Arsenic in waters and sediments of Yangzonghai Lake, China

摘要

This paper indicated that the total arsenic content in Yangzonghai Lake was 71.96-101.2μg/L in April, 2010, and increased slightly with depth. Dissolved arsenic content was 68.14-96.72μg/L, with As(Ⅲ) accounting for 33%. The health risk level of arsenic in the water was 4.77×10~(-4)-6.66×10~(-4)a~(-1), posing a considerable threat to the surrounding environment. Arsenic content in sediments lied between 6.05-396.49mg/kg. In sediments at the depths of 0-2, 2-4, 4-6, 6-8 and 8-10 cm, the average arsenic content was 155.66, 52.01, 29.78, 19.22 and 17.52mg/kg respectively. Arsenic in sediments at 0-2cm had the highest accumulation degree, with the maximum geoaccumulation index up to 5. At the deeper depths, the accumulation degree of arsenic significantly lowered. The sequence of arsenic average contents of seven forms in sediments in the descending order is residual fraction, humic acids fraction, oxide fraction, strong organic fraction, ion exchange fraction, water soluble fraction and carbonate fraction. With increase of sediments depths, the percentage of bioavailable arsenic decreased, and the percentage of residual fraction arsenic increased rapidly. The anthropogenic contribution rate of arsenic in sediments was the highest at 0-2 cm depth, with average of 81.94%. This rate was much lower at the deeper depths. Currently, the total arsenic reserve in water and sediments of Yangzonghai Lake was 70.65t, of which 82.68% was contributed by human activities.