贵州省煤矿区污染农田重金属累积与迁移对生态环境的影响

Influence of accumulation and migration of heavy metals in polluted farmland on ecological environment in coal mining area of Guizhou province

通过对贵州省中西部3个煤矿区煤矸石堆场周边污染农田进行调查与采样分析,探讨污染农田土壤重金属累积与迁移对生态环境的影响。结果表明,煤矿区污染农田土壤中Cd、Hg含量分别高于农用地土壤污染风险筛选值(水田)的2.20~9.33倍、0.34~2.48倍,86.7%的污染农田中Cd含量水平高于农用地土壤污染风险管控值,煤矿区造成农田污染的重金属元素首要是Cd,其次是Hg,再次是Cu、Cr。调查对应的污染农田排水中Cd含量都超过地表水环境质量Ⅲ类水质标准值或农田灌溉水质标准一类限值(水作),而Hg含量均超过地表水环境质量Ⅲ类水质标准值,污染农田排水对周边水体质量的影响主要是Cd、Hg。此外,调查区稻米中Cd、Hg、As含量分别是食品安全国家标准中污染物限量值的0.74~1.77倍、0.45~1.35倍、0.50~1.16倍,超标率分别为73.3%、33.3%和20.0%,煤矿区污染农田中生产的稻米出现明显的Cd污染及一定程度的Hg、As污染。

Through the investigation and sampling analysis of the polluted paddy soil around the gangue yard in three coal mines in midwestern Guizhou province,the impact of heavy metal accumulation and migration on the ecological environment in polluted farmland was discussed.The results showed that the content of Cd and Hg in polluted paddy soil in coal mining area was higher than the soil pollution risk screening value of 2.20~9.30 times and 0.34~2.48 times for agricultural land,respectively;which the content of Cd in 86.7%of farmland was higher than the control value of soil pollution risk of agricultural land.So the element that causes heavy metal pollution in farmland around the coal gangue yard was Cd first,Hg second,and Cu and Cr third.The content of Cd in the drainage from contaminated farmland around gangue yard was exceeded the limit of class III water quality standard of surface water or the standard of farmland irrigation water quality,and the content of Hg in drainage was exceeded class III water quality standard of surface water,so the heavy metal that affected the change of water quality was mainly Cd,followed by Hg.In addition,the contents of Cd,Hg and As in rice in the survey area were 0.74~1.77 times,0.45~1.35 times and 0.50~1.16 times of the limit value of pollutants in the national food safety standard,respectively;and the exceeding rates of Cd,Hg and As were 73.3%,33.3%and 20.0%,respectively,which indicated significant Cd pollution and a certain degree of Hg pollution occured in rice from the polluted paddy soil in coal mine areas.