Trends in CH <sub>4</sub> Emission Sources in the Los Angeles Basin from 2010 to 2023 Using Airborne Measurements
California legislation mandates a 40% reduction in CH<sub>4</sub> emissions from 2013 levels by 2030. Achieving this requires an accurate inventory of greenhouse gas sources, including urban CH<sub>4</sub>. This study determined summertime CH<sub>4</sub> and C<sub>2</sub>-C<sub>5</sub> alkane emissions from the Los Angeles (L.A.) Basin using airborne field campaign measurements from 2010, 2019, and 2023. Our analysis combined enhancement ratios of CH<sub>4</sub> and alkanes versus CO from <i>in situ</i> airborne measurements with the California Air Resources Board's CO emissions inventory. By incorporating known alkane abundances from various sectors, we apportioned the emission sources. We found an annual decline in CH<sub>4</sub> emissions from the L.A. Basin at a rate of -7.2 ± 5.8 Gg/year, consistent with literature and ground-site measurements from the Mount Wilson Observatory. The primary CH<sub>4</sub> sources were natural gas (52-57% of total emissions) and CH<sub>4</sub>-dominant sources, like landfills and dairies (41-47%). We also observed an annual increase in ethane emissions of 0.13 ± 0.19 Gg/year, which correlates with increasing ethane abundance in pipeline natural gas and decreasing ethane prices. If this linearly decreasing CH<sub>4</sub> emission trend were to continue, the L.A. Basin would be on track to reach the state's 2030 CH<sub>4</sub> emission reduction goals.
Authors
- Simone Meinardi (ORCID: https://orcid.org/0000-0003-4828-9889)
- Vanessa Selimovic (ORCID: https://orcid.org/0000-0002-3053-2732)
- Alan Fried (ORCID: https://orcid.org/0000-0002-5230-3527)
- Jessica B. Gilman (ORCID: https://orcid.org/0000-0002-7899-9948)
- Victoria Treadaway (ORCID: https://orcid.org/0000-0003-0564-3702)
- Eric C. Apel (ORCID: https://orcid.org/0000-0001-9421-818X)
- Gabrielle Pétron (ORCID: https://orcid.org/0000-0002-7458-5852)
- Dirk Richter (ORCID: https://orcid.org/0000-0002-2156-031X)
- Rebecca S. Hornbrook (ORCID: https://orcid.org/0000-0002-6304-6554)
- Colby Francoeur (ORCID: https://orcid.org/0000-0003-4491-7462)
- D. R. Blake (ORCID: https://orcid.org/0000-0002-8283-5014)
- Joshua P. DiGangi (ORCID: https://orcid.org/0000-0002-6764-8624)
- Nell B. Schafer (ORCID: https://orcid.org/0009-0000-2287-3775)
- Jeff Peischl (ORCID: https://orcid.org/0000-0002-9320-7101)
- Glenn S. Diskin (ORCID: https://orcid.org/0000-0002-3617-0269)
- Barbara Barletta (ORCID: https://orcid.org/0000-0003-3046-014X)
- Xin Lan (ORCID: https://orcid.org/0000-0001-6327-6950)
- P. Weibring (ORCID: https://orcid.org/0000-0001-9567-3803)
- Aaron Lamplugh (ORCID: https://orcid.org/0000-0002-5131-7070)
- Steven S. S Brown (ORCID: https://orcid.org/0000-0001-7477-9078)
- J. Walega
- K. R. Gurney (ORCID: https://orcid.org/0000-0001-9218-7164)
- J. B. Nowak (ORCID: https://orcid.org/0000-0002-5697-9807)
- Morgan Selby (ORCID: https://orcid.org/0009-0007-9259-9960)
- P. Dass (ORCID: https://orcid.org/0000-0003-3957-4055)
- Colin Harkins (ORCID: https://orcid.org/0000-0001-5692-3427)
- Caroline C. Womack (ORCID: https://orcid.org/0000-0002-7101-9054)
- Meng Li (ORCID: https://orcid.org/0000-0001-5418-9177)
Institutions
- NSF National Center for Atmospheric Research (US)
- Langley Research Center (US)
- Cooperative Institute for Research in Environmental Sciences (US)
- Institute of Arctic and Alpine Research (US)
- University of Colorado Boulder (US)
- Northern Arizona University (US)
- University of California, Irvine (US)
- Cyber University (JP)
- University of Michigan (US)
- University of Colorado System (US)
- NOAA Chemical Sciences Laboratory (US)
- NSF NCAR Atmospheric Chemistry Observations & Modeling (US)
Publication Details
- Journal
- Environmental Science & Technology
- Published
- 2025-11-29
- DOI
- https://doi.org/10.1021/acs.est.5c09817
- Citations
- 1
- Primary Topic
- Atmospheric and Environmental Gas Dynamics
- Type
- article
- Field-Weighted Citation Impact
- 1.11