基于土壤重金属污染风险管控的土壤质量评价:以某县级市为例

近年来农用地土壤质量受重金属污染影响进而导致农产品受到威胁的问题愈发严重，然而关于土壤质量评价的研究很少考虑土壤污染状况，忽略了土壤污染风险对土壤质量的影响。本文以某典型制造业县级市为例，在以土壤理化性质为主要指标的土壤肥力状况评价基础上，对研究区土壤重金属进行污染风险管控类型划分。通过建立分段函数将土壤污染风险管控类型划分结果引入土壤质量评价体系，对农用地土壤质量进行评价。结果表明：研究区土壤理化指标的变异系数从大到小为速效磷(AP)含量>土壤电导率(SEC)>全磷(TP)含量>土壤有机碳(SOC)含量>阳离子交换量(CEC)>全氮(TN)含量>pH。土壤肥力状况随地势降低和河流增加呈现升高的趋势，高肥力区主要分布在平原区西北部和平原区东北部，低肥力区主要分布在东南部丘陵山区和西部低洼区，肥力过渡区环绕低肥力区分布。农用地土壤污染风险管控类型的划分结果表明，Cd、Hg、As、Pb、Cr、Ni、Cu和Zn 8种重金属中至少有88.89%的Cd样点和98.61%的Cr样点属于优先保护类，11.11%的Cd样点、1.39%的Cr样点属于安全利用类，该区重金属污染以Cd为主。土壤质量评价结果表明，土壤质量总体分布与土壤肥力状况分布规律类似，但由于受土壤污染风险的影响，研究区西南部低质量土壤范围向东扩张，东南部低质量土壤分布范围更小，更密集化。上述研究结果说明，引入土壤污染风险管控类型划分结果一般会对土壤肥力状况作减幅修正，并在一定程度上改变原土壤肥力状况的空间分布格局。

Soil quality assessment based on risk control of heavy metal pollution in soil: a case study of an industrial city in China

In recent years, social and economic developments in China have caused increasingly serious problems in soil quality in agricultural land affected by heavy metal pollution. However, most soil quality evaluation reports have seldom considered the soil pollution or soil environmental quality issue and largely ignored the effect of soil pollution risk on soil quality evaluation. In this study, we developed a method to introduce soil pollution parameters into the soil quality evaluation system. Taking a typical county-size industrial city as an example, we assessed the soil fertility status based on soil physicochemical properties. We classified the types of risk control of heavy metal pollution in soil in the study area and incorporated the classification into the soil fertility status evaluation system by establishing a piecewise function. Finally, we evaluated the soil quality in agricultural land by our method. The results showed that the coefficient of soil physicochemical property in the study area varied as AP>SEC>TP>SOC>CEC>TN>pH, while soil fertility tended to increase with decreasing terrain and increasing rivers. The high fertility areas were mainly distributed in the plains of the northwest and northeast, whereas low fertility areas, surrounded by fertility transitional areas, were in the southeastern hilly and mountainous areas and the lowland in the west. Classification of the types of risk control of soil pollution in agricultural land showed that, for the 8 heavy metals tested, at least 88.89% samples for Cd and 98.61% for Cr belonged to the priority protection category, and 11.11% samples for Cd and 1.39% for Cr met the safe use standard, indicating heavy metal pollution was dominated by Cd. Soil quality assessment showed that the overall distribution of soil quality was similar to that of soil fertility; however, soil contamination risk evaluation expanded the low-quality soils in the southwestern study area eastwards, resulting in a denser distribution of lower-quality soils in the southeast. The above research results demonstrated that by introducing classification of the soil pollution risk control types, soil fertility correction should generally be reduced, and the spatial distribution of native soil fertility status may also be modified to a certain extent.