The ozone-sensitivity of 24 spinach cultivars was estimated based on the extent of the visible injury that appeared on the leaves due to ozone exposure, and the low ozone-sensitive cultivars, which are strong against ozone, were selected. As a result of investigating the stomatal density of each cultivar, it tended to be high for the cultivar with the high ozone-sensitivity. There was a positive correlation between the extent of damage by ozone and stomatal density. The extent of damage by ozone and stomatal density were changed by the cultivation period. Especially, the damage by ozone and stomatal density of the spinach grown in the spring were high compared to those from other cultivation periods. In the spring, the positive correlation between the extent of damage by ozone and stomatal density was also stronger. Therefore, it was considered that the stomatal density of the spinach grown in the spring could be used as an index for estimating the ozone-sensitivity. The stomatal density of the spinach grown in the cultivated field by the harvest also rose in the spring. Therefore, as a cause of the reports on the damage by ozone from production fields in the spring are frequent, it was considered that the stomatal density of the spinach increased and its ozone-sensitivity became high in the spring, in which the ozone concentration in the atmosphere increases.

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This study investigated the effects of a high ozone concentration on monoterpene emissions from Japanese dominant coniferous trees (C. japonica, C. obtusa and P. densiflora). Sampling experiments were performed with young trees using a growth chamber in which the ozone concentration, air temperature, humidity and light intensity were controlled. In every experiment, the α-Pinene emissions increased immediately after the beginning of the ozone exposure, then decreased and converged. Under baseline experimental conditions (ozone concentration: 100 ppb, increasing rate of ozone concentration at the beginning of ozone exposure: 100 ppb h^-1, air temperature: 30℃, relative humidity: 50%, light intensity: 850 µmol m^-2 s^-1), the α-Pinene emissions from C. obtusa and P. densiflora converged after the ozone exposure were lower than those before the ozone exposure, while the α-Pinene emissions from C. japonica that converged after the ozone exposure were similar to those before the ozone exposure. In addition, the α-Pinene emissions from C. japonica that converged after the ozone exposure increased with the increasing light intensity, decreased with the increasing air temperature, and were affected by the increasing rate of the ozone concentration at the beginning of the ozone exposure. These results indicated that environmental factors other than the ozone concentration level affect the difference between the monoterpene emissions before and after the ozone exposure.

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Trace metals in aerosols were observed at Fukue Island (rural site) and Fukuoka City (urban site) in order to determine the effect of long-range transport from East Asia. A source apportionment of the air masses was conducted based on the constituents and ratios of the metal components. He contributions of the emission sources were evaluated using Positive Matrix Factorization (PMF). The Total Potential Source Contribution Function (TPSCF) analysis was used for assigning the source regions. We categorized the source regions based on five factors predicted by the PMF in Fukue Island and four factors in Fukuoka City. The atmospheric environment not only in the Fukue Island but in Fukuoka City was significantly affected by the long range transport such as Asian dust and coal combustion in terms of factors calculated by the PMF. As a result of the TPSCF analysis at both sites, we found that the Asian dust and emissions from coal combustion, both of which were evaluated on the basis of the PMF analyses, originated on continental Asia, especially in China. The TPSCF plot of road dust factor showed distributions over large cities such as Shanghai and Seoul. The TPSCF plots of the oil combustion factor indicated that the emissions from marine ships were also important at both sites.

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The simultaneous sampling of acidic gases (SO₂ and HNO₃) and aerosols (SO₄^2- and NO₃^-) in the ambient air were performed at seven heights of a 30 m observation tower in a small forest (Tokyo University of Agriculture and Technology Field Museum TAMA Hills, Hachioji City), which is located about 30 km from Shinjuku, during May, June and October from 2010 to 2012. The concentration of acidic gases and aerosols in the fine mode decreased with the decrease in height, suggesting their capture by the canopy, namely the forest filter effect. There were high positive correlations (r>) between the difference in the concentration of acidic gases and aerosols in the fine mode over the canopy (30 m) and under the canopy (6 m) and their concentrations over the canopy (30 m). Application of the developed Forest Filter Model (FFM) indicated that the capture efficiency was 0.55 for SO₂, 0.43 for HNO₃, 0.52 for the fine mode SO₄^2-, and 0.45 for the fine mode NO₃^-, respectively.

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The simultaneous sampling of 26 AVOCs (anthropogenic volatile organic compounds) in the ambient air was performed in Shinjuku (urban area), at the southeastern foot of Mt. Fuji (1284 m a.s.l., mountainous area), and at the top of Mt. Fuji (3776 m a.s.l., free troposphere) during one week in July and August 2012, respectively. The concentration of all the AVOCs at the top of Mt. Fuji was less than half of that at the foot of Mt. Fuji and one tenth of that in Shinjuku. Comparison of the concentration of CHs at the top of Mt. Fuji and at the mountains in the free troposphere showed that the concentrations of carbon tetrachloride were almost the same. On the other hand, the concentration of dichloromethane at the top of Mt. Fuji was more than four times higher than that in the other mountains. The high concentration of dichloromethane over 1 ppbv along with the increases in the benzene and ozone concentrations and with the decrease in the water vapor mixing ratio in the nighttime at the top of Mt. Fuji suggested the influence of the downward transport of the upper air from the backward trajectory analysis. The concentration of toluene, m,p-xylene, and naphthalene showed a diurnal variation, i.e., high in the daytime and low in the nighttime, indicating the transport from the boundary layer by the valley wind.

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The concentrations of water-soluble humic-like substances (HULIS) in particulate matter collected on the Nishiwaseda Campus of Waseda University in Shinjuku, Tokyo, were determined by the DEAE-UV method in March, May, July, October, and December 2012. Particulate matter less than 10 µm (SPM: suspended particulate matter) was collected by a high-volume air sampler every 12 hours (6 : 00–18 : 00 and 18 : 00–6 : 00). The HULIS concentration in SPM was lower in the summer than in the autumn and winter. The fulvic acid fraction was about 90% of the water-soluble HULIS in SPM throughout the year. There were relatively high correlations between the HULIS concentration and the concentrations of NO₂ and CO throughout the year, suggesting that HULIS was mostly of combustion origin like automobiles in the urban area. Comparing humic acid and fulvic acid, the magnitude of the concentration variation was higher in fulvic acid than in humic acid and it was suggested that humic acid has a more stable constructure. In addition, it was revealed that the concentration of fulvic acid tends to be influenced by artificial and burning sources. The behavior of the HULIS concentration was similar to O_X in the summer and this indicated that HULIS was also generated by the secondary formation in addition to the primary sources. The high concentration and correlation between the concentration of levoglucosan (r=0.867), which is a tracer of cellulose in biomass burning, and HULIS in the autumn revealed that the increase in HULIS in the autumn was due to biomass burning.

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From April to December, 2012, Sugi (Cryptomeria japonica) needles and Konara (Quercus serrata Murray) leaves were monthly collected along with the throughfall of both species in a small forest, called “Satoyama” in Japanese, located on the Nishiikuta Campus of Japan Women’s University to clarify the capturing ability of trace metal elements by the forest canopies. The total amounts of ten trace metal elements (Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, V, Zn) in the needles/leaves and throughfall were determined by ICP-AES, but five trace metals (Cd, Cr, Ni, Pb, V) were below their detection limits. The amount of total trace metals in the Konara leaves at the edge of the forest increased from April to November and reached 8.9 µg/cm² in November, which was 2.5 times higher than that inside of the forest. This “edge effect” differed among the trace metal elements and was especially-pronounced for Mn. Based on the amounts of trace metals in the Konara leaves and net throughfall of the Konara for trace metals, the total amount of trace metals captured by the Konara canopy in the studied area was estimated to be 35–81 kg for the nine months from April to December.

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The central Kanto Plain, the eastern parts of Tokyo and Saitama, experiences high concentrations of photochemical oxidants exceeding its warning level of 120 ppb most frequently in Japan, mainly in the summer. Their trend during 1990–2010 has been analyzed. To exclude anomalous climatic variations during every summer, days on which a sea breeze system developed on the south coast of the Kanto Plain and penetrated northward were selected, because it is the most typical weather pattern inducing high O_x levels in the region. Not only yearly number of days with high O_x levels (high O_x days), but their ratio within the sea breeze days steeply increased after 2000 compared with those in the 1990s. As for the 11 years since 2000, the ratio of high O_x days seems to be somewhat decreasing, but a high rank of concentrations has been maintained. High O_x days tend to appear in the southern to middle areas in the examined region under lower sea breeze speeds, and in the middle to northern areas under higher sea breeze speeds. When the period since 2000 is divided into earlier and later periods, days with such strong sea breezes that a high O_x hardly occurs increased in the later term, and at the same time, days with weak sea breezes associated with southern high O_x decreased. These changes in the occurrence tendency of the sea breeze types, connected with the areas where high O_x’s occur, can be related with the decadal changes in the tendency of the pressure pattern covering eastern Japan in the summer, and possibly with longer-term climate changes.

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