大宝山矿区农田土壤重金属污染及其植物累积特征

对金属矿山选冶活动影响的农田土壤,不同灌溉水源会影响重金属的分布累积特征。根据实际情况将大宝山矿区农田土壤分为污水灌溉区、清水灌溉区、自然修复区和对照区,并进行土壤和植物样品采集,调查研究了土壤的基本理化性质,Cd、Pb、Cu、Zn、Mn 5种重金属的含量和化学形态分布,以及不同区域植物中重金属的含量。结果表明:污灌区Cd、Pb、Cu、Zn的含量最高,是自然修复区和清水灌溉区的1.75倍~10.51倍,对照区最低;Mn在各采样点的含量无显著差别。土壤Cd、Cu、Zn、Pb含量两两之间显著正相关,Mn与Cu、Zn、Cd、Pb呈负相关关系;土壤pH与重金属环境有效态关系密切。残渣态是5种重金属的主要存在形态,有机态含量也较高;Cd的环境有效态含量占总量的比例是其他4种重金属的2倍左右。稻米中5种重金属在清水灌溉区的含量均比污水灌溉区低,其中Cu和Zn的含量在两区域均未超标(NY861-2004),而Pb和Cd的含量严重超标。重金属在自然修复区和清水灌溉区呈现较低的土壤污染和人体健康风险,该研究数据可为金属矿区土壤污染控制提供科学的依据。

Characteristics of Heavy Metal Pollution in Agricultural Soils and Bioaccumulation in Plants of Dabaoshan Mine

The distribution and cumulative characteristics of heavy metals in agricultural soils caused by mining activities are different. Samples of agricultural soils and plants were collected from 4 districts according to the sources of irrigation water, that is, sewage irrigation area, clean water irrigation area, natural remediation area and contrast area. The contents of extractable fractions of Cd, Pb, Cu, Zn, and Mn, soil physical-chemical properties and heavy metal contents in plants were analyzed. The results showed that: 1) The contents of Cd, Pb, Cu and Zn are the lowest in the contrast area and highest in the sewage irrigation area, which were 1.75-10.5 times of those of clean water irrigation area and natural remediation area. The contents of Mn in all soil samples were nearly the same. 2) Significant correlations existed among Cd, Cu, Zn and Pb, while significant negative correlations existed between Mn and other 4 heavy metals. Moreover, correlation analysis indicated that soil pH played a significant role in the contents of environmental available states of the studied 5 heavy metals. Soil organic matter content and mechanical composition also affected the contents of heavy metals in soil. 3) Residual fraction was the major fraction of all the 5 heavy metals and organic matter binding fraction was relatively high in all the sampling sites. The contents of environmental available state of Cd were about 2 times those of other studied heavy metals. 4) The contents of Mn, Cu, Zn, Cd and Pb in rice were lower in clean water irrigation area than those in sewage irrigation area. The contents of Cu and Zn in rice were within the standard limit in NY861-2004, while those of Pb and Cd far exceeded the corresponding limits. 5) The heavy metals in clean water irrigation area and natural remediation area exhibited significantly lower risk of soil pollution and human health. The data will provide scientific basis in mine environmental pollution control.