工业区周边典型小流域耕地土壤重金属污染源解析

小流域是耕地土壤重金属分布与再迁移的基本景观单元，厘清其污染特征及来源是精准治污与科学治污的重要基础，然而小流域尺度耕地土壤重金属污染源解析研究仍亟待加强。本研究以典型工业区周边小流域耕地为例，利用土壤调查和正定矩阵因子法(PMF)结合源排放清单法，研究土壤重金属污染特征并解析耕地土壤重金属污染来源。结果表明，受污染耕地主要分布在小流域中部工业企业密集区域以及小流域西南部，主要为Cd污染，污染点位比例为90.5%；As、Hg和Pb污染点位比例1.1%～6.3%，无Cr污染。表层土壤Cd和Hg累积明显，地质累积指数均值为1.41和0.87；而Pb、As和Cr地质累积指数均值均小于或接近0。灌溉水和肥料等农业投入品重金属含量均未超标。当前耕地土壤主要污染物的输入途径中，Cd和Pb主要为大气沉降，占比71.0%～82.6%；As和Hg主要为大气沉降和灌溉水输入，占比39.0%～58.9%。农业投入品使用对耕地土壤Cd、Hg、As、Pb和Cr的输入通量占比较小，仅2.1%～18.7%。PMF模型分析显示，耕地土壤重金属污染来源包括土壤母质与工业企业混合源、工业企业源和农业源，相对贡献依次为38...

Sources identification of heavy metals contamination in farmland soils of a typical small watershed around industrial area

Small watershed is the basic landscape unit for the distribution and relocation of heavy metals in farmland soils, so it is fundamental to clarify the characteristics and sources of soil heavy metals for accurate and scientific prevention and remediation of soil contamination. However, the relevant source identification deserve further investigation at a small watershed scale. In the present study, the farmlands within a typically industrial small watershed were taken as samples to clarify the characteristics and sources of soil heavy metals contamination, using soil sampling and the positive matrix factor (PMF) model combined with the source emission inventory. The results showed that heavy metal-contaminated farmlands mainly distributed in the central area around industrial enterprises and southwestern of the small watershed. These farmlands were primarily contaminated by Cd with 90.5% of the sampling sites above the Chinese Soil Environmental Quality standard limit, and secondarily by As, Hg and Pb with 1.1%~6.3% of the sampling sites above the standard limit. There was no soil Cr contamination for these farmlands. Mean geo-accumulation index for Cd and Hg were relatively higher, as 1.41 and 0.87 respectively, reflecting their significant accumulation within surface soils. However, mean geo-accumulation index for Pb, As and Cr were relatively less or around zero. Heavy metals contents of both irrigation water and agricultural inputs (i.e., fertilizers and manures) did not exceeded limits. The current main input pathways of heavy metals for farmland soils are atmospheric deposition for Cd and Pb, accounting for 71.0%~82.6%, and atmospheric deposition and irrigation for As and Hg, accounting for 39.0%~58.9%. However, agricultural inputs only accounted for 2.1%~18.7% of the total annual input of heavy metals for the farmland soils. Further source identification and quantification results with PMF model and GIS mapping revealed that the mixed source (soil parent materials and industrial activities, 38.8%) accounted for the largest contribution to the soil heavy metals, followed by industrial activities (32.6%) and agricultural activities (28.6%). These reflected that source control should be furtherly strengthened for emissions of heavy metals from industry activities and livestock and poultry breeding. In conclusion, the receptor model (i.e., PMF) combined with the source emission inventory may effectively identify the sources of heavy metals in farmland soils at a small watershed scale. Our results are of great significance for the accurate source identification and prevention of heavy metals contamination in farmland soils at a small watershed scale.