Speciation Distribution and Potential Ecological Risks of Metals in Sediments of Changjiang Estuary

摘要

Five elements (Fe, Co, Ni, Cu, Ti) in 8 sediment samples from the Changjiang estuary along the plume were analyzed with a modified Tessier sequential extraction procedure to obtain the concentrations of metals in five fractions, and then the metal speciation distribution patterns and the potential ecological risks were studied. The results show that most of the elements mainly (more than 50%) occurred in the residual fraction, followed by iron-manganese oxides fraction and organic fraction (up to 33%), while the proportions of the exchangeable and carbonates fraction were relatively low (<14%). The proportions of Fe and Ti in the non-residual fractions were rather low and the distributions did not show a significant variation. The percentages of Co, Ni and Cu in first four fractions were much higher. Along the spreading direction of the Changjiang Diluted Water, the concentrations of Co, Ni and Cu in first four fractions increased firstly and then decreased. However, the proportions of these fractions to the total contents changed completely different. The percentages of Co, Ni decreased firstly and then increased along the profile studied, and Cu showed a decreasing trend. Finally, the assessment of potential ecological risks demonstrates rather low level in this area.