建筑垃圾填埋场周边地下水化学组分来源解析

建筑垃圾是城市市政垃圾的重要组成部分，对其堆填处理可能造成场地及周围一定范围内的地下水污染。传统观念认为，建筑垃圾中多为惰性或无害成分，对地下水影响有限，缺乏关于建筑垃圾堆填对地下水水质造成影响的研究。选取2处建筑垃圾堆填场地，通过对场地周围地下水采样分析，得到场地周边地下水化学指标空间分布特征，并利用正定矩阵因子分解法(PMF)识别研究区地下水化学组分来源，从而定量评价建筑垃圾填埋对周边地下水水质变化的贡献。结果表明，建筑垃圾填埋会显著影响周边区域地下水组分的浓度和质量，尤其是TDS、TH、Ca2+、SO42-等组分显著受到影响，填埋时间越长、填埋体量越大，影响程度越深。两场地区域范围内Na+、Ca2+、Mg2+、SO42-和TDS 5个组分或指标的空间分布整体变化趋势较一致，均表现为垃圾填埋场附近沿地下水流下游方向的点位浓度较高，其他点位浓度较低，验证了建筑垃圾填埋对区域地下水质量的影响。PMF来源解析确定两场地周边地下水化学组分来源有建筑垃圾填埋、岩石风化溶解、水岩相互作用和农业活动，在场地一来源贡献占比分别为29.2%、21.6%、24.2%和15.1%，在场地二贡献占比分别为15.6%、23.2%、28.4%和18.2%。两场地周围地下水质量受人类活动影响程度较深，人为污染源正在成为地下水中离子组分的重要来源。

Source identification of chemical compounds in groundwater surrounding the landfill sites dumping construction and demolition waste

Construction and demolition waste(CDW)accounts for a great portion of municipal solid waste, and the landfill treatment of CDW may cause groundwater pollution in the site and surrounding area.However, CDW is typically considered inert or harmless, presenting limited impact on groundwater quality, so that little research has been conducted on the impact of CDW landfills on groundwater.In this study, two CDW landfills were selected, and the spatial distribution of groundwater chemical components around the landfills were obtained by groundwater sampling and monitoring.The source of chemical components of groundwater in the study area was identified by using Positive Matrix Factorization(PMF)method.The contribution of CDW landfill to the deterioration of groundwater quality was quantitatively evaluated.Results show that the landfill of CDW can significantly affect the contents of hydro-chemical components and indexes in groundwater, especially total dissolved solid(TDS), total hardness(TH), Ca2+and SO42-.The spatial distribution of Na+, Ca2+, Mg2+, SO42- and TDS in the two sites were similar in trend, that is, sampling sites near the landfills present greater concentrations of Na+, Ca2+, Mg2+, SO42- and TDS, while sites far away from the landfills show lower concentration of those indexes.This distribution pattern suggests that CDW landfill probably have influence on the regional groundwater quality.The source apportionment results from PMF model suggest that sources of chemical components of groundwater around the two sites include CDW landfill leachate, rock weathering and dissolution, water-rock interaction and agricultural activities, with the corresponding contributions being 29.2%, 21.6%, 24.2% and 15.1%, respectively at Field 1 and 15.6%, 23.2%, 28.4% and 18.2%, respectively at Field 2.The quality of groundwater around the two sites is deeply affected by human activities, suggesting that anthropogenic pollution is becoming an important source of ion components in groundwater.