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Dissolved Hydrogen Dynamics Associated with Emulsified Vegetable Oil Bioremediation of Chloroethenes
Author(s) -
Chapelle PhD Francis H.
Publication year - 2021
Publication title -
groundwater monitoring and remediation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 47
eISSN - 1745-6592
pISSN - 1069-3629
DOI - 10.1111/gwmr.12457
Subject(s) - bioremediation , biostimulation , chemistry , environmental chemistry , groundwater , electron donor , hydrogen , fermentation , bacteria , food science , biology , biochemistry , organic chemistry , genetics , geotechnical engineering , engineering , catalysis
Emulsified vegetable oil (EVO) is widely used as a fermentable substrate to enhance the reductive dechlorination of chlorinated ethenes (CEs) in groundwater systems. The fermentation of EVO by naturally occurring bacteria produces molecular hydrogen (H 2 ) which acts as an electron donor driving microbially mediated reductive dechlorination. While dissolved H 2 drives much of the dechlorination associated with CE bioremediation, the dynamics of H 2 production and consumption associated with EVO addition to groundwater systems is seldom documented. The present study shows how H 2 concentrations changed over a 4‐year period following EVO addition to a sandy coastal plain aquifer underlying Naval Air Station Pensacola, Florida, USA. Prior to EVO addition, H 2 concentrations at the site were in the range characteristic of Fe(III)‐reducing conditions (0.2–0.6 nM). Following EVO addition, H 2 concentrations increased exponentially, peaking at approximately 25,000 nM. Hydrogen concentrations then began decreasing exponentially, and by 4 years after EVO addition had stabilized at 4.0 nM. That pattern suggests symbiotic cross‐feeding between fermentative and respirative microbial populations resulting in a Gaussian rise and fall of H 2 concentrations. That, in turn, suggests while EVO biostimulation can temporarily increase H 2 concentrations to very high levels, those higher concentrations are unlikely to be sustained indefinitely.