Biogeochemical Characteristics Of Arsenic And Selenium In The Changjiang Drainage Area And Its Estuary

A method for the determination of dissolved selenium and arsenic by Hydride Generate Atomic Absorbed spectrometry (HG-AAS) are established in this study. The method is applied to the study of selenium and arsenic in the Changjiang, Changjiang Estuary and Chongming wetland.The chemistry of major elements, dissolved arsenic and selenium, suspend arsenic and selenium in the river water of the Changjiang (Yangtze River) and its tributaries were studied in April-May 2003. HCO₃^- is the most abundant anion of the changjiang, concentrations of anions follows the order HCO₃^->SO₄^2->Cl^-; Among the cations, Ca²⁺ is predominant, Concentrations of cations vary in the order Ca²⁺>Na⁺>Mg²⁺>K⁺. The result show that the dissolved load of the Changjiang relative to water discharge and in absoulate terms is very high compared with other major waters. Atmosphere input of major elements to the Changjiang is very limited. Weathering and erosion are primary importance in affecting river chemistry, which accelerated by anthropogenic activities (e.g. farming). Comparison of major element fluxes reveals high chemical loads of Changjiang, which are disproportionate to its limited water discharges.The chemistry of trace element (arsenic and selenium) in the river water of Changjiang (Yangtze River) was studied, based on continuously monitored data at Nantong station, the main Changjiang channel and major tributaries. The results show that the dissolved inorganic arsenic (DIAs) and dissolved inorganic selenium (DISe) concentrations of the Changjiang varies over an order of magnitude throughout the basin (6.95-68.9 nmol/L for DIAs, 1.16-9.92 nmol/L for DISe). Source rock composition is the primary control on the concentrations of DIAs and DISe in the Changjiang water. Several tributaries (e.g. Xiangjiang, Minjiang and Tuojiang) are contaminated human activities. Flux calculations at Datong (the most downstream main-channel station without tidal influence) indicate that the Changjiang transports 17.6×10⁶mol/a of DIAs and 3.27×10⁶mol/a of DISe to the East China Sea.Two cruises of "Hiajian 47" and "Hiajian 47" were carried out in September 2004 and August 2005, respectively, to understand the behaviors of selenium and arsenic in the Changjiang Estuary. Selenium and Arsenic concentrations display short-term variability and seasonal change in the Changjiang Estuary, with higher...