[Contamination and Ecological Risk Assessment of Mercury in Hengshuihu Wetland, Hebei Province].

Investigation on the concentrations and the distribution characteristics of total mercury in atmosphere, water surface and soil/ sediments of Hengshuihu wetland was carried out based on a uniform set point sampling method. The geoaccumulation index and potential ecological risk index methods were simultaneously used to assess the mercury pollution in Hengshuihu wetland ecosystem. The results showed that: the total mercury content in Hengshuihu wetland atmosphere ranged from 1.0 to 5.0 ng · m⁻³, with an average of (2.9 ± 0.85) ng · m⁻³; the total mercury content in water surface ranged from 0.010 to 0.57 µg · L⁻¹, with the average value of (0.081 ± 0.053) µg · L⁻¹; the total mercury content in soil/sediment ranged from 0.001 0 to 0.058 mg · kg⁻¹, with an average of (0.027 ± 0.013) mg · kg⁻¹. The distribution features of total mercury in Hengshuihu wetland were as follows: the total mercury concentration in surface water of the shore was significantly higher than that in the center (P < 0.05), but the total mercury concentration of sediments in the center of the lake was significantly higher than that at the shore (P < 0.05); the total mercury in the soil of shore had a consistent trend with that in the atmosphere; high concentrations of total mercury pollution were accompanied by severe human activities. The geoaccumulation index showed that mercury pollution in Hengshuihu wetland was at clean level; potential ecological risk index showed mercury contamination had a low ecological risk in Hengshuihu wetland.

[Characteristics of Bacterial Communities in Surface-flow Constructed Wetlands].

Employing high-throughput sequencing as the method, this study analyzed the relationship between the water environment and the microbial community structure in the surface-flow constructed wetland. The results showed that: the mean Shannon-Wiener index was 6.57 and there were mainly 18 categories in the microbial community, including Proteobacterice (38.97%), Bacteroidetes (15.63%) etc. Of these, the total content of 22 genera was over 1%. The microbial biodiversity showed an increasing trend at the beginning and then turned to a decreasing trend in the flowing direction. The results also revealed that pH, ORP, NH4+-N, NO2--N and TN acted as important restricting factors for the microbial community.