Atmospheric Methane Mixing Ratio in a South Indian Coastal City Interlaced by Wetlands

Industrialisation and urbanization leads to an increase in concentration of greenhouse gases, which eventually alters the radiation balance of the climate system. Urban regions are hotspots of greenhouse gas emissions which include CO2, CH4, N2O, etc. Methane emitting sources hosted by cities include fossil fuel combustion, municipal waste and sewage management, blocked drains and pools etc. Waste discharges from the residences, food wastes, market places etc., contribute to the methane production. Urban heat island causing warm nights in the city is also a suitable condition for the generation of methane.Ground level mixing ratio of methane in the tropical coastal city of Cochin in South India, during calm early morning periods was measured in this study. A mobile traverse method was employed from January 2011 to March 2013. Measurements were taken during both winter and summer seasons. It was observed that the ground level methane concentrations were significantly higher than the global average value. Intra-city variation in ground level mixing ratio was also significant. The maximum value of ground level methane in winter and summer were 3.85 ppm and 3.21 ppm respectively. The study reveals that the city acts as a source of atmospheric methane.