Radium attenuation and mobilization in stream sediments following oil and gas wastewater disposal in western Pennsylvania

摘要

Centralized waste treatment facilities (CWTs) in Pennsylvania discharged wastewater from conventional and unconventional oil and gas (O&G) wells into surface waters until 2011, when a voluntary request from the Pennsylvania Department of Environmental Protection (PA DEP) encouraged recycling rather than treating and discharging unconventional O&G wastewater. To determine the effect of this request on the occurrence of radium in streams, we sampled sediments at five CWTs that processed conventional O&G wastewater from 2011 to 2017 and compared results to published data. Despite the policy change in 2011 that reduced disposal of unconventional wastes (i.e., Marcellus) to surface water in Pennsylvania, the continued disposal of conventional O&G wastewater led to elevated radium activities in sediments at the point of discharge that were often hundreds of times higher than background. While these elevated activities were also present in downstream sediments (1.5 x higher than background), the elimination of unconventional O&G wastewater disposal through the CWTs since 2011 decreased radium loading to the stream by approximately 95%.