 |
| Titel |
Quantifying sources of methane and light alkanes in the Los Angeles Basin, California |
| VerfasserIn |
Jeff Peischl, Thomas Ryerson, Elliot Atlas, Donald Blake, Jerome Brioude, Bruce Daube, Joost de Gouw, Gregory Frost, Drew Gentner, Jessica Gilman, Allen Goldstein, Robert Harley, John Holloway, William Kuster, Gregory Santoni, Michael Trainer, Steven Wofsy, David Parrish |
| Konferenz |
EGU General Assembly 2013
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250084164
|
|
|
|
|
|
| Zusammenfassung |
| We use ambient measurements to apportion the relative contributions of different source
sectors to the methane (CH4) emissions budget of a U.S. megacity. This approach uses
ambient measurements of methane and C2-C5 alkanes (ethane through pentanes) and
includes source composition information to distinguish between methane emitted from
landfills and feedlots, wastewater treatment plants, tailpipe emissions, leaks of dry natural gas
in pipelines and/or local seeps, and leaks of locally produced (unprocessed) natural
gas. Source composition information can be taken from existing tabulations or
developed by direct sampling of emissions using a mobile platform. By including C2-C5
alkane information, a linear combination of these source signatures can be found to
match the observed atmospheric enhancement ratios to determine relative emissions
strengths.
We apply this technique to apportion CH4 emissions in Los Angeles, CA (L.A.) using
data from the CalNex field project in 2010. Our analysis of L.A. atmospheric data shows the
two largest CH4 sources in the city are emissions of gas from pipelines and/or from geologic
seeps (47%), and emissions from landfills (40%). Local oil and gas production
is a relatively minor source of CH4, contributing 8% of total CH4 emissions in
L.A.
Absolute CH4 emissions rates are derived by multiplying the observed CH4/CO
enhancement ratio by State of California inventory values for carbon monoxide (CO)
emissions in Los Angeles. Apportioning this total suggests that emissions from the combined
natural and anthropogenic gas sources account for the differences between top-down and
bottom-up CH4 estimates previously published for Los Angeles. Further, total CH4 emission
attributed in our analysis to local gas extraction represents 17% of local production. While a
derived leak rate of 17% of local production may seem unrealistically high, it is qualitatively
consistent with the 12% reported in a recent state inventory survey of the L.A. oil and gas
industry. |
|
|
|
|
|
|