Deng Shuai, Duan Jia-Hui, Ning Mo-Huan, Tan Lin, Pu Gang, Chen Ji-Xing, Qi Xiao-Bing, Jiang Shang-Zhi, Xie Tao-Yuan, Liu Yi-Zhang
No. 205 Geological Team, Chongqing Bureau of Geology and Minerals Exploration, Chongqing 401120, China.
Chongqing Institute of Geological Survey, Chongqing 401120, China.
Huan Jing Ke Xue. 2023 Apr 8;44(4):2234-2242. doi: 10.13227/j.hjkx.202205115.
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.
重金属污染土壤是中国重要的环境问题，区域地质背景是影响土壤中重金属富集的关键因素。以往研究表明，源自黑色页岩的土壤通常富含重金属，具有较高的潜在生态环境风险。然而，很少有研究调查不同农产品中的重金属，这限制了黑色页岩地区土地的安全利用和粮食作物的安全生产。本研究调查了重庆某典型黑色页岩地区土壤和农产品中重金属的含量、污染风险及形态。结果表明，研究区土壤中镉、铬、铜、锌和硒含量较高，铅含量较低。约98.7%的土壤总含量超过风险筛选值，47.3%的土壤总含量超过风险干预值。镉的污染水平和潜在生态风险最高，是研究区土壤的主要污染物。大部分镉存在于离子交换态（40.6%），其次是残渣态（19.1%）和弱有机结合态（16.6%），而铬、铜、铅、硒和锌以残渣态为主。此外，有机结合态对硒和铜有贡献，铁锰氧化物结合态对铅有贡献。这些结果表明，镉的迁移性和有效性高于其他金属。农产品积累重金属的能力较弱。约18.7%的镉超标样品超过安全限值，但富集系数相对较低，表明重金属污染风险较低。本研究结果可为高地质背景黑色页岩地区土地安全利用和粮食作物安全生产提供指导。
