 Although landfill gas components can react with minerals and alter inorganic constituents present in groundwater samples such as alkalinity, calcium, and magnesium, a frequent major leachate constituent, chloride, can be used to evaluate whether leachate has affected the sample.Highly soluble VOCs, such as MtBE, diethyl ether, and tetrahydrofuran, are evidence of leachate effects, since they are too water-soluble to migrate in landfill gas.The presence of highly soluble semi-volatile organic compounds, such as phenols, are also consistent with leachate effects on the sample.