川南山区土壤与农作物重金属特征及成因

土壤及农作物中的重金属超标会影响人类生存环境和身体健康，为研究重金属在川南山区土壤与农作物中的富集特征及成因，以四川省南部山区的沐川县北部为研究区，采集了耕作土壤样品1699件，水稻籽实样品30件，玉米籽实样品31件，茶叶样品15件，对应农作物根系土壤样品76件，应用数理统计、主成分分析、相关分析等技术，研究土壤和农作物中重金属富集特征及成因、重金属在农作物与根系土的相关性.结果表明耕作土壤中重金属含量较高，其算术均值高于全国土壤背景值，且均存在超过风险筛选值采样点，其中Cd超标点数达770个；耕作土壤中重金属主要来源于地质背景，其次受土壤中的有机质及酸碱度和人类活动的影响.农作物中重金属均低于国家标准，农作物对重金属的富集系数总体表现为：茶叶 > 水稻 > 玉米.通过相关分析表明，土壤中重金属总体特征为含量高和活性低，未对3种农作物的质量安全造成影响，而土壤中CaO、Fe₂O₃和MgO对玉米和水稻籽实中重金属含量有一定影响.

Characteristics and Origins of Heavy Metals in Soil and Crops in Mountain Area of Southern Sichuan

Excessive heavy metals in soils and crops will affect the human living environment and health. In order to study the enrichment characteristics and causes of heavy metals in soils and crops in a mountainous area of southern Sichuan, 1699 cultivated soil samples, 30 rice seed samples, 31 corn seed samples, 15 tea samples, and 76 crop root soil samples were collected. The enrichment characteristics and origins of heavy metals in the soil were studied using mathematical statistics, principal component analysis, and correlation analysis. The enrichment characteristics of heavy metals in crops and their correlations with root soil were discussed. The results showed that the content of heavy metals in cultivated soil was higher than the national soil background value, and many sampling points exceeded the risk screening value. Among them, 770 points of Cd, 176 points of Cu, 116 points of Cr, and 106 points of Ni exceeded the standard. Combining the factor analysis results, it was found that Cd, Cr, Cu, Ni, and Zn in cultivated soil mainly originated from the geological background, and Cd was also affected by soil organic matter and pH. Meanwhile, Hg and Pb were mainly related to human activities. The results showed that the contents of heavy metals in the crops were lower than the national standards; the enrichment coefficients of heavy metals in crops were generally small, and were mainly in the following order: tea > rice > corn. The correlation analysis of the heavy metal contents in the root soil and crops showed that there was no significant correlation among them. Thus, the heavy metals in the soil generally had a high content and low activity, which did not affect the quality and safety of the three crops. However, Cu in corn and CaO in root soil, As in corn seed and Fe₂O₃ in root soil, and Ni in corn seed and Fe₂O₃ in root soil showed significant correlations, whereas As in rice seed and CaO in root soil and Hg in rice seed and MgO in root soil showed significant correlations, and no significant correlations were found in tea.