HR: 0800h
AN: B51C-0969    [Abstracts]
TI: Annual Methyl Halides Fluxes and Isotopic Signatures of Methyl Chloride from Irish Soil Ecosystems
AU: * Redeker, K R
EM: k.redeker@qub.ac.uk
AF: Queens University Belfast, Environmental Engineering Research Centre, David Keir Bldg, Stranmillis Rd., Belfast, BT9 5AG United Kingdom
AU: Harper, D
EM: david.harper@dardni.gov.uk
AF: Queens University Belfast, Department of Agriculture and Rural Development, Newforge Lane , Belfast, BT9 5PX United Kingdom
AU: Hamilton, J T
EM: jack.Hamilton@dardni.gov.uk
AF: Queens University Belfast, Department of Agriculture and Rural Development, Newforge Lane , Belfast, BT9 5PX United Kingdom
AU: McRoberts, C
EM: Colin.McRoberts@dardni.gov.uk
AF: Queens University Belfast, Department of Agriculture and Rural Development, Newforge Lane , Belfast, BT9 5PX United Kingdom
AU: Kalin, R M
EM: r.kalin@qub.ac.uk
AF: Queens University Belfast, Environmental Engineering Research Centre, David Keir Bldg, Stranmillis Rd., Belfast, BT9 5AG United Kingdom
AB: Methyl halides (CH3X, where X = Cl, Br or I) provide a significant portion of reactive halide radicals to the atmosphere, where the radicals are responsible for ozone catalysis within the stratosphere and decreasing the oxidative capacity of the troposphere. One of the least understood reservoirs within the methyl halide budgets is the soil, or subsurface, ecosystem. Here we present an annual study of methyl halide emissions and consumption in two Irish ecosystem soils, forested and agricultural pastureland. Pastureland is a net consumer of methyl chloride but consistently produces methyl iodide. Forested soils are highly variable, with general overall production of methyl chloride and consumption of methyl iodide. Methyl bromide is slightly produced in both ecosystems. Isotopic analysis of methyl chloride from forested soil sampling chambers gives significantly enriched values for methyl chloride d13C. Isotopic analysis of methyl chloride from pastureland soils shows no significant deviation from atmospheric values. Further tests on soil cores from forested soils confirm the enrichment of methyl chloride d13C by biological processes. Addition of water to soil cores appears to drive a biological cycle (presumably bacterial) that consumes methyl chloride and methyl bromide more rapidly than under dry conditions. Abiotic production and consumption of methyl halides in the forested ecosystem is very small compared to biological processes.
DE: 1040 Isotopic composition/chemistry
DE: 1615 Biogeochemical processes (4805)
DE: 0315 Biosphere/atmosphere interactions
DE: 0322 Constituent sources and sinks
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting