Comparison and source apportionment of groundwater quality in urban construction waste landfill areas
In this study,two landfill sites mainly disposing construction and demolition wastes(CDW)were selected from two typical small or medium-sized cities in China.An entropy weighted water quality index was used to evaluate the groundwater quality in surrounding areas of the two sites.An integrated source apportionment approach was developed to reduce the uncertainty of the inverse modelling process.The sources of chemical composition in groundwater was firstly identified using multivariate statistical methods such as cluster analysis.Then a positive matrix factorization(PMF)model was used for source apportionment calculation,quantifying the contributions of two CDW landfills to changes in groundwater compositions in surrounding areas.Results showed that CDW landfill site could make groundwater quality deteriorate,with the degree of the impact depending on a variety of factors such as site properties,landfill history,and contamination prevention capacity of vadose zone.The overall deterioration of groundwater quality in the surrounding area of site 1was more severe than that of site 2.The concentration of seven monitored compositions in site 1exceeded the class Ⅲ standard limit of the groundwater quality standard(GB/T 14848-2017),while only one composition in site 2exceeded the limit.The PMF source analysis identified five natural and anthropogenic sources for the chemical compositions of groundwater in both locations,namely dissolution of minerals in soils and rocks,solute transport,agricultural sources,CDW sources and industrial sources.The contributions of these sources were 18.2%,18.0%,25.9%,19.5%and 9.8%in site 1,and 19.8%,23.5%,18.9%,12.6%and 15.1%in site 2,respectively.The impact of human activities and CDW landfill on the groundwater surrounding site 1is greater than that on site 2.
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