典型小城市土壤重金属空间异质性及其风险评价:以临安市为例

城市土壤是城市生态系统不可分割的一部分,与城市居民的人体健康和生活质量密切相关.本研究以浙江省典型小城市——临安市为研究样区,共采集62个土壤表层样品(0~15 cm,样品采样密度:5个·km~(-2)),基于多元统计学、地统计学结合GIS技术研究该地区土壤重金属的污染特征、空间变异结构与分布规律.土壤重金属Mn全量、Cu全量、Zn全量、Pb全量、Cr全量、Cd全量的平均含量分别为439.42、42.23、196.80、62.55、63.65、0.22 mg·kg~(-1),与浙江省土壤背景值及环境质量标准相比较,这些重金属在临安市存在不同程度的累积,局部污染严重.单个重金属潜在生态风险危害指数表明,Pb的潜在生态危害指数最高.p H与大部分重金属全量以及重金属全量之间存在显著相关关系.研究区土壤Pb、Zn和Cu主要来自于城市交通运输工具的使用和尾气排放,而Mn和Cr主要来自于母岩,Cd主要由市区工厂的长期有害物质排放.研究区土壤重金属全量及其有效态均具有较强的空间自相关性C_0/(C_0+C)50%],其空间分布特征受人为活动的影响极为明显.

Spatial Variation of Soil Heavy Metals in Lin'an City and Its Potential Risk Evaluation

Urban soil is an important part of the urban ecosystem, which is strongly correlated with human health and life quality. In this study, Lin''an city was chosen as a typical small city to study the spatial variation and distribution of heavy metals in urban soils and their pollution characteristics using multivariate analysis, geostatistics, and GIS techniques. A total of 62 soil samples were collected from the study areas. The results indicated that the average concentrations of soil Mn, Cu, Zn, Pb, Cr, and Cd were 439.42, 42.23, 196.80, 62.55, 63.65, and 0.22 mg·kg^-1, respectively. Compared with the background values and the environmental quality standards, these heavy metals were accumulated in urban soils to some extent. Almost 80% of the study area was polluted by heavy metals. The single potential ecological risk index of heavy metals indicated that Pb had the highest ecological risk. The pH and most of the heavy metals had strong correlations, and there were strong correlations among the heavy metals. The principle component analysis (PCA) showed that Pb, Zn, and Cu had the same pollution source, which was related to vehicle exhausts; Mn and Cr were mainly from the parent material; and Cd was from the emissions of manufacturing plants. The spatial structure and distribution of heavy metals and their corresponding available fractions had strong spatial autocorrelation with all of the C₀/(C₀+C)<50%. Their spatial patterns were influenced by human activities.