Distribution and enrichment of particulate trace metals in the southern East China Sea

抄録

This study investigates the distribution and enrichment of trace metals in suspended and sinking particulate matter from southern East China Sea (ECS) north of Taiwan during the period of April 1992 to April 1993. According to these results, concentrations of suspended particulate matter (SPM) in the inner shelf of southern ECS, the upwelling-influenced shelf break, and Kuroshio water are 1.2 (surface)-4.2 (bottom) mg/l, ca. 0.3-0.5 mg/l, and 0.1-0.3 mg/l, respectively, reflecting various influences of terrestrial inputs. A benthic nepheloid layer (BNL), apparently owing to resuspension of local and/or remote bottom sediments, formed over the shelf region. Temporal variation in trace metal contents and enrichment in suspended matter from the shelf region reflect the variability of metal inputs from Chinese rivers, particularly from Changjiang runoff. The abundance of a particulate metal is largely determined by the SPM content. Hence, the abundant profiles of most particulate metals closely correspond to the distribution pattern of SPM. However, concentrations of most particulate metals (except for Al and Fe), based on the dry weight of SPM, increase from the China coastal water to the Kuroshio water. The enriched metals are more likely to have derived from terrestrial inputs, rather than solely from biological accumulation. In addition, a decrease in metal contents and an increase in salinity confirm the transport of suspended particulate metals from the ECS shelf to the open ocean. Such an occurrence is verified by the feature of metal plume in the intermediate layer (550-800 m) of Kuroshio water. Moreover, the sinking particles collected from sediment traps deployed on the upper slope are relatively enriched in lithogenic matter and trace metals. Terrestrial inputs apparently control the distribution of most trace metals in suspended and sinking particulates in the southern ECS.