Aerobic Cometabolism of Chlorinated Aliphatic Hydrocarbons Stimulated by Wetland Plant Root Products and Root-Associated Microorganisms

摘要

Aerobic cometabolic degradation of various chlorinated aliphatic hydrocarbons (CAHs) has been previously reported by numerous researchers. Those reports showed that providing microorganisms with a primary substrate such as phenol, methane, or ammonia could yield rapid degradation of otherwise recalcitrant CAHs. Among the CAHs of interest, TCE is a very common groundwater contaminant, and cis-DCE often accumulates downgradient of TCE plumes. Our ongoing study has shown the degradation potential of cis 1,2 dichloroethene (cis-DCE) and trichloroethene (TCE) by aerobic cometabolism with roots of wetland plants and with no exogenous substrates added. The results thus far indicate that the plant root exudates that often provide a carbon source for rhizosphere microorganisms may also provide substrates to the rhizospheric microorganisms to cometabolize cis-DCE and TCE. Average cis-DCE removal up to 86% was observed in 14 days with simultaneous loss in oxygen and production of inorganic production. Initial concentrations of 500-2000 μg L~(-1) cis-DCE yielded similar degradation profiles, and variations in the root mass led to proportional loss in cis-DCE. Further, aerobic cometabolism of cis-DCE and TCE did not require microbial enrichment, and their degradation kinetic did not increase significantly over time. Overall, wetland plant roots appear to provide dissolved organic products and microorganisms to support cometabolic cis-DCE and TCE degradation under aerobic condition.