改进的地累积指数法在重金属生态风险评价中的应用

Application of improved geo-accumulative index method in the ecological assessment of heavy metals

地累积指数法是土壤或沉积物中重金属生态风险评价的常用方法,只能够对样点中的单一重金属污染进行评价,不能综合分析区域内的重金属污染程度.为了扩大地累积指数法的应用范围,尝试利用最大污染量和平均污染量这2个指标对该评价模型进行改进.为了验证改进的地累积指数法的科学性与可靠性,以天津于桥水库流域河流沉积物的重金属综合生态风险评价为例,比较分析改进的地累积指数法、潜在生态风险指数法、污染负荷指数法的评价结果.在评价单一样点的重金属生态风险时,改进的地累积指数法和潜在生态风险指数法的评价结果一致,均为较轻污染水平,而污染负荷指数法的评价结果为中等污染水平;在评价区域的综合重金属生态风险时,改进的地累积指数法和污染负荷指数法的结果相同,均为中等污染水平.利用中等污染距对单一样点重金属生态风险进行评价时,改进的地累积指数法与潜在生态风险指数法的中等污染距相近,略低于污染负荷指数法的数值;在对区域综合重金属生态风险进行评价时,改进的地累积指数法与污染负荷指数法的中等污染距接近,即区域整体属于中等污染水平.由此可见,改进的地累积指数法可以用于综合评价区域的重金属生态风险.

The geo-accumulatie index method is a common method to evaluate the ecological risk of heavy metals in soil or sediment. This method only can evaluate the single heavy metal in a sample site but can not comprehensively analyze the pollution degree of heavy metals in a region. In order to expand the application scope of the geo-accumulative index method,the evaluation model was improved using the two indexes of the maximum pollution and the average pollution. In or-der to verify the scientificity and reliability of the improved geo-accumulative index method,the Yuqiao Reservoir Basin in Tianjin was taken as an example to evaluate the ecological risk of the heavy metals,and the evaluation results of the improved geo-accumulative index method were compared with the evaluation results using the potential ecological risk assessment method and the pollution load index method. When the ecological risk of heavy metals in a single sample site was evaluated,the results of the improved geo-accumulative index method and the potential ecological risk index method are consistent,all of which are in light pollution levels,but the evaluation results of the pollution load index method are in medium pollution level. When the comprehensive ecological risk of heavy metals in the region was evaluated,the results of the improved geo-accumulative index method and the pollution load index method are both in middle pollution level. When the medium pollution distance is used to evaluate the ecological risk of heavy metal in single sample site,the results of improved geo-accumulative index method are similar with those of the potential ecological risk index method,and they are slightly lower than the value of the pollution load index method. When comprehensirely evaluating the ec ological risk of heavy metals in a region,the results of improved geo-accumulative index method are close to those of the pollution load index method,and the area belongs to the middle pollution level. It can be seen that the improved geo-accumulative index method can be used to comprehensively evaluate the ecological risk of heavy metals in region.