中原油田周边农田重金属含量特征、来源解析与风险评估

以中原油田周边农田为研究对象,分析了360个土壤表层(0~20 cm)样品中As、Cd、Pb、Cu、Zn、Ni、Cr含量,基于地统计法研究了土壤重金属的空间分布规律,利用内梅罗综合污染指数法、地累积指数法和Hakanson潜在生态危害指数法评价了农田土壤重金属污染的潜在生态风险程度,利用多元统计分析法解析了土壤中重金属的来源。结果表明:土壤重金属的空间分布具有显著特征,Zn、Cr含量平均值是河南省土壤背景值的1~2倍且存在积累效应,其余重金属含量均低于河南省背景值;所有元素的变异系数均小于1,属于轻微变异性,Kolmogorov-Smirnov检验结果均为显著(P<0.05),呈非正态分布,该区域土壤受人类活动的轻微影响;土壤重金属存在潜在生态风险且总体处于轻微水平,Cd风险指数范围为18.1~69.6,存在轻微至强生态风险,轻微风险指数占96%,为该研究区域土壤的主要生态危害元素;土壤中Ni、Cr、Cd的含量存在一定的相关性,主要受成土母质及地质活动的影响,As、Cu、Pb等重金属元素受油田开发、农业生产和当地居民生活污染等人类活动的影响;研究区土壤重金属含量都处于清洁范畴,仅0.3%的检测结果超过风险筛选值(GB 15618—2018);受自然积累和人类活动影响,研究区的Cr、As、Cd存在一定的潜在生态风险,但土壤环境质量总体处于安全水平。

Characteristics,source analysis and risk assessment of heavy metal content in farmland around Zhongyuan Oilfield

Based on the analysis of As,Cd,Pb,Cu,Zn,Ni and Cr contents in 360 soil surface samples(0~20 cm)surrounding Zhongyuan Oilfield,the spatial distribution of heavy metals in the soil was analyzed by geostatistics,the potential ecological risk of heavy metal pollution in farmland soil was evaluated by Nemero comprehensive pollution index,geo-accumulation index and Hakanson potential ecological harm index,and the sources of heavy metals in soil were analyzed by multivariate statistical analysis.The results show that heavy metals in soil has significant characteristics of spatial distribution.The average content of Zn and Cr is 1~2 times of the background value of soil in Henan with accumulation effect,however,the contents of other heavy metals are lower than the background value.The coefficients of variation(CV)of all elements are less than 1,which belongs to slight variability.The results of Kolmogorov Smirnov test are all significant(P<0.05)with non normal distribution,which indicates that the soil in this area is slightly affected by human activities.Soil heavy metals have a slight level of potential ecological risk.The Cd risk index ranges from 18.1 to 69.6 with a slight to strong ecological risk.It is the main ecological hazard element in the study area with a risk index accounting for 96%.The contents of Ni,Cr and Cd in the soil have a certain correlation,which is mainly affected by the parent material and geological activities.The contents of As,Cu,Pb and other heavy metal elements are affected by human activities such as oilfield development,agricultural production and domestic pollution of local residents.Only 0.3%of the test results exceed the risk screening value(GB 15618—2018),and the rest are in the cleaning category.Influenced by natural accumulation and human activities,Cr,As and Cd have certain potential ecological risk,but the soil environmental quality is at a safe level in generally.