Program

Trace metals (U, Cr, V) were studied in pore waters of five core sediments in the Changjiang Estuary and adjacent shelf of East China Sea. To assess the redox conditions of this area, the pH, concentrations of nutrients and sulfate were also measured in the pore water. Data of TOC and 210Pbxs showed that this area is characterized by relatively low organic carbon (0.33-0.63%) with fast sedimentation rate (0.3-0.6 cm/y). The relatively low bottom water oxygen concentrations (1.1-3.4 mg/l), combined with the high proportion of ammonium-N of the inorganic forms of nitrogen (>95%) and almost non-depleting of sulfate in the pore water of uppermost sediment near the sediment-water interface, indicated a suboxic condition in the upper sediment of this area. The pore water profiles of Fe, Mn, NH4+ in the core near the estuary of Changjiang River (12#) exhibited stronger redox gradient than the other southern cores. The redox sensitive trace metals (U, Cr, V) have the same response. This may relate to the abundant of organic matter in the estuary than the other coastal area. The trace metals from the pore water of the three cores (44#, 34#, 33#) with similar latitude did not show that the sediments become less reducing away from the continent, reflecting that the sediments of these three sites may have different origins.