Exploring correlation between redox potential and other edaphic factors in field and laboratory conditions in relation to methane efflux

Abstract

Methane is primarily a biogenic gas, which is implicated in global warming. Although its production in the anoxic conditions is regulated by several edaphic factors, aquatic macrophytes also influence methane emission by providing aerenchyma to act as chimney for CH 4 transport from the sediment to troposphere, by releasing root exudates to the sediment to serve as substrate for methanogenic bacteria and by transporting atmospheric O 2 to rhizosphere, which stimulates CH 4 consumption. Among the edaphic factors, redox potential (Eh) is the most important, which largely determines the action of methanogenic bacteria. Hence, a study was undertaken first to find out the correlation between CH 4 emission and edaphic factors in the field conditions and then to understand the relationship between Eh and other edaphic factors. The field studies revealed that natural wetlands were the major source of CH 4 emission, and the vegetation plays an important role in CH 4 emission from the water bodies. However, it was very difficult to establish a strong relationship between the CH 4 emission and the edaphic factors in the field conditions due to other limiting factors and their constant fluctuations. In this connection, the laboratory experiments exhibited that soil temperature, pH, moisture regime and incubation period were negatively correlated with Eh, which determines the initiation of methanogenic process. However, organic carbon and the water regime over the soil surface did not show any impact on Eh in this study.