MEASUREMENTS OF ATMOSPHERIC AND RAINWATER ORGANIC-ACIDS IN THE HIROSHIMA PREFECTURE, JAPAN

Concentrations of atmospheric and rainwater organic acids such as form ic, acetic and oxalic acids in the Hiroshima prefecture, western Japan , during 1993-1995 were determined by ion chromatography. Concentratio n ranges of formic and acetic acids detected in the ambient air were 0 -8 and 0-12 ppbv, respectively and in rainwaters 0-38 and 0-24 mu M, r espectively. Oxalic acid was detected only in rainwaters at the range of 0-1.5 mu M. The percentage of free acidity (hydrogen ion concentrat ion) generated from organic acids to that from the total acidic substa nces (inorganic and organic acids) was 8.0% in average with a range of 3.5-15.1%, implying that organic acids contribute to the acidificatio n of rain. Measurements of organic acid concentrations in car exhausts and combustion gases of incinerator were carried out to evaluate the role of anthropogenic activities in the production of atmospheric orga nic acids. The results indicate that these fossil fuel combustion gase s contain from ppbv level to hundreds ppbv level of formic and acetic acids.