Abstract

The concentrations of polycyclic aromatic hydrocarbons (PAHs) in aerosol were measured in Shinjuku, which is central Tokyo, Japan, for 10 years from 2007 to 2016. The effects of changes in emission sources and their degradation by reaction with ozone were assessed in this study. There was no significant increasing or decreasing trend of the PAH concentrations during 10 years (P > 0.05). The average selected seven the PAH concentrations (0.88 ng m⁻³) during 10 years was lower than those in New York and Paris. However, the trend of ozone concentrations is increasing in central Tokyo. This inconsistency raises a question. Did the fact that the ozone concentration was higher than the PAH concentrations promote PAH degradation? To apportion the PAH sources, we used PAH concentration profiles and positive matrix factorization analysis. The contribution of vehicle emissions to the PAHs ranged from 40 to 80%. Ozone concentrations increased by 3.70%/year during 10 years. The theoretical degradation rates of PAHs by ozone, which were calculated using a pseudo-first-order rate equation, suggested that the lifetimes of benzo[a]pyrene (BaP) decreased by 1 min from 2007 to 2016. We investigated the aging of BaP using the profile of the isomer ratios. We found that the aging of BaP at the urban and roadside sites were nearly identical indicating aging regardless of the season. Although the decomposition of BaP is promoted by the photochemical oxidation reaction, this result suggests that a certain threshold value exists as the degree of the decomposition. This degradation of PAH can improve chemical loss processes in air quality model.

Fog is formed frequently in mountain areas and is apt to cause forest decline, because fog has highly concentrated air pollutants and is readily acidified. The elucidation of the fog characteristics in the areas has been limited because successive observation is difficult in mountains. We have observed wet depositions and meteorological conditions at Mt. Oyama, located about 56 km west–southwest of Tokyo. The mountain meteorology was observed with various devices and the fog frequencies dependent on the altitude were roughly estimated from the meteorology of the base of the mountain. The precipitation amount of the throughfall at the mountain is much larger than that of rainfall, and the large deposition on the canopy is caused by not only fog but also drizzle. Fog and drizzle sample was collected by string-type passive fog collector, PFC, and the meteorological data relating to the collecting rate of PFC sample were observed. PFC samples were affected by rainwater under windy condition and the contribution of the rain to the PFC sample volume was evaluated to be about 30% in average. The sampling rate of PFC was related to the precipitation intensity of throughfall, and it became possible to estimate the air pollutants deposition on the canopy via wet deposition by the analysis of the samples of PFC as well as rain. The fog and drizzle may cause several times larger deposition of air pollutants on the canopies than the deposition via rain at high mountain forest.

During the summer of 2018, we monitored the concentrations of water-soluble acid gases and particulate anions at the southeastern foot (1284 m a.s.l.) of Mt. Fuji, Japan, using gas/particleion chromatographs. All samples analyzed contained quantifiable levels of anions. The average concentrations of acid gas and particulate anion concentrations were, respectively, 1.10 +/- 0.37 nmol m(-3) for HCl, 3.49 +/- 1.72 nmol m(-3) for HONO, 1.23 +/- 0.59 nmol m(-3) for HNO3, 0.33 +/- 0.20 nmol m(-3) for SO2, 3.61 +/- 3.69 nmol m(-3) for Cl-, 0.65 +/- 0.22 nmol m(-3 )for NO2-, 4.29 +/- 2.98 nmol m(-3) for NO3- and 4.47 +/- 3.57 nmol m(-3) for SO42-. We found that the concentration of soluble acidic gases increased during the daytime, while no characteristic diurnal patterns were observed in the particulate anions.

Fixed-point and multi-point field survey was conducted to determine the actual contamination of the Japanese coast by microcapsules derived from coated fertilizers. The results indicated that the amount of microcapsules increased during the irrigation season (9423-74,869 pieces/m2) and decreased in the non-irrigation season (77-1471 pieces/m2). Microcapsules accounted for 90% of all microplastics sampled during the irrigation season. The lack of correlation between the area of agricultural land in the watershed and the microcapsule density on the coast suggested that the density of microcapsules on the coast was not only dependent on the total load to the ocean, but also on topographic and meteorological conditions. More than 90% of the microcapsules collected from the shoreline were made of polyethylene. Scanning electron microscopic observation of the surface of the microcapsules revealed that portions of the microcapsules were removed as secondary microplastics in the process of migration to the ocean.

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.

<p>2010年から2018年までの7月と8月に富士山頂（標高3,776 m）で大気および雲水を採取して、27種類の人為起源揮発性有機化合物 (AVOCs) （塩素化炭化水素16種、単環芳香族炭化水素8種、二環芳香族炭化水素3種）と6種類の生物起源揮発性有機化合物を分析した。雲水中VOCs （体積加重平均VOCs濃度：2.07 nM、n=159）の約9割はAVOCsであり、主成分はトルエンであった。これは富士山頂における大気中トルエン濃度が高いことを反映していた。雲水中AVOCs濃度は空気塊が大陸南部から輸送されたときに高く、最低濃度を示した海洋由来時の約1.5倍であった。雲水中トルエン濃度は総無機イオンの低下とともに指数関数的に減少した。雲水中クロロホルム、o-キシレン、リモネン濃度は大気中濃度とヘンリー定数から求めた計算値に比べて実測値は数倍高く、ヘンリー則からの予測値以上に濃縮されていた。疎水性が高いVOCsほど雲水に高濃縮されており、自由対流圏における雲水でもHULIS （フミン様物質）のような界面活性物質がVOCsの高濃縮に関与していることが示唆された。</p>

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.

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.

015年夏季は、関東地域においてPM2.5、光化学オキシダント(Ox)濃度が繰り返し上昇した。我々は、夏季の大気汚染について、地上の測定局だけでなく、上空も含めて評価するため、7月21日〜8月20日の31日間にわたり、自由大気に位置する富士山頂にPM2.5シーケンシャルサンプラーを設置し、24時間単位の試料採取を行った。試料中に含まれる金属元素成分を調べ、埼玉県加須における24時間単位のPM2.5試料との比較を行った。富士山頂で採取したPM2.5には土壌由来の元素が多く含まれていたが、人為起源元素の濃縮が確認された。ヒ素(As)を石炭燃焼の指標、バナジウム(V)を石油燃焼の指標として、比率As/Vを調べたところ、富士山頂でのみ上昇した期間と、富士山頂と加須で同時に明瞭な上昇が見られた期間があり、夏季の関東地域においても、長距離輸送の影響を受けていたことがわかった。(著者抄録)

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.

2012年より積雪期を除き1ヵ月もしくは2ヵ月ごと(2015年以降)に、福島県浪江町南津島の山林でスギと落葉広葉樹の生葉、落葉、表層土壌、底砂の放射性Cs濃度を調査した。福島市-浪江町間の走行サーベイでは、除染により空間線量率は急速に減衰したが、未除染の山林では物理的減衰と同程度であった。2014年以降、落葉広葉樹林では林床(落葉と表層土壌)で放射性Csは物理的減衰以上に減少していないが、スギ林では生葉と落葉で減少し、表層土壌に蓄積した。2014年までスギ落葉中放射性Csは降水による溶脱が顕著であった。2013年春季には放射性Csはスギ林よりも広葉樹林で表層土壌から深層に移行していたが、2015年冬季にはスギ林で深層への移行率が上回った。小川では放射性Csは小粒径の底砂に蓄積しており、一部は浮遊砂として流出するが、表層土壌に対する比は広葉樹林で2013年:0.54、2015年:0.29、スギ林で2013年:1.4、2016年:0.31と下がっており、森林に保持されていることが分かった。しかし、春季にはスギ雄花の輸送による放射性Csの生活圏への流出が懸念された。(著者抄録)

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.

2013年1月に中国広域で発生した深刻なPM_2.5汚染を契機に、日本国内でもPM_2.5への関心が急速に高まった。我々はこれまで、日中で微小エアロゾルの同時採取を行ってきた。希土類元素 （レアアース） は、いわゆるハイテク産業に不可欠な金属元素であるが、そのほとんどが中国で産出される。しかしながら、中国、日本ともに都市部のPM_2.5中のレアアース濃度の報告例は限られている。 2013年8月に北京、上海、新宿、加須の4地点で同時に採取したPM_2.5に含まれる金属元素の分析を行った。既報の2013年1月の北京のPM_2.5データも含め、従来の元素に加え、レアアースに着目した解析を試みた。 北京と上海の金属元素を比較すると、上海では船舶や石油燃焼、鉄鋼に由来する元素の比率が高く、北京では石炭燃焼に由来する元素の比率が高いことがわかった。冬季の北京では、中国最大級のレアアース鉱床であるBayan obo方面からの気塊の飛来が多かったことから、Bayan oboで採取されたPM₁₀中のレアアースを基準として濃縮係数を求めた結果、北京のPM_2.5では、ネオジム (Nd)、ジスプロシウム (Dy) に明瞭な濃縮が見られた。また、エルビウム (Er)、イッテルビウム (Yb) にも濃縮が見られた。レアアースの濃縮の組み合わせから、発生要因となる産業に関する情報が得られる可能性が示唆された。

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.

2012年6月27日から2013年7月30日にかけて、福島県浪江町南津島地区の里山でスギと落葉広葉樹の生葉、落葉、表層土壌、底砂を一月ごとに採取し、NaI(Tl) シンチレーション検出器で放射性セシウム(¹³⁴Csおよび¹³⁷Cs)濃度を測定した。放射性セシウム濃度は落葉>表層土壌>生葉>底砂の順であり、放射性セシウムは落葉に蓄積している状況にあった。冬季の積雪と春先の融雪は落葉の放射性セシウム濃度に影響を及ぼさなかった。森林内を流れる小川の上流域の底砂と1ヶ月後の下流域の底砂では放射性セシウム濃度に正の相関関係があり (r=0.87, n=9)、この里山では放射性セシウムが浮遊砂として平均的に1ヶ月で500 mを移動したことが示唆された。

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.

26種類のAVOCs（塩素化炭化水素17種、単環芳香族炭化水素6種類、二環芳香族炭化水素3種類）の大気および大気水相のサンプリングを、2007年から2010年まで富士山と新宿で行った。2010年における大気中AVOCs濃度は富士山頂で最も高く（7月の平均総濃度：11.6 ppbv、n=5）、新宿（10～12月の平均総濃度：7.9 ppbv、n=52）、富士山南東麓（7月の平均総濃度：6.8 ppbv、n=9）の順であった。富士山頂における単環芳香族炭化水素（MAHs）の大気中濃度は都市域の新宿や国内外の高高度観測地点に比べて異常に高く、局地的な影響を受けている可能性がある。一方、2010年における大気水相中AVOCs濃度は富士山南東麓の雨水で15.8 nM（n=8）、富士山頂の雲水で15.7 nM（n=19）であり、新宿の露水で5.33 nM（n=15）、雨水で3.36 nM（n=30）であった。富士山における大気水相にはAVOCsが高濃度に含まれており、とくに塩素化炭化水素（CHs）は富士山南東麓の雨水および富士山頂の雲水ともにヘンリー則からの予測値以上に高濃縮されていた。大気水相へのAVOCsの高濃縮は大気中濃度、気温、各AVOCsの疎水性だけでは説明ができず、大気水相中の共存物質の影響が大きいものと推測された。

東京都新宿区から33km離れた東京都八王子市の小規模森林（東京農工大学FM多摩丘陵、16ha）にある高さ30 mの観測タワーを用いてコナラ樹冠上部（14 m）、樹冠下部（1 m）、森林内の樹冠のない開けた地点を林外とし、計3地点で生物起源揮発性有機化合物（BVOCs; イソプレン、α-ピネン、β-ピネン、リモネン、δ-3-カレン）の採取を行った。イソプレンは3地点ともに明確な昼夜変動が見られ、日中に高く、夜間に低下した。樹冠上部で最高濃度11.1 ppbvを示した。モノテルペン（α-ピネン、β-ピネン、リモネン）は明確な昼夜変動は見られず、樹冠下部および林外で樹冠上部よりも高濃度になる傾向にあった。δ-3-カレンはいずれの地点も検出限界だった。イソプレンとモノテルペンには相関はみられず、モノテルペンではピネン類とリモネンの相関性が低いことから、イソプレンとピネン類とリモネンでそれぞれ別の放出源を持つ可能性を示唆した。一方、α－ピネンとβ－ピネンは正の高い相関性を示すことから、同一樹種からの放出と考えられた。FM多摩のBVOCs濃度は都心部の新宿の約10倍であり、日本の森林面積の約30％を占める里山におけるBVOCsの観測の重要性を確認した。

東京都新宿区から33km離れた東京都八王子市の小規模森林（東京農工大学FM多摩丘陵、16ha）にある高さ30 mの観測タワーを用いてコナラ樹冠上部（14 m）、樹冠下部（1 m）、森林内の樹冠のない開けた地点を林外とし、計3地点で生物起源揮発性有機化合物（BVOCs; イソプレン、&amp;alpha;-ピネン、&amp;beta;-ピネン、リモネン、&amp;delta;-3-カレン）の採取を行った。イソプレンは3地点ともに明確な昼夜変動が見られ、日中に高く、夜間に低下した。樹冠上部で最高濃度11.1 ppbvを示した。モノテルペン（&amp;alpha;-ピネン、&amp;beta;-ピネン、リモネン）は明確な昼夜変動は見られず、樹冠下部および林外で樹冠上部よりも高濃度になる傾向にあった。&amp;delta;-3-カレンはいずれの地点も検出限界だった。イソプレンとモノテルペンには相関はみられず、モノテルペンではピネン類とリモネンの相関性が低いことから、イソプレンとピネン類とリモネンでそれぞれ別の放出源を持つ可能性を示唆した。一方、&amp;alpha;－ピネンと&amp;beta;－ピネンは正の高い相関性を示すことから、同一樹種からの放出と考えられた。FM多摩のBVOCs濃度は都心部の新宿の約10倍であり、日本の森林面積の約30％を占める里山におけるBVOCsの観測の重要性を確認した。

26種類のAVOCs（塩素化炭化水素17種、単環芳香族炭化水素6種類、二環芳香族炭化水素3種類）の大気および大気水相のサンプリングを、2007年から2010年まで富士山と新宿で行った。2010年における大気中AVOCs濃度は富士山頂で最も高く（7月の平均総濃度：11.6 ppbv、n=5）、新宿（10～12月の平均総濃度：7.9 ppbv、n=52）、富士山南東麓（7月の平均総濃度：6.8 ppbv、n=9）の順であった。富士山頂における単環芳香族炭化水素（MAHs）の大気中濃度は都市域の新宿や国内外の高高度観測地点に比べて異常に高く、局地的な影響を受けている可能性がある。一方、2010年における大気水相中AVOCs濃度は富士山南東麓の雨水で15.8 nM（n=8）、富士山頂の雲水で15.7 nM（n=19）であり、新宿の露水で5.33 nM（n=15）、雨水で3.36 nM（n=30）であった。富士山における大気水相にはAVOCsが高濃度に含まれており、とくに塩素化炭化水素（CHs）は富士山南東麓の雨水および富士山頂の雲水ともにヘンリー則からの予測値以上に高濃縮されていた。大気水相へのAVOCsの高濃縮は大気中濃度、気温、各AVOCsの疎水性だけでは説明ができず、大気水相中の共存物質の影響が大きいものと推測された。

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.

ヘッドスペース固相マイクロ抽出/ガスクロマトグラフ質量分析（HS SPME/GC/MS）法による降水中揮発性有機化合物（VOCs）の定量条件を検討した．試料液量16 mLにNaCl 3.5 gを添加し，SPMEファイバー〔100 &amp;mu;m PDMS（polydimethylsilozane）〕への抽出温度40℃，20分間保持で最大感度が得られた．最適条件を用いて，ハロゲン化炭化水素17種と単環芳香族炭化水素6種の合計23種について標準溶液1 ppbの繰り返し再現性，検量線の直線性，検出下限，定量下限及び実試料への添加回収率を調べた．1,2-ジクロロエタンを除くVOCs 22種の標準溶液1 ppbにおける変動係数は10％ 未満であり，検出下限は0.02 nM（ジクロロメタン）から0.30 nM（ベンゼン）であった．雨水及び露水試料への添加回収率は，ジクロロメタンを除くVOCs 22種について80％ から120％ の範囲にあり，HS SPME/GC/MS法は雨水及び露水中VOCsの定量に適用可能であった．本法を東京都西部（日野市）で採取した雨水と露水に適用した結果，塩素化炭化水素6種，単環芳香族炭化水素5種の合計11種のVOCsが検出された．雨水及び露水ともに，塩素化炭化水素に比べて単環芳香族炭化水素の濃度が高く，単環芳香族炭化水素の中ではトルエンが最高濃度を示した．観測期間中のトルエンの体積加重平均濃度は雨水で3.31 nM（&lt;i&gt;n&lt;/i&gt;＝39），露水で5.21 nM（&lt;i&gt;n&lt;/i&gt;＝38）であった．雨水及び露水中VOCsの実測濃度は，大気中VOCs濃度とヘンリー定数から算出した計算値の数万倍にも達し，大気中VOCsが雨水及び露水に促進吸収されていることが明らかになった．

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&lt;sup&gt;+&lt;/sup&gt;, NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;, NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt;, and SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2&amp;minus;&lt;/sup&gt; at Tarobo were 48.9, 35.0, 38.0 and 69.4 meq/m&lt;SUP&gt;2&lt;/SUP&gt;/y during three years from 2006 to 2008, respectively, and were higher than those at remote sites in Japan, particularly NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt; 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.

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.

On the mountain side of Mt. Oyama, fog is frequently formed and pH of fogwater is low due to nitric acid formed from NOx. Recently, the concentration of fog components has increased because of a decrease in liquid water content (LWC) , which may be caused by a decrease of SPM as the condensation nuclei. The concentration of fog components becomes high when LWC is low, and acid fog events with fog water pH lower than 3.5 occur for about 20 % of fog duration at the mountainside (680 m a.s.l.) every year. It has been observed that the throughfall amount increased with an increase in altitude, although the precipitation amount does not depend on the altitude. It is caused by the fog deposition, which may be dominated by the fog formation frequency and the deposition rate of fog droplets depending on the wind velocity. The deposition of air pollutants on the canopies is caused by many path ways, rain, fog, gas, and aerosol. Deposited hydrogen ion is exchanged with metal ions in the leaves, and the application of simulated acid fog to the seedlings of fir, cedar, and beech in an experimental chamber showed that the amount of base cations leaching from leaves increased with decreasing pH of the applied acid fog solutions. Fir and beech seedlings were severely damaged by the long term application of simulated acid fog. Acid depositions on the surface soil is large in Mt. Oyama, and the soil has been acidified for recent years.

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 &amp;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 &amp;mu;eq/L and NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt; 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&lt;sup&gt;+&lt;/sup&gt; and NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt; were higher in south regions. There were high correlations between the concentrations of Na&lt;sup&gt;+&lt;/sup&gt; (&lt;i&gt;r&lt;/i&gt; = &amp;minus;0.854), Cl&lt;sup&gt;&amp;minus;&lt;/sup&gt; (&lt;i&gt;r&lt;/i&gt; = &amp;minus;0.815) and NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt; (&lt;i&gt;r&lt;/i&gt; = &amp;minus;0.922) and the distance from the coast of Odawara City, Oisomachi, and Ninomiyamachi. In addition, a high correlation between the NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt; and Cl&lt;sup&gt;&amp;minus;&lt;/sup&gt; concentrations (&lt;i&gt;r&lt;/i&gt; = 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.&lt;br&gt;

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.

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).

横浜市のほぼ中心部に位置する神奈川大学において,露の発生状況を観測するとともに,露水を採取し,溶存成分の定量を行った。1998年の年間の露の発生頻度は22%(観測日348日中に77日発生)で,冬季に最も多く発生した。また,最大露水量の総和は7.7mmで横浜における年間降雨量(1901mm)の約1/250となった。露の体積加重平均pHは5.08(3.04から7.82)であり,総イオン濃度は雨水,霧水よりも高く,その化学組成は雨水,霧水と大きく異なっていた。また,都市部(横浜),郊外地域(町田),山間部(丹沢大山)において,露水を同時採取し溶存成分濃度を比較した。その結果,露水の化学組成は都市部,郊外地域,山間部で大きく異なり,大気中のガス,エーロゾル濃度を強く反映していることが明らかとなった。露水に対するガス,エーロゾル成分の乾性降下速度を求るため,露水内成分濃度に対して,露水量,大気中のガス,エーロゾル濃度および露水採取器の設置時間を説明変数として重回帰を行ったところ,硝酸ガスの乾性沈着速度(1.28cm s&lt;-1&gt;)はエーロゾルの硝酸イオン(0.11cm s&lt;-1&gt;)の約10倍高く,硝酸ガスの濃度変動が,露水中の硝酸イオン濃度に大きく影響することが予想された。この重回帰により求めた乾性沈着速度と大気中のガス,エーロゾル濃度の実測値より算出した露水中硝酸イオン濃度の計算値は実測値の多くとほぼ一致していたことから,露水中の硝酸濃度は大気中のガス,エーロゾル濃度によりほぼ説明できることが明らかとなった。ただし,低pHを示した露水の硝酸濃度の実測値は計算値より高く,五酸化二窒素などが吸収されることにより露水中硝酸イオン濃度が増加している可能性が示唆された。

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.

揮発性有機化合物(VOC)の降水中濃度についてはこれまでほとんど知られていないことから, 大気試料および雨水試料の分析を行い, これらの濃度の支配要因について検討した。雨水試料については自動雨水採取装置により, 大気試料については連続大気サンプラーにより吸着捕集した後, それぞれをパージ・トラップ法あるいは加熱脱着法によって, ATD-GC/MSにより分析した。得られた分析結果によると, VOCの濃度変動は大きく, ジクロロメタン等はわが国の水質汚濁に係わる環境基準において定められている基準値に近い値まで降水に含まれることがあることが示された。大気中のVOC濃度は, 成分によりては相互に高い相関が見られたが, 降水中VOC濃度間の相関はこれに比して低かった。降水中VOC濃度には無機イオンで見られるような降り始めに高い濃度を示す傾向は見られず, 降雨強度にも依存しなかった。このことはVOCが主に雲内洗浄により雨水に取り込まれることを示唆している。また, 大気中VOC濃度と雨水中VOC濃度との間の相関は成分により異なり, 1,2-ジクロロエタンやm, p-キシレンでは高い値を示した。

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.

1994年4月35日に大山においてpH1.95の霧が観測された。この霧は非海塩起源の塩化物イオン濃度が12.8mmol/lと極めて高く, 塩化水素ガスの吸収によりpHが低下したことを示していた。非海塩起源の塩化物イオン濃度が高くpHの低い霧はこの他にも観測されたが, いずれも夕方を中心とした時間帯に限定され, また濃度は急激に増加し短時間の内に再び減少することから, 局地的な塩化水素ガスの汚染が考えられた。霧水量と霧水内濃度から霧発生前の大気中塩化水素ガス濃度は約2ppbと推測されるが, この値は都市部では普通に観測される濃度であることから, 塩酸により強酸性となる霧は都市近郊山岳部で今後も発生することが予想される。

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.

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.

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 9.28～209 μg l^&lt;-1&gt; and 0～120μg l^&lt;-1&gt;, 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 NO_3^-/Na^+ and Br^-/Na^+ indicates the influence of bromide exhausted from automobiles on fogwater.

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.

酸性雨の環境影響を見積もるには,水素イオン濃度だけではなくアルカリ消費量を表す酸度を測定する必要がある.酸度は滴定により求められるが,繁雑な操作を必要とする.本研究では,FIAによる簡便な酸度の測定法の検討を行った.詳細な条件検討によって確立したFIAによる酸度の定量値は,滴定法による酸度の定量値とよく一致し,簡便な酸度の測定が可能となった.本法により霧水,雨水の分析を行ったところ,水素イオン濃度に比して数倍量の酸度を示し,酸度測定の重要性が明らかになった.

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.

金属は地表水中において,様々な形態をとって存在している.本研究では,孔径の異なるメンブランフィルターと限外濾過膜を用いた濾過による,金属を含む化学種のサイズ分布の測定を行う方法を検討すると共に,実際に分布測定を行った.濾過に伴って生成するゲル層は,微量に存在する金属化学種の濾液濃度の減少を招くが,特に鉄について顕著にその影響が見られた.このゲル層の生成を避けるためには,濾過する試料の量を少なくする必要がある.又,試料の保存時間が長くなると,鉄やアルミニウムなどの微量金属の形態が大きく変化する.河川水中の主な金属化学種のサイズ分布を測定した結果,鉄やアルミニウムは粒子状物質として存在しているが,ナトリウムやカルシウムなどの多量に存在する金属は,ほとんどが遊離のイオンの形で存在していることが明らかになった.