Concentrations of volatile organic @entity599 compounds (VOSC) were measured in water and sediment columns of ditches in a minerotrophic peatland in The Netherlands. VOSC, with @entity24591 (4 to 40 nM) as the major compound, appeared to be mainly of sediment origin. Both VOSC and @entity3957 concentrations decreased dramatically towards the water surface. High @entity24591 and high @entity27094 concentrations in the sediment and just above the sediment surface coincided with high concentrations of @entity3957 (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 @entity24591 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 @entity597 -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 @entity24591 production rates with the combination of @entity577 production rates (indicative of total anaerobic mineralization) and @entity3957 concentrations (r = 0.90) or with the combination of @entity577 production rates and the @entity597 / @entity68 ratios in the sediment (r = 0.82). These findings and the observed stimulation of @entity24591 formation in sediment slurry incubations in which the @entity3957 concentrations were artificially increased provided strong evidence that the anaerobic methylation of @entity3957 is the main mechanism for VOSC formation in most freshwater systems. Methoxylated aromatic compounds are likely a major source of @entity5498 groups for this methylation of @entity3957 , since they are important degradation products of the abundant biopolymer lignin. Increased @entity597 concentrations in several freshwater ecosystems caused by the inflow of water from the river Rhine into these systems result in higher @entity3957 concentrations. As a consequence, higher fluxes of VOSC towards the atmosphere are conceivable.

Formation of @entity27094 and XXXX in anoxic freshwater sediments.

@entity24591 :: ('MESH:C005231', 'Chemical') :: ['methanethiol'] @entity27094 :: ('MESH:C004784', 'Chemical') :: ['dimethyl sulfide'] @entity577 :: ('MESH:D008697', 'Chemical') :: ['methane'] @entity5498 :: ('CHEBI:32875', 'Chemical') :: ['methyl'] @entity599 :: ('MESH:D013455', 'Chemical') :: ['sulfur'] @entity3957 :: ('MESH:D006862', 'Chemical') :: ['hydrogen sulfide'] @entity68 :: ('MESH:D007501', 'Chemical') :: ['iron'] @entity597 :: ('CHEBI:16189', 'Chemical') :: ['sulfate']
@entity24591 :: (MESH:C005231,Chemical) :: ['methanethiol']
