Duan Baoling, Zhang Wuping, Zheng Haixia, Wu Chunyan, Zhang Qiang, Bu Yushan
College of Resources and Environment, Shanxi Agricultural University, Taigu 030801, Shanxi, China.
College of Forestry, Shanxi Agricultural University, Taigu 030801, Shanxi, China.
Int J Environ Res Public Health. 2017 Jul 21;14(7):823. doi: 10.3390/ijerph14070823.
Land use of sewage sludge is the primary disposal method in Shanxi, accounting for 42.66% of all. To determine the ecological risk of heavy metals in sewage sludge, contents of seven heavy metals in sewage sludge from 9 municipal waste water treatment plants (WWTPs) that had the highest application for land use were determined. The order of the measured concentrations was: Zn > Cr > Cu > Ni > Pb > As > Cd, and all heavy metals contents were within the threshold limit values of the Chinese Control Standards for Pollutants in Sludge from Agriculture Use (GB4284-84). Four indices were used to assess the pollution and the ecological risk of heavy metals. By the mean values of the geoaccumulation index (I), heavy metals were ranked in the following order: Cd > Zn > Cu > As > Cr > Ni > Pb. The values showed that the pollution of Zn in station 3 and Cd in station 1, 2, 3, 4, 8 and 9 were heavily; Cu in station 8 and 9, Zn in station 1, 2, 4, 8 and 9 and Cd in station 5 and 7 were moderately to heavily, and the accumulation of other heavy metals were not significant. The single-factor pollution index (PI) suggested that none of the stations had heavy metals contamination, except for Cu in station 9, Zn in station 3 and 8, and Cd in station 1 and 9, which were at a moderate level. According to the results of the Nemerow's synthetic pollution index (PN), sewage sludge from all stations was safe for land use with respect to heavy metals contamination, except for stations 3, 8 and 9, which were at the warning line. The monomial potential ecological risk coefficient (Eri) revealed that heavy metals ecological risks in most stations were low. However, station 9 had a moderate risk for Cu; station 6 had a moderate risk, stations 5 and 7 had high risk, other stations had very high risk for Cd. According to the results of the potential ecological risk index (RI), station 1, 8 and 9 had high risk; station 2, 3, 4, 5 and 7 had a moderate risk, and station 6 had a low risk. The preliminary results indicated that the potential risk of land exposure to heavy metals in sewage sludge was relatively low, with Zn and Cd as the main contributor to the ecological risk for the applying of sewage sludge on land. Additionally, stations 3, 8 and 9 require more attention regarding the land applications related to heavy metals pollution.
污泥土地利用是山西省污泥的主要处置方式，占比达42.66%。为确定污泥中重金属的生态风险，测定了9座土地利用量最大的城市污水处理厂污泥中7种重金属的含量。测定浓度顺序为：锌＞铬＞铜＞镍＞铅＞砷＞镉，所有重金属含量均在《农用污泥中污染物控制标准》（GB4284 - 84）的阈值范围内。采用4种指标评估重金属的污染及生态风险。根据地累积指数（I）平均值，重金属排序如下：镉＞锌＞铜＞砷＞铬＞镍＞铅。结果表明，3号站的锌污染以及1、2、3、4、8和9号站的镉污染严重；8号和9号站的铜、1、2、4、8和9号站的锌以及5号和7号站的镉为中度至重度污染，其他重金属的累积不显著。单因子污染指数（PI）表明，除9号站的铜、3号和8号站的锌以及1号和9号站的镉为中度污染外，其他站点均无重金属污染。根据内梅罗综合污染指数（PN）结果，除3、8和9号站处于警戒线外，所有站点的污泥用于土地利用时重金属污染均安全。单项潜在生态风险系数（Eri）显示，多数站点的重金属生态风险较低。然而，9号站的铜有中度风险；6号站有中度风险，5号和7号站有高风险，其他站点的镉有极高风险。根据潜在生态风险指数（RI）结果，1、8和9号站有高风险；2、3、4、5和7号站有中度风险，6号站有低风险。初步结果表明，污泥土地暴露重金属的潜在风险相对较低，锌和镉是污泥土地利用生态风险的主要贡献者。此外，3、8和9号站在与重金属污染相关的土地利用方面需要更多关注。
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