不同城市功能区绿地土壤重金属分布及其生态风险评价

对山东中部某典型城市9个城市功能区64个绿地土壤样品中的Cu，Zn，Pb，Cd 4种重金属元素含量进行了测定，评价了土壤重金属污染特征及其生态风险。结果表明:各功能区绿地表层土壤Cu，Zn，Pb和Cd的平均含量均高于当地自然植被土壤背景值，已表现出富集状态，其中Cd平均含量超标严重；工业区、风景名胜区、商业区和居民区等绿地土壤污染程度居前；单因子污染评价表明，该市绿地土壤中Cu，Zn和Pb已处于潜在污染状态，而Cd已经处于重污染状态；综合污染评价研究表明，处于“中度污染”污染级别的绿地类型有工业绿地、商业区绿地、风景名胜区和居住区绿地，而且苗木生产区和道路绿地也接近“中度污染”级别；潜在生态危害评价表明，该市绿地土壤处于轻微生态风险，但Cd潜在生态危害指数已经处于中等生态风险；土壤中Cu-Zn，Cu-Cd，Pb-Cd显著相关，Cu-Pb，Zn-Cd极显著相关，重金属之间存在一定复合污染现象，表明这些重金属元素的来源可能相同。该市绿地土壤Cd污染的防治应该引起重视。

Distribution and Ecological Risk Assessment of Heavy Metal Elements in Soils of Green Spaces at Different Urban Functional Areas

The contents of four heavy metal elements (Cu, Zn, Pb and Cd) in 64 soil samples of green spaces from 9 urban functional areas in a typical city of central Shandong Province were measured to analyze and evaluate both the pollution characteristics and ecological risk of soil heavy metals. The results showed that:(1) the average contents of Cu, Zn, Pb and Cd in soils of green spaces at each urban functional area were higher than the background values in local soils under natural vegetation; at the same time, those heavy metal elements exhibited an enrichment state and the average content of Cd exceeded the standard seriously; (2) the most polluted soils of green spaces were found in the industrial area, scenic area, business district and residence community, respectively; (3) based on the single factor pollution assessment, Cu, Zn and Pb in soils of the city green spaces were in a potential pollution state while Cd was in a heavy pollution state; (4) according to the research of comprehensive pollution evaluation, the green spaces at medium pollution level were industrial green space, business district green space, scenic area and residence community green space, respectively; in addition, the seedling production area and road green space were close to the medium pollution level; (5) the potential ecological hazard assessment showed that the soils in study city were in slight ecological risk, but the Cd potential ecological risk index had been in medium ecological risk; (6) the relationship between Cu and Zn, Cu and Cd, Pb and Cd were significant, and the correlations between Cu and Pb, Zn and Cd were extremely significant. The combined pollution phenomenon found in different heavy metal elements indicated that those heavy metal elements may have the same pollutant source. In the end, more attentions should be paid to the prevention of Cd pollution in soils of green spaces in the study city.