不同年限和利用类型复垦煤矸山土壤重金属污染评价

为研究不同复垦年限和不同土地利用类型对复垦煤矸山土壤重金属污染的影响,以山西省霍州市曹村煤矿复垦煤矸山为例,以3种复垦年限(3、5和7 a)和4种土地利用类型(农田、菜园、果园和退化荒地)的复垦样地为研究对象,分析了土壤重金属Hg、Cd、Pb、As和Ni的质量分数,并运用内梅罗指数法对其污染状况进行了评价。结果表明,(1)随年限的增加,复垦地0~40 cm土层含Pb量和含Ni量以及20~40 cm土层含As量均呈增加趋势,单因子污染指数和综合污染指数也呈现类似趋势。同时,煤矸山复垦地土壤重金属质量分数均不同程度地高于当地普通农田,尤其在20~40 cm土层表现更明显。(2)利用类型对复垦地土壤重金属也有影响,复垦3 a菜地土壤含Hg量和含Pb量高于或等于复垦3 a农田,但含Cd量、含As量和含Ni量低于或等于复垦3 a农田。复垦7 a退化荒地含As量高于复垦7 a果园,Hg、Pb元素的单因子污染指数以及所有5种元素的综合污染指数也偏高,表明与撂荒状态的土地相比,复垦后种植植物可在一定程度上降低土壤中的重金属危害。

Evaluatingthe Impact of Time after Starting Remediation of Coal-waste Piles Using Plants on Change of Heavy Metals in Soils

Soil contamination by heavy metals occurring inreclaiming coal-waste piles by planting cropsis a key environmental process and affected by many processes.To investigate the impact of the types of plants on soil contamination,four land uses-arable crops,vegetables,orchard and fallow-were tested in Cao Village of Shanxi Province to study the change in heavy metals three years,five years and seven years after the remediation started.The contents of five heavy metals:Hg,Cd,Pb,As and Ni were measured and their pollution levels were evaluated using the Nemerow index method.The results showed that the contents of the five heavy metals increased significantly with time after the remediation started.The contents of Pb and Ni increased in the top 0～40cm soil;the single pollution index and the Nemerow index increased in the 20～40 cm soil.It was found that the contents of the five metals in the remediated soil is higher than those in the ordinary arable soil,especially in the 20～40 cm.Land usage affected heavy metal pollution and the contents of Hg and Pb were higher in the vegetable field than in the arable soils,while the content of Ni was lower in the vegetable and than in the arable land three years after remediation started.Seven years after the remediation,the contents of Pb and Ni,as well as their single pollution index and Nemerow index,in the fallow soil are higher than those in the orchard,suggesting that,compared with the fallow,vegetation can reduce heavy metal pollution.