Hydraulic fracturing fluids are injected into shales to extend fracture networks that enhance oil and natural gas production from unconventional reservoirs. The scale of these activities necessitates they be developed in less populated areas, as such regions dominated by agricultural land use. Here we evaluated the biodegradability of three widely used nonionic polyglycol ether surfactants in agricultural soils and groundwater. These were alkyl ethoxylates (AEOs), nonylphenol ethoxylates (NPEOs), and polypropylene glycols (PPGs) that function as weatherizers, emulsifiers, wetting agents, and corrosion inhibitors in injected fluids. We observed removal of AEOs and NPEOs from solution within three weeks under anaerobic conditions, regardless of whether surfactants were part of a chemical mixture or amended as individual additives. PPGs bioattenuated the slowest, producing sizeable concentrations of acetone. Microbial enzymatic chain shortening was responsible for a shift in ethoxymer molecular weight distributions and the accumulation of metabolites. Surfactant chain shortening was related to increased abundance of the diol dehydratase gene cluster (<i>pduCDE</i>) in <i>Firmicutes</i>. These enzymes are responsible for ethoxylate cleavage into aldehydes before their fermentation into alcohols and carboxylic acids. This data provides new insight into the environmental fate of hydraulic fracturing surfactants after accidental release to agricultural soils and emphasizes the importance of compound structure disclosure for predicting degradation products.

Pathways and mechanisms for natural attenuation of nonionic surfactants in hydraulic fracturing fluids if released to agricultural soil and groundwater

255th National Meeting (2018)

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