DBNPA, and some of its degradation products, can also be harmful to humans and animals. This biocide inhibits essential biological functions by reacting with nucleophiles (particularly sulfur-containing nucleophiles) inside the cell ( 8). DBNPA is a fast-acting electrophilic biocide it is quick and effective in contact, but the protection is not long lasting ( 7). ![]() The biocide 2,2-dibromo-3-nitrilopropionamide (DBNPA) is the second most commonly used biocide in UOG after glutaraldehyde. The fate of these biocides in the environment and their impact on microbial communities are poorly understood. Additionally, their toxicity and potential impact on the environment remain a contentious topic ( 2, 6). Biocides have various degrees of reported efficacy due to potential resistance or inactivation of the biocides in HF conditions ( 2, – 5). However, biocides have warranted concern for several reasons. ![]() Biocides are used in HF operations to control microbially induced corrosion of casings and pipes and gas souring caused by acid-producing and sulfate-reducing bacteria ( 2). ![]() Among the most commonly added chemicals to HF fluids are biocides. Multiple environmental concerns have accompanied this energy production growth. The use of hydraulic fracturing (HF) has made previously unreachable UOG reserves available for economically feasible extraction and pushed the United States toward energy independence ( 1). Unconventional oil and gas (UOG) extraction has revolutionized the energy industry in the United States. Moreover, some DBNPA degradation by-products are even more toxic and recalcitrant than DBNPA itself, and this work identifies novel brominated degradation by-products formed. These findings are of interest, as understanding microbial responses is key for formulating remediation strategies in unconventional oil and gas (UOG)-impacted environments. These findings also demonstrate that DBNPA has low efficacy in environmental microbial communities regardless of HF impact. These findings demonstrate that 2,2-dibromo-3-nitrilopropionamide (DBNPA), a common hydraulic fracturing (HF) biocide, affects microbial communities differently as a consequence of past HF exposure, persisting longer in HF-impacted (HF+) waters. IMPORTANCE Unconventional oil and gas activity can affect pH, total organic carbon, and microbial communities in surface water, altering their ability to respond to new environmental and/or anthropogenic perturbations. These findings suggest that past HF activity in streams can affect the microbial community response to environmental perturbation such as that caused by the biocide DBNPA. Similar taxa were able to tolerate glutaraldehyde and DBNPA however, DBNPA was not as effective for microbial control, as indicated by a smaller overall decrease of 16S rRNA gene copies/ml after exposure to the biocide, and a more diverse set of taxa was able to tolerate it. Many of the brominated by-products detected that are believed to be uncharacterized may pose environmental and health impacts. ![]() A total of 17 DBNPA by-products were detected, many of them not widely known as DBNPA by-products. HF-impacted microbial communities were more sensitive to DBNPA, causing the biocide and by-products of the degradation to persist for longer than in HF-unimpacted microcosms. The differences in microbial community changes affected degradation dynamics. The microbial community responded to DBNPA differently in HF-impacted versus HF-unimpacted microcosms in terms of the number of 16S rRNA gene copies quantified, alpha and beta diversity, and differential abundance analyses of microbial community composition through time. A commonly used biocide in HF, 2,2-dibromo-3-nitrilopropionamide (DBNPA), was studied in microcosms of HF-impacted (HF+) versus HF-unimpacted (HF−) surface water streams to (i) compare the microbial community response, (ii) investigate DBNPA degradation products based on past HF exposure, and (iii) compare the microbial community response differences and similarities between the HF biocides DBNPA and glutaraldehyde. Production of unconventional oil and gas continues to rise, but the effects of high-density hydraulic fracturing (HF) activity near aquatic ecosystems are not fully understood.
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