[Impact of Enclosure Culture on Heavy Metal Content in Surface Sediments of Hongze Lake and Ecological Risk Assessment].

In order to explore the concentrations of heavy metals and the influence of fencing on Hongze lake, the content, source, and spatial distribution characteristics of heavy metals in surface sediments and ecological risks were analyzed in 2018 after part of the fence around Hongze Lake was removed. The results showed that the average contents of Cr, Ni, Cu, Zn, As, Cd, and Pb in the surface sediments in Hongze Lake were 66.78, 33.89, 25.35, 74.77, 16.55, 0.23, and 27.20 mg·kg-1, respectively. Cr, Ni, Cu, Zn, and Pb contents were at non-polluting levels, with As and Cd at the lowest level, based on the accumulation index evaluation. Except for Cd, all the elements showed low potential ecological risk. The results showed that the heavy metal content in the fenced, dismantled, and peripheral areas increased and accumulated towards the center of the lake. The removal of the fence did not significantly reduce the heavy metal content in the short-term. Overall, Hongze Lake presented a state of low ecological risk. In the future, environmental policies should include surface sediment accumulation areas and fencing culture in the north and northeast of Hongze Lake.

[Distribution and Risk Assessment of OCPs in Surface Water, Sediments, and Fish from Lake Gucheng and Inflow and Outflow Rivers].

To investigate the distribution, source, and ecological risk of organochlorine pesticides (OCPs) residues in Lake Gucheng, surface water, sediment, and biological samples were collected from 12 sampling sites of Lake Gucheng and its inlets and outlets during summer and winter, and the concentrations of 19 OCPs were analyzed. The results showed that the concentration (dry weight) of OCPs in Lake Gucheng ranged from 26.74 to 48.12 ng·L-1 in surface water, 9.01 to 35.34 ng·g-1 in sediment, and 13.39 to 124.29 ng·g-1 in organisms. The pollution characteristics of OCPs in surface water showed that the concentration was much higher in summer than in winter, and much higher at inflow and outflow rivers than in farming ponds and the central region of Lake Gucheng; the seasonal pollution characteristics in sediment were not obvious. All 19 kinds of OCPs in water, sediment, and organisms were detected in different degrees, and the dominant contaminants were HCHs and DDTs. α-HCH was the main pollutant at all sites in both surface water and sediment, with 21% to 42% of total HCHs in two seasons. p,p'-DDD was the main pollutant in surface water with 30% to 76% of total DDTs, whereas p,p'-DDT was the main pollutant in sediment with 68% to 93% of total DDTs in two seasons. Source analysis based on ratios of HCHs isomers and DDTs isomers indicated that there was a new input of OCPs under anaerobic conditions in the study area. The ecological risk assessment showed that the OCPs in surface water did not lead to significant health risks, but the OCPs in sediments might pose ecological risks to the Lake Gucheng ecosystem. The organisms were within the acceptable potential carcinogenic risk range.