INFLUENCE OF METHIONINE AND SOIL MOISTURE ON SOIL-ATMOSPHERE EXCHANGE FLUXES OF VOLATILE ORGANIC SULFUR COMPOUNDS

The influence of methionine(Met)and soil moisture on the soil-atmosphere fluxes of volatile organic sulfur compounds(VOSCs),including carbonyl sulfide(COS),carbon disulfide(CS2),dimethyl sulfide(DMS)and dimethyl disulfide(DMDS),were studied by static chamber enclosure followed by laboratory determination using an Entech 7100 preconcentrator coupled with a Agilent 5973 GC-MS.The results showed that COS and DMS fluxes were influenced significantly by soil water contents.Soil acted as sink for COS and source for DMS at low soil moisture,but as sources for both COS and DMS with significant increase of DMS emission rates when near or exceeding the maximum water holding capacity.This might be attributed to the change of soil Eh values.DMDS and DMS emission rates increased sharply after addition of Met to soils.DMDS and DMS amounted for 99.97% of total four VOSCs,implying that Met was an important precursor for DMDS and DMS.Emission rates peaked at the same time for DMS and DMDS while emission of COS and CS2 shared a late peak,indicating that soil microorganisms and enzymes varied for their influence on the formation of VOSCs in soils.