南京市中心城区道路绿地土壤中重金属含量及污染评价

Content of Heavy Metals of Road Greenbelt Soil in Nanjing City and Pollution Evaluation

为了解不同绿化时间段道路绿地土壤中重金属的含量特征,采集了南京市中心城区不同绿化时间段道路绿地土壤0～5 cm、5～20 cm土样共50个。土壤经微波消解后,用原子吸收分光光度计分别测定土壤中Cu、Zn、Pb、Cd和Cr的全量。结果表明,南京城市土壤中Cu、Zn、Pb、Cd和Cr的全量分别为38.8±14.31、13.4±25.55、3.1±27.7、0.114±0.06、51.8±8.9 mg/kg,最高值约为最低值的2.4～18.5倍。从变异系数来看,除Zn、Cr元素的变异系数在20%左右,其它重金属元素均在35%～55%之间。2000年前绿化的道路绿地土壤中重金属含量显著高于2000年后的绿地土壤(p<0.05)。Pb、Cu和Zn存在不同程度的污染,Pb和Cu在2000年前绿化的道路绿地土壤中达到中度污染水平,Cr处于警戒限水平,Cd处于清洁水平。由于受交通和人为活动的影响,绿地表层土壤中重金属出现积累。

In order to study the accumulation characteristic of heavy metals in road greenbelt soil in different green time, soil samples with 0 -5 cm and 5 - 20 em depth of road greenbelt were collected at the centre of Nanjing City. After microwave digestion of soil, the total heavy metals, such as Cu, Zn, Pb, Cd and Cr were determined by atomic absorption spectrophotometer. The results showed that the average contents of total Cu, Zn, Pb , Cd and Cr of the soils were 38.8 ± 14.3, 113.4± 25.5, 53.1± 27.7, 0.114 ± 0.06, 51.8 ± 8.9 mg/kg respectively. The maximum value was 2.4 - 18.5 times of the minimum value. Coefficient of variation of Zn and Cr was about 20% , other heavy metals were between 35% ~ 55%. The contents of heavy metal were significantly higher in soil of green time before 2000 than that of after 2000. Pb, Cu and Zn were in different pollution level. Pb and Cu were in the moderate pollution level evenly. While Cr was limited to the level of alert, and Cd was in the cleanliness level. There existed surface accumulation of heavy metals in road greenbelt soil because of traffic and human activity.