Arsenic content and fractionation in the surface sediments of the Guangzhou section of the Pearl River in Southern China

The Guangzhou section of the Pearl River (GSPR) has been seriously affected by long-term intensive industrial and urban activities. The objectives of this study were to determine the total As (TAs) content and the forms of that As in order to investigate the geochemical relationships between As forms and sediment mineral phases of the surface sediments of the GSPR. Fifteen samples of surface sediment were collected and analyzed for TAs as well as As chemical forms. Results indicated that TAs in the sediment samples averaged 24.6 mg kg−1 and ranged from 16.7 to 33.4 mg kg−1. These values are generally higher than the probable effect level of 17.0 mg kg−1. The As was mostly associated with iron oxides (53.5%), followed by association with the residual fraction (36.2%). Amor-Fe bound As and Cry-Fe bound As quantities were positively correlated to the Amor-Fe and Cry-Fe quantities, respectively. In addition, organic matter (OM), clay and Sum-Fe contents were positively correlated to TAs in the sediment fractions. The molar ratios of iron oxide-bound As to iron content approached the maximum molar ratios of As to Fe for natural hematite, magnetite, and goethite. Adverse effects caused by As will likely frequently occur at these high levels of As contamination. Thus, it is necessary to remediate the sediment of the GSPR to reduce the potential risks of As contamination.