Greenhouse gas budgets of severely polluted urban lakes in India

Inland waters are important sources of greenhouse gases and emissions from polluted subtropical systems may be contributing to the observed global increase in atmospheric methane concentrations. Here we detail a scoping study where dissolved concentrations (CH4), carbon dioxide (CO2) nitrous oxide (N2O) were measured two contrasting urban lakes Bangalore (Bengaluru), Karnataka, India, June 2018 February 2020. Bellandur Lake is severely system whilst Jakkur has been subject partial restoration via treatment organic matter inputs. Methane three orders magnitude higher than Lake, with mean concentration 3.02 ± 1.57 mg CH4-C L?1 compared 1.72 1.22 ?g L?1. At CO2 same order as for CH4, whereas at greater CH4. Concentrations N2O negligible both lakes. Extrapolating our data estimate gas fluxes, daily fluxes consistently excess 1000 CH4 m2 d?1, rendering lake source GHGs 148,350 21,790 ton yr?1 CO2-e yr?1, 100 37 primarily this difference. We propose that contribution production warrants further investigation, particularly evidence suggests standard secondary wastewater support these potential significantly reduce emissions.