典型黑色岩系地质高背景区土壤和农产品重金属富集特征与污染风险

土壤重金属污染是我国的重要环境问题，而区域地质高背景是土壤重金属富集的重要影响因素.黑色岩系风化土壤普遍存在重金属富集的现象，潜在生态环境风险较高，但目前农产品重金属富集的基础数据较缺乏，限制了黑色岩系地质高背景区的土地安全利用与农产品安全生产.对重庆典型黑色岩系地质高背景区313件土壤和289件主要农产品重金属的富集特征、污染风险和土壤重金属赋存形态进行研究.结果表明，相对于我国土壤环境背景值和重庆市表层土壤，研究区土壤Cd、 Cr、 Cu、 Zn和Se富集，Pb不富集；其中98.7%的土壤Cd含量超过风险筛选值，47.3%的土壤Cd含量超过风险管制值，Cd的污染水平和潜在生态风险最高，是研究区土壤的特征污染物.土壤Cd主要以离子交换态存在(40.6%),其次为残渣态(19.1%)和弱有机结合态(16.6%); Cr、 Cu、 Pb、 Se和Zn主要以残渣态存在，Se和Cu的有机结合态、 Pb的铁锰结合态也占较高比例；说明Cd的迁移能力和活性高于其它重金属.研究区主要农产品富集重金属的能力较弱，约18.7%的农产品Cd超标，超标倍数相对较低，重金属污染风险较低.研究可为黑色岩系地质高...

Accumulation and Pollution Risks of Heavy Metals in Soils and Agricultural Products from a Typical Black Shale Region with High Geological Background

Soil polluted by heavy metals (HMs) is an important environmental issue in China, and regional geological background is a vital factor that influences the enrichment of HMs in soils. Previous studies have shown that soils derived from black shales are commonly enriched in HMs and present high potential eco-environmental risks. However, few studies have investigated the HMs in different agricultural products, which inhibit the safe use of land and safe production of food crops in black shale regions. This study investigated the concentrations, pollution risks, and speciation of HMs in soils and agricultural products from a typical black shale region in Chongqing. The results showed that the study soils were enriched in Cd, Cr, Cu, Zn, and Se but not in Pb. Approximately 98.7% of total soils exceeded the risk screening values, and 47.3% of total soils exceeded the risk intervention values. Cd had the highest pollution level and potential ecological risks and was the primary pollutant in soils of the study area. Most of the Cd resided in ion-exchangeable fractions (40.6%), followed by residual fractions (19.1%) and weak organic matter combined fractions (16.6%), whereas Cr, Cu, Pb, Se, and Zn were dominated by residual fractions. Additionally, organic combined fractions contributed to Se and Cu, and Fe-Mn oxide combined fractions contributed to Pb. These results indicated that Cd had higher mobility and availability than those of other metals. The agricultural products presented a weak ability to accumulate HMs. Approximately 18.7% of the collected samples with Cd exceeded the safety limit, but the enrichment factor was relatively low, indicating low pollution risks of the heavy metals. The findings of this study could provide guidelines for safe use of land and safe production of food crops in black shale regions with high geological background.