Anthropogenic forcing on methane efflux from polluted wetlands (Adyar River) of Madras City, India

Wetlands are the largest natural source of methane to the atmosphere. Methane emission from a polluted, tropical coastal wetland in Madras City was measured throughout the year adopting the closed-chamber technique. Distinct spatial and temporal variations in methane emission were observed in the wetlands, based on the degree of pollution, at each of these locations. The inhibiting influences of sulfate and salinity on methanogenesis were also obvious features in the present study. Soil temperature, sediment water content, salinity and sulfate were found to be critical natural variables influencing the methane emission rates. This study indicates that due to human interference in this ecosystem, on an average, ∼ 15.58 mg${\rm m}^{-2}\ {\rm hr}^{-1}$of methane is emitted from the Adyar Estuary, which is significantly higher than that reported for similar unpolluted natural wetlands (∼ 6.02 mg${\rm m}^{-2}\ {\rm hr}^{-1}$). At the confluence of the Adyar Estuary with the Bay of Bengal, the emission characteristics were significantly reduced (3.27 mg${\rm m}^{-2}\ {\rm hr}^{-1}$) due to the influence of seawater.