ANTHROPOGENIC FORCING ON METHANE EFFLUX FROM POLLUTED WETLANDS (ADYARRIVER) 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 C ity was measured throughout the year adopting the closed-chamber techn ique. Distinct spatial and temporal variations in methane emission wer e 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. Soi l temperature, sediment water content, salinity and sulfate were found to be critical natural variables influencing the methane emission rat es. This study indicates that due to human interference in this ecosys tem, on an average, similar to 15.58 mg m(-2) hr(-1) of methane is emi tted from the Adyar Estuary, which is significantly higher than that r eported for similar unpolluted natural wetlands (similar to 6.02 mg m( -2) hr(-1)). At the confluence of the Adyar Estuary with the Bay of Be ngal, the emission characteristics were significantly reduced (3.27 mg m(-2) hr(-1)) due to the influence of seawater.