The Central Research Institute of Electric Power Industry (CRIEPI) established a cooperative monitoring network for precipitation chemistry to survey acidic deposition in October 1987. The major objectives of this monitoring program were to collect fundamental data on the temporal and spatial distribution of acidicdeposition and to provide a database to assess the effects of acidification on terrestrial ecosystems. On the basis of the data collected between October 1987 and September 1996, we analyzed (i) wet depositions of major ions in precipitation;(ii) seasonal variation and long-term trend of chemical composition;(iii) atmospheric sulfur budget over the Japanese Archipelago; and developed a long-range transport model to estimate acidic deposition. In this paper, I describe the design of the CRIEPI monitoring network, meteorological and geological factors affecting the chemical composition of precipitation, and the present status of acidic deposition in East Asia.

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The active volcano Oyama on Miyake Island has been emitting a huge amount of volcanic gases since the first eruption in July 2000. High concentrations of SO₂ gas originating from Oyama have frequently appeared over a wide area of Honshu, Japan. This paper describes real-time prediction of SO₂ dispersion covering the Tokai and Kanto Districts, and verification by comparing SO₂ data observed from October to November 2000. The atmospheric dispersion of SO₂ was calculated by using a combination of software systems that combines a regional atmospheric dynamic model and a particle random walk model.
It was proved that the real-time prediction system is adequately precise. The importance of including the effect of wet deposition for more accurate calculation was also shown. The release amounts estimated from the comparison between the calculated results and the monitored data were 20, 000-50, 000 tons/day, which is consistent with results measured from Miyake Island. The transport of SO2 to the Tokai District mainly occured under synoptic meteorological conditions, during which traveling anticyclones move their centers in the eastern region of the Kanto District with troughs approaching from the west. The frequent appearance of high concentrations of SO₂ in the Tokai District from late October to early November 2000 would have been promoted by low pressure or the seasonal rain front in the southwestern region, since pressure off the Pacific was unusually high at that time.

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Exhaust gases from diesel and gasoline fueled vehicles which were run on a chassis dynamometer, were analyzed for PCDDs and PCDFs. The medium duty diesel truck was tested over the Japanese Diesel 13 Modes Test Cycle, and the gasoline passenger vehicle was tested over the Japanese 10·15 Modes Test Cycle.
The average WHO-TEQ values of PCDDs/PCDFs of exhaust gases from diesel and gasoline vehicles were 0.82 pg-TEQ/m³, and 1.09 pg-TEQ/m³, respectively. Those levels were markedly low compared with exhaust gas levels from waste incinerators. The emission factor of the diesel vehicle was 1.41 pg-TEQ/km (13.5 pg-TEQ/L), and that of the gasoline vehicle was 1.05 pg-TEQ/km (11.0 pg-TEQ/L). As a result, it is suggested that the contribution of vehicle exhaust gas to PCDDs/PCDFs concentrations in the ambient air is comparatively low.
Among the congeners of PCDDs/PCDFs, O8CDD showed the highest ratio in exhaust gas from both diesel and gasoline vehicles. However, the ratio of PCDFs corresponded to about 70% of the total concentration. The isomer profiles of the diesel vehicle and the gasoline vehicle were similar to the isomer profile of a municipal waste incineration. Therefore, it is suggested that PCDDs/PCDFs are generated from the combustion process in engines.

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Emission factors of 38 volatile organic compounds (VOCs) for total traffic and separately for heavy-duty and light-duty vehicles (HDV and LDV) were obtained by measuring emissions and traffic at an urban highway tunnel in the Tokyo metropolitan area in Japan. Emissions were calculated from tunnel ventilatio speed and measured VOC concentrations in both intake and exhaust air for 14 periods, both during the day and night and on both weekdays and weekends. The emissions were regressed against the traffic counts, which were recorded simultaneously. An iterative weighted-least-squares regression analysis was used, including an unequal error variance assumption and an error estimation. Emission factors and their 95% confidence intervals were obtained for 38 compounds that were clearly judged to be emitted from the tunnel among 85 measured VOCs. Emission factors obtained for the total traffic ranged from 0.13 mg vehiclekm^-1 for cyclopentene to 9.9 mg vehicle^-1 km^-1 for formaldehyde. The next most abundant after formaldehyde were toluene (8.8), iso-pentane (5.6), benzene (5.5), and propylene (5.2 mg vehicle^-1 km^-1). The largest emission factor for HDV or LDV was for HDV formaldehyde (40), followed by HDV propylene (15), LDV toluene (9.4), HDV benzene (8.2), HDV 1, 3-butadiene (7.6), and LDV iso-pentane (7.3 mg vehicle^-1 km^-1). Emissions from HDV and LDV roughly represent those from diesel-engine and gasoline-fueledengine vehicles, respectively. Average vehicle speed was 76 km/h and the average HDV ratio was 24%. The emission factors obtained were compared with published data.

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Elevated concentrations of sulfur dioxide (SO₂) exceeding the environmental standard were observed in Nagano Prefecture as well as in the Kanto and Tokai areas of Japan in August and September 2000, prompting many residents to complain of the offensive smell. Maximum concentrations of 383 ppb SO₂ at Iida (in the south of the prefecture) and 76 ppb SO₂ at Nagano (in the north of the prefecture) were observed. Backward trajectory analysis suggested the source to be volcanic gas from Miyake Island, whose volcanic activity has dramatically intensified recently. Measurements of gases and aerosols by a four-stage filter pack method were made at Nagano, Mt. Happo, and the village of Hakuba in the north of Nagano prefecture. The concentration of SO₄^2- in aerosols was extremely high at 44.4 μg/m³ in Nagano on September 14, and on September 15 it exceeded 30 μg/m³ at both Mt. Happo and Hakuba. On the basis of the assumed ion balance of SO₄^2- and NH₄⁺, unusually high levels of sulfuric acid (H₂SO₄) and high molar concentration ratios for H₂SO₄/SO₄^2- were estimated for each of the 3 locations: H₂SO₄ concentrations were 21-33 (Nagano), 11-21 (Mt. Happo), and 6.8-18μg/m³ (Hakuba); molar concentration ratios were 46%-2%, 34%-5%, and 22%-58%.

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[in Japanese]

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