Elevated sediment radionuclide concentrations downstream of facilities treating leachate from landfills accepting oil and gas waste

Abstract

Management of oil and gas (O&G) waste streams from extraction of unconventional reservoirs challenges the sustainable development of these reservoirs. Landfilling of waste materials is an emerging strategy for unconventional O&G waste disposal. However, the effectiveness of effluent management systems designed for historical landfill waste streams in treating O&G waste is not established. This creates the potential for contamination associated with landfills accepting O&G waste. Yet, tracers of O&G waste are not necessarily included in routine effluent monitoring and environmental surveillance monitoring is too sparse to reliably detect this contamination. This study reviewed administrative records and analyzed grab samples of surface waters and stream sediments near effluent outfalls from facilities accepting O&G waste to evaluate this potential contamination. Administrative records are conflicting and inadequate, with only one landfill out of twenty-five agreeing within a factor of two between waste delivery and receipt volume reporting in 2019. Moreover, total radium was enriched in sediments downstream of effluent discharges, up to 4x relative to upstream values, magnitudes consistent with sediment accumulations downstream of known O&G waste inputs. Water chemistry measurements indicate that the largest upstream to downstream changes are consistent with O&G waste chemistry. These findings suggest landfill effluent influenced by O&G waste should be carefully scrutinized to avoid potential contamination of surface waters.