| Autor: |
Fairley, David1 fairley@baaqmd.gov, Fischer, Marc L.2 |
| Předmět: |
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| Zdroj: |
Atmospheric Environment. Apr2015, Vol. 107, p9-15. 7p. |
| Abstrakt: |
Methane is a potent greenhouse gas (GHG) that is now included in both California State and San Francisco Bay Area (SFBA) bottom-up emission inventories as part of California's effort to reduce anthropogenic GHG emissions. Here we provide a top-down estimate of methane (CH 4 ) emissions from the SFBA by combining atmospheric measurements with the comparatively better estimated emission inventory for carbon monoxide (CO). Local enhancements of CH 4 and CO are estimated using measurements from 14 air quality sites in the SFBA combined together with global background measurements. Mean annual CH 4 emissions are estimated from the product of Bay Area Air Quality Management District (BAAQMD) emission inventory CO and the slope of ambient local CH 4 to CO. The resulting top-down estimates of CH 4 emissions are found to decrease slightly from 1990 to 2012, with a mean value of 240 ± 60 GgCH 4 yr −1 (at 95% confidence) in the most recent (2009–2012) period, and correspond to reasonably a constant factor of 1.5–2.0 (at 95% confidence) times larger than the BAAQMD CH 4 emission inventory. However, we note that uncertainty in these emission estimates is dominated by the variation in CH 4 :CO enhancement ratios across the observing sites and we expect the estimates could represent a lower-limit on CH 4 emissions because BAAQMD monitoring sites focus on urban air quality and may be biased toward CO rather than CH 4 sources. [ABSTRACT FROM AUTHOR] |
| Databáze: |
GreenFILE |
| Externí odkaz: |
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Full Text from ScienceDirect