Feasibility of Using Freshwater Mussels to Monitor BA and SR Contaminations in Pennsylvania Streams

Elaine Langone Center, Terrace Room

With the extensive Marcellus Shale natural gas development, horizontal drilling, combined with hydraulic fracturing, produces a large quantity of saline flowback water high in Ba and Sr contents, raising health and ecological concerns in case of spills or leaks. Freshwater mussels, as sedentary filter feeders, could potentially take up Ba and Sr in the growth rings of their shells, reflecting the chemistry of the aquatic environment over time. The experimental site mussels (E. complanata and L. cariosa) were obtained from the West Branch Susquehanna River near Williamsport PA; the control site is on Buffalo Creek, Union County. From 2010 to 2014, PA Department of Environmental Protection data, at two monitoring points near West Branch sample sites, showed that the river water Ba concentrations (± 1$) were 30 (5) and 34 (13) %g/L, Sr 100 (44) and 98 (50) %g/L. In two tributaries, Ba concentrations were 19 (6) and 26 (6) %g/L, Sr 23 (8) and 32 (8) %g/L. X-ray diffraction confirmed that the mineralogy of the shell is mostly aragonite (CaCO3). Cross-sectional thin sections (0.5 mm) were observed under transmitted light microscope and environmental scanning electron microscope back-scattered electron mode to identify possible growth rings. Major (Ca) and trace elements (Ba, Sr) were analyzed along transects in shell layers using electron probe micro-analysis (EPMA). Results were reported as molar ratios of [X/Ca]shell (X Ba, Sr). Correlating [X/Ca]shell and historical [X/Ca] in the water was challenging, because of the uncertainty in the shell layer ages and the scarcity of data. If shell and water chemistry data had sufficiently high spatial and temporal resolutions, freshwater mussel shell layers could potentially be interpreted as water chemistry records.