基于生物可利用性评估城市道路沉积物重金属生态风险

Assessment of Ecological Risks of Heavy Metals in Urban Road Sediments Based on Bioavailability

城市道路沉积物重金属风险评价是表征城市环境质量的有效途径。采用重金属化学形态和生物可利用性来评估其生态风险更合理,越来越受到人们的关注。本文采集山东省青岛市崂山区10条次干道沉积物样品,分析不同粒径沉积物中Zn、Cd、Cu、Pb的含量、化学形态和生物可利用性,采用地累积指数(Igeo)和改进的生态风险指数(RIm)评价细粒径(小于75μm)沉积物中重金属污染水平和生态风险。结果表明:(1)沉积物粒径越小,重金属含量则越多。当粒径小于75μm时,Zn、Cd、Cu和Pb平均含量分别为山东省土壤元素背景值的10.63、6.07、3.39、2.70倍。(2)随粒径的减小,生物可利用性增大。小于75μm粒径的Zn、Cd、Cu和Pb的生物可利用态百分比为74%、78%、66%和55%。(3)评价结果显示,Zn、Cd、Cu和Pb的值分别为2.83、2.01、2.22和2.05,结果均为偏重度污染。(4)评价结果为较高生态风险,其中Cd属于极高风险,Cu和Pb属于中等风险,Zn属于低风险,Cd对的贡献高达75%。以重金属污染水平、迁移率、生物可利用性和生态风险为评价依据,认为Zn、Cd、Cu、Pb的风险均较大。该研究可为青岛市道路重金属污染防控提供指导。

The risk assessment of heavy metals in urban road sediments is an effective way to characterize the quality of urban environment.It is more reasonable to evaluate the ecological risk of heavy metals by their chemical fraction and bioavailability,which has attracted increasing attentionfrom the public.We collected sediment samples of 10 accessary roads in Laoshan District,Qingdao,Shandong,China,and analyzed the content,chemical fraction and bioavailability of Zn,Cd,Cu,Pb in the sediments with different particle sizes.The geo-accumulation index(Igeo)and the modified ecological risk index(RIm)were used to evaluate the heavy metal pollution levels and ecological risks of thefine particle size(<75μm).The results showed that(1)The smaller the sediment particle sizes,the heavier heavy metal content.When the particle size was less than 75μm,the average content of Zn,Cd,Cu and Pb was 3.37,1.70,1.63 and 0.28 times of the level-II standard of the soil environmental quality standard(GB 15618—1995),respectively.(2)The bioavailability increased with the decrease of particle sizes.The bioavailability percentages of Zn,Cd,Cu and Pb with particle size<75μm were 74%,78%,66%and 55%,respectively.(3)The assessment results of Igeo showed that the Igeo values of Zn,Cd,Cu and Pb were 2.83,2.01,2.22 and 2.05,respectively,indicating heavily pollution.(4)The results of RIm showed that the ecological risk was high,Cd was categorized as extremely high risk,Cu and Pb was categorized as medium risk,Zn was categorized as low risk,Cd contributed up to 75%to the RIm.Considering heavy metal pollution level,migration rate,bioavailability and ecological riskas the evaluation indexes,the risk of Zn,Cd,Cu and Pb were considered to be high.The presentstudy provideda guidance for the prevention and control of heavy metal pollution in urban road in Qingdao.