贵州水城煤矸石风化土壤-农作物系统中汞分布规律研究

Distribution of Mercury Species in the Soils from Weathered Coal Mine Spoils and Crops in Shuicheng,Guizhou Province,China

通过冷原子荧光方法测定了贵州水城汪家寨煤矿和那罗煤矿不同年限的煤矸石风化土壤及农作物中总Hg含量和甲基汞含量,并采用BCR连续提取法分析了煤矸石风化土壤中汞的不同赋存形态,系统地对此矿区煤矸石风化土壤-农作物系统中汞的分布规律及其环境效应进行了研究。结果表明,煤矸石风化土壤样中汞含量范围在0.07～1.06 mg.kg-1之间,和pH值存在显著负相关关系(r=-0.68,P<0.01)。风化年限较长的煤矸石土壤汞浓度接近对照点自然土壤汞含量,而在风化年限较短的煤矸石风化土壤中,大部分样品汞浓度超过了国家Ⅱ类土壤环境标准,不宜在上面种植食用的农作物。煤矸石风化土壤中甲基汞含量在0.52～2.68μg.kg-1之间,和总汞存在显著正相关关系(r=0.65,P<0.05)。煤矸石风化土壤中汞主要以有机/硫化态和残渣态存在,风化年限较短的煤矸石山土壤中酸交换态汞浓度及比例都明显高于老煤矸石山。虽然汪家寨煤矿风化年限较短的煤矸石山土壤存在着较高的汞含量,但其上种植的马铃薯、玉米、菜豆的汞含量均没有超过国家标准食品中Hg限量值,然而高于风化年限较长的煤矸石山中同类植株的汞含量。

The distributions of mercury（Hg）in the soils-crops system from weathered coal mine spoils and environmental impacts on the study area in Shuicheng,Guizhou Province,China were studied and discussed in detail.Hg and methyl mercury in soils and the crops from weathered coal mine spoils were measured using cold vapor atomic fluorescence technique.And occurrence mode of Hg were analyzed using the BCR method.The results showed that total Hg concentrations in the soils from weathered coal mine spoils changed from 0.07 to 1.06 mg.kg-1,and negatively correlated with pH（r=-0.68,P0.01）.Total Hg concentrations in the soils from coal mine spoils with long-term weather-ing process were in the same lever with those in the background soils.Total mercury in the soils from coal mine spoils with short-term weath-ering process,however,exceeded the national environmental quality standard for soils Ⅱ.Thus,these fields were condemned unfit to grow crops.Methyl mercury in the soils from the weathered coal mine spoils changed from 0.52 to 2.68 μg.kg-1,and correlated positively with total mercury concentrations（r=0.65,P0.05）.The proportions of methylmercury to total mercury in these soils were higher than those in nature soils with mercury pollution or no pollution.The BCR results showed Hg mainly existed in residual fraction and organic/sulfide fraction.The exchangeable mercury fractions in the soils from coal mine spoils with short-term weathering process were slightly higher than those in the soils from coal mine spoils with long-term weathering process.There were relatively higher mercury concentrations in the soils from coal mine spoils with short-term weathering process,but mercury concentrations in Solanum tuberosum,corn,and phaseolus vulgaris.L in these areas did not exceed the national standard,and were higher than those in the same plant species in the soils from coal mine spoils with long-term weathering process.