Atmospheric methane (CH4) oxidation occurs in soils at sites in the Bonanza Creek L.T.E.R. near Fairbanks, Alaska, USA, at rates ≤2 mg CH4 m-2 d-1; the maximum CH4 oxidizing activity is located in loess at a depth of ∼15 cm. Methane, carbon dioxide, and stable isotope (δ13C-CH4, δ13C-CO2) depth distributions were measured at two sites: South facing Aspen (AS2) and North facing Black Spruce (BS2). The combined effects of diffusion and oxidation are similar at both sites and result in a CH4 concentration decrease (1.8-0.1 ppm) and a δ13C-CH4 increase (-48‰ to -43‰) from the soil surface to 60-80 cm depth. Isotope flux ratio and diffusion-consumption models were used to estimate the kinetic isotope effect (KIE); these results agree with the observed top-to-bottom difference in δ13C-CH4, which is the integrated result of isotope fractionation due to diffusion and oxidation. The KIE for CH4 oxidation determined from these measurements is 1.022-1.025, which agrees with previous KIE determinations based on changes in headspace CH4 concentration and δ13C-CH4 over time. A much lower soil respiration rate in the North facing Black Spruce soils is indicated by fivefold lower soil CO2 concentrations. The similarity in CH4 oxidation at the two sites and the differences in inferred soil respiration at the two sites suggest that soil CH4 oxidation and soil respiration are independent processes. The soil organic matter responsible for the CO2 flux has a δ13C estimated to be -27 to -28‰. Copyright © 1997 Elsevier Science Ltd.

We analyze the North American budget for carbon monoxide using data for CO and formaldehyde concentrations from tall towers and aircraft in a model-data assimilation framework. The Stochastic Time-Inverted Lagrangian Transport model for CO (STILT-CO) determines local to regional-scale CO contributions associated with production from fossil fuel combustion, biomass burning, and oxidation of volatile organic compounds (VOCs) using an ensemble of Lagrangian particles driven by high resolution assimilated meteorology. In many cases, the model demonstrates high fidelity simulations of hourly surface data from tall towers and point measurements from aircraft, with somewhat less satisfactory performance in coastal regions and when CO from large biomass fires in Alaska and the Yukon Territory influence the continental US. Inversions of STILT-CO simulations for CO and formaldehyde show that current inventories of CO emissions from fossil fuel combustion are significantly too high, by almost a factor of three in summer and a factor two in early spring, consistent with recent analyses of data from the INTEX-A aircraft program. Formaldehyde data help to show that sources of CO from oxidation of CH4 and other VOCs represent the dominant sources of CO over North America in summer. © Author(s) 2008.

Abstract. We analyze the North American budget for carbon monoxide using data for CO and formaldehyde concentrations from tall towers and aircraft in a model-data assimilation framework. The Stochastic Time-Inverted, Lagrangian Transport model for CO (STILT-CO) determines local to regional-scale CO contributions associated with production from fossil fuel combustion, biomass burning, and oxidation of volatile organic compounds (VOCs) using an ensemble of Lagrangian particles driven by high resolution assimilated meteorology. In most cases, the model demonstrates high fidelity simulations of hourly surface data from tall towers and point measurements from aircraft, with somewhat less satisfactory performance in coastal regions and when CO from large biomass fires in Alaska and the Yukon Territory influence the continental US. Inversions of STILT-CO simulations for CO and formaldehyde show that current inventories of CO emissions from fossil fuel combustion are significantly too high, by almost a factor of three in summer and a factor two in early spring, consistent with recent analyses of data from the INTEX-A aircraft program. Formaldehyde data help to show that sources of CO from oxidation of CH4 and other VOCs represent the dominant sources of CO over North America in summer.