应用富集系数法和地累积指数法研究济宁南部区域土壤重金属污染特征及生态风险评价

评价土壤中重金属污染的方法有单因子指数法、内梅罗综合指数法、地累积指数法、潜在生态危害指数法等,但迄今尚没有成熟的、统一的标准。本文以济宁城区南部农田为研究区域,采集77件土壤样品进行调查,光谱、质谱等技术分析结果表明土壤环境中8种重金属(As、Cd、Cr、Cu、Hg、Ni、Pb、Zn)平均含量分别为16.7、0.270、88.4、33.0、0.050、40.4、29.3、89.1 mg/kg,与黄淮海平原土壤生态地球化学基准值相比,Hg、Cd分别高于基准值的1.50倍、1.39倍,其他重金属高于基准值的0.26~0.52倍。Hg与As、Cr、F、p H、Cu、Ni、TFe2O3呈显著负相关,表明土壤受到了Hg的不同程度人为污染。用富集系数法和地累积指数法分析区内8种重金属元素的污染(富集)程度,均表明土壤环境中Hg、Cd为轻微污染(富集)程度,其他6种元素均为无污染。将该区域重金属含量与其生物毒性系数、生态效应、环境效应相结合,运用潜在生态危害指数法对重金属污染进行生态风险评价。结果显示,8种重金属的潜在生态危害由强至弱依次为:HgCdAsCuPbNiCrZn,与污染(富集)程度排序差异明显;尽管Hg、Cd在研究区内仅仅为轻微(富集)程度,但都具有较高的毒性响应系数,两元素对土壤综合潜在生态危害的贡献率之和达到了81.26%。借助Map GIS绘制研究区潜在生态风险程度评价图,表明区内土壤环境总体上处于"中度"潜在生态风险,约6.83%的面积呈"强"和"很强"潜在生态风险,其中复兴河、姚楼河、京杭运河3条河流交汇处的局部区域(占研究区面积的0.50%)达到了"很强"潜在生态风险。通过调查可疑人为污染源发现,"强"和"很强"潜在生态风险区域的布局恰好与区内煤矿生产开采活动相关。本文提出,应当注重对煤矿开采矿井周边区域土地复垦及污染防治工作,尤其是加强土壤中Cd、Hg的物理化学改良及生物治理修复工作,防止Hg、Cd进一步污染扩散。

Characteristics of Soil Heavy Metal Pollution and Its Ecological Risk Assessment in South Jining District Using Enrichment Coefficient Method and Geoaccumulation Method

Many methods, including single factor index method, Nemero comprehensive index method, potential ecological risk index method and geoaccumulation index method, have been employed to evaluate soil heavy metal pollution. However, no well-developed or standard method has yet been established. Herein, 77 samples of farmland soil in south Jining were collected and analyzed. The results show that average concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in the samples were 16.7, 0.270, 88.4, 33.0, 0.050, 40.4, 29.3 and 89.1 mg/kg, respectively. The values of Hg and Cd were 1.50 and 1.39 times higher than the benchmark value of the Huang-Huai-Hai Plain and values of other elements were 0.26-0.52 times higher than the benchmark value. All of the samples were evaluated by bivariate correlation analysis method, and the results show that soils are polluted by Hg. The enrichment coefficient method and geoaccumulation method were employed to evaluate the pollution level of 8 elements (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) in the target area soil. Both results show that there was light accumulation of Hg and Cd, while other elements were at normal levels. Combining heavy metal concentration in the selected area, the biotoxicity index of heavy metals, ecological effect and environmental effect, and the potential biological hazard index method were applied to evaluate the biological risk. The results show that the potential hazard sequence is as follows: Hg>Cd>As>Cu>Pb>Ni>Cr>Zn with obvious differences to the accumulation level. Although there was only light accumulation of Hg and Cd, their potential hazards contributed up to 81.26% of the total contribution of potential ecological risk index. The result was schematized by using MapGIS. It showed that about 6.83% of the selected area had the problem of strong or very strong potential ecological risk, and the remainder was at the medium level. Despite the junction of Fuxing River, Yaolou River and Jinghang canal faced the problem of very strong potential biological risk. According to the investigation on the anthropogenic emission sources in the research area, it was found that the risk had positive correlation with coal mining activities. Therefore, taking effective measures to remedy the polluted soil, especially the remediation of the Hg and Cd pollution, will be of great significance to prevent the further deterioration of the soil environment.