Hyogo Prefecture has been conducting various surveys and investigations regarding the challenge of acid rain. The fruits of the activities were reviewed and summarized from the viewpoint of wet deposition, dry deposition, the impact on the forest ecosystem, and transboundary transport. Wet deposition was studied for precipitation and fog (cloud) water. The precipitation samples collected at five sites with different site classifications were studied to clarify the features of precipitation, such as the degree of acidification and its mechanism. Fog (cloud) water was compared with precipitation. The survey was carried out for 7 years at Mt. Rokko, located near an urbanized area. In addition, the generation of the fog (cloud) water, the trend of the concentration of the chemical components in the fog (cloud) water, and the relationship of the generation and disappearance of the fog (cloud) water with the behaviors of atmospheric gases and aerosols were studied. The dry deposition of sulfur dioxide and nitric acid was estimated based on a survey done by the four-stage filterpack method. The impact and input-output balance of material were studied for the watershed located at sites with different site classifications: Mt. Rokko, an urbanized area, and Mt. Awaga, a rural area. The wet-only precipitation, the bulk precipitation collected by the filtering-type bulk sampler, the fog (cloud) water, the throughfall, the stemflow, and atmospheric gases and aerosols were comprehensively surveyed and studied. The input-output balance of sulfur was studied in the catchment area set up on Mt. Awaga. The concentrations of aerosol and gases in ambient air in winter at the site facing the Sea of Japan were surveyed by 6-h interval sampling using the four-stage filter-pack method, and the transboundary transport of air pollutants from the Eurasian Continent and/or the Korean Peninsula to Japan was quantified. The surveys and the research will progress continuously, more comprehensively, and more progressively. More inclusive approaches to limiting air pollution and protecting the atmospheric environment from acid rain will be promoted.

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Recently, in studies on measuring methods of dust emitted from stationary sources, special attention has been paid to PM₁₀/PM_2.5 particulates from the point of view of their effect on human beings. Measurements with the use of current source PM₁₀/PM_2.5 samplers are based on isokinetic sampling with a constant suction flowrate, which is difficult to carry out in the case of gas velocity variations that, in turn, producs large measurement errors.
With the objective of finding an easy and accurate measurement method of source PM₁₀/PM_2.5 emissions, an automatic sampling system that combines a changeable inlet diameter nozzle with a PM₁₀/PM_2.5 impactor and microcomputer for automatic sampling systems has been developed and tested.
The results from the characteristics investigation using test particles and in-situ field tests indicate that this source PM₁₀/PM25 measurement system is applicable for isokinetic sampling with a constant flowrate. At the same time, several basic characteristics and critical points were clarified through the measurements using the PM₁₀/PM_2.5 impactor.
1) The tested source PM₁₀/PM_2.5 measurement system gave an instantaneous response to sudden changes in the velocities of test gases, indicating that PM₁₀/PM_2.5 measurements are easily carried out through isokinetic sampling with a constant flowrate.
2) Assembly and disassembly of the PM₁₀/PM_2.5 impactor, exchange of the classifier plate and the collection plate (plane filters), etc., were easily achieved during in-situ measurements.
3) In the case of fly-ash as the test particle, the amount of coarse particles taken in through anisokinetic sampling changed considerably, but the collection ratio of PM₁₀ and PM_2.5 remained almost constant in relation to the sampling error. On the other hand, particles re-entrained from the PM_10-2.5 collection plate were accompanied by the downstream flow, and collected into the PM_2.5 collection section. This caused a concentration error, and may have resulted in an increase of the PM_2.5 measured value.
4) Re-entraining on the flat filter paper was not observed for dust in the combustion flue gas.

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The input-output balance of sulfur was studied in a catchment area in Japan. Precipitation (collected using a wet-only sampler), cloud water, and sulfur dioxide (SO₂(g)) and particulate sulfate (SO₄^2-(p)) in ambient air were considered agents providing input to the catchment area, while stream water was considered an agent carrying output from the catchment area. The input amounts of sulfur by precipitation, cloud water, and SO₂(g) and SO₄^2-(p) in ambient air were approximately 1900, 5100, and 270 and 80 kgS during the survey period, respectively, equivalent to 6.2, 23.2, and 1.5 and 0.45kgS/ha/year, respectively. However, the output amount of sulfur by the stream water was approximately 5900 kgS for the period from April 21st 1999 to April 22nd 2000, equivalent to 13.7 kgS/ha/year. The input was approximately 2 times greater than the output, showing that the excessive load and the accumulation of the sulfur are advanced around the catchment area.

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A wind tunnel study of short-term concentration fluctuations and peak concentrations under three stratification conditions, unstable condition, neutral condition and stable condition, in an urban street canyon was conducted. Tracer gas was emitted from a point source in the canyon and was measured with a fast-response concentration detector.
The peak concentrations under the stable condition in the canyon showed a value that was two times higher than the neutral condition and unstable condition. The values of the standard deviation of the fluctuating concentration in stable condition were also higher than the other two stabilities, however the values of the normalized concentration fluctuation intensity did not depend on the stability conditions. The peak-to-average concentration ratios of the inside canyon in the stable condition had a range of 3-5 and the peak-to-average concentration ratio in the stable condition was smaller than that of the neutral and unstable conditions.
An auto-correlation analysis showed that longer residence time of tracer gas in the canyon was measured in the stable condition, due to the low wind speed. The cumulative density functions of concentration under the stable condition was only slightly changed by smoothing the time series with averaging times up to 13.5s compared to the other two stabilities. This shows that the instantaneous eddies in the stable condition were less fragmented than those in the other two conditions.

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Lichen is known as an excellent bioindicator of air pollution, and Parmotrema tinctorum is one of the most popular bioindicators of SO₂ pollution in Japan. However, we have a little knowledge about the behavior of P. tinctorum in an area reducing SO₂ and/or the response to the other air pollutants such as NO_x, SPM and Ox. The purpose of this study is re-evaluation of P. tinctorum as bioindicator based on the field investigations carried out in 1972, 1978, 1994 and 2003, with the consideration of various air pollutants investigated in Shimizu Ward, Shizuoka City, Japan. The following results are obtained. 1) Recolonization of P. tinctorum was observed within six years following with the amelioration of SO₂ pollution after 1972. 2) P. tinctorum had disappeared around the crossing point of Tomei Highway and Route 1 since 1978, and this disappearance area had extended along Route 1 in 1994 and 2003. Because concentrations of NO, NO₂ and NO_x were higher around the disappearance area of P. tinctorum, automobile exhaust or traffic jam may be involved with the changes of air quality at the place. However, there was no distinct correlation between the distribution of P. tinctorum and concentration of NO, NO₂, NO_x, SO₂, SPM and Ox through the investigated area. 3) Investigated area can be divided into three zones based on the distribution of P. tinctorum in 2003: i. e., desert zone along Route 1, transitional zone in urban area around Shimizu Ward Office, and normal zone in the suburbs. These zones may be formed depending on air quality of the environment. From the results of this study, we recommend long-term monitoring of P. tinctorum which reflects qualitative changes of air pollution in urban area.

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Increasing of surface ozone with the recent increase in the emissions of NOx and volatile organic compounds (VOC) significantly affects human health and vegetation in East Asia. In this study, we estimated the impact of the surface ozone on rice yields in China in 2000 as Relative Yield Loss (RYL), Rice Production Loss (RPL), and associated Economic Cost (EC) of RPL, using a crop loss function and ozone concentration simulated by a regional chemical transport model (CMAQ) with regional emission inventory in Asia (REAS). Additionally we projected the future RYL, RPL, and EC of RPL in 2020, using the surface ozone concentration predicted under three different emission scenarios of NOx and VOC: Policy Succeed Case (PSC), Reference Case (REF), and Policy Failed Case (PFC). Consequently, we found the following results: First, RYL, RPL, and EC in 2000 are estimated to be 6.4%, 12.8Mt, and 20.5 billion RMB, respectively. Second, RYL, RPL, and EC for each scenarios in 2020 are projected to be 6.7%, 13.4Mt, and 21.4 billion RMB for PSC, 7.6%, 15.2Mt, and 24.4 billion RMB for REF, and 9.3%, 18.6Mt, and 29.7 billion RMB for PFC, respectively. For this reason, RYL, RPL, and EC will be almost proportional to the emissions of NOx (RYL is 1.8% up, RPL is 3.6Mt up, and EC is 5.7 billion RMB up for NOx 10Mt increase, respectively). Third, the projected RPL in China in 2020 will strongly depend on the scenarios, because the RYL in the basin of Yantze river, where rice production is more than half of the total yields in China, varies with the scenarios, significantly.

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The concentrations of 4 regulated and 18 non-regulated substances emitted from heavy-duty diesel vehicles and an engine were measured through the decreasing their emission levels and change of their emission trends, and the effects of regulations on emissions of these substances are discussed.
THC and CO emissions were highly correlated with 1, 3-butadiene, benzene, formaldehyde, acetaldehyde, PM, and B [b] F emissions (r>0.86; p<0.01). As for the correlations between PM emissions and SO42-or individual PAHs emissions, SO₄^2- and B [b] F had a high correlation coefficient, but the other PAHs had low coefficients, ranging from 0.19 (p<0.01) to 0.62 (p<0.01). These low correlations were due to the considerable discrepancy between the emission trends of the various vehicles tested. 1-NP emission was not correlated with THC, CO, NOx, and PM emissions, and its emission trend differed from the trends of other non-regulated substances. In a D13 test cycle, the amount of SO₄^2--S emitted from a test vehicle equipped with an oxidation catalyst and a DPF was higher than the amount of sulfur in the consumed fuel. Because the sulfur concentration in the test fuel was low, this result suggests that sulfur in the lubricating oil contributed to the emission or that discharged SO₄^2- in the exhaust gas accumulated on the DPF during the high-load drive mode. No marked decrease in NOx emitted from the test vehicles as a function of fuel consumption was observed. Thus, effective countermeasures to reduce NOx emissions are required. However, non-regulated air pollutant emissions from the test vehicles that meet Japan's new short-term regulations for auto-exhaust gas either were not detected or were under the limit of detection, owing to the effects of the DPF and the oxidation catalyst.

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