Concentrations and sources of organic carbon aerosols in the free troposphere over North America

[1] Aircraft measurements of water-soluble organic carbon (WSOC) aerosol over NE North America during summer 2004 (ITCT-2K4) are simulated with a global chemical transport model (GEOS-Chem) to test our understanding of the sources of organic carbon (OC) aerosol in the free troposphere (FT). Elevated concentrations were observed in plumes from boreal fires in Alaska and Canada. WSOC aerosol concentrations outside of these plumes average 0.9 ± 0.9 μg C m−3 in the FT (2–6 km). The corresponding model value is 0.7 ± 0.6 μg C m−3, including 42% from biomass burning, 36% from biogenic secondary organic aerosol (SOA), and 22% from anthropogenic emissions. Previous OC aerosol observations over the NW Pacific in spring 2001 (ACE-Asia) averaged 3.3 ± 2.8 μg C m−3 in the FT, compared to a model value of 0.3 ± 0.3 μg C m−3. WSOC aerosol concentrations in the boundary layer (BL) during ITCT-2K4 are consistent with OC aerosol observed at the IMPROVE surface network. The model is low in the boundary layer by 30%, which we attribute to secondary formation at a rate comparable to primary anthropogenic emission. Observed WSOC aerosol concentrations decrease by a factor of 2 from the BL to the FT, as compared to a factor of 10 decrease for sulfate, indicating that most of the WSOC aerosol in the FT originates in situ. Despite reproducing mean observed WSOC concentrations in the FT to within 25%, the model cannot account for the variance in the observations (R = 0.21). Covariance analysis of FT WSOC aerosol with other measured chemical variables suggests an aqueous-phase mechanism for SOA generation involving biogenic precursors.

[1]  R. Martin,et al.  North American Pollution Outflow and the Trapping of Convectively Lifted Pollution by Upper-Level Anticyclone , 2005 .

[2]  D. Jacob,et al.  Summertime influence of Asian pollution in the free troposphere over North America , 2007 .

[3]  Michael Fromm,et al.  Transport of forest fire smoke above the tropopause by supercell convection , 2003 .

[4]  J. A. de Gouw,et al.  Airborne measurements of carbonaceous aerosol soluble in water over northeastern United States: Method development and an investigation into water-soluble organic carbon sources , 2006 .

[5]  F. Fehsenfeld,et al.  An efficient photolysis system for fast-response NO2 measurements , 2000 .

[6]  Jonathan Crosier,et al.  Chemical composition observed over the mid-Atlantic and the detection of pollution signatures far from source regions , 2007 .

[7]  R. Kamens,et al.  Characterization of secondary aerosol from the photooxidation of toluene in the presence of NOx and 1-propene. , 2001, Environmental science & technology.

[8]  J. Seinfeld,et al.  Global distribution and climate forcing of carbonaceous aerosols , 2002 .

[9]  Alan Fried,et al.  Surface and Lightning Sources of Nitrogen Oxides over the United States: Magnitudes, Chemical Evolution, and Outflow , 2007 .

[10]  A. Stohl,et al.  Volatile organic compounds composition of merged and aged forest fire plumes from Alaska and western Canada , 2006 .

[11]  G. J. Frost,et al.  A chemical ionization mass spectrometry technique for airborne measurements of ammonia , 2007 .

[12]  W. Malm,et al.  Spatial and seasonal trends in particle concentration and optical extinction in the United States , 1994 .

[13]  R. Martin,et al.  Estimating ground-level PM2.5 using aerosol optical depth determined from satellite remote sensing , 2006 .

[14]  R. Martin,et al.  Model evidence for a significant source of secondary organic aerosol from isoprene , 2007 .

[15]  M. Andreae,et al.  Smoking Rain Clouds over the Amazon , 2004, Science.

[16]  C. Liousse,et al.  Construction of a 1° × 1° fossil fuel emission data set for carbonaceous aerosol and implementation and radiative impact in the ECHAM4 model , 1999 .

[17]  D. Streets,et al.  A technology‐based global inventory of black and organic carbon emissions from combustion , 2004 .

[18]  R. Hirsch,et al.  METHODS OF FITTING A STRAIGHT LINE TO DATA: EXAMPLES IN WATER RESOURCES , 1984 .

[19]  M. Molina,et al.  Secondary organic aerosol formation from anthropogenic air pollution: Rapid and higher than expected , 2006 .

[20]  D. Jacob,et al.  Constraints from 210Pb and 7Be on wet deposition and transport in a global three‐dimensional chemical tracer model driven by assimilated meteorological fields , 2001 .

[21]  Daniel J. Jacob,et al.  The impact of transpacific transport of mineral dust in the United States , 2007 .

[22]  D. Jacob,et al.  In situ measurements of HCN and CH3CN over the Pacific Ocean: Sources, sinks, and budgets , 2003 .

[23]  J. Jaffrezo,et al.  Seasonal variations of the water soluble organic carbon mass fraction of aerosol in two valleys of the French Alps , 2005 .

[24]  R. Derwent,et al.  Simulating regional scale secondary organic aerosol formation during the TORCH 2003 campaign in the southern UK , 2005 .

[25]  F. Fehsenfeld,et al.  Design and initial characterization of an inlet for gas-phase NOy measurements from aircraft , 1999 .

[26]  Annmarie G Carlton,et al.  Isoprene forms secondary organic aerosol through cloud processing: model simulations. , 2005, Environmental science & technology.

[27]  U. Baltensperger,et al.  Identification of Polymers as Major Components of Atmospheric Organic Aerosols , 2004, Science.

[28]  D. Jacob,et al.  Formaldehyde Distribution over North America: Implications for Satellite Retrievals of Formaldehyde Columns and Isoprene Emission , 2006 .

[29]  D. R. Worsnop,et al.  Hydrocarbon-like and oxygenated organic aerosols in Pittsburgh: insights into sources and processes of organic aerosols , 2005 .

[30]  D. Jacob,et al.  Global budget of methanol : Constraints from atmospheric observations , 2005 .

[31]  John H. Seinfeld,et al.  Aromatics, Reformulated Gasoline, and Atmospheric Organic Aerosol Formation , 1997 .

[32]  D. Dokken,et al.  Climate change 2001 , 2001 .

[33]  J. Drummond,et al.  Airborne intercomparison of vacuum ultraviolet fluorescence and tunable diode laser absorption measurements of tropospheric carbon monoxide , 2000 .

[34]  D. Blake,et al.  Distributions of brominated organic compounds in the troposphere and lower stratosphere , 1999 .

[35]  A. Weinheimer,et al.  Fraction and composition of NOy transported in air masses lofted from the North American continental boundary layer , 2004 .

[36]  J. Houghton,et al.  Climate change 2001 : the scientific basis , 2001 .

[37]  F. Flocke,et al.  A thermal dissociation–chemical ionization mass spectrometry (TD‐CIMS) technique for the simultaneous measurement of peroxyacyl nitrates and dinitrogen pentoxide , 2004 .

[38]  A. Stohl,et al.  Alaskan and Canadian forest fires exacerbate ozone pollution over Houston, Texas, on 19 and 20 July 2004 , 2006 .

[39]  Kostas Tsigaridis,et al.  Atmospheric Chemistry and Physics Global Modelling of Secondary Organic Aerosol in the Troposphere: a Sensitivity Analysis , 2003 .

[40]  D. Jacob,et al.  Inventory of boreal fire emissions for North America in 2004 : Importance of peat burning and pyroconvective injection , 2007 .

[41]  John H. Seinfeld,et al.  Global secondary organic aerosol from isoprene oxidation , 2006 .

[42]  Eric P. Shettle,et al.  Observations of boreal forest fire smoke in the stratosphere by POAM III, SAGE II, and lidar in 1998 , 2000 .

[43]  James M. Roberts,et al.  Budget of organic carbon in a polluted atmosphere: Results from the New England Air Quality Study in 2002 , 2005 .

[44]  P. Crutzen,et al.  Biomass burning as a source of formaldehyde, acetaldehyde, methanol, acetone, acetonitrile, and hydrogen cyanide , 1999 .

[45]  P. Saxena,et al.  Water-soluble organics in atmospheric particles: A critical review of the literature and application of thermodynamics to identify candidate compounds , 1996 .

[46]  Jay R. Herman,et al.  Pyro-cumulonimbus injection of smoke to the stratosphere: Observations and impact of a super blowup in northwestern Canada , 2005 .

[47]  Rodney J. Weber,et al.  A Particle-into-Liquid Collector for Rapid Measurement of Aerosol Bulk Chemical Composition , 2001 .

[48]  Mian Chin,et al.  Sources of carbonaceous aerosols over the United States and implications for natural visibility , 2003 .

[49]  Annmarie G. Carlton,et al.  Link between isoprene and secondary organic aerosol (SOA): Pyruvic acid oxidation yields low volatility organic acids in clouds , 2006 .

[50]  T. Eck,et al.  A review of biomass burning emissions part III: intensive optical properties of biomass burning particles , 2004 .

[51]  M. Chin,et al.  Natural and transboundary pollution influences on sulfate‐nitrate‐ammonium aerosols in the United States: Implications for policy , 2004 .

[52]  D. Blake,et al.  Hydrocarbon ratios during PEM‐WEST A: A model perspective , 1996 .

[53]  Ann M. Middlebrook,et al.  Single-particle mass spectrometry of tropospheric aerosol particles , 2006 .

[54]  A. Weinheimer,et al.  Fast‐response airborne in situ measurements of HNO3 during the Texas 2000 Air Quality Study , 2002 .

[55]  D. Jacob,et al.  Global simulation of tropospheric O3-NOx-hydrocarbon chemistry , 1998 .

[56]  Maria Cristina Facchini,et al.  Chemical features and seasonal variation of fine aerosol water-soluble organic compounds in the Po Valley, Italy , 2001 .

[57]  B. Jobson,et al.  Emissions lifetimes and ozone formation in power plant plumes , 1998 .

[58]  Mike Fromm,et al.  A case study of pyro-convection using transport model and remote sensing data , 2006 .

[59]  D. Jacob,et al.  Transpacific Transport of Asian Anthropogenic Aerosols and its Impact on Surface Air Quality in the United States , 2006 .

[60]  C. N. Hewitt,et al.  A global model of natural volatile organic compound emissions , 1995 .

[61]  Robert McLaren,et al.  Reactive uptake of glyoxal by particulate matter , 2005 .

[62]  J. Seinfeld,et al.  Gas/Particle Partitioning and Secondary Organic Aerosol Yields , 1996 .

[63]  John H. Seinfeld,et al.  Organic aerosol formation from the oxidation of biogenic hydrocarbons , 1999 .

[64]  Barry J. Huebert,et al.  A large organic aerosol source in the free troposphere missing from current models , 2005 .

[65]  Tami C. Bond,et al.  Export efficiency of black carbon aerosol in continental outflow: Global implications , 2005 .

[66]  M. Andreae,et al.  Emission of trace gases and aerosols from biomass burning , 2001 .

[67]  A. Limbeck,et al.  Dependence of in-cloud scavenging of polar organic aerosol compounds on the water solubility , 2000 .

[68]  Naresh Kumar,et al.  Regional Visibility Statistics in the United States: Natural and Transboundary Pollution Influences, and Implications for the Regional Haze Rule , 2006 .

[69]  John H. Seinfeld,et al.  Secondary organic aerosol formation from isoprene photooxidation under high‐NOx conditions , 2005 .