环鄱阳湖区农田土壤重金属空间分布及污染评价

Spatial distribution and pollution assessment of heavy metals in farmland soils in Poyang Lake area

为了解环鄱阳湖区农田土壤重金属污染状况,采用单因子指数法、内梅罗指数法、地质累积指数法、潜在生态危害指数法对环鄱阳湖区农田表层土壤(0~20 cm)中7种重金属元素进行污染及生态风险评价,并将地统计学方法与GIS技术相结合分析环鄱阳湖区农田土壤重金属的空间分布特征.结果表明:(1)土壤中重金属Hg、As、Pb、Cd、Cu、Cr、Zn的平均含量分别为0.12、13.15、35.44、0.18、38.45、81.91、80.45 mg·kg^(-1),与江西省土壤环境背景值相比较,均有不同程度累积,Cr、Cu、Cd累积富集情况最严重,内梅罗指数法与潜在生态危害指数法评价结果均表明,环鄱阳湖区土壤重金属综合污染情况为轻度污染,鄱阳县、进贤县、乐平市、南昌县、万年县、新建县以及余干县累积污染情况较严重.(2)以国家土壤环境质量二级标准为评价标准,超标率12.24%=Cu>Cd>As>Hg>Cr=8.85%>Zn>Pb,表明研究区部分农田土壤样点Cu、Cd、As、Hg、Cr累积程度已威胁到农作物产量和质量,但总体上为清洁状态.土壤中Hg、Cd达到中等生态危害程度,研究区农田土壤中重金属总体表现为轻微危害程度.(3)半方差函数模型拟合结果显示,Hg、Pb、Cr、Zn符合指数模型,As符合球状模型,Cu、Cd符合线性模型.As、Pb、Cd、Cu的含量总体上呈现出东部地区高、西部地区低的趋势,主要在鄱阳县、乐平市、万年县及余干县等地富集.Zn的含量在中北部地区偏低、在东南部地区较高,乐平市、万年县富集相对严重.Hg、Cr是由西南地区向东北地区递减的梯度变化,两种重金属元素均主要在南昌市各县区累积.

To explore the contamination status of heavy metal in farmland soils in Poyang Lake area,single factor index method,Nemerow comprehensive index method,geo-accumulation index method and potential ecological risk index method were used to assess the pollution degree and ecological risk of seven heavy metal elements in the surface soil（ 0 - 20 cm） in Poyang Lake area,and geostatistics method and GIS technology was applied to analyze the spatial distribution of soil heavy metals. The results showed that：（1）The average contents of heavy metal Hg,As,Pb,Cd,Cu,Cr and Zn in soils were 0.12,13.15,35.44,0.18,38.45,81.91 and 80.45 mg·kg-（-1）,respectively. Compared with the soil environmental background values of Jiangxi Province,the seven kinds of heavy metal elements accumulated in different degrees,and the accumulation of Cr,Cu and Cd were the most serious. Nemerow comprehensive index method and potential ecological risk index method showed that the comprehensive pollution degree of soil heavy metals in the Poyang Lake area was slightly,and the cumulative pollution in Poyang County,Jinxian County,Leping City,Nanchang County,Wannian County,Xinjian County and Yugan County were more serious.（2）According to the secondary standard of national soil environmental quality,the rates of exceeding standard were ranked as follow： 12.24% = Cu Cd As Hg Cr = 8. 85% Zn Pb,indicated that the accumulation level of Cu,Cd,As,Hg,Cr has threatened the crop yield and quality,but in general,the farmland soils in the study area was clean. Hg,Cd reached the degree of moderate ecological damage. Overall,the heavy metals in farmland soils in the study area showed a slight degree of ecological damage.（3）Based on the analysis of the semi-variance function,Hg,Pb,Cr and Zn were fit for the exponential model,As was fit for the spherical model,and Cd,Cu was fit for the linear model. The contents of As,Pb,Cd and Cu showed a trend of high in the east and low in the west as a whole,they were mainly accumulated in Poyang County,Leping City,Wannian County and Yugan County. The content of Zn was lower in the middle and north but higher in the south-east,and Zn was mainly accumulated in Leping City and Wannian County. Hg and Cr were decreasing gradient from the south-west region to the north-east region,both two heavy metals were mainly accumulated in the Counties of Nanchang City.