Evaluation Of Redox Capacity Of Dissolved Organic Matter In Peat Swamp Wetlands

Peatland store about 30% of the global soil carbon(C)with covering only 3% of the global land surface,which is an important carbon pool in terrestrial ecosystems.Dissolved organic matter(DOM)plays a key role in the biogeochemical process of peatland and contributes significantly to carbon cycle.In this study,two typical peatlands in Germany were selected as the research area,MP as the minerotrophic fen while OP as the ombrotrophic bog.The variation characteristics of redox ability of DOM in pore water profile,surface water and ground water,as well as the relationships between the redox ability and functional group of DOM were analyzed via mediated electrochemical method and three-dimensional fluorescence-parallel factor analysis etc.,to explore the change mechanism of redox ability of DOM in peat decomposition process.It provides theoretical basis for evaluating the mechanism of organic matter participating in carbon cycle in peatland.The main conclusions are as follows.Anaerobic respiration dominated by inorganic salt was the major process in minerotrophic fen(MP),only when the inorganic electron acceptors are depleted can organic matter participate in anaerobic respiration in this type of peatland.Furthermore,the interaction between organic matter and inorganic salt can also affect the anaerobic respiration in peat soil,but the complex mechanism requires further quantitative and qualitative analysis.The organic matter contributed significantly to anaerobic respiration as the electron acceptors in ombrotrophic bog(OP),which is poor in inorganic electron acceptors.And the redox ability changed at different depths in the profile,attributing to the actual redox potential and the heterogeneity of substance at different depths in peat soil.The results show that the mediated electrochemical method can accurately and quantitatively evaluate the change of the redox ability of DOM in environmental samples.In addition,we can only analyze the change of DOM redox ability by the mediated electrochemical method quantitatively.And three-dimensional fluorescence-parallel factor analysis were used to recognize the functional groups of DOM which are mainly involved in the redox properties.The results show that electron transfer capacity(ETC)is strongly related to the redox functional groups(phenol and quinone)in DOM in peatland,indicating that quinone and phenol groups are the key driving factor to the variation of redox ability of DOM in peat soil.During the peat decomposition process,quinone group in DOM affected the redox ability of DOM only in the first 20 cm near the land surface,where is oxic and without flooding and oxygen;while phenol group participates in the whole process of redox reaction and is a key variable in assessing DOM participating in wetland biogeochemistry process.Meanwhile,the content of phenol in DOM changes with the degree of decomposition of peat,which plays an important role in controlling the peat decomposition as well as the output of DOM.In conclusion,the key role of DOM in peat soil anaerobic respiration process were discussed quantitatively and qualitatively,which enrich the theory of wetland ecosystem anaerobic respiration,and provide theoretical support for the carbon emission budget accounting in wetland ecosystem.