Date of Award

8-2017

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Engineering and Earth Sciences

Committee Member

Dr. David L. Freedman, Committee Chair

Committee Member

Dr. Kevin T. Finneran

Committee Member

Dr. David A. Ladner

Abstract

Bacteria that degrade natural organic matter in groundwater contain oxygenases that can co-oxidize trichloroethene (TCE). This degradation pathway is promising for large dilute plumes, but its evaluation is limited because the density of the bacteria with oxygenase enzymes has not been correlated to field scale rates of degradation. A 14C-TCE assay was developed to determine pseudo first-order rate coefficients for the aerobic co-oxidation of TCE. The assay involved the development of a first-order model that determined rate coefficients based on product accumulation and accounting for volumetric changes in the serum bottles due to sampling and subsequent changes to the distribution of TCE between the aqueous and gaseous phases. Of the 19 wells evaluated at five sites, eight wells at three sites had 14C product accumulation rates that exceeded the accumulation rate in filter-sterilized groundwater controls. First-order rate coefficients ranged from 2.65 to 0.0066 yr-1, which is equivalent to half-lives of 0.26 to 105 yr. A few of the wells in which co-oxidation occurred had volatile organic contaminants in addition to TCE; their presence may have induced the oxygenases needed for TCE co-oxidation. 14CO2 represented ~37-97% of the 14C products that accumulated; the balance of the products was soluble and non-volatile.

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