云贵地区磷矿分布区农田土壤重金属污染特征及对农产品质量的影响

Characteristics of Heavy Metal Pollution in Soils of Yunnan-Guizhou Phosphate Ore Areas and Their Effects on Quality of Agricultural Products

为了解云贵地区磷矿背景下农田土壤重金属污染和生物有效性特征,对云贵地区重点磷矿分布区玉米、水稻和设施蔬菜3种农田土壤和作物可食部分重金属(Cd、Cu、Pb和Zn)含量进行测定,分析农田土壤重金属污染特征,并探究其对农产品重金属含量的影响。结果表明,云贵地区磷矿分布区农田土壤普遍富集Cd和Pb,与当地背景值相比,Cd和Pb的平均富集系数分别达到2.31和2.39;玉米、水稻和大棚青菜可食部分中Cd的生物富集因子平均值分别为0.09、0.17和0.32,而Pb的生物有效性水平较低;磷矿分布区不同类型农作物对土壤重金属的吸收能力不同,大棚青菜对重金属的富集能力最强,水稻对Cd和Pb的吸收能力高于玉米;回归模型结果表明,土壤有效态重金属含量以及pH、有机质和MgO等理化性质显著影响3种农作物可食部分重金属含量(P<0.05)。

In order to understand the contamination characteristics and bioavailability of heavy metals in the areas with abundant phosphate ore mines,the concentrations of Cd,Cu,Pb and Zn in samples of farmland soils and samples of different crops such as maize,rice and vegetables collected from Yunnan and Guizhou phosphate ore mine areas were determined and then the pollution characteristics of soils were evaluated.The regression equations were used to explore the effect of available heavy metals and soil properties on the quality of the agricultural products.The results show that Pb and Cd were enriched in most soil samples,the average enrichment factors of Cd and Pb reached to 2.31 and 2.39,respectively,compared to the local background values.About 84.8%and 28.3%of soil samples were polluted by Cd and Pb,respectively,and Pb concentrations were markedly higher than that of the farmland soils of other geological high background areas.The average biological accumulation factors of Cd in maize,rice and leaf vegetables were 0.09,0.17 and 0.32,respectively.The soil Pb bioavailability in the studied area was lower than those in other high background areas.The crops had different abilities to absorb heavy metals,and the Chinese cabbage had the largest absorbing ability to four heavy metals and the absorbing ability of rice to Cd and Pb were higher than those of maize.It is not advised to plant Chinese cabbage in those areas,and the risks of Cd and Pb that exceeding the safety limits in crops should be considered.Correlation analysis and regression equations show that available heavy metals,along with pH,organic matters,and MgO in soils were the key factors affecting the accumulation of heavy metals in crops(P<0.05).