Airborne particulates were collected at a roadside site in Kanazawa, Japan, in the summer and winter, 1999, 2004/2005, 2007/2008 and 2010. The polycyclic aromatic hydrocarbons (PAHs) and nitropolycyclic aromatic hydrocarbons (NPAHs) were determined by HPLC with fluorescence and chemiluminescence detections, respectively. The total concentration of six PAHs (pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene and benzo[a]pyrene) decreased by the factor of 63.9% in the winter and 75.6% in the summer from 1999 to 2010. The total concentration of seven NPAHs (1,3-, 1,6-, 1,8-dinitropyrenes, 1-nitropyrene, 6-nitrochrysene, 7-nitrobenz[a]anthracene and 6-nitrobenzo[a]pyrene) significantly decreased by the factor of 88.0% in the winter and 89.2% in the summer during the same period. The concentration ratio of 1-nitropyrene to pyrene also significantly decreased in this period, suggesting a decrease in the emission amount. As the main reason for the significant decrease in the PAHs and NPAHs, the regulation of exhaust gas/particulates from automobiles was considered.

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We measured the concentration and OH reactivity of Biogenic Volatile Organic Compounds (BVOCs) emitted from Picea glauca, using Proton Transfer Reaction-Mass Spectrometry (PTR-MS), a Gas Chromatography-Flame Ionization Detector (GC-FID) and Laser Pump Probe Laser Induced Fluorescence (LIF) Technique. By controlling the temperature, the concentrations and OH reactivity of the BVOCs were changed. We investigated the consistency between (1) the OH reactivity derived from the LIF technique, and (2) the sum of the products of the VOC concentrations and OH reaction rate constants. As a result, the differences in the OH reactivity obtained from these two methods increased with the increasing temperature. The difference is referred to as the contribution to the OH reactivity of the VOCs species that we have not yet measured . The OH reactivity of the unmeasured VOCs is found to linearly correlate to that of the cyclic monoterpenes. This result implies that many of the unmeasured VOCs emitted from Picea glauca, which significantly contribute to the total OH reactivity, are associated with cyclic monoterpenes.

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Intensive measurements of organic aerosols were performed in March-April and October, 2009 at Cape Hedo, Fukue Island and Fukuoka. Twenty n-alkanes and fifteen PAHs were selected as the target molecules. In Fukuoka, the concentrations of TSP, total n-alkanes and total PAHs were the highest among the three sites, followed by Fukue. Based on the BaP/BeP ratio, the air that arrived at Hedo was aged. This indicated that the compounds collected at Hedo were transported long range, probably from East Asia. Source regions of the air masses observed were classified into three areas [China (CH), Korea/Japan (K/J), and Pacific Ocean (PA)] based on the back trajectories. The concentrations of TSP and total PAHs were the highest in the air masses from CH. A seasonal change in the aerosol concentrations was seen only for the PAHs. Total PAHs in the autumn were about 1.5 times higher than those in the spring. Based on the back trajectories arriving at Fukue, the air masses in the autumn mainly passed over China, while those in spring mainly passed over Korea and Japan. The origins types were evaluated based on the ratios of FLT/PYR and IcdP/(IcdP + BghiP). Oil combustion was the main source in the spring, whereas coal combustion and biomass burning were the main sources in the autumn.

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Nitrogen oxides consist of NO, NO₂, NO₃, HONO, N₂O₅, gaseous nitric acid (HNO₃), particulate nitrate (NO₃^-(p)) and so on. Each nitrogen oxide shows different chemical characteristics. The concentrations and chemical composition are important for evaluating the effects of nitrogen oxides to the atmospheric environment in a remote area. We conducted continuous measurements of total odd nitrogen species (NO_y), HNO₃ and NO₃^-(p) at Cape Hedo, Okinawa, Japan. Diurnal variations of NO_y, HNO₃ and NO₃^-(p) were analyzed to reveal local effects. NO_y and HNO₃ concentrations had a peak at 11:00 and 14:00, respectively, while NO₃^-(p) concentration was minimized during the daytime. We analyzed the relationship between the diurnal variations of NO_y, HNO₃ and NO₃^-(p) and meteorological conditions. The diurnal amplitudes of HNO₃/NO_y and the monthly averaged solar radiations had a good positive correlation (R² = 0.73). Therefore, the diurnal variations of HNO₃ and HNO₃/NO_y were due to the photochemical production of HNO₃ in the remote area. The local production was not ignored for the variations of the concentrations of HNO₃ in the remote area.

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

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We have been measuring several air pollutants, such as the total odd nitrogen species (NO_y), ammonium (NH₄⁺), sulfate (SO₄ = HSO₄^- + SO₄^2-), organic aerosol (Org), carbon monoxide (CO) and PM_2.5 at Cape Hedo, Okinawa, focusing on the long-range transport of air pollutants from the Asian continent. Yearly variations in their concentrations were analyzed using these observational data. Although the amount of air pollutants emitted from East Asia would increase year by year, the corresponding increase of their concentrations was not observed at Cape Hedo. The average concentrations of NO_y, NH₄⁺, SO₄, and Org in the spring of 2008 were relatively high. The CO concentration in 2008 was not high in comparison to that in the other years, there fore the influence of emissions by combustion in East Asia would not be so large. In order to discuss the influence of the air mass originating from that East Asia for the yearly variations, we classified the origins of air masses arrived at Cape Hedo using backward trajectory analyses and investigated the yearly variations of these concentrations for each air mass. The result suggested that the contribution of air pollutants from the North China air mass origin has been increasing year after year..

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

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To reduce air pollutants, which primarily consist of NO_X, on the roadsides, the use of the purifying characteristics of ACF was studied. In this report, we evaluated the “Natural wind ventilation system”. We installed a plate-shaped slit structured PAN based ACF on the median strip. Even after two years without watering, there was no decline in the NO₂ removal ability. The NO removal ability had slightly declined. After a simple tap water washing, the NO removal ability recovered.
We selected the pitch based ACF, which is commonly available, and has the same or better ability of the PAN based ACF for de-NO_X, and conducted the basic de-NO_X experiments. After the most appropriate ACF calcination, we designed the pitch based ACF units as follows: a plate thickness of 0.7 cm, a slit wide of 0.8 cm and a corrugated plate of wire gauze inserted into the space between the slits of the felt-shaped ACF, which improved the contact ratio between the polluted air and ACF. This made the ACF maintdina 20 - 30 % breathability to the natural wind in the field, and allowed the NO removal ability to improve to 16% and the NO₂ removal ability to improve to 97 %.

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NO₂ concentrations on a roadway and its penetration effects into a vehicle cabin were measured using an NO₂ sensor placed on a vehicle which can perform simultaneously real time monitoring on the road and in the car. The NO₂ concentrations on the regional road, where the heavy duty truck ratio was high, was almost 150 ppb, and it was strongly affected by the heavy duty trucks ratio. The NO₂ concentrations on the highway were high enough to exceed the daily average value of Japanese air quality standards at almost all locations, and it increased over 200 ppb at uphill with a high H. D. ratio condition. In a long tunnel on the highway, the maximum NO₂ concentration reached 3 ppm. The NO₂ concentrations in the car were the same as those on the road when its air conditioning was in the fresh air mode. It was found that changing the mode to internal circulation prevented NO₂ penetration into the vehicles. However, in this situation, there will be the possibility of a high CO₂ concentration due to breathing of the passengers. The NO penetration efficiency into the car was higher than that of NO₂. The diffusion features of NO and NO₂ from a roadway into a residential district were investigated by measuring NO and NO₂. NO disappeared almost 100 % at a point 7 meters from the road, however, almost 50 % of the NO₂ still remained. It is suggested that 150 ppb NO₂, which is observed on regional roads might have some effects on close residential districts. These results indicated that pollutants on the road have a significant influence on passengers who travel in vehicle along the road and citizens who are living close to the road.

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