蚌埠及周边地区土壤和蔬菜的重金属污染研究
Heavy metal pollution in soil and vegetables in Bengbu City and its vicinities
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摘要:
目的 了解蚌埠市及周边地区土壤和蔬菜重金属污染状况，并对其潜在生态危害进行评价，为该地区土壤重金属污染防治及无公害蔬菜生产提供科学依据。
方法 以蚌埠市及周边地区土壤和蔬菜为研究对象，2013年3月采集7个不同区域的56个土样和4个不同区域的15个蔬菜样品，经四酸（HCl-HNO3-HF-HClO4）消解处理后，用原子吸收法测定土壤和蔬菜样品铬（Cr）、镉（Cd）、铜（Cu）和铅（Pb）含量，用原子荧光法测定土样砷（As）含量。采用单因子污染指数法和潜在生态风险指数法对蚌埠市及周边地区土壤进行评价。
结果 蚌埠市及周边地区土壤和蔬菜受到不同程度的重金属污染，其中土样Cr、Cd、Cu、Pb和As含量中位数分别为65.94（30.91~119.88）、4.39（0.74~8.84）、18.64（0.25~63.62）、90.94（48.47~171.04）和0.62（0.13~1.90）mg/kg；蔬菜（鲜重）Cr、Cd、Cu和Pb含量中位数分别为1.71（0.17~11.42）、0.97（0.08~3.78）、1.39（0.03~8.24）和1.44（0.19~5.40）mg/kg。蔬菜（鲜重）中Cr、Cd和Pb含量与标准（GB 2762—2012）中相应元素含量限值的比值分别为3.43、5.21和6.39，存在食品安全风险。蔬菜对Cr、Cd、Cu和Pb的富集系数均小于1，富集能力由大到小，叶菜类依次为Cd > Cu > Cr=Pb，块茎类依次为Cd > Cu > Cr > Pb。单因子污染指数法评价结果显示，土壤受Cd污染严重，各重金属污染程度由大到小呈Cd > Pb > Cr > Cu > As变化。潜在生态风险评价结果，土样中Cr、Cu、Pd和As均表现为轻微潜在生态危害，Cd为强潜在生态危害，各重金属潜在生态危害程度从大到小呈Cd > Pb > Cu > Cr > As变化，综合潜在生态危害为中等危害程度。
结论 蚌埠市及周边地区土壤和蔬菜存在重金属污染风险，所产蔬菜存在食品安全隐患。
Abstract:Objective To understand heavy metal pollution in soil and vegetables in Bengbu City and its vicinities, evaluate potential ecological hazards, and provide scientific basis for the prevention and control of soil heavy metal pollution and the production of pollution-free vegetables in studied areas.
Methods A total of 56 soil samples from 7 sampling sites and 15 vegetable samples from 4 sampling sites were collected in Bengbu City and its surrounding areas in March 2013. After the samples were digested by four acids (HCl-HNO3-HF-HClO4), the contents of Cu, Cr, Cd, and Pb in soil or vegetable samples were measured by atomic absorption spectrometry, and the contents of As in soil samples by atomic fluorescence spectrometry, respectively. Single-factor pollution index and potential ecological risk index were used to evaluate heavy metal pollution in studied areas.
Results The results showed that the soil of Bengbu city and its surrounding areas were polluted by heavy metals to varying degrees in this study. The median levels (ranges) of Cu, Cr, Cd, Pb, and As in soil samples were 65.94 (30.91-119.88), 4.39 (0.74-8.84), 18.64 (0.25-63.62), 90.94 (48.47-171.04), and 0.62 (0.13-1.90) mg/kg, respectively. The median levels (ranges) of Cu, Cr, Cd, and Pb in vegetable samples (fresh weight) were 1.71 (0.17-11.42), 0.97 (0.08-3.78), 1.39 (0.03-8.24), and 1.44 (0.19-5.40) mg/kg, separately. The contents of Cr, Cd, and Pb in vegetables (fresh weight) exceeded the limits stipulated in the Standard of Limits on Contaminants in Food(GB 2762-2012) and the ratios were 3.43, 5.21, and 6.39, respectively, indicating that there was food safety risk. The enrichment coefficients of vegetables for Cr, Cd, Cu, and Pb were all less than 1, and the enrichment capacities were ranked as Cd > Cu > Cr=Pb in leaf vegetables and Cd > Cu > Cr > Pb in tuber vegetables, respectively. The single-factor pollution index evaluation showed that the soils were seriously polluted by Cr, with a high-to-low order of Cd > Pb > Cr > Cu > As according to contamination degrees of the 5 heavy metals. The results of ecological risk assessment showed that the potential ecological hazards of Cr, Cu, Pd, and As in the soil were all slight, but the potential ecological hazard of Cd was very strong, with a high-to-low order of Cd > Pb > Cu > Cr > As; however, the comprehensive potential ecological hazard was moderate.
Conclusion There are risks of heavy metal pollution in soil and vegetables in Bengbu City and its vicinities, and there are also food safety hazards in vegetables.
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