城市生活垃圾填埋场垃圾-土壤-植物中汞含量的分布特征

在贵阳和武汉市的4座城市生活垃圾填埋场,研究了其中的生活垃圾、土壤和植物中的汞含量分布特征。结果显示,城市生活垃圾的汞含量分布极不均匀,浓度为0.170~46.222 mg.kg-1,几何均值0.574 mg.kg-1,一半以上的样品汞含量低于0.5 mg.kg-1,个别含量异常偏高,可能是被混入的含汞废弃产品污染了,而各个填埋场的垃圾汞含量几何均值相差不大。不同垃圾填埋场覆盖土壤的汞含量差异显著,反映了填埋场所在区域的土壤背景值以及垃圾填埋活动对覆盖土壤的污染程度,有时覆盖土壤的汞含量超过区域土壤背景值的2~23倍。填埋场附近的农田土壤存在一定的汞污染迹象。填埋场生长的植物因生活习性的不同汞含量分布特征也不同,无喙齿冠草为叶>根>茎,狗牙根和硬质早熟禾为地下部分>地上部分。随着填埋场运行时间的增长,附近生长的苔藓汞含量不断升高,封闭填埋场种植的玉米果实有一部分汞含量超过了食用标准,这些都说明填埋场的运行会给周围的生态环境带来一定的汞污染风险。

DISTRIBUTION CHARACTERISTICS OF MERCURY IN THE WASTE,SOIL AND PLANT AT MUNICIPAL SOLID WASTE LANDFILLS

Mercury(Hg) in waste,soil and plant were analyzed at four municipal solid waste(MSW) landfills in Guiyang and Wuhan City,China.The results shown that Hg in MSW was highly heterogeneous,with range of 0.170-46.222 mg·kg~(-1) and geometric mean(GM) of 0.574 mg·kg~(-1),more than half of the samples with Hg concentration less than 0.5 mg·kg~(-1),some samples with extremely high Hg content which may be polluted by the co-disposal of Hg-bearing waste products.Hg GM concentration of MSW was roughly equal at different landfills.Hg in cover soils varied distinctively between different landfills,reflecting the local soil background and the pollution extent caused by MSW disposal activities,in some cases,Hg content was 2 to 23 times higher than the local soil background. Agricultural soils nearby the landfills also exhibited a sign of Hg pollution.Hg distribution pattern was dissimilar in different plants growing on the cover soils,with leaf > root > stem in Myriactis nepalensis,underground parts > aboveground parts in Cynodon dactylon and Poa sphondylodes.Hg concentration in moss growing nearby one operational landfill increased obviously with the landfill operation duration,and Hg in part of corn seeds from a closed landfill exceeds the national edible threshold for grains,this indicated that there have Hg pollution risk associated with MSW landfilling.