[Distribution and sources of arsenic in Yangzonghai Lake, China]

By collecting water and sediment samples from Yangzonghai Lake and analyzing the total amount and speciation of arsenic, the spatial distribution of arsenic in surface water and sediments was analyzed, the current status of arsenic pollution were estimated, the anthropogenic contribution rate and the arsenic reserve in the lake were calculated respectively. Meanwhile, the sources of arsenic were investigated. The results indicated that the total arsenic content in Yangzonghai Lake was 71.96-101.2 microg x L(-1) in April, 2010, and increased slightly with depth. Dissolved arsenic content was 68.14-96.72 microg x L(-1), with As (III) accounting for 32%. The health risk level of arsenic in the water was 4.77 x 10(-4) - 6.66 x 10(-4) a(-1), posing a considerable threat to the surrounding environment. Arsenic content in sediments lied between 6.05-396.49 mg x kg(-1). In sediments at the depths of 0-2, 2-4, 4-6, 6-8 and 8-10 cm, the average arsenic contents were 155.66, 52.01, 29.78, 19.22 and 17.52 mg x kg(-1) respectively. Arsenic in sediments at 0-2 cm 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 70.65 t, of which 82.68% was contributed by human activities. The phosphate fertilizer plant on the south bank made the greatest contribution to arsenic accumulation in Yangzonghai Lake, followed by golf course on the east bank, thermal power station and hot spring on the north bank.