Factors influencing changes in rainwater composition from urban versus remote regions of the Yellow Sea

Rainwater samples were collected from three stations at the Yellow Sea in 1 992-1993 and analyzed for some major species (Ca2+, K+, Na+, Mg2+, NO3-, NH 4+, pH, PO43-, and SO42-). Absolute concentrations and element-to-sodium ra tios show clear seasonal variations with higher levels in winter and lower levels in summer for most of the species. Levels of major species from urba n areas can be twice as high as those of remote regions, in terms of both a bsolute concentration and element-to-sodium ratio. The contrasts between ur ban and remote and between low and high elevations can be explained by prox imity to the ocean, local pollution sources, and scavenging processes. Comp arison with other world areas shows rather high levels of chemical species in rainwater from the Yellow Sea relative to remote world oceans or even so me other coastal urban areas. Using sodium as a sea-salt tracer, it was est imated that more than 50% of major species in rainwater could come from non -marine contributions, and for some species like NH4+, NO3-, and SO42-, ant hropogenic emissions are definitely the major source. The high concentratio n of nitrogen species and elevated N/P ratio of rainwater, as compared to r iverine input, suggest the significance of atmospheric wet deposition to th e marine production and biogeochemical circulation of nutrients in this reg ion.