title: Determination of rate constants and branching ratios for TCE degradation by zero-valent iron using a chain decay multispecies model.
abstract: The applicability of a newly-developed chain-decay multispecies model (CMM) was validated by obtaining kinetic rate constants and branching ratios along the reaction pathways of trichloroethene (TCE) reduction by zero-valent iron (ZVI) from column experiments. Changes in rate constants and branching ratios for individual reactions for degradation products over time for two columns under different geochemical conditions were examined to provide ranges of those parameters expected over the long-term. As compared to the column receiving deionized water, the column receiving dissolved CaCO3 showed higher mean degradation rates for TCE and all of its degradation products. However, the column experienced faster reactivity loss toward TCE degradation due to precipitation of secondary carbonate minerals, as indicated by a higher value for the ratio of maximum to minimum TCE degradation rate observed over time. From the calculated branching ratios, it was found that TCE and cis-dichloroethene (cis-DCE) were dominantly dechlorinated to chloroacetylene and acetylene, respectively, through reductive elimination for both columns. The CMM model, validated by the column test data in this study, provides a convenient tool to determine simultaneously the critical design parameters for permeable reactive barriers and natural attenuation such as rate constants and branching ratios.
authors.affiliation: Aquanty Inc., 564 Weber Street North, Unit 12, Waterloo, ON N2L 5C6, Canada; Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, ON N2L 3G1, Canada.
authors.forename: Hyoun-Tae
authors.initials: HT
authors.lastname: Hwang
authors.affiliation: Department of Earth and Environmental Sciences, Chonbuk National University, Jeonju-si, Jeollabuk-do 561-756, Republic of Korea; The Earth and Environmental Science System Research Center, Chonbuk National University, Jeonju-si, Jeollabuk-do 561-756, Republic of Korea. Electronic address: sjeen@jbnu.ac.kr.
authors.forename: Sung-Wook
authors.initials: SW
authors.lastname: Jeen
authors.affiliation: Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, ON N2L 3G1, Canada.
authors.forename: Edward A
authors.initials: EA
authors.lastname: Sudicky
authors.affiliation: Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, ON N2L 3G1, Canada.
authors.forename: Walter A
authors.initials: WA
authors.lastname: Illman
mesh_terms: D000114:Acetylene / Q000737:chemistry; D001673:Biodegradation, Environmental; D002119:Calcium Carbonate / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D008962:Models, Theoretical; D015203:Reproducibility of Results; D014241:Trichloroethylene / Q000737:chemistry* / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000378:metabolism
chemical_list: D014874:Water Pollutants, Chemical; D014241:Trichloroethylene; D007501:Iron; D002119:Calcium Carbonate; D000114:Acetylene
keywords: Branching ratio; Multispecies model; Rate constant; Reaction pathway; Trichloroethene (TCE); Zero-valent iron (ZVI)