Light hydrocarbon production in freshwater marsh soil as influenced by soil redox conditions

Abstract

The potential role of wetland soil redox condition to global atmospheric light hydrocarbon budget was evaluated. The effect of soil redox condition on gaseous hydrocarbon production in freshwater marsh soil was studied. Soil from a Mississippi River Deltaic plain freshwater marsh was equilibrated under controlled redox levels ranging from +550 mV to −170 mV The production of methane, ethane, propane, butane, ethylene, propylene and isobutane as influenced by redox condition was quantified. The production of all hydrocarbon gases increased as soil redox potential decreased. A soil redox value of -100 mV was critical for methane production. Isobutane production was also sensitive to redox potential, with emission occurring only at soil redox levels below 0 mV Results show the significance of degree of soil reduction in production or emission of light hydrocarbons in wetland soil or sediment. In addition to methane significant amounts of non-methane hydrocarbons are produced in wetland soils.