanged with hydroxide ions in the base compartment across an anion-exchange membrane. A simple index (C/J), where C is the source phase concentration (mol cm(-3)) and J is the flux (mol cm(-2) min(-1)), was proposed for the estimation of the desalination properties in neutralization dialysis. The index was based on the concepts of the ion-exchange reaction rate at the membrane interface and was related to the permeation constant in the source-phase boundary layer at the membrane interface, P-a (cm min(-1)), as C/J = 1/(k(1).C-ex) + 1/P-a, where k(1) is the rate constant of ion-exchange reaction (mol(-1) cm(4) min(-1)) and C-ex is the ion exchange capacity of the membrane (mol cm(-3)). The desalination efficiency increased with the decrease of the desalination compartment thickness and the decrease of the linear velocity, which can be estimated well by using the index. Tap water was desalinated by neutralization dialysis and pure water was obtained at the outlet of the desalination cell.

The lubrication characteristics of the olive oils, which are used as biodegradable lubricants, on the steel ball were examined on the viewpoint of their growing area and quality of the olive oil. The discoloration of virgin olive oil and the friction face and/or the friction force of the steel ball were found to be dependent on their growing area as well as pure olive oil.&lt;br&gt;&amp;nbsp;&amp;nbsp;Property of the constituent metal constituents of steel ball on the air oxidation of methyl ester of oleic acid, which is major constituent fatty acid of olive oil and the lubrication characteristics of the resulting oxidation products, were investigated. The autoxidation of methyl oleate under the existence of each acetylacetonatos of Cr, Mn, Fe, Ni, Cu, and V was carried out by blowing dry air at 80&amp;deg;C. All the metal salts except V facilitated the oxidation. The metals employed affect the yields and the types of the products, &lt;i&gt;i.e.,&lt;/i&gt; hydroperoxide, hydroxide and epoxide whom the functional group exists for the center location of molecular chain.&lt;br&gt;&amp;nbsp;&amp;nbsp;Friction test for ball bearing was conducted by using each oxidation product and parent methyl oleate. The surface of the steel ball was the abrasive wear condition by hydroperoxide. The hydroxide gave excellent lubrication characteristics by hydroxy group adsorbed on the surface of steel ball. Epoxide increased the coefficient of friction. Methyl linoleate, having two double bonds, provided the flatted frictional surface at the ball bearing, but it is easy to be oxidized.&lt;br&gt;&amp;nbsp;&amp;nbsp;To sum up the major characteristics of the autoxidation products which affect friction surface of steel ball, the function groups of center position in molecular chain of methyl oleate are of most significance. It was found that double bond and hydroxyl function of &amp;alpha;-position of double bond are effective under the boundary lubrication.

We have observed acid fog in Mt. Oyama adjacent to the Kanto Plains in Japan, where acid fog under pH 3 has been frequently observed and natural fir forest (Abies firma) has been declining. We applied the simulated acid fog to the needles of fir twigs and the treatment removed calcium, boron, and cell-wall acidic sugars from the needles. We also observed high contents of calcium, boron, and acidic sugars in throughfall collected under the declining forest canopy. Ca++ and Mg++ ion leach via ion-exchange with major cations of fog-water and the amount of leached boron increased with the increase in the concentration of leached Ca++. The deficiency of calcium and boron by leaching could be one of the main causes of decline of the fir forest.

Heavy metal ions can be selectively transported under the concentration gradient across a cation-exchange membrane with a chelating agent in the receiving phase. The selectivity depends on the complex formation constants of the ions with the agent. Metal ions are adsorbed into a cation-exchange membrane via the ion-exchange reaction and diffuse across the membrane. The desorption process is facilitated by the complexation in the receiving phase, which causes a large transport rate across the membrane. A transport equation was established and the theoretical values estimated by the equation and the permeation characteristics values obtained experimentally agreed well with the measured ion flux. The selectivity of the metal ions in the mixed solution is increased in the adequate concentration of the chelating agent in the receiving phase, when the chelate formation reaction may occur competitively between the ions with the agent in the receiving phase. The metal ions in the complex solution can be stripped as free ions across a cation-exchange membrane via the ion-exchange reaction with protons under a concentration gradient of acid.

Dew droplets have a distribution of sizes up to 1.5 mm diameter. Large-sized droplets controlled the dewwater amount and the number of small-sized droplets decreased during the evaporation process. The wetting by dew formation enhances the dry deposition of air pollutants.

Dewwater was collected from January 1993 to December 2000 in Yokohama, Japan, and analyzed for weak acid anions with other major chemical components. The volume-weighted average and medium pH of the dewwater were 4.88 and 6.08, respectively, at our sampling site. Weak acids (carbonate, nitrite, sulfite, formate, and acetate ions) were the major species in the dewwater and were several times higher than those in the rain- and fogwater. The concentrations of these species and ammonium ion can be estimated by the resistance model. The estimated values of N(III) correlate relatively well with the measured values, which shows the origin of N(III) in dewwater is nitrous acid in the ambient air. On the other hand, ammonium ion in the dewwater originated from not only gaseous ammonia but also aerosol ammonium ions. Hydrogensulfite ions in the dewwater which originated from sulfur dioxide are an important species as the precursor of the sulfate and they were stabilized by forming hydroxyalkanesulfonate (HASA). Formic acid and acetic acid in the dewwater originated mainly from gas, while the oxalic acid is from aerosol.

It is possible that metal-organic complexation enhances the uptake of gaseous organic compounds and the solubility of metals in aerosols and atmospheric water. We investigated potential atmospheric organic ligands and the enhanced uptake of hydroxy-, oxo-, and dicarboxylic acids as well as dicarbonyls into atmospheric aqueous aerosol. We examined complexation with transition metals (iron, manganese, nickel, copper, zinc) and lead on the basis of available references and our experimental data. Humic-like substances are most likely ligands in the atmosphere, although this is a poorly characterized material. A number of polycarboxylic acids and hydroxy forms (e.g., citric and tartronic acids) effectively complex metals such as copper in atmospheric aerosols. The simple equilibrium model calculations show that the effect of the complexation on the gas-aqueous phase partition of gaseous atmospheric ligands is quite small for the ligands with the high physical Henry's law constants, e.g., dicarboxylic acids represented by oxalic acid, even if they have high affinity with metal ions. The lower Henry's law constants of the alpha-dicarbonyls, such as glyoxal and methylglyoxal, mean that the complexation could lead to profound increases in their partition into the aqueous phase. Despite quantum mechanical arguments for copper-glyoxal complexes, experiments showed no evidence of complexation between either hydrated or unhydrated alpha-dicarbonyls and the cupric ion. By contrast the beta-dicarbonyl, malondialdehyde, has properties that would allow it to partition into atmospheric water via the complexation with metal ions under some conditions.

We have collected and analyzed fogwater on the mountainside of Mt. Oyama (1252 m) in the Tanzawa Mountains of Japan and observed the fog event frequency from the base of the mountain with a video camera. The fog event frequency increased with elevation and was observed to be present 46% of the year at the summit. The water deposition via throughfall increased with elevation because of the increase in fogwater interception and was about twice that via rain at the summit, where the air pollutant deposition via throughfall was several times that via rainwater. The dry deposition and the deposition via fogwater were dominant factors in the total ion deposition at high elevation sites. In a fog event, nitric acid, the major acid component on the mountain, is formed during the transport of the air mass from the base of the mountain along the mountainside, where gases including nitric acid deposit and are scavenged by fogwater. Therefore, high acidity caused by nitric acid and relatively low ion strength are observed in the fogwater at high elevation sites.

We have measured the components of the throughfall under fir trees (Abies firma) in the field around Mt. Oyama, where the forest appears to be declining, for the period 1994-1998. Exposure experiments of a simulated acid fog to fir twigs were performed under field conditions. There was a similarity between the acid response in the field and that in the laboratory. In both studies, the severe leaching of calcium ions from the needle surface was caused by exposure to acid fog. We also applied acid fog to fir seedlings over 1 year and observed a decrease in the growth of the seedlings due to this application in the dormant season. These results suggest that the severe leaching of calcium ions due to acid fog may cause the deficiency of calcium and be responsible for the decline of the fir trees.

Dew-water was collected from January 1999 to February 2000 in Yokohama, Japan and analyzed for not only soluble major components but also insoluble or trace components. The pH of dew-water ranged from 5.36 to 6.71 and volume-weighted average pH was 5.81. In dew-water, Si, Al, Fe, Cl, and Na were abundant and they were confirmed to be transported from natural sources, sea and soil dust. The concentrations of Si, Al, Fe, and Ti contained in coarse mode aerosol were several times higher in dew-water than those in rain-water, while the concentrations of V and Pb contained in fine mode aerosol were about the same level to each other. Besides these elements derived from aerosol, the elements derived from gaseous species are also major components in dew-water. The high concentration of weak acid is one of the significant characteristics of dew-water. Bisulfite ion in dew-water is the important species as the precursor of the sulfate ion but it is stable by forming hydroxyalkanesulfonate (HASA). The HASA concentrations were evaluated by using concentrations of total S(IV) and aldehydes and hydroxymethanesulfonate (HMSA) was shown to be the dominant species in S(IV).

We have observed acid fog in Mt. Oyama since 1988. Fog events occur frequently in Mt. Oyama; 47% of the time the mountain top is covered with fog. The pH of fog is lower than that of rain collected at the fog sampling station by about 1 unit and the lowest pH was 1.95. We have also collected gas and aerosol components at the station and observed fog events by a video camera from the mountain base, where there is an air pollution monitoring station. The air quality at the fog sampling station was affected by not only the air quality at the base but also the wind direction, valley or mountain wind. It is ascertained by using back trajectory analyses that polluted air masses are transported to the base from the Kanto plains or other big urban areas, Osaka and Nagoya. When the base is polluted, the relative humidity increases, and the valley wind blows, acid fog is formed at the mountainside. In the acid fog, nitrate ion is the most abundant anion. Nitrate ion concentration correlates well with hydrogen ion concentration. The annual mean total ion concentration has not changed much since 1988, but the concentration ratio of nitrate ion to sulfate ion has increased in recent years. The nitric acid gas concentration in the station is comparable to that in urban areas, while other gas concentrations are much lower.

Virgin fir trees have been dying on Mt. Oyama, which is located in the southwestern part of Kanto Plain, although the frequency of death seems to be reducing recently. We report elevational patterns of acid depositions in precipitation and throughfall under fir and cedar canopies and nitrogen saturation in the forest ecosystem on Mt. Oyama. The deposition fluxes of major inorganic ions in precipitation were nearly constant regardless of elevation except for hydrogen and ammonium ions, whereas the deposition fluxes of all major inorganic ions in throughfall among cedar increased. The 5-year average of annual nitrate deposition in precipitation from 1994 to 1998 showed 19.3 - 23.5 kg ha(-1) yr(-1) (annual inorganic total N deposition: 9.6 - 10.7 kgN ha(-1) yr(-1)) at four sites ranging in elevation from 500 to 1252 m, whereas the deposition in both cedar and fir throughfall was over 6 times greater than that inn precipitation. The average soil surface nitrate concentration in 1998 was 140 mug g(-1) (the range: 21.1 - 429 mug g(-1), n=80) and the 7-year average of nitrate concentration in stream water from 1992 to 1998 was 4.81 mg L-1 (the range: 2.38 - 20.6 mg L-1, n=317). Our results indicate that nitrogen saturation is occurring in the forest ecosystem because of high N deposition, probably via acid fog, on Mt. Oyama.

Dew-water was collected from January 1999 to February 2000 in Yokohama, Japan and analyzed for not only soluble major components but also insoluble or trace components. The pH of dew-water ranged from 5.36 to 6.71 and volume-weighted average pH was 5.81. In dew-water, Si, Al, Fe, Cl, and Na were abundant and they were confirmed to be transported from natural sources, sea and soil dust. The concentrations of Si, Al, Fe, and Ti contained in coarse mode aerosol were several times higher in dew-water than those in rain-water, while the concentrations of V and Pb contained in fine mode aerosol were about the same level to each other. Besides these elements derived from aerosol, the elements derived from gaseous species are also major components in dew-water. The high concentration of weak acid is one of the significant characteristics of dew-water. Bisulfite ion in dew-water is the important species as the precursor of the sulfate ion but it is stable by forming hydroxyalkanesulfonate (HASA). The HASA concentrations were evaluated by using concentrations of total S(IV) and aldehydes and hydroxymethanesulfonate (HMSA) was shown to be the dominant species in S(IV).

Dew-water was collected from 1995 to 1998 in Yokohama, Japan and analyzed for various chemical components. The frequency of dew events in 1998 was 22% and is the highest during the winter season. Precipitation resulting from dew was 7.7 mm/year and corresponded to about 0.4% of that from rain (rain precipitation, 1901 mm) in Yokohama. The pH of dew-water ranged from 3.04 to 7.82 and the volumeweighted average pH was 5.08. Dew-water chemistry was characterized by a relatively high ion concentration compared to rain- and fog-water. The dew-water composition was strongly affected by aerosol and gaseous components, and therefore varied depending on the location where dew-water was collected. The dry deposition velocities of dew-water were estimated from the concentrations of dew-water components, gas and aerosol concentrations, dewfall, and the period between dew collector set up and dew collection by regression analysis. Dew-water was acidified primarily by nitric acid gas absorbed in dew-water. The deposition velocities of nitric acid gas and nitrate ion in aerosol were calculated to be 1.28 cm s^&lt;-1&gt; and 0.11 cm s^&lt;-1&gt;, respectively, and estimated values from the atmospheric concentrations of gas and aerosol corresponded well with the measured values. The nitrate ion concentration in acidic dew-water differed slighty from the estimated value which may have been the result of dinitrogen pentaoxide gas absorption by the dew-water.

Deterioration of concrete structures caused by acid deposition was investigated by laboratory and field exposure of portland cement mortar specimens to acid deposition. Laboratory exposure experiment showed that the dissolved amount of calcium hydrates, which were the major components in mortar, increased with the increase in the acidity of simulated acid rain solution and the decrease in the flow rate. There was little difference in their amount among different temperature treatments after each exposure to the solution with the same acidity, namely left at room temperature, heated at 70 degrees C, and cooled at - 2 degrees C. The neutralization progressed more deeply under the heated and cooled condition and was accelerated by even acid rain with pH 4.7 during a long period (90 exposure cycles, which correspond to the rainfall amount of 15 years in Japan). A field exposure experiment for two years indicated that the carbonation of calcium hydrates and the formation of other corrosion products such as chloride, nitrate, and sulfate were limited to the surface of mortar specimens. The neutralization progressed more deeply in mortar specimens sheltered from rainwater than in those washed by rainwater. (C) 2000 Elsevier Science Ltd. All rights reserved.

Volatile organic compounds in rainwater and in the atmosphere were determined in Yokohama, Japan by purge and trap or adsorption column &#039;methods and GC/MS. The average concentrations of dichloromethane, toluene, chloroform, and 1,2-dichloromethane in rainwater were 9.8,2.4,2.1,and 1.5 nmol/L. The contribution of rainwater to VOCs pollution in surface water can be significant. The relative standard deviations of VOCs were very high (140-730%) in rainwater. In contrast with the ion concentration, the VOCs concentrations in rainwater were not dependent on the precipitation intensity and were not high at the beginning of the precipitation. The scavenging effect below cloud level was very small for VOCs. The concentrations of VOCs in rainwater were dependent on their concentrations in the atmosphere near the ground with some exceptions, such as benzene.

Pertracion of hydrophobic organic solutes with a hydrophobic membrane is a continuous separation process, which can be used as a substitute of activated carbon. The permeability was affected by the hydrophobicity of the solute and the dissociation in the receiving phase. The pertraction of a hydrophobic solute against its concentration gradient is also possible under a concentration gradient of hydroxide ion.

Fogwater chemistry has been observed at Mt. Oyama abutting on the Kanto Plain in Japan. Many air pollutants are deposited via fog droplets, and the nitrogen deposition rate via fogwater is at the same level as that via rainwater. The fogwater concentrations depend on the air pollutant concentrations, liquid water content, and the fog base altitude estimated from the meteorological data for the mountain base. The air pollution dominating the concentrations of fogwater components can be estimated from the sulfur dioxide concentration at the base of the mountain. The concentrations of fogwater components were dominated by the absorbing rates of air pollutants into the fog droplets and were not inversely proportional to the LWC. The concentration of fogwater can be estimated approximately from the SO2 concentration at the mountain base, the fog base altitude, and the LWC measured for the fogwater.

Fir seedlings (Abies firma) were treated with simulated acid fog from September 1992 to April 1995. The simulated acid fog was at pH 3 and consisted of 1 mM nitric acid, 1 mM sodium chloride, and 1 mM ammonium sulfate. In 1993 spring, needles of the seedlings treated with the simulated acid fog became greener than those of the control, which were treated with pH 5 fog water of one hundredfold diluted solution of pH 3 fog water. However, from June 1993 in the acid-fog-treated seedlings, the needles shed, and the growth in height declined. Many buds with their bearing sprouts died in 1993, and few twig tips put forth new sprouts in the spring of 1994. Other symptoms also developed because of the treatment with the simulated acid fog: the water loss from the needles increased and the needles became susceptible to water stress, the weight per area of the needles decreased, and chlorophyll concentration increased. The results were observational in nature and the data were generated from plants exposed to the atmosphere in Yokohama so that there is a possibility of interaction with other pollutants. The long-term treatment with simulated acid fog at pH 3 induced a decline of fir seedling growth and general well-being, although the data warrant further study of the effects of chronic exposure of acid fog on plant growth. (C) 1997 Published by Elsevier Science B.V.

An extremely acidic fog of pH 1.95 was observed in Mt.Oyama, Tanzawa Mountains on April 25,1994. The major ions were H^+ and C1^-, and non-sea-salt chloride ion concentration of 12.8 mmol/1 was detected. The occurrence of acid fogs containing over 1 mmol/1 of non-sea-salt chloride ion was limited to the period between 15 : 00 and 19 : 00,and the concentration increased rapidly, then decreased again in a short time. The extremely acidic fog event may be caused by a local pollution of hydrogen chloride gas, which was discharged from an incinerator. The ion loading of hydrochloric acid in the extremely acidic fog corresponded to about 2 ppb of hydrogen chloride gas in atmosphere, which was often observed in an urban area in Japan. As a result, fog water pH will reach to an extremely low values again in future in a mountainous site close to an urban area.

Oscillation coupled with transport phenomena occurred in a liquid membrane system containing polyoxyethylene p-nonylphenyl ether under the concentration gradient of ethyl alcohol. The solutes of ethyl alcohol and some alkaline metal salts were transported without oscillation but their transport rates were enhanced by the periodical convection synchronous with the oscillation in this system.

Dews or frosts formed on artificial collectors were collected during the early morning in Yokohama in 1993 and 1994 and analyzed for weak acids as well as major inorganic ions. In 1993 (n = 21) the dew pH ranged from 3.23 to 7.12 and averaged 4.60; in 1994 (n = 56) it ranged from 4.11 to 7.74 and averaged 5.41. Based on the average, NH4+ and Ca2+ were major cations (423 and 178 mu equiv L(-1) for NH4+ and Ca2+ in 1993, respectively, and 454 and 274 mu equiv L(-1) in 1994, respectively) and SO42- was the dominant anion (344 mu equiv L(-1) in 1993 and 271 mu equiv L(-1) in 1994) in dew water. The dew chemistry was characterized by relatively high concentrations of weak acid anions, particularly hydrogensulfite ion (HSO3-). Dew water sometimes had very high acidity (the minimum pH was 3.23 during the period of this research), which might have been due to the aqueous oxidation of S(IV). From a resistance model calculation, the S(IV) concentration in dew water was suggested to be influenced by the dissolution of HCHO from the atmosphere and the subsequent formation of HMSA.

Hydroxymethanesulfonate ion (HMSA) is an important species in dewwater and the formation of HMSA enhances the dissolution of SO2. The HMSA stability constant calculated from the measured concentrations of free formaldehyde and S(IV) in dewwater agreed in the order with the reported value, which suggested the formation of HMSA and other S(IV) complexes.

Neutralization dialysis is a deionization method based on a Donnan dialysis. Weak acids and bases, even urea and alcohols, were also removed by this method, and their transport rates increased with the decrease of their dissociation constants and with the increase of the concentrations of acid and base solutions in the neutralization system. Aqueous silica, which is a typical inorganic weak acid and abundant in surface water, was also effectively removed by this method. Therefore, tap water was effectively deionized to be pure water with a resistivity of 15 M Omega cm and a silica concentration ofless than 10 ppb as SiO2 and the neutralization dialysis was proven to be an effective deionization method.

The transport of sugar was facilitated via complexation with borate ion fixed on an anion-exchange membrane. The sugar was highly distributed on the membrane and was transported by the carrier-relay mechanism. The flux across the borate ion type membrane increased with increasing concentration but became constant at a lower flux than across a chloride ion type membrane. Sugars were selectively transported and the permeability of the sugar depends on its distribution in the membrane. © 1995.

Acid deposition causes the forest decline and the acidification of lakes and marshes. Furthermore, historic stone monuments, which were made of marble, limestone, and so on, have been reported to be deteriorated by acid deposition and concrete structures may be deteriorated as well. There are few studies on the effects of acid rain on mortar and concrete, though the effects of CO2 and SO2 have been studied. Deterioration of concrete structures by acid rain is guessed to proceed as follows. (1) Dissolution of aggregate, hydrated and unhydrated materials at the surface. (2) Conversion of CaCO3, which is formed by carbonation of hydrated materials, to water soluble salts. (3) Elution of the salts at the surface and development of stress by deposition of the salt beneath the surface. (4) Cracking by formation of corrosion materials such as ettringite, which occupy a large volume. (5) Cracking and spalling by the corrosion of reinforcing steel, which is lead to by neutralization and penetration of chloride and sulfate. At present, there is no obvious evidence showing that deterioration of well-constructed concrete structures is accelerated by acid rain, though the investigation is limited. © 1995, Japan Society of Corrosion Engineering. All rights reserved.

The transport phenomena of salts across a liquid membrane containing a nonionic surfactant, polyoxyethylene p-nonylphenyl ether, as a carrier were investigated. The surfactant, complexing with metal cations selectively, functions as a monomeric carrier or a reversed micellar carrier of a self-assembly system depending on the concentrations of the carrier and the source phase salt. The fluxes of the hydrophobic salts were large in general, and potassium ion was selectively transported by the carrier containing 20 ethylene oxide units. The mole ratio of the salt to the carrier in the complex was 1 in the forms of both monomer and reversed micelle. The transport equation was derived from the complex formation, and its destruction rates and the diffusion resistance were found to be functions of the activities of the source phase salt and the carrier. The theoretical values agreed very well with the measured values. Both the reaction rate constant and the diffusion coefficient decreased significantly with the change of the carrier form from the monomer to the reversed micelle. Therefore, the increase of the flux with the increase of the concentrations of the source phase salt and the carrier was suppressed by the formation of the reversed micelle.

Fluoride and bromide ions in fogwater were studied at an altitude of 700m on Mt. Oyama (1252 m a.s.l.). Concentration ranges of fluoride and bromide were 9.28 similar to 209 mu g 1(-1) and 0 similar to 120 mu g l(-1), respectively. Concentrations of both ions were higher than those estimated by the sea salt ratios, which shows that these ions originated not only from sea salt but also from other sources. The effects of volatilization of HBr from sea salt (Br loss) were also observed in the composition of some fogwater. A positive correlation coefficient (r=0.84) between NO3-/Na+ and Br-/Na+ indicates the influence of bromide exhausted from automobiles on fogwater.

Fogwater had been collected from 1992 to 1993 at the midslope of Mt. Oyama (a.s.l. 1252 m) at the southwest of the Kanto Plains. The concentrations of five species of aldehydes, formaldehyde, acetaldehyde, glyoxal, 2-oxopropanal, and hydroxyacetaldehyde, in fogwater were measured. The maximum value of the total concentration of these aldehydes was 187 mu M (April 1992). The maximum concentration of glyoxal, whose concentration was the highest among these aldehyde, was 97 mu M (June 1992). Much aldehydes were contained in highly polluted fogwater and the aldehyde concentrations in fogwater increased with the decrease of pH. When the lowest altitude of the upslope fog rose up to the sampling station, the total concentration of aldehydes increased. The fraction of aldehyde with a high Henry's law constant increased with the elevation of the lowest altitude of fog. Aldehyde concentrations in fogwater are affected not only by liquid water content and air pollution but also by the lowest altitude of fog.

Fogwater had been observed for 4.5 years from July 1988 to December 1992 at the midslope of Mt. Oyama at the southwest of the Kanto plains. Rainwater, aerosol, and gases had been also collected and analyzed at the fog sampling station to investigate the characteristics and acidification mechanism of fogwater. The pH of fogwater ranged from 2.61 to 7.00 and the fog with very low pH values and high ion and aldehyde concentrations were frequently observed in spring and summer. The fogwater at the site was acidified primarily by nitric acid gas absorbed in fogwater and the acid fraction of most of the fogwater ranged from 0.3 to 0.01. The acidity of fogwater is controlled by the amount of the acidic pollutants in the atmosphere, the concentrations of the neutralizing components for the acidic fogwater, primarily NH3 gas concentration, the liquid water content in air, and the distance between the sampling station and the lowest altitude of the fog in upslope fog.

Formaldehyde was transported efficiently across hydrogensulfite ion form anion-exchange membrane via the adduct formation reaction. The transport of formaldehyde was facilitated but onlywhen the concentration of formaldehyde in the source phase solution was low. The ion-exchange capacity of the membrane was saturated by formaldehyde distributed as its adduct in a low source phase concentration because the adduct formation constant was high. The transport of formaldehyde can be further facilitated and formaldehyde was transported against the concentration gradient with the counter-transport of hydrogensulfite ion when hydrogensulfite salt was added to the receiving phase.

Both pH 4.8 and 8.3 acidities were determined by FIA. The carrier solution was a carbonate-free 1 X 10(-3) mol/l sodium hydroxide solution. For the pH 8.3 acidity measurement, the indicator was Bromothymol Blue; for pH 4.8, however, Bromophenol Blue was used. The half-width of the signal peak was used for the calibration. The values obtained by the FIA method agree with those obtained by the corresponding titration method, except for one case, in which the carrier sodium hydroxide concentration was much lower than those of the solutes in the sample solution. For all fog- and rain-water samples, both the pH 8.3 acidity obtained by FIA and the total acidity obtained by Gran's plots in the titration method were much larger than the hydrogen-ion concentrations because of the presence not only of ammonium ions, but also organic acids.

Neutralization dialysis is a very effective deionization method and the transport of weak acids and bases is also facilitated by the neutralization reaction in the system. The transport rates of weak acids and bases increased with the increase of their dissociation constants.

In the surface water analysis, the existing forms of iron nd aluminium are apt to change during the preservation period and the filtration. The sample should be filtered within a day after the sampling and the sample volume should be small to avoid gel layer formation during filtration. Size distribution of metal in surface water was evaluated by filtration method. Sodium, potassium, calcium and magnesium are dissolved predominantly as free ions, whereas aluminium and iron are existing as particulate matters in surface water samples.

　東アジアにおける全球大気観測拠点として富士山を中心に据え，日本上空・離島の清浄大気の常時監視体制の確立を目的として行った．2014年は富士山における大気化学観測の充実に焦点を絞り，気相・固相・水相の大気汚染物質について総合大気化学観測を行った．大気中ガス状水銀（GEM），雲水中微量重金属の観測を初めて行い，富士山頂における日中GEM濃度は国内地上域よりも高いことを初めて明らかにした．これらの成果はInternationalConference&nbsp;on&nbsp;AsianEnvironmental Chemistry&nbsp;(ICAEC) 2014で優秀学生賞を獲得し，大気環境学会誌に掲載された．

１．研究目的と概要　大気エアロゾルと大気水相(雨，雲/霧，露/霜，林内雨)中の界面活性物質濃度を明らかにし，その起源，大気圏動態，界面活性能の解明を目指して，大気中イオン界面活性物質濃度の簡易迅速定量を確立し，都市，郊外，山間部，自由対流圏における大気中陰イオン性界面活性物質濃度を明らかにすることを目的に行った．さらに，主要な界面活性物質と考えられるフミン様物質を定量し，季節変化，経時変化の解明を試みた．２．研究成果概要①メチレンブルー吸光光度法は操作が煩雑であり，誤差が生じやすいことから，メチレンブルー吸光光度法を大気試料に適用するため，再現性が高く，より高感度かつ迅速な陰イオン界面活性物質（MBAS）の定量法を検討した．その結果，50 mLガラス製遠沈管を1本用い，20回手で攪拌後に，振とう機（1000 rpm）で5分間振とうすることにより，0 - 0.12 &#181;Mの低濃度範囲で直線性が高く（r = 0.996），高感度（検量線の傾き：1.07 &#181;M-1）の検量線が得られた．最適条件を用いたエアロゾル捕集用の石英繊維フィルター水抽出液（ブランク）からのドデシル硫酸ナトリウム（SDS）の添加回収率は94.7 ± 3.3 %（n = 3），エアロゾルを捕集した石英繊維フィルター水抽出液（実試料）からの添加回収率は92.3 ± 1.5 %（n = 4），降水試料からの添加回収率は90.8 ± 3.5 %（n = 3）であった．このことから，本法は陰イオン界面活性物質の抽出・分析方法として大気試料に適用可能であった．本法を，2011年5月に採取した都市大気エアロゾルに適用した結果，陰イオン界面活性物質濃度は44.9 - 163 pmol/m3（n = 8）の範囲であり，平均は84.3 pmol/m3 であることが分かった．②東京都新宿区に位置する早稲田大学西早稲田キャンパスで、大気エアロゾル中フミン様物質（HULIS）の定量を行った。試料採取はハイボリウムエアサンプラーにて昼夜12時間毎（6:00 &#8211; 18:00、18:00 &#8211; 6:00）に行い、 DEAE-UV法でHULISをフミン酸、フルボ酸分画に分けて分析した。その結果、HULIS中90 %をフルボ酸が占めていることが分かった。HULIS濃度は夏季に低く、秋・冬季に高いという季節変化を示すことが分かった。年間を通じて、HULIS濃度はNO2、CO濃度と相関が見られたことから、都市域におけるHULISは自動車などの移動排出源から主に生成されていることが示唆された。夏季にはOxと正の相関があり、一次生成以外に二次生成の可能性が考えられた．

１．はじめに　　全球大気観測拠点としての富士山の有効性を検証するため，自由対流圏高度に位置する富士山頂で以下の大気化学観測を行い，以下の3点を明らかにすることを目的とした。①日本上空自由対流圏における気相，固相（エアロゾル），水相（雲水）中化学種のバックグランド大気濃度を明らかにする．②日本上空自由対流圏における夏季バックグランド汚染機構を明らかにする．具体的には，越境汚染と日中の谷風による局地的・地域的汚染の影響評価を行う．③雲を介した化学的変質過程が自由対流圏大気質に及ぼす影響を解明する．　上記目的を達成するために、本年度はPILSを借用（東大海洋研から借用）してガス状・粒子状酸性物質の高時間分解能観測を行い，フィル-パック法およびウェットデニューダー法(徳島大)との比較を行った。また、ポータブルGCMS TRIDION-9（エス・ディ・ジャパンから借用）を借用して大気中VOCsの高時間分解能観測を行い，熱脱離法と比較について検討した。２．観測期間・観測地点・観測項目　自由対流圏高度に位置する富士山頂の旧富士山測候所は夏季しか利用できないため、2013年7月と8月に集中観測を行った。とくに、2013年7月18日から8月22日までは旧富士山測候所に泊まりこんで、エアロゾル(水溶性成分，多環芳香族炭化水素，フミン様物質，球状炭化粒子，黄砂)，ガス（酸性ガス、揮発性有機化合物），雲水，雨水の観測を行い，日本上空のバックグランド濃度の測定を行った．さらに，ウェットデニューダーを用いて富士山頂および富士山南東麓太郎坊における酸性ガス（塩化水素，亜硝酸，硝酸，二酸化硫黄）の連続観測を行うとともに，PILSを用いた粒子状物質の連続モニタリングを富士山頂で行った。３．観測結果　本研究により、以下のことが明らかになった。　①空気塊の流入経路と雲水内化学成分との関係を調べたところ，中国北部および南部からの空気塊のときにHg, Cd，Pb，As，SO42-が高濃度であった。②8月18日夕方に桜島最大規模の噴火があり，この空気塊が8月21日早朝に富士山頂に到達したが，このときにはHg，Pb，As，H+，SO42-が高濃度であった。大気中SO2濃度はフィルターパック法で計測したが，桜島噴煙到達時に高濃度であり、フィルターパック法で計測した塩化水素濃度も高いことから桜島噴火プリュームが富士山頂に渡到達していることを明らかにした。また，このときに発生した雲水は噴煙由来のH2SO4により酸性化していた。このように、桜島噴煙の影響により，雲水の酸性化が生じることを実証したのは本研究が初めてである。③フィルターパック法は6時間毎の採取であるため時間分解能が悪いものの，首都大学東京・加藤准教授による自動モニターの計測値，PILSを用いたSO2とSO42-の総和（PILS（SO2+SO42-））と同様な挙動を示し，濃度レベルも比較的一致することが分かった。④ポータブルGCMS TRIDION-9（エス・ディ・ジャパンから借用）を富士山で使用する前に予備観測を本学51号館屋上で行った結果から、富士山頂でVOCs観測を行うには感度が不足していることが分かった。そこで、富士山麓で大気中VOCsの高時間分解能観測を試みたが、ほとんどVOCsを検出することができなかった。

　本研究では，富士山を「越境大気汚染（国境を越えて運ばれてくる大気汚染）監視塔」とみたて、経済発展の著しいアジア大陸から上空（自由対流圏）を運ばれてくる酸性ガスや粒子状酸性物質の自動連続観測とともに、雲の採取・分析を早稲田大学と徳島大学との共同研究で行った．　自由対流圏とは、私達が普段生活している空気層（大気境界層）の上にある綺麗な空気層であり，およそ２ｋｍから１０ｋｍの範囲である．通常，地上から放出された大気汚染物質は大気境界層に留まっていて，なかなか上空の自由対流圏に運ばれないが，雲の発生を伴うような激しい上昇気流が起こると，大気汚染物質も上空の自由対流圏に運ばれる．日本列島が位置する北半球中緯度帯の自由対流圏では，偏西風と呼ばれる強い西風が常に吹いている．偏西風は冬季に強く，夏季に弱くなるが，大気汚染物質がいったん自由対流圏まで上昇すると，夏季であっても地上より速く運ばれるので，越境大気汚染をいち早く知ることができる．　本研究では，越境汚染物質として，特に酸性物質に着目した．酸性物質が地上に降り注ぐと，森林の立ち枯れを引き起こしたり，土壌を酸性化して有害な重金属が河川に流出し，河川や湖沼の水棲生物が住めなくなる．また，河川水や湖沼は私達の飲用水としても重要である．現在，日本国内の酸性物質排出量は減少しているが，国境を越えて酸性物質が運ばれてくれば，日本の自然環境を守ることはできない．そこで，上空のガス、粒子、雲の中の酸性物質を精密に分析して、大陸から酸性物質がどのような形態（ガス・粒子）でどれくらい運ばれてくるのか，それらが雲に取り込まれると雲水をどれくらい酸性化するのかを明らかにすることを本研究の目的とした．　上空の空気は綺麗なので，地上で使用されている採取装置では，長時間に渡って空気を吸引する必要がある．このため、これまでの観測では時々刻々と変化する空気中のガスや粒子を追跡することができなかった．そこで，本研究課題では，徳島大学の竹内政樹准教授が開発した酸性ガス・粒子の高時間分解能型自動分析装置（ウェットデニューダー＋イオンクロマトグラフ）を富士山頂と富士山麓に設置して観測を行った．これまでのフィルターパック法による観測では６時間を要したが，この装置では約１５分毎に連続観測を行うこと可能であった．　2011年には富士山麓で予備的な観測を行い，2012年には富士山頂と富士山麓で同時観測を行った．2012年7月14日から8月中旬までに膨大なデータ（3000以上）が得られたが，8月中旬以降には富士山頂，富士山山麓ともに流路内で目詰まりが起こった．データを取得できた7月中旬から8月中旬まで富士山頂で得られたデータについて，同時観測を行ったフィルターパック法によるSO2濃度，SO2計との比較を行った．フィルターパック法は時間分解能は悪いものの，市販のS02計と概ね同程度の値が得られたが，高時間分解能型自動分析装置では高めの値が得られた．現在，この原因について検討を行っているが，装置内のバックグランドの上昇の可能性が考えられた．絶対値についてはずれがあるものの，高時間分解能型自動分析装置とSo2計による変動は概ね一致していた．　高時間分解能型自動分析装置ではSO2以外にも，HNO3，HClの観測を行うことができたが，自由対流圏において酸性ガス濃度を１ヶ月以上に渡って自動連続観測した例は世界的にも例がなく，本課題の大きな成果と言える．今後は，酸性ガスに加えて水溶性エアロゾルとの同時観測を行う予定である．

１．近年，界面活性物質が大気中に存在することが確認されている．界面活性物質は親水基と疎水基からなる有機化合物であり，溶媒の表面張力を低下させる性質を持つ．界面活性物質が雲粒に取り込まれると雲粒径を低下させ，雲の寿命を延ばすことから地球規模の水循環や気候に影響を及ぼす．また，雲粒への疎水性有害有機物の溶解度を増加させる．そこで，水中陰イオン界面活性物質の分析法として用いられているメチレンブルー吸光光度法を大気試料に適用するための最適条件を検討し，大気エアロゾル試料に適用した．また，陽イオン界面活性物質の定量法についても検討を行った．２．観測は早稲田大学西早稲田キャンパス(新宿)，富士山南東麓（御殿場口太郎坊，標高1284 m），富士山頂（3776 m）で行った．大気中エアロゾルはハイボリュームエアサンプラーを用いて捕集し，水抽出した後にメチレンブルー吸光光度法で定量した．富士山南東麓では雲水の採取も行った．３．Koga et al. (1999) は，分液ロートの代わりに遠沈管を用いる陰イオン界面活性物質の迅速分析法を報告しているが，2本の遠沈管を使用するため操作が煩雑であった．そこで，本法では，より簡便かつ迅速な分析法を確立するために遠沈管を1本とし，分析感度および再現性を向上させるために遠沈管の振とう条件を検討した．その結果，遠沈管を手で20回振とう後に1000 rpmで5分間振とうすることにより，水中濃度として0 &#8211; 0.8 &#181;Mの低濃度範囲で直線性が高い検量線が得られ，分析感度も向上した．最適条件を用いたエアロゾル捕集用の石英繊維フィルター水抽出液（ブランク）からの添加回収率は94.7±3.2 % (n=3)，エアロゾルを捕集した石英繊維フィルター水抽出液（実試料）からの添加回収率は92.3±1.4 %（n=4）であり，本法は界面活性物質の抽出・分析方法として大気エアロゾルに十分に適用可能であることが分かった．そこで，本法を実試料に適用でした．2011年5月17～20日の早稲田大学西早稲田キャンパス(新宿)における大気エアロゾル中陰イオン界面活性物質(MBAS)濃度を浮遊粒子状物質(SPM)濃度の動態を調べたところ，MBASは日中に高く，夜間に低い傾向があることが分かった．粒子状物質濃度（SPM）との相関は低いが(r=0.481)，SO2との相関は高かった(r=0.768)．したがって，大気中MBASはSO2と同排出源をもつか，同方向からの輸送されている可能性が示された．　大気中陰イオン界面活性物質が表面張力に及ぼす影響については引き続き検討を行っているところである．

１．富士山は孤立峰で斜面が急峻であり，山頂は自由対流圏高度に位置することから，日本上空における大気中および雲水中の様々な大気汚染物質のバックグランド濃度，大陸からの長距離輸送によるバックグランド汚染，エアロゾルーガスー雲ー降水相互作用の観測を行うことができる．2010年に行った夏季集中観測で得られた結果を以下に述べる． ２．観測は富士山南東麓の太郎坊(1300 m)と富士山頂(3776m)で行った．富士山頂での雲水採取には細線式パッシブサンプラー(臼井工業, FWP-500)，南東麓での雲水採取には自動雲水採取機(北都電気，DFC-2200)を用いた．また，同時にフィルターパック法によりエアロゾル，酸性ガスおよびアンモニアを捕集した．試料は直ちに持ち帰り，分析を行った． ３．2010年夏季集中観測期間(7月13日～8月25日)における富士山頂の雲水pHは3.59～5.66 (平均4.95, n=40)，南東麓の雲水pHは3.23～5.53 (平均4.01, n=21)であった．山頂における観測期間中の平均雲水内総イオン濃度は113 &#181;eq/L であり，南東麓の1/10程度であった．雲水のNO3-/nss SO42-比は山頂で0.30～1.80 (平均0.84)，南東麓で0.46～3.24 (平均2.63)であることから，富士山頂では南東麓に比べて大気中硝酸濃度が低いために雲水pHが高いと考えられる．　2010年8月中旬の山頂における雲水化学性状を示す．海洋性気塊が卓越していた8月9-12日には，雲水内総イオン濃度は20 &#181;eq/L以下であり，pHは5.5付近を推移した．8月13日以降に大陸性気塊に変わると総イオン濃度は増加して1 meq/Lに達し，NO3-/nss SO42-比は0.30，pHは3.59まで低下した．この時にはCOとO3濃度も増加していることから，大陸からの汚染大気の輸送を示唆している．

大気エアロゾルや雲・霧水中にフミン物質と類似した構造と特性を有する高分子有機物，すなわち，フミン様物質(HULIS)の存在が確認され，その起源と大気圏動態が注目されている．大気中フミン様物質は，エアロゾルの吸湿特性，界面活性特性，光学特性の変化を引き起こし，雲粒形成過程（雲粒の生成・蒸発速度，雲粒粒径分布）や疎水性有機化合物の大気水相への促進吸収などに関与することが指摘されている．しかし，エアロゾル粒子中フミン様物質の同定には至らず，その起源やエアロゾルの光学特性，吸湿特性に及ぼす影響については未解明のままであった．本研究では，以下の4点を目的に研究を行った．　１）大気中フミン様物質の計測手法の開発　２）大気中フミン様物質のキャラクタリゼーション　３）大気中フミン様物質の起源および動態解析　４）大気中フミン様物質の大気環境影響評価　2009年7月17日～8月25日まで夏季集中観測を行った．観測地点は，富士山頂（富士山測候所，3776 m），富士山南東麓（太郎坊，1300 m），早稲田大学西早稲田キャンパスである．観測項目は，エアロゾル化学特性（水溶性主要無機成分，水溶性有機物（WSOC），HULIS，PAHs），エアロゾル生物特性（細菌株の同定と細菌数，），ガス状物質（VOCs，酸性ガス，アンモニア），霧水・雨水・露水中化学成分（主要無機成分，溶存有機炭素（DOC），HULIS，VOCs）である．大気中フミン様物質の測定には，水圏フミン物質の分析手法であるHiraide et al. (1994)の方法を改良したDEAE-XAD-UV法を用いた．　2009年7月は梅雨明けが遅く，天候不順であったことから，富士山頂では観測期間中に54試料の雲水が得られた．雲水中フミン様物質(HULIS)濃度は日中に高く，夜間低いという明瞭な日変動を示した．富士山頂の雲水では，富士山南東麓で同時期に得られた霧水，雨水，大気エアロゾル中 HULISに比べて，フミン酸の割合が高い傾向にあるが，日中にはフルボ酸の割合が増加した．　HULISは界面活性能を有することが指摘されていることから，単位無機イオン濃度あたりのHULIS濃度，すなわち，HULIS濃度と主要無機イオン濃度(total ion concentration, TIC)との比(以下，HULIS/TIC比)が，大気中VOCsの雲水への促進吸収過程に及ぼす影響について検討した．その結果，雲水中のHULIS/TIC比が高いほど，雲水中VOCsの濃縮係数(定義：(降水中VOCsの実測値)/(降水中VOCsのヘンリー則からの予想値))が増加することが分かった．　本研究により，自由対流圏高度における雲水中HULISの濃度変動，フミン酸とフルボ酸の割合，さらに雲水中HULIS濃度が高いほど気相VOCsを効率的に取り込むことが明らかになった．

　雲はエアロゾルを凝結核として生成し，その成長過程で水溶性ガスを吸収する．雲粒径が臨界直径より小さければ，雲粒は消失して気相にエアロゾルを放出するが，この過程を通じてエアロゾル径を増加させるとともに，水溶性成分を増加させる．雲粒径が臨界直径より大きければ，雲粒はさらに液滴成長して併合衝突により雨滴となって地上に落下する．このエアロゾルー雲ー降水相互作用は，地球温暖化とその環境影響の将来予測の観点から注目されている．本研究では，自由対流圏高度に位置する富士山頂で雨水，霧水，水溶性ガス・エアロゾルの連続観測を行い，日本上空のバックグランド大気濃度の解明を行うとともに，エアロゾル-雲-降水相互作用について検討した．　観測期間は2008年7月19日～8月25日であり，7月23日～30日までは泊まり込んでの集中観測を行った．観測地点は，富士山頂（富士山測候所，3776 m）と富士山南東麓（太郎坊，1300 m）である．観測項目はエアロゾル水溶性主要無機成分，酸性ガス(二酸化硫黄，硝酸，塩化水素)およびアンモニア，雲水および雨水中主要無機成分である．エアロゾルおよびガス成分の捕集には４段フィルター法，富士山頂における雲水の採取には受動型霧水採取器，富士山南東麓における雲水の採取には強制通風型自動霧水採取機を用いた．富士山麓では通年観測も行った。　7月集中観測期間中の富士山頂における雲水pHは4.04 ～ 5.61（平均：4.71），同時期に南東麓で採取された雲水pHは3.85～ 5.85（平均：4.12）であり，富士山頂では雲水のpH範囲が狭く，南東麓の雲水に比べて酸性度が低かった．雲水の主要な酸性物質である硝酸イオン濃度と非海塩性硫酸イオン濃度の比（NO3-/nss SO42-比）は富士山頂で0.24 ～ 1.98（平均：0.66），南東麓で0.28 ～ 2.42（平均：1.51）であり，富士山頂では硝酸イオンの存在割合が小さかった．一方，７月集中観測期間中の山頂におけるHNO3濃度は0 ～ 0.09 ppbv（平均：0.02 ppbv），SO2濃度は0.06 ～ 0.33 ppbv（平均：0.19 ppbv）であり，南東麓におけるHNO3濃度は0 ～ 0.14 ppbv（平均：0.03 ppbv），SO2濃度は0 ～ 0.38 ppbv（平均：0.14 ppbv）であった．HNO3濃度は富士山頂と南東麓でほぼ同じか，富士山頂で低濃度の傾向にあるが，SO2濃度は富士山頂で高濃度となる傾向が見られた．SO2濃度の上昇時には，CO濃度（燃焼起源の指標）とラドン濃度（陸地起源）の上昇を伴い，このときにはアジア大陸方向から空気塊が輸送されていた．したがって，アジア大陸由来のSO2が偏西風によって日本上空に輸送され， その輸送過程における粒子化とともに，SO2が雲水に取り込まれることによって富士山頂の雲水では富士山麓に比べてNO3-/nss SO42-比が低下したものと考えられた．　

　富士山を自然の観測タワーとみなせば，大気汚染物質の鉛直分布の解明に利用できる．また，霧水の化学組成を霧発生時から経時的に調べることにより，ガスおよびエアロゾルの雲内洗浄過程や霧水の酸性化機構の解明を行うことが期待できる．本研究では，富士山南東麓における霧水，ガスおよびエアロゾルの通年観測を行うとともに，夏季には富士山頂，富士山山麓における同時観測を行い，越境大気汚染物質の動態と雲(霧)による洗浄機構について検討を行った． 　霧水の採取は富士山南東麓の太郎坊(標高1300 m)で，本研究助成により新規開発した分割採取型自動霧水採取機DFC-2200(北都電機)を用いて行った．また，4段フィルター法により酸性ガス(SO2, HCl, HNO3, HNO2)およびアンモニア，大気エアロゾルを2週間毎に採取した．夏季集中観測時には，山頂と南東麓で揮発性有機化合物と多環芳香族炭化水素などの有害有機汚染物質の観測も行った．　富士山南東麓における霧水の最低pHは3.19であり，体積加重平均pHは3.86であることが分かった(n = 114)．霧水の主要陽イオンはNH4+で，主要陰イオンはNO3-であった．霧水酸性化の指標となるNO3-/nss SO42-比(当量比)は0.243～4.01(平均1.72)であり，富士山南東麓では霧水酸性度に及ぼす硝酸の寄与が大きいことが分かった．日本国内の他の山岳域(0.236 (立山)～2.81 (六甲山・夏季))で採取された霧水に比べても高い傾向にある．　夏季に富士山頂と南東麓で同時に観測を行ったところ，富士山頂の霧水ではNO3-に比してSO42-の割合が高いことが分かった．日本国内ではSO2濃度がきわめて低いことから，S042-濃度が高くなる要因としては越境汚染の可能性が考えられる．また，約4000m近い自由対流圏高度に位置する富士山頂においても，ベンゼン，トルエンなどの揮発性有機化合物の大気濃度は南東麓(1300m)と同程度のレベルにあることが分かった．さらに，富士山頂で採取された雲(霧)水中には，これらの揮発性有機化合物がヘンリー則からの予測値以上に雲(霧)水に取り込まれていることがはじめて明らかになった．本研究により，富士山を用いた大気化学観測の有用性が示された．

富士山は孤立した高峰であり，4000m近い高さの観測用鉄塔に見なせる可能性に着目し，富士山山体を鉛直的に利用して大気化学観測を行った．今年度は，富士山山頂および山麓において夏期集中大気化学観測を行うとともに，富士山麓において雨水および霧水の通年観測を行った．その結果，以下のようなことが明らかになった．１） 本研究で新たに開発した“太陽電池駆動小型自動雨水採取装置”と従来から湿性沈着用の評価に使用されてきたろ過式採取器を用いて，富士山山麓における湿性沈着量の通年観測を行った．その結果，自動採取装置では降雨採取ロスがなく，乾性沈着の影響を防げることから，山岳域等の無電源地域における湿性沈着量を評価する上で有用な装置であることが明らかになった．２）山頂と山麓で雨水と霧水の同時採取を行った．その結果，山頂に比べて山麓で成分濃度は高く、pHは低いことが分かった．観測期間中の山頂における霧水の体積加重平均pHは4.49であり，山麓における霧水の体積加重平均pHは3.47であった．３）山頂，山麓ともに霧水pHの低下には，(硝酸イオン/硫酸イオン)比の増加を伴うことから，霧水pHの低下は大気中HNO3ガスの吸収によるものと推測された．４）山頂と山麓で，大気中および霧水中VOCs（塩素化炭化水素，単環芳香族炭化水素，二環芳香族炭化水素，カルボニル類）の同時観測を行った．大気および霧水ともにトルエンが主要なVOCsであることが分かった．カルボニル類ではアセトン濃度が高濃度であった．現時点では大気中VOCsの起源は特定できていないが，山頂のVOCs濃度は山麓や都心部と同程度に高いことが分かった．５）霧水中VOCsには大気中VOCsからヘンリー則によって予測される以上のVOCsが溶解しており，その濃縮率は山麓の方が高いことが分かった．特に，ナフタレン類の濃縮率が高く，霧水中に含まれる非溶存態のフミン様物質が関与している可能性が示唆された．６）都心域に比べて，富士山山麓ではエアロゾル中の多環芳香族炭化水素(PAHs)は低濃度であり，都心域の１／３以下であることが分かった．測定を行ったPAHsのなかでは，フルオランテンとピレンが主要であることが明らかになった．