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Appl. Environ. Microbiol., Dec 1997, 4741-4747, Vol 63, No. 12
BP Lomans, AJP Smolders, LM Intven, A Pol, HJM Op Den Camp and C Van Der Drift
Concentrations of volatile organic sulfur compounds (VOSC) were measured in
water and sediment columns of ditches in a minerotrophic peatland in The
Netherlands. VOSC, with methanethiol (4 to 40 nM) as the major compound,
appeared to be mainly of sediment origin. Both VOSC and hydrogen sulfide
concentrations decreased dramatically towards the water surface. High
methanethiol and high dimethyl sulfide concentrations in the sediment and
just above the sediment surface coincided with high concentrations of
hydrogen sulfide (correlation factors, r = 0.91 and r = 0.81,
respectively). Production and degradation of VOSC were studied in 32
sediment slurries collected from various freshwater systems in The
Netherlands. Maximal endogenous methanethiol production rates of the
sediments tested (up to 1.44 (mu)mol per liter of sediment slurry (middot)
day(sup-1)) were determined after inhibition of methanogenic and
sulfate-reducing populations in order to stop VOSC degradation. These
experiments showed that the production and degradation of VOSC in sediments
are well balanced. Statistical analysis revealed multiple relationships of
methanethiol production rates with the combination of methane production
rates (indicative of total anaerobic mineralization) and hydrogen sulfide
concentrations (r = 0.90) or with the combination of methane production
rates and the sulfate/iron ratios in the sediment (r = 0.82). These
findings and the observed stimulation of methanethiol formation in sediment
slurry incubations in which the hydrogen sulfide concentrations were
artificially increased provided strong evidence that the anaerobic
methylation of hydrogen sulfide is the main mechanism for VOSC formation in
most freshwater systems. Methoxylated aromatic compounds are likely a major
source of methyl groups for this methylation of hydrogen sulfide, since
they are important degradation products of the abundant biopolymer lignin.
Increased sulfate concentrations in several freshwater ecosystems caused by
the inflow of water from the river Rhine into these systems result in
higher hydrogen sulfide concentrations. As a consequence, higher fluxes of
VOSC towards the atmosphere are conceivable.
Copyright © 1997, American Society for Microbiology
Formation of Dimethyl Sulfide and Methanethiol in Anoxic Freshwater Sediments
Department of Microbiology and Evolutionary Biology and Department of Ecology, Section of Environmental Ecology, Faculty of Science, University of Nijmegen, NL-6525 ED Nijmegen, The Netherlands
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