Greenhouse gas budgets of severely polluted urban lakes in India

Pickard, Amy ORCID: https://orcid.org/0000-0003-1069-3720; White, Stella ORCID: https://orcid.org/0000-0001-5716-2404; Bhattacharyya, Sumita; Carvalho, Laurence; Dobel, Anne; Drewer, Julia ORCID: https://orcid.org/0000-0002-6263-6341; Jamwal, Priyanka; Helfter, Carole ORCID: https://orcid.org/0000-0001-5773-4652. 2021 Greenhouse gas budgets of severely polluted urban lakes in India. Science of the Total Environment, 798, 149019. 8, pp. https://doi.org/10.1016/j.scitotenv.2021.149019

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Abstract/Summary

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

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1016/j.scitotenv.2021.149019
UKCEH and CEH Sections/Science Areas:	Atmospheric Chemistry and Effects (Science Area 2017-) Water Resources (Science Area 2017-)
ISSN:	0048-9697
Additional Keywords:	greenhouse gases, polluted lakes, lake restoration
NORA Subject Terms:	Hydrology Atmospheric Sciences
Date made live:	28 Jul 2021 10:34 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/530809

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