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

Abstract

Abstract. 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-sulfatenitrate-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 2− 4(a) ), 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.

ANISORROPIA: the adjoint of the aerosol thermodynamic model ISORROPIA

“…A number of thermodynamic models have been developed to model aerosol thermodynamic equilibrium with varying degrees of comprehensiveness, accuracy, and efficiency (e.g., AIM (Clegg et al, 1998); GFEMIN (Ansari and Pandis, 1999a); EQSAM3 (Metzger et al, 2006;Metzger and Lelieveld, 2007); EQUISOLV II (Jacobson et al, 1996;Jacobson, 1999); ISORROPIA and ISORROPIA II (Nenes et al, 1998(Nenes et al, , 1999Fountoukis and Nenes, 2007); MARS-A (Saxena et al, 1986;Binkowski and Roselle, 2003); MESA (Zaveri et al, 2005); SCAPE2 (Kim et al, 1993a,b;Meng and Seinfeld, 1996); UHAERO (Amundson et al, 2006)). …”

Hygroscopic behavior of atmospherically relevant water-soluble carboxylic salts and their influence on the water uptake of ammonium sulfate

“…Typically, sodium salts of organic acids can be found in marine aerosol particles (Kerminen et al, 1998). In other atmospheric environments, such as in the Amazon Basin, the aerosol ion balance calculation shows that with an excess of inorganic bases, gaseous organic acids can act to neutralize particles by forming organic salts (Mircea et al, 2005;Trebs et al, 2005;Metzger et al, 2006). Recently, the formation of organic salts such as aminium salts was proposed to be Published by Copernicus Publications on behalf of the European Geosciences Union.…”

Treatment of non-ideality in the SPACCIM multiphase model – Part 1: Model development

“…In the Gibbs free energy minimization approach (e.g., AIM, Clegg et al, 1998b, a;GFEMIN, Ansari and Pandis, 1999a;ADDEM, Topping et al, 2005a Amundson et al, 2006Amundson et al, , 2007, the equilibrium state of the aerosol system is predicted through the solution of minimization of the Gibbs free energy of the system. Some of the thermodynamic models mentioned above have been compared and evaluated in several studies (Ansari and Pandis, 1999b;Zhang et al, 2000;Yu et al, 2005;Metzger et al, 2006). The equilibrium approach assumes that particles are in thermodynamic equilibrium with the corresponding gas phase; i.e., the mass transfer between the phases is instantaneous.…”

“…They can be divided into two types, i.e., equation-based approach and Gibbs free energy minimization approach. In the equationbased approach (e.g., ISORROPIA II, Fountoukis and Nenes, 2007;Nenes et al, 1998;EQSAM3, Metzger and Lelieveld, 2007;Metzger et al, 2006;EQUISOLV II, Jacobson, 1997;Jacobson et al, 1996; MARS-A, Binkowski and Roselle, 2003;Saxena et al, 1986;MESA, Zaveri et al, 2005b), a set of reactions is assumed to occur in the atmospheric chemical system (including both gas phase and aerosol phase). The equilibrium state is predicted through the solution of the nonlinear equations system.…”

“…While the interactions between inorganic compounds are relatively well known, interactions between organic components as well as organic-electrolyte mixtures comprised in complex multiphase systems have remained elusive for some time, due to the large number of organic species with highly variable properties available in the gas phase and in ambient particles. Starting with the more conceptual paper of Clegg et al (2001), several approaches for the treatment of organic-inorganic mixtures in ambient particles were developed and incorporated into thermodynamic models (e.g., Ming and Russell, 2002;Topping et al, 2005b;Erdakos et al, 2006;Metzger et al, 2006;Clegg et al, 2008;Zaveri et al, 2008;Zuend et al, 2008Zuend et al, , 2011Ganbavale et al, 2015). Raatikainen and Laaksonen (2005) have compared different activity coefficient models, and four models were extended by fitting new parameters for aqueous organic-electrolyte solutions.…”