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| Titel |
Size-resolved aerosol emission factors and new particle formation/growth activity occurring in Mexico City during the MILAGRO 2006 Campaign |
| VerfasserIn |
A. J. Kalafut-Pettibone, J. Wang, W. E. Eichinger, A. Clarke, S. A. Vay, D. R. Blake, C. O. Stanier |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 17 ; Nr. 11, no. 17 (2011-09-01), S.8861-8881 |
| Datensatznummer |
250010042
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| Publikation (Nr.) |
 copernicus.org/acp-11-8861-2011.pdf |
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| Zusammenfassung |
| Measurements of the aerosol size distribution from 11 nm to 2.5 microns were
made in Mexico City in March 2006, during the MILAGRO (Megacity Initiative:
Local and Global Research Observations) field campaign. Observations at the
urban supersite, referred to as T0, could often be characterized by morning
conditions with high particle mass concentrations, low mixing heights, and
highly correlated particle number and CO2 concentrations, indicative
that particle number is controlled by primary emissions. Average
size-resolved and total number- and volume-based emission factors for
combustion sources impacting T0 have been determined using a comparison of
peak sizes in particle number and CO2 concentration. Peaks are
determined by subtracting the measured concentration from a calculated
baseline concentration time series. The number emission and volume emission
factors for particles from 11 nm to 494 nm are 1.56 × 1015 particles, and
9.48 × 1011 cubic microns per kg of carbon, respectively. The uncertainty
of the number emission factor is approximately plus or minus 50 %. The
mode of the number emission factor was between 25 and 32 nm, while the mode
of the volume factor was between 0.25 and 0.32 microns. These emission
factors are reported as log normal model parameters and are compared with
multiple emission factors from the literature. In Mexico City in the
afternoon, the CO2 concentration drops during ventilation of the
polluted layer, and the coupling between CO2 and particle number breaks
down, especially during new particle formation events when particle number
is no longer controlled by primary emissions. Using measurements of particle
number and CO2 taken aboard the NASA DC-8, the determined primary
emission factor was applied to the Mexico City Metropolitan Area (MCMA)
plume to quantify the degree of secondary particle formation in the plume;
the primary emission factor accounts for less than 50 % of the total
particle number and the surplus particle count is not correlated with
photochemical age. Primary particle volume and number in the size range
0.1–2 μm are similarly too low to explain the observed volume
distribution. Contrary to the case for number, the apparent secondary volume
increases with photochemical age. The size distribution of the apparent
increase, with a mode at ~250 nm, is reported. |
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