Stable isotope ratio of atmospheric and seawater nitrate in the East Sea in the northwestern Pacific ocean

Abstract

The nitrogen and oxygen isotopic values of anthropogenic NOx- (including NO2- and NO3-) are preserved in precipitation and airborne total suspended particles. Hence, isotope analyses of these atmospheric samples allow for the identification of the NOx- sources. In this study, atmospheric delta N-15- and delta O-18-NOx- values were measured in an eastern coastal site of South Korea over a three-year period, and compared with seawater values observed from coastal waters of the East Sea. The highest seasonal atmospheric delta N-15-NOx- values were associated with wintertime air masses blowing from northeastern China, and similar to those produced by coal and biomass burning. By contrast, the lowest atmospheric delta N-15-NO(x)(- )values were observed in summer, and the major source appeared to be vehicle exhaust. In addition, the reductions in the seawater delta(15) N-NOx- and Delta(15 -18) (i.e., delta(15) N-NOx- minus delta(18) O-NOx-) values in the East Sea could be at least partially attributed to atmospheric deposition.