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Title: Mexico city aerosol analysis during MILAGRO using high resolution aerosol mass spectrometry at the urban supersite (T0) - Part 2: Analysis of the biomass burning contribution and the non-fossil carbon fraction

Abstract

Submicron aerosol was analyzed during the MILAGRO field campaign in March 2006 at the T0 urban supersite in Mexico City with a High-Resolution Aerosol Mass Spectrometer (AMS) and complementary instrumentation. Positive Matrix Factorization (PMF) of high resolution AMS spectra identified a biomass burning organic aerosol (BBOA) component, which includes several large plumes that appear to be from forest fires within the region. Here, we show that the AMS BBOA concentration at T0 correlates with fire counts in the vicinity of Mexico City and that most of the BBOA variability is captured when the FLEXPART model is used for the dispersion of fire emissions as estimated from satellite fire counts. The resulting FLEXPART fire impact factor (FIF) correlates well with the observed BBOA, acetonitrile (CH3CN), levoglucosan, and potassium, indicating that wildfires in the region surrounding Mexico City are the dominant source of BBOA at T0 during MILAGRO. The impact of distant BB sources such as the Yucatan is small during this period. All fire tracers are correlated, with BBOA and levoglucosan showing little background, acetonitrile having a well-known tropospheric background of {approx}100-150 pptv, and PM2.5 potassium having a background of {approx}160 ng m3 (two-thirds of its average concentration), which does notmore » appear to be related to BB sources. We define two high fire periods based on satellite fire counts and FLEXPART-predicted FIFs. We then compare these periods with a low fire period when the impact of regional fires is about a factor of 5 smaller. Fire tracers are very elevated in the high fire periods whereas tracers of urban pollution do not change between these periods. Dust is also elevated during the high BB period but this appears to be coincidental due to the drier conditions and not driven by direct dust emission from the fires. The AMS oxygenated organic aerosol (OA) factor (OOA, mostly secondary OA or SOA) does not show an increase during the fire periods or a correlation with fire counts, FLEXPART-predicted FIFs or fire tracers, indicating that it is dominated by urban and/or regional sources and not by the fires near the MCMA. A new 14C aerosol dataset is presented. Both this new and a previously published dataset of 14C analysis suggest a similar BBOA contribution as the AMS and chemical mass balance (CMB), resulting in 13% higher non-fossil carbon during the high vs. low regional fire periods. The new dataset has {approx}15% more fossil carbon on average than the previously published one, and possible reasons for this discrepancy are discussed. During the low regional fire period, 38% of organic carbon (OC) and 28% total carbon (TC) are from non-fossil sources, suggesting the importance of urban and regional non-fossil carbon sources other than the fires, such as food cooking and regional biogenic SOA. The ambient BBOA/CH3CN ratio is much higher in the afternoon when the wildfires are most intense than during the rest of the day. Also, there are large differences in the contributions of the different OA components to the surface concentrations vs. the integrated column amounts. Both facts may explain some apparent disagreements between BB impacts estimated from afternoon aircraft flights vs. those from 24-h ground measurements. We show that by properly accounting for the non-BB sources of K, all of the BB PM estimates from MILAGRO can be reconciled. Overall, the fires from the region near the MCMA are estimated to contribute 15-23% of the OA and 7-9% of the fine PM at T0 during MILAGRO, and 2-3% of the fine PM as an annual average. The 2006 MCMA emissions inventory contains a substantially lower impact of the forest fire emissions, although a fraction of these emissions occur just outside of the MCMA inventory area.« less

Authors:
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Publication Date:
Research Org.:
Brookhaven National Lab. (BNL), Upton, NY (United States)
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
984433
Report Number(s):
BNL-93717-2010-JA
Journal ID: ISSN 1680-7316; R&D Project: 2012-BNL-EE630EECA-Budg; KP1701000; TRN: US201015%%1173
DOE Contract Number:  
DE-AC02-98CH10886
Resource Type:
Journal Article
Journal Name:
Atmospheric Chemistry and Physics
Additional Journal Information:
Journal Volume: 10; Journal Issue: 12; Journal ID: ISSN 1680-7316
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; 54 ENVIRONMENTAL SCIENCES; ACETONITRILE; AEROSOLS; BIOMASS; CARBON; CARBON SOURCES; DUSTS; FACTORIZATION; FORESTS; MASS BALANCE; MASS SPECTROMETERS; MASS SPECTROSCOPY; MEXICO; PLUMES; POLLUTION; POTASSIUM; RESOLUTION; SPECTRA; FIRES

Citation Formats

Aiken, A C, Wang, J, de Foy, B, Wiedinmyer, C, DeCarlo, P F, Ulbrich, I M, Wehrli, M N, Szidat, S, Prevot, A S. H., Noda, J, Wacker, L, Volkamer, R, Fortner, E, Laskin, A, Shutthanandan, V, Zheng, J, Zhang, R, Paredes-Miranda, G, Arnott, W P, Molina, L T, Sosa, G, Querol, X, and Jimenez, J L. Mexico city aerosol analysis during MILAGRO using high resolution aerosol mass spectrometry at the urban supersite (T0) - Part 2: Analysis of the biomass burning contribution and the non-fossil carbon fraction. United States: N. p., 2010. Web. doi:10.5194/acp-10-5315-2010.
Aiken, A C, Wang, J, de Foy, B, Wiedinmyer, C, DeCarlo, P F, Ulbrich, I M, Wehrli, M N, Szidat, S, Prevot, A S. H., Noda, J, Wacker, L, Volkamer, R, Fortner, E, Laskin, A, Shutthanandan, V, Zheng, J, Zhang, R, Paredes-Miranda, G, Arnott, W P, Molina, L T, Sosa, G, Querol, X, & Jimenez, J L. Mexico city aerosol analysis during MILAGRO using high resolution aerosol mass spectrometry at the urban supersite (T0) - Part 2: Analysis of the biomass burning contribution and the non-fossil carbon fraction. United States. https://doi.org/10.5194/acp-10-5315-2010
Aiken, A C, Wang, J, de Foy, B, Wiedinmyer, C, DeCarlo, P F, Ulbrich, I M, Wehrli, M N, Szidat, S, Prevot, A S. H., Noda, J, Wacker, L, Volkamer, R, Fortner, E, Laskin, A, Shutthanandan, V, Zheng, J, Zhang, R, Paredes-Miranda, G, Arnott, W P, Molina, L T, Sosa, G, Querol, X, and Jimenez, J L. 2010. "Mexico city aerosol analysis during MILAGRO using high resolution aerosol mass spectrometry at the urban supersite (T0) - Part 2: Analysis of the biomass burning contribution and the non-fossil carbon fraction". United States. https://doi.org/10.5194/acp-10-5315-2010.
@article{osti_984433,
title = {Mexico city aerosol analysis during MILAGRO using high resolution aerosol mass spectrometry at the urban supersite (T0) - Part 2: Analysis of the biomass burning contribution and the non-fossil carbon fraction},
author = {Aiken, A C and Wang, J and de Foy, B and Wiedinmyer, C and DeCarlo, P F and Ulbrich, I M and Wehrli, M N and Szidat, S and Prevot, A S. H. and Noda, J and Wacker, L and Volkamer, R and Fortner, E and Laskin, A and Shutthanandan, V and Zheng, J and Zhang, R and Paredes-Miranda, G and Arnott, W P and Molina, L T and Sosa, G and Querol, X and Jimenez, J L},
abstractNote = {Submicron aerosol was analyzed during the MILAGRO field campaign in March 2006 at the T0 urban supersite in Mexico City with a High-Resolution Aerosol Mass Spectrometer (AMS) and complementary instrumentation. Positive Matrix Factorization (PMF) of high resolution AMS spectra identified a biomass burning organic aerosol (BBOA) component, which includes several large plumes that appear to be from forest fires within the region. Here, we show that the AMS BBOA concentration at T0 correlates with fire counts in the vicinity of Mexico City and that most of the BBOA variability is captured when the FLEXPART model is used for the dispersion of fire emissions as estimated from satellite fire counts. The resulting FLEXPART fire impact factor (FIF) correlates well with the observed BBOA, acetonitrile (CH3CN), levoglucosan, and potassium, indicating that wildfires in the region surrounding Mexico City are the dominant source of BBOA at T0 during MILAGRO. The impact of distant BB sources such as the Yucatan is small during this period. All fire tracers are correlated, with BBOA and levoglucosan showing little background, acetonitrile having a well-known tropospheric background of {approx}100-150 pptv, and PM2.5 potassium having a background of {approx}160 ng m3 (two-thirds of its average concentration), which does not appear to be related to BB sources. We define two high fire periods based on satellite fire counts and FLEXPART-predicted FIFs. We then compare these periods with a low fire period when the impact of regional fires is about a factor of 5 smaller. Fire tracers are very elevated in the high fire periods whereas tracers of urban pollution do not change between these periods. Dust is also elevated during the high BB period but this appears to be coincidental due to the drier conditions and not driven by direct dust emission from the fires. The AMS oxygenated organic aerosol (OA) factor (OOA, mostly secondary OA or SOA) does not show an increase during the fire periods or a correlation with fire counts, FLEXPART-predicted FIFs or fire tracers, indicating that it is dominated by urban and/or regional sources and not by the fires near the MCMA. A new 14C aerosol dataset is presented. Both this new and a previously published dataset of 14C analysis suggest a similar BBOA contribution as the AMS and chemical mass balance (CMB), resulting in 13% higher non-fossil carbon during the high vs. low regional fire periods. The new dataset has {approx}15% more fossil carbon on average than the previously published one, and possible reasons for this discrepancy are discussed. During the low regional fire period, 38% of organic carbon (OC) and 28% total carbon (TC) are from non-fossil sources, suggesting the importance of urban and regional non-fossil carbon sources other than the fires, such as food cooking and regional biogenic SOA. The ambient BBOA/CH3CN ratio is much higher in the afternoon when the wildfires are most intense than during the rest of the day. Also, there are large differences in the contributions of the different OA components to the surface concentrations vs. the integrated column amounts. Both facts may explain some apparent disagreements between BB impacts estimated from afternoon aircraft flights vs. those from 24-h ground measurements. We show that by properly accounting for the non-BB sources of K, all of the BB PM estimates from MILAGRO can be reconciled. Overall, the fires from the region near the MCMA are estimated to contribute 15-23% of the OA and 7-9% of the fine PM at T0 during MILAGRO, and 2-3% of the fine PM as an annual average. The 2006 MCMA emissions inventory contains a substantially lower impact of the forest fire emissions, although a fraction of these emissions occur just outside of the MCMA inventory area.},
doi = {10.5194/acp-10-5315-2010},
url = {https://www.osti.gov/biblio/984433}, journal = {Atmospheric Chemistry and Physics},
issn = {1680-7316},
number = 12,
volume = 10,
place = {United States},
year = {2010},
month = {6}
}