露天堆放粉煤灰对地下水的污染研究

Effects of Air Exposed Coal Fly Ash on Groundwater Contamination

中国是煤炭资源非常丰富的国家,大多数火力发电厂均以煤炭为其电力生产的基本燃料,而其副产品粉煤灰则露天露天堆放。粉煤灰中含有的大量重金属和放射性元素是潜在的污染源,尤其是对水环境的污染。文中选取一位于安徽淮北的火力发电厂的储灰场,对其周边地表及地下水进行野外采样和分析,并取该灰场粉煤灰进行元素含量、矿物成分的分析及室内淋滤实验。结果表明粉煤灰堆放场周边12个取样点的地下水水样中NO3-,Cr6+,Se含量超标,其中超标最严重的Se的超标率占检测水样的58.3%,最大浓度值达到Ⅲ类标准的6.6倍。进一步应用主成分分析和聚类分析方法对研究区地下水离子进行水源分析,发现地下水化学成分主要有3个来源:天然背景下,很少受人为影响的水源,其贡献率为53.32%;第二个来源反映了处于径流区或排泄区的地下水源并受到一定程度人为因素的影响,其贡献率为17.37%;第三个来源反映了粉煤灰对地下水的污染,其贡献率为14.96%。聚类分析的结果进一步验证了粉煤灰场污染地下水中的空间分布特征:即离灰场越近,埋深越浅受污染的风险就越大。主成分分析和聚类分析法的应用为今后开展灰场对周围地下水影响的研究,确定地下水是否受到污染及污染来源,提供了一条有效途径。

There are abundant coals in China. The majority of thermal power plants utilize coal as major fuel for producing electric power. Coal fly ash as a by-product of consuming coal usually stored in an open-air yard. The leaching of fly ash brings the toxic elements such as heavy metals and radioactive elements into the groundwater and is potential source for the water environment pollution. Water samples were collected from the groundwater and surface water body surrounding a thermal power plant located in Huaibei, Anhui Province. Moreover, the fly ash in the storage yard was sampled. The analysis including the element and mineral composition for coal fly ash, and the ICP-AES and hydrochemically analysis for water samples was carried out, as well as the leaching experiments. The results show that the concentration of NO3-, Cr6＋, Se in 12 groundwater samples around fly ash landfill are above water quality standard IlI set in quality standard for ground water. Contamination from Se is the heaviest among them and its concentration is 6.6 times higher than that in water quality standard HI. Further analysis of groundwater samples using principal component analysis combined with hierarchical cluster analysis method show that hydrochemical constituents of groundwater come from three sources： the first is natural water, accounting for 53.32%; the second is the water from sink areas slightly polluted by human activities, accounting for 17.37%; the third source represents fly ash leachatd, accounting for 14.96%. Hierarchical cluster analysis further identifies the spatial distribution of groundwater polluted by coal fly ash landfill： contamination is heavier where close to the coal fly ash landfill and shallow groundwater depth. Principal component analysis combined with hierarchical cluster analysis is an efficient method for investigating the effects of coal fly ash landfill on groundwater and identifying the origin of coal fly ash polluting groundwater.