HR: 1340h
AN: B43A-0249    [Abstracts]
TI: Field and Laboratory Measurements of H₂ Uptake by Soils Designed to Yield Parameters for a Global Model
AU: * Downey, N V
EM: nicolev@gps.caltech.edu
AF: California Institute of Technology, MS 100-23 1200 E. California Blvd., Pasadena, CA 91125 United States
AU: Randerson, J T
EM: jranders@uci.edu
AF: University of California, Irvine, 3212 Croul Hall, Irvine, CA 92697 United States
AU: Eiler, J M
EM: eiler@gps.caltech.edu
AF: California Institute of Technology, MS 100-23 1200 E. California Blvd., Pasadena, CA 91125 United States
AB: Soil uptake of molecular hydrogen (H₂) is the dominant loss term for atmospheric H₂, but the distribution and magnitude of this global sink are not well known. We combined field and laboratory experiments to estimate the sensitivity of H₂ fluxes to temperature and soil moisture controls. H₂ uptake by soils was measured at three sites in California for one year. Our sites included forest, desert and marsh ecosystems. Uptake rates, vertical profiles of soil H₂ concentrations, soil temperature, soil moisture and CO₂ fluxes were measured at each site. H₂ uptake rates ranged from 0 to 23 nmol/m²/s. CO₂ fluxes and H₂ fluxes did not correlate at our field sites. Soil moisture was positively correlated with H₂ uptake rate in the desert ecosystem. Soil samples were returned to the lab, where uptake rates as a function of temperature and soil moisture were measured with a flow through system. We observed a strong temperature dependence of uptake rate in laboratory experiments for temperatures ranging from -20 ° C to 60 ° C. H₂ uptake reached a maximum at 37 ° C and persisted to temperatures below -10 ° C. Between 0 ° C and 20 ° C H₂ fluxes increased by 350%. These results were used to develop a global model of the soil H₂ sink.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0490 Trace gases
DE: 0793 Biogeochemistry (0412, 0414, 1615, 4805, 4912)
DE: 3322 Land/atmosphere interactions (1218, 1631, 1843)
SC: Biogeosciences [B]
MN: Fall Meeting 2005