title: Methane oxidation in biofilters measured by mass-balance and stable isotope methods.
abstract: Simultaneous flux and isotope measurements on compost and sand biofilters showed that the fraction of CH4 oxidized, calculated from delta13C measurements using a closed system model (f(oxir,C)), averaged only 0.455 of the fraction oxidized based on mass-balance measurements (f(oxm)). The discrepancy between f(oxm) and f(oxir,C) may be partly due to complete oxidation of a portion of the inflow gas, thereby eliminating its contribution to the emitted methane on which isotopic measurements are conducted. To relate f(oxir,C) and f(oxm) a simple binary closed-system model is proposed that assumes that f(oxir,C) refers to only part of the inflow, P, and that the remainder of inflow (1 - P) is completely oxidized before reaching the outlet. This model is compared to the standard open-system model. The H-isotope fraction oxidized (f(oxir,H)) was determined for a subset of samples and found to be not significantly different from f(oxir,C). The carbon isotope fractionation factor, alphaox,C = 1.0244, and the H-isotope fractionation factor, alphaox,H = 1.2370, were determined by incubation studies. Delta13C measurements indicated that the emitted flow was more strongly oxidized by the compost biofilters (f(oxir,C) = 0.362, f(oxm) = 0.757) than the sand biofilters (f(oxir,C) = 0.222, f(oxm) = 0.609).
authors.affiliation: Department of Oceanography, 0102 OSB, West Call Street, Florida State University, Tallahassee, Florida 32306, USA. powelson@eng.fsu.edu
authors.forename: D K
authors.initials: DK
authors.lastname: Powelson
authors.forename: J P
authors.initials: JP
authors.lastname: Chanton
authors.forename: T
authors.initials: T
authors.lastname: Abichou
mesh_terms: D000393:Air Pollutants / Q000378:metabolism*; D000397:Air Pollution / Q000517:prevention & control*; D000704:Analysis of Variance; D001419:Bacteria / Q000378:metabolism*; D002247:Carbon Isotopes / Q000032:analysis; D005374:Filtration; D008697:Methane / Q000378:metabolism*; D008956:Models, Chemical; D010084:Oxidation-Reduction; D012822:Silicon Dioxide; D012987:Soil
chemical_list: D000393:Air Pollutants; D002247:Carbon Isotopes; D012987:Soil; D012822:Silicon Dioxide; D008697:Methane