喀斯特高原石漠化治理示范区土壤和农作物重金属含量特征

通过采集贵州毕节撒拉溪石漠化治理示范区土壤和主要农作物样品,分析了土壤和农作物样品中重金属Cr,Co,Cu,Cd, Pb,Zn,As和Ni含量,采用富集因子评价了土壤中重金属的污染状况,并分别采用潜在生态风险指数(RI)和生物富集系数评价了示范区土壤重金属的潜在生态风险和农作物对重金属的富集特征.结果表明,示范区土壤中Cr,Co,Cu,Cd,Pb, Zn,As和Ni平均含量分别为123,28.0,67.8,1.52,32.7,132,25.6和56.5mg/kg,除Cd外,其他均低于农用地土壤污染风险筛选值;其中森林土重金属污染程度的评价等级均为无污染-轻度污染,旱地土中Cd和Cu个别样点存在中度污染,其他均为无污染-轻度污染.潜在生态风险评价结果表明,示范区土壤重金属Cr,Co,Cu,Pb,Zn,As和Ni的单项潜在危害指数分别为1.23,4.67,3.39, 1.36, 0.53,8.54和2.83,潜在危害等级均为轻微生态危害,Cd的单项潜在危害等级为中等生态危害,8种重金属的综合生态危害等级为轻微生态危害.Cd在土豆中的生物富集系数为4.05,其他重金属的富集系数均小于2.不同农作物对土壤中不同重金属的富集能力有较大差异,其中Cd,Zn,Co,Cu, Pb和Ni在土壤-土豆系统中的迁移富集能力相对较高,Cr和As在土壤-玉米系统中的迁移富集能力相对较高,其他农作物对重金属的迁移富集能力较弱.

Contents of heavy metals in soils and crops in the demonstration area of karst rocky desertification control of the Karst Plateau-Gorge

In this study, we collected samples of agriculture soils and dominant crops in Salaxi of Bijie Guizhou Province, and analyzed the contents of heavy metals Cr, Co, Cu, Cd, Pb, Zn, As, and Ni in soil and crop samples. The enrichment factor were calculated to assess the pollution status of soils and crops. Furthermore, the potential ecological risk index (RI) and bioconcentration coefficient were used to evaluate the potential ecological risk of soil heavy metals and the characteristics of crops' heavy metal enrichment in the demonstration area.The results showed that the average contents of Cr, Co, Cu, Cd, Pb, Zn, As, and Ni in the soil of the demonstration area were 123, 28.0, 67.8, 1.52, 32.7, 132, 25.6, and 56.5mg/kg, all elements are below the risk screening values for soil contamination of agricultural land, except Cd. Among them, the evaluation grade of heavy metal pollution in forest soil is non-pollution-slight pollution, individual samples of Cd and Cu in dry land soil have moderate pollution, and the others are non-pollution-light pollution. The results of potential ecological risk assessment showed that the moderate ecological risk was posed by Cd. Followed by Cr, Co, Cu, Pb, Zn, As and Ni were all of low ecological risk, and the comprehensive ecology of 8heavy metals the risk level is minor ecological risk.Meanwhile,the bioconcentration factor of Cd in potatoes is 4.05, and the enrichment factor of other heavy metals is less than 2.Through this study, we can know that different crops have different heavy metal enrichment capacities in the soil. Among them, Cd, Zn, Co, Cu, Pb and Ni have relatively high migration and enrichment capacities in the Soil-Potato system, Cr and As have relatively high migration and enrichment capacities in the Soil-Maize system, while the remaining crops have relatively weak heavy metal enrichment capacities.