MEASUREMENTS OF ATMOSPHERIC SO2 AND SO42-, AND DETERMINATION OF THE WET SCAVENGING COEFFICIENT OF SULFATE AEROSOLS FOR THE WINTER MONSOON SEASON OVER THE SEA-OF-JAPAN

In order to determine the scavenging coefficient of oxides of sulfur i n winter monsoon over the Sea of Japan both air and precipitation conc entrations of sulfur dioxide and sulfate were measured on Sado Island on the Sea of Japan coast. The measurements were taken during the peri od between 28 January and 3 February 1992. The atmospheric concentrati ons of SO42- were 0.57-1.11 mu g S m(-3) whereas those of SO2 were bel ow 0.27 mu g S m(-3), much lower than SO42- concentration. A back traj ectory analysis showed that these sulfur species would have been trans ported from Eurasian continent over the Sea of Japan. A layer-average scavenging coefficient, k, for sulfate by precipitation including snow , graupel and rain was determined on the basis of the equation k = HP/ h, where H, P and h are the scavenging ratio, precipitation intensity and mixing layer height, respectively, under the assumption of a unifo rmly mixed layer over the warm sea current along the Sea of Japan coas t. The scavenging coefficients were calculated to be 3.5 x 10(-5) -2.9 x 10(-4) s(-1) for precipitation intensities of 0.13-3.1 mm h(-1). A regression analysis of these datasets gave a k value for submicron SO4 2- aerosol over the Sea of Japan of k = 1.38 x 10(-4) P-0.74 where P i s precipitation intensity. These values are very close to a recently o btained result by Jylha for radioactive aerosols. Summarizing the meas urements taken by the authors and other investigators the wet scavengi ng coefficient k may be represented by k = aP(b) where a is around 10( -4), and b is between 0.67 and 0.76. Copyright (C) 1996 Elsevier Scien ce Ltd