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 SO₄^2-.The spatial distribution of Na⁺, Ca²⁺, Mg²⁺, SO₄^2- and TDS in the two sites were similar in trend, that is, sampling sites near the landfills present greater concentrations of Na⁺, Ca²⁺, Mg²⁺, SO₄^2- 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.