黑龙江省海伦市农田土壤重金属分布特征及污染评价

海伦市是以农业为主导产业的黑龙江省县级市,为了解该市土壤重金属时空分布特征及其污染现状,对农田耕层及亚耕层土壤中Cd、Cr、Cu、Ni、Pb、Zn、Hg和As等重金属全量进行了分析,并采用单因子污染指数法和Nemerow综合污染指数法分别对土壤的重金属污染状况进行了评价。结果表明,该地区土壤重金属含量较低,总体表现为西南和西北含量较高、西部含量高于东部的空间分布特征。以松嫩平原土壤元素背景值为标准进行评价,已出现一定程度的污染。以GB15618-1995土壤环境质量标准二级标准进行评价,综合污染指数为0.504,所有样点土壤重金属均未达到污染水平。与耕层土壤相比,亚耕层土壤Hg和Cd含量显著下降,其他元素含量及分布特征则与耕层相似。从1980年到2008年,随着时间的变化,该区域土壤重金属含量增加趋势不明显,近期土壤出现重金属污染风险较小。

Heavy metals distribution characteristics and pollution assessment in farmland soils of Hailun City, Heilongjiang Province

In order to study the distribution and status of heavy metal pollution in farmland soils of Hailun,a typical agricultural city of Heilongjiang Province,494 topsoil samples and 95 subsoil samples were collected from the farmland.The contents of Cr,Cu,Ni,Pb,Zn,Hg,As and Cd in these soil samples were determined,and monomial pollution index and Nemerow aggregate pollution index were applied to evaluate the topsoil environmental quality.The results showed that the contents of heavy metals were relatively low in most topsoil samples,and the contents in west were higher than in east,especially in southwest and northwest.The contents of several heavy metals in the topsoils were beyond their respective background values,suggesting that some heavy metals were slightly accumulated in the topsoils.According to the Environmental Quality Standard for Soils,the contents of heavy metals in topsoils were below GradeⅡCriterion,and the Nemerow aggregate pollution index was 0.504.The contents of Hg and Cd in subsoil were lower than in topsoil,but other element contents and spatial distribution characteristics of subsoil were similar to those of topsoil.The variation trend of heavy metal accumulation was not evident from 1980 to 2008,and the risk of heavy metal pollution was low in the short term.