Bredesen Center for Interdisciplinary Research and Graduate Education, University of Tennessee, Knoxville, Tennessee, USA.
Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA.
Appl Environ Microbiol. 2019 Oct 16;85(21). doi: 10.1128/AEM.01336-19. Print 2019 Nov 1.
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. 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. 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. The differences in microbial community changes affected degradation dynamics. 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. A total of 17 DBNPA by-products were detected, many of them not widely known as DBNPA by-products. Many of the brominated by-products detected that are believed to be uncharacterized may pose environmental and health impacts. 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. 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. 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 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. These findings also demonstrate that DBNPA has low efficacy in environmental microbial communities regardless of HF impact. These findings are of interest, as understanding microbial responses is key for formulating remediation strategies in unconventional oil and gas (UOG)-impacted environments. 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.
非常规油气的产量持续增长，但高密度水力压裂（HF）活动对水生生态系统的影响尚未完全了解。HF 中常用的杀菌剂 2,2-二溴-3-亚硝基丙酰胺（DBNPA）在 HF 影响（HF+）与 HF 未影响（HF-）地表水微宇宙中进行了研究，以（i）比较微生物群落的反应，（ii）根据过去 HF 暴露情况研究 DBNPA 降解产物，以及（iii）比较 HF 杀菌剂 DBNPA 和戊二醛之间微生物群落反应的差异和相似性。在 HF 影响和 HF 未影响的微宇宙中，微生物群落对 DBNPA 的反应不同，具体表现在定量的 16S rRNA 基因拷贝数、α和β多样性以及随时间变化的微生物群落组成的差异丰度分析方面。微生物群落变化的差异影响了降解动力学。HF 影响的微生物群落对 DBNPA 更为敏感，导致该杀菌剂及其降解的副产物在 HF 未影响的微宇宙中持续存在的时间更长。共检测到 17 种 DBNPA 副产物，其中许多并非广泛认为是 DBNPA 的副产物。许多被认为是未被描述的溴化副产物可能会对环境和健康造成影响。相似的类群能够耐受戊二醛和 DBNPA；然而，由于暴露于杀菌剂后 16S rRNA 基因拷贝数/ml 的总体下降较小，并且能够耐受的类群更为多样化，因此 DBNPA 的杀菌效果并不理想。这些发现表明，过去在溪流中的 HF 活动会影响微生物群落对环境干扰的反应，例如由杀菌剂 DBNPA 引起的干扰。非常规油气活动会影响地表水的 pH 值、总有机碳和微生物群落，从而改变它们对新的环境和/或人为干扰的反应能力。这些发现表明，2,2-二溴-3-亚硝基丙酰胺（DBNPA），一种常见的水力压裂（HF）杀菌剂，由于过去的 HF 暴露而对微生物群落产生不同的影响，在 HF 影响（HF+）水域中持续时间更长。这些发现还表明，DBNPA 在环境微生物群落中的功效无论 HF 影响如何都很低。这些发现很有趣，因为了解微生物的反应是制定在非常规油气（UOG）影响环境中修复策略的关键。此外，一些 DBNPA 降解副产物甚至比 DBNPA 本身更具毒性和难降解性，而这项工作确定了形成的新型溴化降解副产物。
