城乡过渡区土壤-蔬菜中重金属耦合分异特征及形成机理解析

Geographic Distribution and Source Apportionment of Heavy Metals in Soils and Vegetables in Urban Fringe

重金属污染农业土壤已成为关系粮食安全和人类健康风险的全球性问题。采集天津市武清区的95个农田表层土壤样品和相应的34个蔬菜样品、20个有机肥样品、27个灌溉水样品,并对上述4类样品中Pb、Cu、Cr、Ni、Zn、Cd和As含量进行测定。基于地统计法分析农田土壤重金属的空间分布规律,探索土壤和蔬菜重金属的累积、潜在生态风险以及土壤中重金属的来源。结果表明,Cd和As是土壤主要污染物,Cd在土壤中的有效性最高,其在蔬菜中的平均含量略高于允许阈值(0.02 mg·kg^(-1));蔬菜富集指数显示,Cd和Pb是蔬菜中占主导地位的重金属污染元素,蔬菜对Cd有较强的富集能力;土壤重金属的空间分布特征显示,污染具有不均性,各重金属元素在部分地区出现高值区,表明人类活动对农田土壤环境产生负面影响;根据正定矩阵因子分析模型(PMF)的分析结果,潜在污染源为工业活动(Cd)、农药化肥和地膜影响(As和Pb)、自然来源(Ni、Cu、Cr和As)、有机肥(Zn和Cu)、交通排放(Pb和Cd)以及污水灌溉(Cr、Ni和Pb);造成重金属累积的主要成因是工业活动,包括大气沉降以及工业废水、废渣与废气等排放。

Contamination of agricultural soil by heavy metals has become a global issue concerning food security and human health risk.A total of 95 surface soil samples(bulk soil),34 vegetable samples,27 irrigation water samples,and 20 fertilizer samples were collected from Wuqing District,Tianjin,China.The concentrations of heavy metals(i.e.,As,Cd,Cu,Cr,Ni,Pb,and Zn)in these samples were tested.After determining the metal accumulation and potential ecological risks in farmland soil,kriging interpolation and positive matrix factorization(PMF)were used to identify and quantify the sources of soil heavy metals.The results showed that(1)Cd and As were the main contaminants in the soil in the studied area,and Cd had the highest effectiveness in soil,with its average content in vegetables slightly higher than the allowable threshold(0.02 mg·kg^(-1)).(2)The results of the enrichment index of vegetables show that Cd and Pb were the dominant heavy metals in vegetables,and vegetables had a strong enrichment ability to Cd.(3)The spatial distribution of heavy metals in the soil showed that the contaminants were non-homogeneous,and all the heavy metals showed high-value areas in some parts of the studied area,indicating the negative effects of human activities on the soil environment of farmlands.(4)Industrial activity(for Cd),effects of pesticides,fertilizers,and plastic film mulching(for As and Pb),natural sources(for Ni,Cu,Cr,and As),Organic fertilizer(for Zn and Cu),traffic discharges(for Pb and Cd)and sewage irrigation(for Cr,Ni,and Pb)were ascertained as the potential sources based on the Positive matrix factorization(PMF)analysis results.(5)The accumulation of heavy metals in the studied area was mainly caused by industrial activities,including atmospheric deposition,the discharge of industrial waste water,the disposal of waste residue,and the emission of waste gas,and so on.