Assessment of anaerobic biodegradation of bis(2-chloroethyl) ether in groundwater using carbon and chlorine...

Carbon and chlorine compound specific isotope analysis (CSIA) of bis(2-chloroethyl) ether (BCEE) was performed to distinguish the primary processes contributing to observed concentration reductions in an anaerobic groundwater plume. Laboratory microcosms were constructed to demonstrate and obtain isotopic enrichment factors and dual-element CSIA trends from two potential transformation processes (1) anaerobic biodegradation using saturated sediment samples from the field site (ε_C=-14.8 and ε_Cl=-5.0) and (2) abiotic reactions with sulfide nucleophiles in water (ε_C=-12.8 and ε_Cl=-5.0). The results suggested a nucleophilic, S_N2-type dechlorination as the mechanism of biodegradation of BCEE. Identical dual-element CSIA trends observed in the field and in the microcosm samples suggested that the same degradation mechanism was responsible for BCEE degradation in the field. While biodegradation was the likely dominant mechanism of BCEE mass destruction in the aquifer, potential contribution of abiotic hydrolysis to the net budget of degradation could not be confidently excluded. To our knowledge, this is the first unequivocal demonstration of BCEE biodegradation at a field site.