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Freshwater shells serve as recording devices for the contamination of wastewater by fracturing.
In Pennsylvania, the contaminated water created by the hydraulic fracturing oil and gas recovery in the Marcellus Formation has been authorized to be discharged into state-owned wastewater treatment facilities, in accordance with authorizations issued by the National Pollutant Release Elimination System (NPDES). After treatment, the waters were released into the Alleghany River.
This practice continued from 2008 to 2011, when it was shown that the chemical contamination associated with fracking fracturing was increasing despite the treatment. The authorities quickly banned any further fracking discharge in the treatment facilities, after which the industry began recycling most of its wastewater.
Penn State researchers have now shown that freshwater mussels can be used to read the history of contamination from this period. They collected Elliptio dilatata and Elliptio complanata mussels, upstream and downstream of an NPDES-licensed facility, as well as rivers with no known spill of fracking. Nathaniel Warner, an assistant professor of environmental engineering at Penn State explains what they were looking for:
"Freshwater mussels filter the water and when they have a hard shell, the shell material registers some of the water's quality over time. </ P> <p> Like dark circles, you can count the seasons and years in their shells and have a good idea of the quality and quality of water, the chemical composition of the water for specific periods. "
Indeed, when they analyzed the composition of the shell layer by layer, they found that the downstream molds had significantly high strontium levels, an element brought to the surface with the fracturing waters. In addition, scientists have been able to recognize the distinctive signature of the Marcellus shale wastewater in the characteristic values of the strontium isotopes discovered (an isotope is a variation of a chemical element with a different number of neutrons).
Surprisingly, the levels did not drop as expected when the releases stopped. This indicates that the contamination remains in the sediments of the river and may continue to affect aquatic life for a long time. Warner points out that "the wells expand, that they use more water, that they produce more wastewater and that the water has to go somewhere. Making the right choices to manage this water is going to be pretty vital. "
This work on the pollution assessment left in the mussel shells could also be useful for tracking spills and accidental releases of fracking operations. The team then looks for soft tissue contaminants that can affect fish and muskrat that eat mussels.
L & # 39; study Accumulation of metals in Marcellus oil and gas sewage in freshwater mussel shells has been published in Environmental Science & Technology. DOI: 10.1021 / acs.est.8b02727
Freshwater shells serve as recording devices for the contamination of wastewater by fracturing.
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