RELATIONSHIP BETWEEN WET DEPOSITION OF SULFATE AND NITRATE AND RAINFALL AMOUNT IN JAPAN

A regression model of wet deposition on rainfall amount for non-seasal t sulfate (nss-SO42-) and nitrate (NO3-) was applied to a data set obt ained through a nationwide survey from April 1989 to March 1993. Wet-o nly samples on a biweekly basis were collected at 29 sites over Japan. Reparameterized bivariate lognormal distribution was employed to desc ribe the joint distribution of concentration (C) and rainfall amount ( R) for each site. Ranges of geometric mean (mu(D)) of biweekly deposit ion (D = C.R) for each site were 0.54-2.90 meg m(-2) for nss-SO42-, an d 0.21-1.36 meg m(-2) for NO3-; that of biweekly rainfall amount (mu(R )) was 24.1-78.0 mm. Urban or industrialized areas had high values of mu(D) for these ions. Ranges of estimates of the slope of the regressi on equation of log(D/mu(D)) on log(R/mu(R)), were 0.45-0.99 for nss-SO 42-, and 0.35-0.86 for NO3-; thus estimates of the slope for nss-SO42- tend to be larger than those for NO3-. The present analysis, conseque ntly, statistically clarified some differences between the two ions in deposition processes which is understood in the light of current know ledge of atmospheric chemistry.