Lead in the southern East China Sea

At present, in most oceans the lead (Pb) biogeochemical cycling has been di sturbed by anthropogenic Pb through atmospheric input. The Pb concentration s in the upper water positively correlate with atmospheric input fluxes of Pb. The North Pacific is affected greatly by atmospheric substances via lon g-range transport from eastern Asia, especially from Mainland China. Mainla nd China may export considerable amounts of pollutants into the seas via ri vers and the atmosphere owing to its recent fast growth in industry and eco nomy. The East China Sea lies in an important geographical position-a trans it between Mainland China and the western North Pacific. However, no data a re available for seawater concentrations of Pb, a representative element wi th anthropogenic origin. In this work seawater samples from both 5 and 30-5 0 m water layers of 15 stations occupied over a cyclonic eddy in the southe rn East China Sea were analyzed for particulate Pb (PPb) and dissolved Pb ( DPb). The Mean concentration of DPb (similar to 128 ng/l) in the southern E ast China Sea upper waters (less than or equal to 50 m) is approximately se veral times higher than those in the Pacific; the high DPb concentrations i n the southern East China Sea waters correspond to much higher atmospheric supplies of Pb to the East China Sea. Thus, this study partly fills the 'da ta gap' of the marginal seas. Also, it indicates that the East China Sea ma y be considerably contaminated by deposited polluted aerosols. Spatial dist ributions of DPb in the surface water show a tendency of increasing concent rations with distance offshore, that depends on the magnitudes of atmospher ic Pb inputs and on particle scavenging processes. In contrast to DPb, spat ial distributions of PPb basically display an 'Omega'-like picture and a te ndency of decreasing concentrations with distance offshore. These are relat ed to riverine and scavenging sources and to the drive by the eddy. Additio nally, the residence times df DPb in the surface water were estimated to be about 2 years, agreeing well with the reported data. (C) 2000 Elsevier Sci ence Ltd. All rights reserved.