Ion concentrations of NO3- and SO42- in individual rains were observed
at Nagagute in the suburbs of Nagoya, Japan, from July 1, 1991 to Jun
e 30, 1992. Decreasing concentrations of NO3- and SO42- in rainwater c
ollected during precipitation were frequently observed and this decrea
sing pattern is expressed by exponential functions. The ion concentrat
ion decrease is more influenced by the ion scavenging loss in the prec
ipitation area than the ion supply due to transportation and oxidation
processes. Under calm atmospheric conditions, the empirical ion scave
nging coefficients were derived from changes in ion concentration in a
drizzling rain with a rain intensity of below 15 mm h(-1). These coef
ficients were linearly proportional to the rain intensity. The average
empirical scavenging coefficients of NO3- and SO42- were 5.2 X 10(-4)
and 2.2 x 10(-4) s(-1) respectively. The coefficient of NO3- is 2.5 t
imes more sensitive to the rain intensity than that of SO42-. The NO3-
and SO42- concentrations and pH were well simulated in a numerical mo
del containing the obtained empirical scavenging coefficients. (C) 199
7 EIsevier Science B.V.