Natural Gas as the Source of Benzene in Groundwater

An investigation to evaluate the source of benzene in groundwater samples at a rural landfill in southwestern Louisiana was performed using isotopic and geochemical parameters as tracers of the fluids potentially transporting the benzene to groundwater. Leachate water had 2,649 tritium units while background groundwater and samples with benzene detections were both below 1. 14C in groundwater methane was 2.3% modern carbon compared to 120% in landfill methane. Groundwater methane stable isotopes were consistent with natural gas methane and not landfill methane. Ethane in the groundwater samples correlated with benzene and dissolved CO2 did not. The direction of partitioning of methane was assessed by comparing the headspace and dissolved methane concentrations and results showed a source below the water table. These results were consistent with natural gas as the source of benzene in the groundwater.