Importance of mineral cations and organics in gas-aerosol partitioning of reactive nitrogen compounds : case study based on MINOS results

The partitioning of reactive nitrogen compounds between the gas and the aerosol phase, as observed during the MINOS (Mediterranean INtensive Oxidant Study) campaign in Crete, Greece, in July and August 2001, has been studied with three thermodynamic gas-aerosol equilibrium models (EQMs) of different chemical complexity: ISORROPIA, which is limited to the ammonium-sulfate-nitrate-sodium-chloride-water-system; SCAPE2, which also includes mineral elements (calcium, magnesium and potassium); and EQSAM2, which additionally accounts for organic acids. The different EQMs are constrained by measured gas (g) and aerosol (a) concentrations: Total ammonia (NH 3(g) and NH 4(a) + ), total nitrate (HNO 3(g) and NO 3(a) - ), total sulfate (H 2 SO 4(g) and SO 4(a) 2- ), total chloride (HCl (g) and Cl - (a) ), sodium (Na + (a) ), calcium (Ca 2+ (a) ), magnesium (Mg 2+ (a) ), potassium (K + (a) ) and organic acids (a). Although the three EQMs differ considerably in particular aspects, their application at the same level of complexity yields comparable results for the equilibrium composition and phase partitioning of ammonia and nitric acid, i.e. within the range of measurement uncertainties (~10%). Their application at different levels of complexity, however, gives rise to substantial differences for the gas-aerosol partitioning of reactive nitrogen compounds. Our results show that only if (soluble) mineral components and (lumped) organic acids are accounted for, the observed gas-aerosol partitioning of ammonia and nitric acid can be accurately reproduced for air pollution episodes characterized by a complex chemical mixture, typical for the Mediterranean lower atmosphere.

[1]  W. Maenhaut,et al.  Aerosol mass closure and reconstruction of the light scattering coefficient over the Eastern Mediterranean Sea during the MINOS campaign , 2005 .

[2]  M. Andreae,et al.  The NH4+ – NO3– – Cl– – SO42– – H2O aerosol system and its gas phase precursors at a pasture site in the Amazon Basin: How relevant are mineral cations and soluble organic acids? , 2005 .

[3]  N. Mihalopoulos,et al.  Characterization of carbonaceous aerosols during the MINOS campaign in Crete, July–August 2001: a multi-analytical approach , 2003 .

[4]  J. Lelieveld,et al.  Ground-based PTR-MS measurements of reactive organic compounds during the MINOS campaign in Crete, July-August 2001 , 2003 .

[5]  N. Mihalopoulos,et al.  OH in the coastal boundary layer of Crete during MINOS: Measurements and relationship with ozone photolysis , 2003 .

[6]  J. Lelieveld,et al.  Chemical characteristics assigned to trajectory clusters during the MINOS campaign , 2003 .

[7]  J. Lelieveld,et al.  Global Air Pollution Crossroads over the Mediterranean , 2002, Science.

[8]  M. Blumthaler,et al.  Chemical, physical, and optical characterization of aerosols during PAUR II experiment , 2002 .

[9]  C. Moulin,et al.  Aerosol sources and their contribution to the chemical composition of aerosols in the Eastern Mediterranean Sea during summertime , 2002 .

[10]  Jos Lelieveld,et al.  Gas/aerosol partitioning: 1. A computationally efficient model , 2002 .

[11]  J. Lelieveld,et al.  Gas/aerosol partitioning 2. Global modeling results , 2002 .

[12]  Martijn Schaap,et al.  Constructing the European aerosol nitrate concentration field from quality analysed data , 2002 .

[13]  Nikos Mihalopoulos,et al.  Seasonal variation of dimethylsulfide in the gas phase and of methanesulfonate and non-sea-salt sulfate in the aerosols phase in the Eastern Mediterranean atmosphere , 2002 .

[14]  S. Jennings,et al.  Role of organic and black carbon in the chemical composition of atmospheric aerosol at European background sites , 2001 .

[15]  S. Pandis,et al.  Partitioning of nitrate and ammonium between the gas and particulate phases during the 1997 IMADA-AVER study in Mexico City , 2001 .

[16]  S. Metzger.  Gas/Aerosol partitioning: a simplified method for global modeling , 2000 .

[17]  K. Kawamura,et al.  Molecular distributions of water soluble dicarboxylic acids in marine aerosols over the Pacific Ocean including tropics , 1999 .

[18]  A. Nenes,et al.  ISORROPIA: A New Thermodynamic Equilibrium Model for Multiphase Multicomponent Inorganic Aerosols , 1998 .

[19]  J. Seinfeld,et al.  Time scales to achieve atmospheric gas-aerosol equilibrium for volatile species , 1996 .

[20]  L. Barrie,et al.  Source and reaction pathways of dicarboxylic acids, ketoacids and dicarbonyls in arctic aerosols: One year of observations , 1996 .

[21]  W. R. Cofer,et al.  Improved aqueous scrubber for collection of soluble atmospheric trace gases. , 1985, Environmental science & technology.

[22]  M. Lazaridis,et al.  Chemical composition of size-resolved atmospheric aerosols in the eastern Mediterranean during summer and winter , 2003 .

[23]  J. Smol,et al.  Chemical composition of size-resolved atmospheric aerosols in the eastern Mediterranean during summer and winter , 2002 .

[24]  N. Mihalopoulos,et al.  A new technique for sampling and analysis of atmospheric dimethylsulfoxide (DMSO) , 2000 .

[25]  J. Seinfeld,et al.  Atmospheric Gas-Aerosol Equilibrium: IV. Thermodynamics of Carbonates , 1995 .

[26]  J. Seinfeld,et al.  Atmospheric Gas–Aerosol Equilibrium: III. Thermodynamics of Crustal Elements Ca2+, K+, and Mg2+ , 1995 .

[27]  J. Seinfeld,et al.  The distribution of ammonium salts among a size and composition dispersed aerosol , 1990 .

[28]  J. Seinfeld,et al.  Thermodynamic prediction of the water activity, NH4NO3 dissociation constant, density and refractive index for the NH4NO3-(NH4)2SO4-H2O system at 25°C , 1982 .