Comparison of the effects of competitive adsorption and reductive dissolution on migration of arsenic in lake sediment

Abstract

ABSTRACT Arsenic-contaminated sediment of Lake Yangzonghai (Yunnan province, China) and its overlying water was used to investigate the effects of phosphate ion (PO4 3−) and microbial activity on the migration of arsenic in the sediment. The results showed that the competitive adsorption of PO4 3− was the primary factor for the release of arsenic from the sediment to the overlying water, while microbial activity played a minor role in promoting the reductive dissolution of iron/arsenic (hydro) oxides. The reductive dissolution of ferrous ion (Fe2+) occurred in the initial stage, and partly contributed to the increase of arsenic concentration in the overlying water. The increase of PO4 3− concentration in the overlying water enhanced the mobility and biological toxicity of the arsenic in the sediment. After PO4 3− in the overlying water was depleted, arsenic in the overlying water could be adsorbed and precipitated again by iron salts, resulting in the decrease of arsenic concentration in the overlying water. The study implies that among those arsenic-contaminated lakes, eutrophication will aggravate the risks of secondary pollution of arsenic.