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Contemporary Groundwater Methane Production from Pleistocene Carbon

USDA-ARS, National Soil Tilth Lab., 2150 Pammel Dr., Ames, IA 50011;

W. W. Simpkins

Dep. of Geological and Atmospheric Sciences, 253 Science I, Iowa State Univ., Ames, IA 50011.

^* Corresponding author (parkin{at}nstl.gov).

ABSTRACT

Relative to surface systems, microbial activities in groundwater have been poorly studied, especially with regard to methanogenesis. Past studies have reported high concentrations of CH₄ in groundwater in the late Wisconsinan till and Wisconsinan loess of central Iowa. The objectives of this work were to assess whether CH₄ is presently produced in the till and loess, and, if so, to characterize the spatial variability of CH₄ production rates. Groundwater and sediment sampies were collected at several locations within the Des Moines Lobe in central Iowa. Methane concentrations in groundwater ranged from 0.04 µmol L^–1 at 1 m to 2600 µmol L^–1 at 7 m. Incubations of deep sediment obtained from core samples revealed active CH₄ production was occurring, although high variability was observed. Highest specific CH₄ production rates were associated with buried particulate C fragments of Wisconsinan age. Results of our study indicate methanogenesis is an active process in the sediments beneath the Des Moines Lobe, that the substrate for methanogenesis is of late Wisconsinan age, and that the high spatial variability of CH₄ production is controlled by the heterogeneous distribution of particulate organic C fragments in the glacial sediments.

This article has been cited by other articles:

				M. F. Helmke, W. W. Simpkins, and R. Horton Fracture-Controlled Nitrate and Atrazine Transport in Four Iowa Till Units J. Environ. Qual., January 1, 2005; 34(1): 227 - 236. [Abstract] [Full Text] [PDF]