Characterization of Microbial Processes that Degrade Chlorinated Solvents in a Constructed Wetland Using Organic Acid and Inorganic Anion Concentration Profiles

摘要

Chlorinated solvents have been used in industrial cleaning and degreasing processes in the United States since the early 1900s, and their induction into the environment increased significantly with the growth of industrial processes over the past century. PCE, TCE and their daughter products have been associated with a number of human health concerns and are currently the most common contaminants found in groundwater in the United States. Wetlands possess characteristics necessary for the complete degradation of chlorinated ethenes by microorganisms via anaerobic and aerobic regions that foster the necessary oxidation-reduction conditions. Organic acid and inorganic anion concentrations were evaluated in samples taken from a constructed wetland at Wright-Patterson Air Force Base, Ohio during the summer and fall of 2003. These analyses are indicative of redox conditions in the subsurface and suggest the occurrence of microbial activities that degrade chlorinated ethenes to innocuous end products. Organic acid concentrations decreased by 100% from July 2003 to fall 2003. Combined with data collected previously during the months of December and January, this suggested that changing seasons and temperature fluctuations have a significant influence on microbial metabolisms. Nitrate and sulfate reduction above stratum C indicated mildly reducing conditions in the lowest stratum that became more highly reducing in the upper two strata. Based on the changing analyst concentrations throughout the wetland cell over several seasons, it was evident that the appropriate subsurface conditions existed for the reductive dechlorination of chlorinated ethenes.