title: CO2-efflux measurements for evaluating source zone natural attenuation rates in a petroleum hydrocarbon contaminated aquifer.
abstract: In order to gain regulatory approval for source zone natural attenuation (SZNA) at hydrocarbon-contaminated sites, knowledge regarding the extent of the contamination, its tendency to spread, and its longevity is required. However, reliable quantification of biodegradation rates, an important component of SZNA, remains a challenge. If the rate of CO(2) gas generation associated with contaminant degradation can be determined, it may be used as a proxy for the overall rate of subsurface biodegradation. Here, the CO(2)-efflux at the ground surface is measured using a dynamic closed chamber (DCC) method to evaluate whether this technique can be used to assess the areal extent of the contaminant source zone and the depth-integrated rate of contaminant mineralization. To this end, a field test was conducted at the Bemidji, MN, crude oil spill site. Results indicate that at the Bemidji site the CO(2)-efflux method is able to both delineate the source zone and distinguish between the rates of natural soil respiration and contaminant mineralization. The average CO(2)-efflux associated with contaminant degradation in the source zone is estimated at 2.6 μmol m(-2) s(-1), corresponding to a total petroleum hydrocarbon mineralization rate (expressed as C(10)H(22)) of 3.3 g m(-2) day(-1).
authors.affiliation: University of British Columbia, Department of Earth and Ocean Sciences, Vancouver, BC, Canada.
authors.forename: Natasha J
authors.initials: NJ
authors.lastname: Sihota
authors.forename: Olga
authors.initials: O
authors.lastname: Singurindy
authors.forename: K Ulrich
authors.initials: KU
authors.lastname: Mayer
mesh_terms: D001673:Biodegradation, Environmental; D002245:Carbon Dioxide / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D004784:Environmental Monitoring / Q000379:methods*; D006838:Hydrocarbons / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D010578:Petroleum / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism
chemical_list: D006838:Hydrocarbons; D010578:Petroleum; D014874:Water Pollutants, Chemical; D002245:Carbon Dioxide