城市道路沉积物中重金属生态风险的优化评价

城市道路沉积物中的重金属在降水径流的冲刷下会对受纳水体产生生态风险. 基于重金属的总量、毒性、形态，分别采用单因子污染指数法(P_i)、生态风险指数法(RI)和风险编码评价法(RAC)对青岛市崂山区11条主干道沉积物中4种重金属(Cu、Zn、Pb、Cd)的污染状况和生态风险进行评价，评价结果差异较大，建立新的模糊综合评价体系对这3种评价方法进行优化. 结果表明:①道路沉积物中的Cu、Zn、Pb、Cd均存在累积现象，4种重金属的主要来源为交通活动、大气沉降以及路面标识用漆. 重金属各形态分布不均匀，Cu以可氧化态为主，Zn以弱酸提取态为主，Pb以残渣态为主，Cd以生物可利用态(弱酸提取态、可还原态、可氧化态)为主. ②P_i评价结果显示，Cu、Zn、Pb、Cd的P_i值分别为3.80、27.61、1.21、8.33，Zn和Cd表现为重度污染水平，Cu和Pb分别表现为中度和轻微污染水平；RI综合评价结果为高风险，其中Cd属于高风险，其他3种重金属为低风险；RAC评价结果为Zn(40.44%)> Pb(28.24%)>Cd(25.37%)>Cu(3.80%)，Zn表现为高生态风险，Pb和Cd表现为中等生态风险，Cu表现为低生态风险. 导致3种评价结果不同的原因是评价方法分别侧重重金属的总量、毒性或形态. ③建立了模糊综合评价体系，设置了新的综合评价标准，优化评价结果表现为Cd(87.4)>Zn(72.04)>Pb(53.96)>Cu(53.56). 这表明重金属的毒性对其生态风险的影响要大于重金属的总量和形态，总量也会一定程度上影响评价结果. 研究显示，在实际工作中，当各种评价方法所得结果存在分歧时，模糊综合评价体系有利于更准确地了解重金属污染状况和生态风险. 

Optimal Evaluation of Ecological Risk of Heavy Metals in Urban Road Sediments

Heavy metals in urban road sediments can pose ecological risks to receiving water bodies under the erosion of precipitation runoff. Based on the total amount, toxicity and chemical composition of heavy metals, single-factor pollution index method (P_i), ecological risk index method (RI), and risk coding evaluation method (RAC) were used to analyze the sediments in 11 main roads in Laoshan District, Qingdao City. The results showed that the evaluation methods were quite different. A new fuzzy comprehensive evaluation system was established to optimize these three evaluation methods. The results are as follows: (1) Cu, Zn, Pb, Cd were all accumulated in road sediments. The main sources of the four heavy metals were traffic activities, atmosphere deposition and road marking paint. The fraction of heavy metals was unevenly distributed. Cu was mainly in the oxidation fraction, Zn was mainly in the weak acid extraction fraction, Pb was mainly in the residue fraction, and Cd was mainly in weak acid extraction, reducible and oxidizable fractions. (2) The results of the P_i evaluation showed that the P_i values of Cu, Zn, Pb, and Cd were 3.80, 27.61, 1.21, 8.33, respectively. Zn and Cd showed heavy pollution level, Cu showed moderate pollution level, and Pb showed light pollution level. The result of RI comprehensive evaluation was high risk, among which Cd was high risk, and the other 3 metals were low risk. The result of RAC evaluation was Zn (40.44%)>Pb (28.24%)>Cd (25.37%)>Cu (3.80%). Zn presented high ecological risk, Pb and Cd presented medium ecological risk, and Cu presented low ecological risk. The reason for the different results of the three evaluation methods is that they respectively focus on the total amount, toxicity and fraction of heavy metals. (3) A new fuzzy comprehensive evaluation system was established and a new evaluation standard was set to accurately evaluate the pollution status of heavy metals. The optimization evaluation results showed that Cd (87.4)>Zn (72.04)>Pb (53.96)>Cu (53.56). This indicated that the toxicity of heavy metals has a greater impact on the ecological risk of heavy metals than the total amount and form of heavy metals, and the total amount will also affect the evaluation results to a certain extent. In actual work, when the results obtained by various evaluation methods are different, the fuzzy comprehensive evaluation system is conducive to more accurate grasp of heavy metal pollution and ecological risks.