清水塘工业区池塘底泥典型重金属污染特征及其风险评价

为查明株洲清水塘工业区池塘底泥重金属污染现状及其变化趋势,揭示池塘底泥重金属对霞湾港与老霞湾港水体及底泥的潜在影响。将区域内25口池塘分别划属S1、S2、S3区,于2017年12月11日在25口池塘采集32份底泥样品,并进行了Pb、Cd、As含量的测定,采用地累积指数(Igeo)与Hakanson潜在生态危害指数(Eir)对底泥中Cd、Pb、As污染与生态风险进行了评价。结果表明:S1、S2、S3区池塘底泥中Cd、Pb、As含量均超过湖南土壤背景值,分别为土壤背景值的657、44、12倍,表明Cd是清水塘工业区池塘底泥中的主要污染物。变异系数结果显示,各采样点底泥中Cd、Pb、As含量分布离散,受点源输入影响大。底泥中Pb、Cd、As的Igeo均值分别为4. 87、8. 78、2. 95,分别处重度、严重、中度污染等级,不同区底泥中重金属Igeo呈S3>S1>S2的分布特征。潜在生态风险评价结果表明,底泥中重金属Eir呈Cd>Pb>As的分布特征,3个区底泥中Cd的Eir为9396～24 617,污染等级均为生态危害很强; Pb的Eir为101～309,S1、S3区污染等级为生态危害强,S2区则为生态危害较强; As的Eir为74～138,S1、S3区污染等级为生态危害较强,S2区则为生态危害中等。清水塘霞湾港和老霞湾港周边区域池塘底泥中Cd、Pb、As污染严重,呈S3>S1>S2分布,应依据3个区域池塘底泥重金属污染程度顺序,采取挖掘底泥、稳定固化、填埋处理等措施。

Pollution Characteristics and Ecological Risk Assessment of Heavy Metals in Sediments of the Qingshuitang Industrial District

In order to assess the heavy metal pollution in pond sediments of Xiawan and Laoxiawan ports in the Qingshuitang industrial zone of Zhuzhou, 25 ponds in the study area were divided into three sub-divisions (S1, S2 and S3) and a total of 32 sediment samples were collected on December 11th, 2017, and contents of pH, Pb, Cd and As in sediment samples were measured. The geo-accumulation index (I_geo) and the potential ecological risk index (E_rⁱ) were used to evaluate the pollution and ecological risk of Cd, Pb and As. The results showed that contents of Cd, Pb and As in sediments of S1, S2 and S3 all exceeded their background soil values of Hunan, and were 657, 44 and 12 folds higher than the background values, respectively, suggesting that Cd was the major pollutant in ponds of the Qingshuitang industrial area. The variation coefficients analyses showed that Cd, Pb and As contents in sediments distributed discretely and were affected greatly by input sources. The I_geo assessment indicated that average I_geo values of Pb, Cd and As in sediments were 4.87, 8.78 and 2.95, respectively, corresponding to severe, serious and moderate pollution levels. The contamination order of sediments by heavy metals was S3 > S1 > S2. Results of the E_rⁱ assessment indicated that E_rⁱ values of heavy metals in pond sediments followed an order of Cd > Pb > As, E_rⁱ values of Cd obtained from 3 sediments were in the range of 9 396-24 617, indicating the extreme strong ecological risk; E_rⁱ values of Pb were in the range of 101-309, showed strong ecological risk in S1 and S3 and moderate ecological risk in S2; E_rⁱ values of As were in the range of 74-138, showed strong ecological risk in S1 and S3 and moderate ecological risk in S2. In summary, pond sediments around Xiawan and Laoxiawan Ports were polluted seriously by Cd, Pb and As with an order of S3 > S1 > S2. Thus, corresponding treatment measures, such as dredging, stabilizing or landfilling, should be taken according to the pollution levels.