CaltechAUTHORS
  A Caltech Library Service

Investigation of the sources and processing of organic aerosol over the Central Mexican Plateau from aircraft measurements during MILAGRO

DeCarlo, P. F. and Ulbrich, I. M. and Crounse, J. and de Foy, B. and Dunlea, E. J. and Aiken, A. C. and Knapp, D. and Weinheimer, A. J. and Campos, T. and Wennberg, P. O. and Jimenez, J. L. (2010) Investigation of the sources and processing of organic aerosol over the Central Mexican Plateau from aircraft measurements during MILAGRO. Atmospheric Chemistry and Physics, 10 (12). pp. 5257-5280. ISSN 1680-7316. http://resolver.caltech.edu/CaltechAUTHORS:20100701-131659744

[img]
Preview
PDF - Published Version
Creative Commons Attribution.

2113Kb

Use this Persistent URL to link to this item: http://resolver.caltech.edu/CaltechAUTHORS:20100701-131659744

Abstract

Organic aerosol (OA) represents approximately half of the submicron aerosol in Mexico City and the Central Mexican Plateau. This study uses the high time resolution measurements performed onboard the NCAR/NSF C-130 aircraft during the MILAGRO/MIRAGE-Mex field campaign in March 2006 to investigate the sources and chemical processing of the OA in this region. An examination of the OA/ΔCO ratio evolution as a function of photochemical age shows distinct behavior in the presence or absence of substantial open biomass burning (BB) influence, with the latter being consistent with other studies in polluted areas. In addition, we present results from Positive Matrix Factorization (PMF) analysis of 12-s High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) OA spectra. Four components were resolved. Three of the components contain substantial organic oxygen and are termed semivolatile oxygenated OA (SV-OOA), low-volatility OOA (LV-OOA), and biomass burning OA (BBOA). A reduced "hydrocarbon-like OA" (HOA) component is also resolved. LV-OOA is highly oxygenated (atomic O/C~1) and is aged organic aerosol linked to regional airmasses, with likely contributions from pollution, biomass burning, and other sources. SV-OOA is strongly correlated with ammonium nitrate, Ox, and the Mexico City Basin. We interpret SV-OOA as secondary OA which is nearly all (>90%) anthropogenic in origin. In the absence of biomass burning it represents the largest fraction of OA over the Mexico City basin, consistent with other studies in this region. BBOA is identified as arising from biomass burning sources due to a strong correlation with HCN, and the elevated contribution of the ion C_2H_4O_2^+ (m/z 60, a marker for levoglucosan and other primary BB species). WRF-FLEXPART calculated fire impact factors (FIF) show good correlation with BBOA mass concentrations within the basin, but show location offsets in the far field due to model transport errors. This component is small or absent when forest fires are suppressed by precipitation. Since PMF factors represent organic species grouped by chemical similarity, additional postprocessing is needed to more directly apportion OA amounts to sources, which is done here based on correlations to different tracers. The postprocessed AMS results are similar to those from an independent source apportionment based on multiple linear regression with gas-phase tracers. During a flight with very high forest fire intensity near the basin OA arising from open BB represents ~66% of the OA mass in the basin and contributes similarly to OA mass in the outflow. Aging and SOA formation of BB emissions is estimated to add OA mass equivalent to about ~32–42% of the primary BBOA over several hours to a day.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.5194/acp-10-5257-2010 DOIArticle
http://www.atmos-chem-phys.net/10/5257/2010/acp-10-5257-2010.htmlPublisherArticle
ORCID:
AuthorORCID
Crounse, J.0000-0001-5443-729X
Wennberg, P. O.0000-0002-6126-3854
Jimenez, J. L.0000-0001-6203-1847
Additional Information:© Author(s) 2010. This work is distributed under the Creative Commons Attribution 3.0 License. Received: 14 January 2010 – Published in Atmos. Chem. Phys. Discuss.: 2 February 2010. Revised: 20 May 2010 – Accepted: 8 June 2010 – Published: 15 June 2010. This study was supported by NSF (ATM- 0449815, ATM-0513116, ATM-0810950), NSF/UCAR S05-39607, NOAA (NA08OAR4310565), and EPA STAR (RD-83216101-0 and R833747). PFD is grateful for an EPA STAR graduate fellowship (FP-91650801) and an NSF International Postdoctoral Fellowship (0701013). IMU and ACA thank NASA for graduate fellowships (NNG05GQ50H and NNG04GR06H). Edited by: L. Molina.
Funders:
Funding AgencyGrant Number
NSFATM-0449815
NSFATM-0513116
NSFATM-0810950
NSFOISE-0701013
NSFS05-39607
National Oceanic and Atmospheric Administration (NOAA)NA08OAR4310565
Environmental Protection Agency (EPA)RD-83216101-0
Environmental Protection Agency (EPA)R833747
Environmental Protection Agency (EPA)FP-91650801
NASANNG05GQ50H
NASANNG04GR06H
University Corporation for Atmospheric Research (UCAR)UNSPECIFIED
Record Number:CaltechAUTHORS:20100701-131659744
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20100701-131659744
Official Citation:DeCarlo, P. F., Ulbrich, I. M., Crounse, J., de Foy, B., Dunlea, E. J., Aiken, A. C., Knapp, D., Weinheimer, A. J., Campos, T., Wennberg, P. O., and Jimenez, J. L.: Investigation of the sources and processing of organic aerosol over the Central Mexican Plateau from aircraft measurements during MILAGRO, Atmos. Chem. Phys., 10, 5257-5280, doi:10.5194/acp-10-5257-2010, 2010.
Usage Policy:This work is distributed under the Creative Commons Attribution 3.0 License.
ID Code:18898
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:03 Aug 2010 23:07
Last Modified:19 Sep 2017 23:11

Repository Staff Only: item control page