石家庄市栾城区农田土壤重金属分布特征及作物风险评价

Distribution Characteristics and Risk Assessment of Heavy Metal Pollution in Farmland Soils and Crops in Luancheng,Shijiazhuang City

为探讨栾城区内农田土壤重金属的分布特征,对表层土壤As、Cd、Cr、Cu、Hg、Ni、Pb和Zn这8种重金属污染特征、空间分布和污染风险进行分析,并使用PMF模型进行污染源解析,探讨栾城区土壤管控方案.进一步检测作物中重金属含量,利用概率风险评价方法评价研究区农产品的非致癌健康风险,为栾城区内农田土壤重金属污染治理与防控提供理论基础.结果表明,表层土壤ω(Cd)、ω(Cr)、ω(Cu)、ω(Pb)和ω(Zn)分别为0.06~1.08、22.14~473.47、12.83~150.74、10.75~577.72和62.23~652.78 mg·kg^(-1),点位超标率分别为1.83%、1.22%、0.61%、0.61%和1.22%.此外,部分区域土壤中的重金属有向作物中转移并积累的现象,小麦籽粒Cd和Pb含量超标率分别为2.13%和5.32%,玉米籽粒Cd含量超标率为1.20%.健康风险评价结果表明,栾城区玉米的复合非致癌健康风险(TTHQ)小于1,对人体没有明显的负面影响,食用研究区小麦的复合非致癌风险(TTHQ>1),对人体产生负面影响的可能性较大.土壤中重金属的空间分布受工业区涉污企业分布的影响,8种重金属含量较高的区域均主要分布在工业企业较集中的中部、西部和南部.总体而言,研究区大部分表层耕地土壤未受到明显的重金属污染,存在中等强度(2级)的生态危害.Cd为无-中度污染(1级),Cd和Hg存在中等强度潜在生态风险(2级),其余重金属均为无污染,低潜在生态风险(1级).根据PMF污染源解析结果和实地调查推测,土壤重金属主要来自土壤母质(52.05%),历史污灌和工业生产的人为污染源(32.98%)和大气沉降(14.97%).综上所述,研究区北部和东部土壤重金属含量较低,应划分为优先保护类,研究区西部、中部和南部部分点位重金属含量超标,其来源主要为化工、涂料、机械装备等企业,应划分为安全利用类,严控污染物的输入,采用农艺调控等措施,减少重金属向农作物的转移,降低食品安全健康风险.本研究将有助于栾城区土壤的分级治理和污染管控.

In order to explore the distribution characteristics of heavy metal contamination of farmland soil surrounding Luancheng town,Shijiazhuang City,Henan province,the concentrations of As,Cd,Cr,Cu,Hg,Ni,Pb,and Zn in the surface soil and crops were determined and assessed.The principal components were also analyzed for source apportionment.The heavy metal concentrations in crops were further detected,and the non-carcinogenic health risks in the study area were evaluated using the probabilistic risk assessment method,as to provide a theoretical basis for the treatment,prevention,and control of heavy metal pollution in farmland soil in Luancheng.According to the results,ω(Cd),ω(Cr),ω(Cu),ω(Pb),andω(Zn)in the soils were 0.06-1.08,22.14-473.47,12.83-150.74,10.75-577.72,and 62.23-652.78 mg·kg^(-1),which exceeded the standard with over-standard rates reaching 1.83%,1.22%,0.61%,0.61%,and 1.22%,respectively.Further,Cd and Pb were transported into crops,in which Cd concentrations exceeded the standard in some corn samples,and Cd and Pb concentrations exceeded the standard in some wheat samples.The total non-carcinogenic health risks(TTHQ)to the human body caused by the consumption of heavy metals in corn grown in the study area were all less than 1,with no obvious negative effects,and TTHQ was higher than 1 in wheat,increasing the likelihood of negative impacts on the human body.With the influence of the distribution of pollution-related enterprises in the industrial zone,heavy metal concentrations were higher in the south,west,and middle directions of the study area.Among them,the study area soil was slightly contaminated by Cd(Level 1).Cd and Hg had a slight potential ecological risk(Level 2),whereas other heavy metals had low potential ecological risk(Level 1).In general,most of the surface cultivated soil was not obviously polluted by heavy metals in the study area.According to the PMF results and survey,we speculated that soil heavy metals mainly came from soil parent material(52.05%),artificial pollution sources(historical sewage irrigation and industrial manufacture)(32.98%),and atmospheric deposition(14.97%).To summarize,the study area should be divided into a priority protection category and safe utilization category.The input of pollution sources should be strictly controlled for the priority protection category,and alternative planting,rotating,and fallow should be implemented for the safe utilization category to reduce the risk of standard-exceeding agricultural products.