Solid-solution partitioning of arsenic (As) in the paddy soil profiles in Chengdu Plain, Southwest China

To predict the long-term behavior of arsenic (As) in soil profiles, the solid-solution partitioning of As was studied in four paddy soil profiles obtained from agricultural areas in Chengdu Plain, Southwest China. Paddy soil profile samples were collected and soil solution samples were extracted. Total As contents in soil solution and soil solid were analyzed, along with the soil solid phase properties. The As in soil solution was significantly higher in the upper layer (0–20 cm) and had a definite tendency to decrease towards 40 cm regardless of the sampling locations. When the concentration of arsenic in soil solution decreased, its content in solid phase increased. Field-based partition coefficient (Kd) for As was determined by calculating the ratio of the amount of As in the soil solid phase to the As concentration in the soil solution. Kd values varied widely in vertical samples and correlated well with soil pH, total organic carbon (TOC) and total As. The results of this study would be useful for evaluating the accumulation trends of arsenic in soil profiles and in improving the management of the agricultural soils.