基于梯形模糊数的沉积物重金属污染风险评价模型与实例研究

综合考虑到经典确定性污染评价模型的现实缺陷,将梯形模糊数理论引入环境评价领域,通过将研究区域重金属背景值及重金属实测含量的梯形模糊数化,结合聚类分析、α-截集技术和区间数隶属度计算,最后基于定义的重金属生物毒性评价权重系数建立了沉积物重金属污染风险模糊评价模型.采用该评价模型评价了洞庭湖表层沉积物重金属污染的风险状况,结果表明,洞庭湖水系表层沉积物中7种重金属污染风险程度排序为:Hg>Cd>Pb>Cu>Cr>Zn>As,Hg、Cd和Pb应成为洞庭湖水环境污染治理的优先控制因子.与确定性模型评价结果的对比分析表明,模糊评价模型得出了各重金属地累积指数的可能值区间,并进而得出与之对应的隶属可信度水平,从而较好地弥补了确定性评价的不足,更客观地、全面地表征了评价区域沉积物中重金属的真实污染状态与空间分布差异.

Assessment Model for Heavy Metal Pollution in Sediment Based on Trapezoidal Fuzzy Numbers and Case Study

Due to the practical shortcomings of the classical deterministic pollution assessment model,the theory of trapezoidal fuzzy numbers was introduced to the environmental assessment system. A fuzzy risk assessment model was built based on the geo-accumulation index and biotoxicity coefficients of heavy metals. Using the fuzzy pollution risk assessment model, the risk of heavy metal pollution was evaluated for the surface sediment of Dongting Lake. The results showed that the pollution risk in a descending order was Hg>Cd>Pb>Cu>Cr>Zn>As, with Hg,Cd and Pb being the priority pollutants in Dongting Lake. Both the intervals of possible values for the geoaccumulation indexes of heavy metals and their credible levels were calculated using this model. Compared with the results of the deterministic assessment model,the fuzzy pollution risk assessment model gave a better characetriztaion of the actual pollution status and spatial distribution difference of the heavy metals in the sediment of the studied region which is more objective and comprehensive.