Spatial and temporal variation in toxicity and inorganic composition of hydraulic fracturing flowback and produced water
Data files
Sep 13, 2023 version files 40.28 KB
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FPW_LC50s.xlsx
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README.md
Abstract
Hydraulic fracturing for oil and gas extraction produces large volumes of wastewater, termed flowback and produced water (FPW), that are highly saline and contain a variety of organic and inorganic contaminants. In the present study, FPW samples from ten hydraulically fractured wells, across two geologic formations were collected at various timepoints. Samples were analyzed to determine spatial and temporal variation in their inorganic composition. Results indicate that FPW composition varied both between formations and within a single formation, with large compositional changes occurring over short distances. Temporally, all wells showed a time-dependent increase in inorganic elements, with total dissolved solids increasing by up to 200,000 mg/L over time, primarily due to elements associated with salinity (Cl, Na, Ca, Mg, K). Toxicological analysis of a subset of the FPW samples showed median lethal concentrations (LC50) of FPW to the aquatic invertebrate Daphnia magna were highly variable, with the LC50 values ranging from 1.16% to 13.7% FPW. Acute toxicity of FPW significantly correlated with salinity, indicating salinity is a primary driver of FPW toxicity, however organic components also contributed to toxicity. This study provides insight into spatiotemporal variability of FPW composition and illustrates the difficulty in predicting aquatic risk associated with FPW.
README: Spatial and Temporal Variation in Toxicity and Inorganic Composition of Hydraulic Fracturing Flowback and Produced Water
https://doi.org/10.5061/dryad.t4b8gtj79
FPW_LC50s gives raw toxicity results after 48h exposure to specified FPW concentration from a given well. FPW concentration indicates concentration of FPW (diluted with colony water) as % vol/vol. n is the number of Daphnia magna in the exposure vial. Alive is the number of D. magna alive at the end of the 48h exposure, regardless of whether they are immobilized or not. Unaffected is the number of D. magna alive at the end of the 48h exposure that are not immobilized. Dead is the number of D. magna dead at the end of the 48h exposure. Immobilized is the number of D. magna alive but immobilized at the end of the 48h exposure. Effect is the number of D. magna that are affected in some manner, whether immobilized or dead, at the end of the 48h exposure. n is the number of daphnids per exposure vial.