Acid precipitation is now a world wide environmental issue and many information concerning of the effects of acid precipitation on terrestrial ecosystems aer successively reporting. This review describes the impacts of acid precipitation on agricultural crops and forest trees. The focus of this review is foliar injury, growth reduction of plants, and injury mechanisms by acid precipitation and forest decline which is said to be due to acid precipitation.
In simulated acid rain experiments, visible foliar injury of most crop species and some sensitive tree species occurs at below pH 3.5 and pH 3.0, respectively. Furthermore, most studies of effects of simulated acid rain on growth of agricultural crops and tree seedlings have found no effect when the applied solution was above pH 3.0. Therefore, significant effects on agricultural crops and tree seedlings at current ambient levels of acid precipitation (pH 4.0-5.0) are unlikely. However, acid precipitation potentially could affect trees in natural forests in a variety of way such as an increases in soil acidity, increase of phytotoxic aluminum ion, increase of acidic leaching of foliar nutrients and soil nutrients, and inhibition of mycorrhizae. Therefore, acid precipitation may be one of many environmental factors contributing to forest decline. There are five major hypotheses about forest decline:(1) acidification-aluminum toxicity hypothesis, (2) ozone hypothesis, (3) magnesium deficiency hypothesis, (4) excess-nitrogen hypothesis, and (5) multiple stress hypothesis. Acidic precipitation phenomenon is part of four of the five hypotheses. The etiology of forest decline in Europe and North America has not been yet clearly and completely established. However, many researchers believe that forest decline is the result of complex interaction between the environmental factors and natural ecosystems. These complex environmental factors (stresses) can include cold injury, drought stress, soil acidity, aluminum toxicity, insect infection, high concentration of ozone, acid precipitation, acid cloud water and others.

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Atmospheric monitoring was made for airborne particulate matter at Seoul, Korea, for the 2-year period from April 1987 through March 1989. Methods of sampling and analysis of the National Air Surveillance Network, Japan were followed by this monitoring. Sampling was made by a so-called low volume sampler with 10 pm cut off (100%), at a suction rate of 20 l/mmn for 25 days a month. Analysis was made by neutron activation analysis for 31 elements with supplement by the X-ray fluorescence method. The data obtained were compared with NASN data from Tokyo and Kawasaki. Higher values were seen in the Seoul results for the amount of airborne particulate matter and many elements: soil-derived Al, Sc, and Th, fuel combustive As, Se, V and Ni, and automotive Pb and Br. Estimation by CMB calculation showed the highest contribution of soil derived elements: 25% for 2-year average and 60% for spring. The regulation of leaded gasoline was started in 1988, and this could affect the CMB estimation of automotive contribution by the use of Pb and Br as indicator elements. The contribution of coal combustion could be the most important in Seoul in winter, but this was not estimated because an effective indicator element for coal combustion effluents is not presently known.

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The effects of nitrogen dioxide (NO₂) on lung tumorigenesis by N-bis (2-hydroxypropyl) nitrosamine (DHPN) in male Wistar rats were investigated. Rats were given a single intraperitoneal injection of 0.5 g DHPN per kg body weight or saline at 6 weeks of age, and then exposed to clean air, 0.04 ppm, 0.4 ppm or 4 ppm NO₂ for 17 months. Incidence of tumor in lungs of rats in DHPN+4 ppm NO₂ group was 13%, and the tumors were adenoma and adenocarcinoma. Adenoma was seen in 4 of 40 rats (10%) and adenocarcinoma was seen in 1 of 40 rats (3%). The incidence of tumor in lungs of rats in DHPN+ clean air and DHPN+0.04 ppm NO₂groups was 3%(1/40), respectively. The tumors were adenoma. There was no significant difference in the incidence of tumors between DHPN+clean air group and DHPN-I-4 ppm NO₂ group. No lung tumor was seen in DHPN-I-0.4 ppm group and each NO₂-exposed group without DHPN treatment. Alveolar cell hyperplasia occurred at the highest incidence in lungs of rats injected with DHPN. But, there was no correlation between the incidence of hyperplasia and each concentration of NO₂ exposed. Bronchiole mucosal hyperplasia was seen in 17 of 40 rats (43%) in the DHPN+4 ppm NO2 group, and in 1 of 40 rats (3%) in the each clean air, 0.04 ppm or 0.4 ppm NO2-exposed group with DHPN treatment. The hyperplasia in lungs of rats exposed to 4 ppm NO₂ without DHPN treatment was slighter than that seen in the 4 ppm NO₂-exposed group with DHPN treatment.
These results indicate that development of lung tumors in rats injected with subcarcinogenic dose of DHPN was enhanced by exposure to 4 ppm NO₂. However, low levels of NO₂ effect on lung tumor development was not observed in Wistar rats.

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Indoor concentrations and personal exposures to carbon monoxide (CO) were measured in Korea in January 1989. Newly developed passive CO sampler were placed in a kitchen and living room for the indoor concentration measurements and were worn by a housewife for monitoring the personal CO exposures. Thirty-five homes were selected from an urban area and a rural area. Since yeontan (coal briquette) is used as the fuel in all types of ondol (heating systems used in Korean homes), high CO concentrations were expected. In fact daily averages of indoor CO concentrations were 23 ppm in kitchens and 12 ppm in living rooms. The overall daily average of the personal CO exposures, 18 ppm, was between the two inddor CO concentrations. When analyzing effects of household characteristics on the indoor and personal CO levels. CO concentrations in living room varied significantly between the two areas, and the personal CO exposures depended on the type of ondol. House ventilating methods and socioeconomic conditions were also found to be important factors to determine indoor CO concentrations in Korea.

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Dry deposition velocities for sulfur dioxide and particulate sulfate over the terrestrial and nearby oceanic regions in Japan are computed. Surface roughness scale lengths and residences for sulfur uptake are estimated from consideration of land use characteristics and the biological status of vegetation for warm season conditions. Average deposition velocities and deposition rates for sulfur for 80 km mesh grid cells are presented. Estimated deposition velocities are 0.41 cm/s for sulfur dioxide and 0.21 cm/s for sulfate. Total sulfur deposition in Japan is about 0.30 TgS/0.5 y, this value is almost equal to the wet deposition of sulfate for this season. Dry deposition of sulfate is relatively small, sulfur dioxide is found to contribute most of the total dry deposition of sulfur compounds in our country.
This method has the virtue of being able to predict long term deposition patterns using the climatological and environmental data for use in studies of regional air pollution in East Asia.

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