The distribution and partitioning of trace metals (Pb, Cd, Cu, and Zn) and metalloid (As) in the Beijiang River

The concentrations of Cu, Zn, Pb, Cd, and As varied quite differently in the water, suspended particulate matter (SPM), and sediment along the middle reach of the Beijiang River in southern China. The total concentrations of trace metals and As in the water column were significantly affected by the concentration of SPM, while the metals and As in the sediment were mainly influenced by fine particle component, OM and Fe/Mn/Al. The partitioning coefficient of trace metals and As in the water column generally appeared in the following order: Pb > Cd > Cu > Zn > As. Accordingly, approximately 67.9% of Pb migrated with SPM in the river because of its higher particle reactivity, while the SPM-bound Cu, Zn, and As were approximately 43.4, 37.3, and 26.7%, respectively. The fractions of Cd in the dissolved and particulate phases were almost the same. Sediment resuspension and deposition in the Beijiang River were considered as important factors controlling the concentrations of dissolved Cu, Zn, Pb, Cd, and As in the bottom of the water column.