Methane and nitrous oxide fluxes in the polluted Adyar River and estuary, SE India.

Abstract We measured dissolved N 2 O, CH 4 , O 2 , NH 4 + , NO 3 - and NO 2 - on 7 transects along the polluted Adyar River–estuary, SE India and estimated N 2 O and CH 4 emissions using a gas exchange relation and a floating chamber. High NO 2 - implied some nitrification of a large anthropogenic NH 4 + pool. In the lower catchment CH 4 was maximal (6.3 ± 4.3 × 10 4  nM), exceeding the ebullition threshold, whereas strong undersaturation of N 2 O and O 2 implied intense denitrification. Emissions fluxes for the whole Adyar system ∼2.5 × 10 8  g CH 4  yr −1 and ∼2.4 × 10 6  g N 2 O yr −1 estimated with a gas exchange relation and ∼2 × 10 9  g CH 4  yr −1 derived with a floating chamber illustrate the importance of CH 4 ebullition. An equivalent CO 2 flux ∼1–10 × 10 10  g yr −1 derived using global warming potentials is equivalent to total Chennai motor vehicle CO 2 emissions in one month. Studies such as this may inform more effective waste management and future compliance with international emissions agreements.