College of Environmental Science and Engineering, Tongji University, 200092 Shanghai, China.
College of Environmental Science and Engineering, Tongji University, 200092 Shanghai, China.
Sci Total Environ. 2018 Jun 1;625:1272-1282. doi: 10.1016/j.scitotenv.2017.12.338. Epub 2018 Jan 12.
This study characterized the pollution levels and potential ecological risk of heavy metals in combined sewer overflows (CSOs) and their effects on microbial diversity in nearby riparian sediments. The chemical fractionations of Zn, Cd, Cr, and Cu in dry-weather flows, wet-weather flows (CSO discharges), sewer sediments, and surface runoffs were determined. Geo-accumulation (I) and ecological risk (RI) indexes were employed for metal risk assessment. DNA extraction and polymerase chain reaction (PCR) amplification on the Illumina MiSeq platform were conducted. The results show that heavy metals contents in fine-sized fractions have higher values than those in coarse-sized fractions. Chemical fractionation analysis suggests that Zn and Cd are two of the most bioavailable metals impacted by anthropogenic activities. Cr and Cu contents in CSOs are relatively stable and could exist for extended periods. According to the RI analysis, CSOs pose a considerable risk (RI-G2) to receiving waters due to the higher bioavailability of Cd, which was consistent with the I index. Furthermore, under the stress of the highly-bioavailable Cd and Cu, Gram +ves in the riparian benthic sediment gradually became dominant with metal-tolerance property. Therefore, long-term exposure to highly bioavailable metals could exhibit great impacts on microbial diversity.
本研究描述了合流制污水溢流（CSO）中重金属的污染水平和潜在生态风险，以及它们对附近滨岸沉积物中微生物多样性的影响。测定了干季流量、湿季流量（CSO 排放）、污水沉积物和地表径流中 Zn、Cd、Cr 和 Cu 的化学形态。采用地质累积指数（I）和生态风险指数（RI）对金属风险进行评估。采用 Illumina MiSeq 平台进行 DNA 提取和聚合酶链反应（PCR）扩增。结果表明，细颗粒中重金属的含量高于粗颗粒。化学形态分析表明，Zn 和 Cd 是受人为活动影响最具生物可利用性的两种金属。CSO 中的 Cr 和 Cu 含量相对稳定，可以存在较长时间。根据 RI 分析，由于 Cd 的生物可利用性较高，CSO 对受纳水体构成了相当大的风险（RI-G2），这与 I 指数一致。此外，在高生物可利用性的 Cd 和 Cu 的压力下，滨岸底栖沉积物中的革兰氏阳性菌逐渐占主导地位，具有金属耐受性。因此，长期暴露于高生物可利用性的金属可能会对微生物多样性产生重大影响。
