Dissolved Methane Fluctuations in Relation to Hydrochemical Parameters in

Methane is one of the important greenhouse gases that contribute to a rise in global mean surface temperature. Aquatic environments are postulated to contribute > 50% of the total global methane (CH4 ) flux to the atmosphere (de angelis and Lilley, 1987). Dissolved methane concentration in surface waters was measured from January to December 2008 at two selected sites upper reaches (ONGC Bridge) and lower reaches (Dumas) of Tapi estuary, Gulf of Cambay, Gujarat, India. Besides, the important hydrochemical parameters like total organic carbon (TOC), dissolved oxygen (DO), salinity and nutrients (phosphate, nitrate and sulphate) were also analyzed. The mean dissolved CH4 concentration for all water samples at upper reaches was 1369.00 nmol/L and at lower reaches was 1082.04 nmol/L. The positive correlation was found between dissolved methane content and total organic carbon. On the contrary, the negative correlation was observed between methane concentration and nutrients like dissolved oxygen, salinity, phosphate, nitrate and sulphate. The probable causes for varying dissolved methane concentration and saturation at different reaches with hydrochemical parameters are discussed.