优化赋权模糊综合评价法对耕地土壤重金属污染的风险评价

Risk Assessment of Farmland Soil Heavy Metal Pollution Using Modified Empowered Fuzzy Comprehensive Evaluation

为了对工业发达区耕地土壤重金属污染风险进行科学评价,在综合考虑风险模糊性及其概念的基础上,构建了优化赋权模糊综合评价法对耕地土壤重金属污染的风险评价模型,并进行风险影响因素分析。以珠江三角洲为例进行实证研究,结果表明,广州市、东莞市、中山市和江门市最大隶属度原则低效,其风险等级值分别为2.8、2.5、2.4和2.4;深圳市、珠海市、佛山市和惠州市最大隶属度原则有效,最大隶属度分别为0.50(3级)、0.47(2级)、0.46(3级)和0.63(2级)。说明受到人为干扰相对较强的广州市、深圳市、佛山市和东莞市的风险较高,达到3级(中险)水平,而干扰相对较轻的珠海市、惠州市、中山市和江门市均处于2级(轻险)水平。影响因素分析表明,不同行政区内的主导风险因素不同。研究结果可为风险管理策略及其优先管理顺序的确定提供科学依据。

In order to implement scientific assessment of heavy metal pollution of farmland soils in regions well developed in industry,a modified empowered fuzzy comprehensive evaluation model was established based on the concept and fuzzy nature of risk,and moreover,analysis was done of factors affecting the risk. The model consists of a target layer,a criterion layer and an index layer. The target layer is the target object for evaluation,that is,risk of a soil getting polluted by heavy metals. The target layer is composed of 3 criterion layer indexes( tendency,vulnerability and hazardness). The index layer of tendency covers accumulation rates of heavy metals( Hg,Cd,Cr,Pb,As,Cu,Zn and Ni); the index layer of vulnerability consists of p H,organic matter,soil texture; and the index layer of hazardness refers to potential ecological risk index. Weights of the criterion layer are obtained with the analytic hierarchy process,while comprehensive weights of the indices in the index layer are determined with the group decision making analytic hierarchy process( the subjective weight) and the entropy weight method( the objective weight). Risk level is determined with the fuzzy comprehensive evaluation results vector. Validity of the maximum membership degree law is tested in the process of determining risk level. The weighted average method is used to determine risk level when the validity is low. Priority order of the risk management of various indices can be determined according to the importance degree and risk degree of each index. A case study was carried out of the Pearl River Delta Region. Results show that the principle of maximum membership degree is inefficient in Guangzhou,Dongguan,Zhongshan and Jiangmen,with risk grade value being 2.8,2.5,2.4 and 2.4,respectively; and the principle of maximum membership degree is valid in Shenzhen,Zhuhai,Foshan and Huizhou,with maximum membership degree being 0.50( third-level),0.47( second-level),0.46( third-level) and 0. 63( second-level),respectively,both suggesting that Guangzhou,Shenzhen,Foshan and Dongguan,as a result of high human disturbance,are high in risk,reaching up to Grade Ⅲ or "moderate risk",while Zhuhai,Huizhou,Zhongshan and Jiangmen,relatively low in human disturbance are in Grade Ⅱ or "slight risk". Analysis of affecting factor indicates that major risk affecting factors vary with the administrative region. All the findings are expected to serve as scientific basis for designing risk management strategies and defining a priority order of management.