Atmospheric transport of water-soluble ions (NO3(-), NH4(+) and nss-SO4(2-)) to the southern East Sea (Sea of Japan)

Atmospheric deposition of different types of aerosols over the southern East Sea has received little attention in terms of seawater biogeochemistry. We investigated the concentrations of water-soluble ions (NO3(-), NH4+ and nss-SO4(2-)) in the aerosols associated with air mass transport patterns arriving at the east coast of Korea, adjacent to the southern East Sea, in order to determine source regions affecting chemical composition of aerosols and to assess the atmospheric pathway as a significant controlling mechanism of the biogeochemistry in this marginal sea. Concentrations of certain elements (Al, Na, Ca, V, Zn and Pb) together with the water-soluble ions were measured in the aerosol samples (n=34) collected during the period March 2002-February 2003. The geometric mean concentrations of the water-soluble ions were NO3(-) 2.98 (0.56-16.22), NH4+ 1.42 (0.37-6.73) and nss-SO4(2-) 2.47 (0.17-17.35) microgm(-3). The backward trajectories revealed that air masses passing slowly over eastern China contributed more to increases in the concentrations of water-soluble ions than those associated with fast-moving northwesterly and maritime winds. Therefore, the correlation between the NH4+ and NO3+ concentrations increased, suggesting that gas-phase NH3 and HNO3 was forming fine-mode NH4NO3. The atmospheric N input accounted for approximately 10% of new production over the southern East Sea on an annual scale, while it accounted for over approximately 25% of new production during the water column stratification seasons (summer and early fall).