成都平原农地土壤镉含量特征及来源研究

Contents and Sources of Cadmium in Farmland Soils of Chengdu Plain, China

通过土壤采样对成都平原崇州市平原区农地土壤镉含量特征及来源进行分析,结果表明,研究区土壤镉含量在0.16～0.77mg·kg-1之间,平均为0.33 mg·kg-1,高出国家土壤环境质量二级标准10%,样点超标率30.43%。研究区土壤镉总体上处于中等程度的潜在生态风险,对人体的致癌风险尚处于可接受的范围。成土母质、土属类型、水系、农地利用方式和主要交通道路对土壤镉含量变异的独立解释能力分别为20.71%、24.70%、25.68%、12.62%和10.58%,即研究区土壤镉受自然地质过程和人为活动因素的综合影响,自然地质过程对土壤镉含量的主控作用总体上大于人为活动因素。水系和交通道路的影响范围分别主要在其4.0 km和1.5km范围内。自然地质过程和人为活动因素对土壤镉含量的主控作用在距离水系4.0 km前后发生改变:距离水系4.0 km范围内,自然地质过程的主控作用明显大于人为活动因素;距离水系4.0 km之外,人为活动因素则是最重要的控制因素。研究结果为深化对成都平原土壤镉污染机制的认识和镉污染防控提供了参考。

Heavy metal pollution in farmland soils in the Chengdu plain is threatening the security of agricultural products. Here we examined contents and sources of cadmium（Cd） in farmland soils in Chongzhou area of the Chengdu plain. Cadmium contents in the farmland soils ranged from 0.16 mg ·kg-1 to 0.77 mg ·kg-1, with an average of 0.33 mg ·kg-1, which exceeded the Grade Ⅱ limit of the National Bail Environmental Quality Standard（ GB 15618--1995 ）. There were 30.43% of soil samples in which Cd contents exceeded the standard. Assessments of potential ecological and human health risks indicated that Cd in the soils had moderate potential ecological risk. The carcinogenic risks of Cd in these soils were within the acceptable range, which showed a range from 5.67E-07 to 2.77E-06 for adult and from 1.42E-06 to 6.93E-06 for children. Agricultural land uses, parent materials, soil types, rivers and highways respectively contributed to 12.62%, 20.71%, 24.70%, 25.68% and 10.58% of soil Cd variability. This implied that both natural geological and human activity factors determined the heterogeneity of soil Cd, with natural geological factors playing greater roles. Rivers and highways had impacts on soil Cd up to 4.0 km and 1.5 km, respectively. In soils more than 4 km away from rivers, agricultural land use became a dominant factor affecting soil Cd. These findings provide useful information about understanding of soil Cd pollution and sources in the farmland of the Chengdu plain.