ナトリウム量を指標とする環境大気汚染状況の追跡と予測

Abstract

To acquire the information about air pollution in the vicinity of a kraft-paper mill, a network of dust-fall jars, consisting of nearly 60 monitoring stations, has been established around there. The jars, the size of which is each 16.5cm high and 9.5cm in diameter, were set at a height of 1.5m or thereabouts from the ground to be exposed for a month; the dust-fall in the jars was analyzed for Na^+ by atomic absorption spectrophotometry. The survey has been started in 1974 and extended up to now. The present report deals mainly with the result obtained for the period 1977 to 1979,and further, refers briefly to that for the period 1974-1976; the report concerning the result of period 1980-1982 is in preparation. Through these results, it was found that (1) Na-deposit decreases with the increase in distance from the mill and (2) for the second period, the mean of three annual averages of a station is between 15×(10)^<-2> and 7×(10)^<-2>t/(km)^2・month, while for the first period, it is between 30×(10)^<-2> and 8×(10)^<-2>; the air quality is getting better with years. Mention must be made of the finding that the Na-deposit of a station (x) could be estimated by a relation x=(Q/k)・y+Δ in which y stands for a quantity (say, transport index) defined as (downwind frequency)/(distance)^2・(wind speed); Q the emission rate of dust from the mill; k a constant whose magnitude might be a function of the character of dust such as particle size, Nacontent and so on; Δ the background level of Na-deposit.