Sources and transport of Δ<sup>14</sup>C in CO<sub>2</sub> within the Mexico City Basin and vicinity
Radiocarbon samples taken over Mexico City and the surrounding region during the MILAGRO field campaign in March 2006 exhibited an unexpected distribution: (1) relatively few samples (23%) were below the North American free tropospheric background value (57±2‰) despite the fossil fuel emi...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2009-07-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/9/4973/2009/acp-9-4973-2009.pdf |
| _version_ | 1818369359594127360 |
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| author | H. B. Singh G. W. Sachse G. S. Diskin D. R. Blake N. J. Blake Y. Choi S. A. Vay S. C. Tyler |
| author_facet | H. B. Singh G. W. Sachse G. S. Diskin D. R. Blake N. J. Blake Y. Choi S. A. Vay S. C. Tyler |
| author_sort | H. B. Singh |
| collection | DOAJ |
| description | Radiocarbon samples taken over Mexico City and the surrounding region during the MILAGRO field campaign in March 2006 exhibited an unexpected distribution: (1) relatively few samples (23%) were below the North American free tropospheric background value (57±2‰) despite the fossil fuel emissions from one of the world's most highly polluted environments; and (2) frequent enrichment well above the background value was observed. Correlate source tracer species and air transport characteristics were examined to elucidate influences on the radiocarbon distribution. Our analysis suggests that a combination of radiocarbon sources biased the "regional radiocarbon background" above the North American value thereby decreasing the apparent fossil fuel signature. Likely sources include the release of <sup>14</sup>C-enhanced carbon from bomb <sup>14</sup>C sequestered in plant carbon pools via the ubiquitous biomass burning in the region as well as the direct release of radiocarbon as CO<sub>2</sub> from other "hot" sources. Plausible perturbations from local point "hot" sources include the burning of hazardous waste in cement kilns; medical waste incineration; and emissions from the Laguna Verde Nuclear Power Plant. These observations provide insight into the use of Δ<sup>14</sup>CO<sub>2</sub> to constrain fossil fuel emissions in the megacity environment, indicating that underestimation of the fossil fuel contribution to the CO<sub>2</sub> flux is likely wherever biomass burning coexists with urban emissions and is unaccounted for as a source of the elevated CO<sub>2</sub> observed above local background. Our findings increase the complexity required to quantify fossil fuel-derived CO<sub>2</sub> in source-rich environments characteristic of megacities, and have implications for the use of Δ<sup>14</sup>CO<sub>2</sub> observations in evaluating bottom-up emission inventories and their reliability as a tool for validating national emission claims of CO<sub>2</sub> within the framework of the Kyoto Protocol. |
| first_indexed | 2024-12-13T23:22:35Z |
| format | Article |
| id | doaj.art-3dd871b747594973bf9408790c0a9470 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-13T23:22:35Z |
| publishDate | 2009-07-01 |
| publisher | Copernicus Publications |
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| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-3dd871b747594973bf9408790c0a94702022-12-21T23:27:39ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242009-07-0191449734985Sources and transport of Δ<sup>14</sup>C in CO<sub>2</sub> within the Mexico City Basin and vicinityH. B. SinghG. W. SachseG. S. DiskinD. R. BlakeN. J. BlakeY. ChoiS. A. VayS. C. TylerRadiocarbon samples taken over Mexico City and the surrounding region during the MILAGRO field campaign in March 2006 exhibited an unexpected distribution: (1) relatively few samples (23%) were below the North American free tropospheric background value (57±2‰) despite the fossil fuel emissions from one of the world's most highly polluted environments; and (2) frequent enrichment well above the background value was observed. Correlate source tracer species and air transport characteristics were examined to elucidate influences on the radiocarbon distribution. Our analysis suggests that a combination of radiocarbon sources biased the "regional radiocarbon background" above the North American value thereby decreasing the apparent fossil fuel signature. Likely sources include the release of <sup>14</sup>C-enhanced carbon from bomb <sup>14</sup>C sequestered in plant carbon pools via the ubiquitous biomass burning in the region as well as the direct release of radiocarbon as CO<sub>2</sub> from other "hot" sources. Plausible perturbations from local point "hot" sources include the burning of hazardous waste in cement kilns; medical waste incineration; and emissions from the Laguna Verde Nuclear Power Plant. These observations provide insight into the use of Δ<sup>14</sup>CO<sub>2</sub> to constrain fossil fuel emissions in the megacity environment, indicating that underestimation of the fossil fuel contribution to the CO<sub>2</sub> flux is likely wherever biomass burning coexists with urban emissions and is unaccounted for as a source of the elevated CO<sub>2</sub> observed above local background. Our findings increase the complexity required to quantify fossil fuel-derived CO<sub>2</sub> in source-rich environments characteristic of megacities, and have implications for the use of Δ<sup>14</sup>CO<sub>2</sub> observations in evaluating bottom-up emission inventories and their reliability as a tool for validating national emission claims of CO<sub>2</sub> within the framework of the Kyoto Protocol.http://www.atmos-chem-phys.net/9/4973/2009/acp-9-4973-2009.pdf |
| spellingShingle | H. B. Singh G. W. Sachse G. S. Diskin D. R. Blake N. J. Blake Y. Choi S. A. Vay S. C. Tyler Sources and transport of Δ<sup>14</sup>C in CO<sub>2</sub> within the Mexico City Basin and vicinity Atmospheric Chemistry and Physics |
| title | Sources and transport of Δ<sup>14</sup>C in CO<sub>2</sub> within the Mexico City Basin and vicinity |
| title_full | Sources and transport of Δ<sup>14</sup>C in CO<sub>2</sub> within the Mexico City Basin and vicinity |
| title_fullStr | Sources and transport of Δ<sup>14</sup>C in CO<sub>2</sub> within the Mexico City Basin and vicinity |
| title_full_unstemmed | Sources and transport of Δ<sup>14</sup>C in CO<sub>2</sub> within the Mexico City Basin and vicinity |
| title_short | Sources and transport of Δ<sup>14</sup>C in CO<sub>2</sub> within the Mexico City Basin and vicinity |
| title_sort | sources and transport of delta sup 14 sup c in co sub 2 sub within the mexico city basin and vicinity |
| url | http://www.atmos-chem-phys.net/9/4973/2009/acp-9-4973-2009.pdf |
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