Dimethyl Sulfide Emissions From a Peatland Result More From Organic Matter Degradation Than Sulfate Reduction

Abstract

AbstractVolatile sulfur compounds (VSCs) contribute to acid rain, cloud formation, and albedo, and thus influence the climate. Their global emissions are quite uncertain, especially contributions from freshwater wetlands. We investigated the processes leading to hydrogen sulfide (H2S), methanethiol (MeSH), and dimethyl sulfide (Me2S) emissions in a slightly acidic peatland and found multiple indications that organic matter degradation rather than sulfate reduction is the main driver for Me2S emissions in this system. Evidence includes: the lack of labeled Me234S production after addition of Na234SO4 despite high emissions of Me34SH and H234S, and increased emission rates when soils were amended with organic substrates containing thiol groups (H2S emissions), methylthiols (MeSH), and dimethyl sulfonio groups (Me2S). VSC precursors were identified from an Untargeted Metabolomics data set from the same soil. The abundance of sulfur cycling microbes like Acidobacteria SD 1 and Desulfosporosinus correlated with VSC emissions. We conclude that organic matter degradation is more important than sulfate reduction as a source of Me2S in our peatland system, and potentially also in other organic and wetland soils.