RADIOACTIVITY FROM OIL AND GAS PRODUCED WATER DISPOSAL ACCUMULATED IN FRESHWATER MUSSELS, EURYNIA DILATATA

Adult freshwater mussels, Eurynia dilatata, were examined along the Allegheny River in Franklin, Pennsylvania (PA) to investigate the impact of exposure to treated oil and gas produced water (OGPW). Oil and gas production generates billions of liters of wastewater each year. In PA, a small percentage of this OGPW is sent to centralized wastewater treatment facilities (CWTs) for treatment and disposal to surface water under national pollution discharge elimination system (NPDES) permits. These discharges impact downstream water quality and sediment by significantly increasing the activity of radium compared to background levels. Increased radium activities present a health hazard to benthic organisms, such as freshwater mussels, as radium can bioaccumulate in plants and animals. Freshwater mussels are the most endangered wildlife in North America and have experienced high mortality rates downstream of oil and gas discharges even after large dilution effects. Our objective is to determine if mussels living downstream of these CWTs that have historically discharged treated OGPW accumulate radium isotopes and if their soft tissue and hard shell retain a ²²⁸Ra/²²⁶Ra and ⁸⁷Sr/⁸⁶Sr signature indicative of Marcellus OGPW. In this study, radium-226 and radium-228 were measured in streambed sediment and adult E. dilatata freshwater mussel soft tissue samples collected upstream, downstream, and at a historical CWT with documented OGPW treatment and disposal. Total radium activity was significantly higher (p<0.05) in downstream mussel tissue (mean = 3.32 pCi/g) and sediment (mean = 1.38 pCi/g) samples than background levels taken upstream (mean = 1.52; 0.90 pCi/g respectively). In downstream samples, ²²⁸Ra/²²⁶Ra demonstrated a declining trend in both the soft tissue and sediment, with a significant (p<0.05) difference found in the hard shell. This notable difference suggests the influence of Marcellus OGPW. This project assesses the impact OGPW radioactivity can have on freshwater mussels confirming radium bioaccumulation and ²²⁸Ra/²²⁶Ra signatures indicative of exposure to Marcellus OGPW. Future work will evaluate ⁸⁷Sr/⁸⁶Sr strontium isotopic signatures in the hard shell and soft tissue, as well as a broader analysis on the spatial extent of exposure.