Abstract
Abstract. This study assesses the chemical composition and global aerosol load of the major inorganic aerosol components, focusing on mineral dust and aerosol nitrate. The mineral dust aerosol components (i.e., Ca2+, Mg2+, K+, Na+) and their emissions are included in the ECHAM5/MESSy Atmospheric Chemistry model (EMAC). Gas/aerosol partitioning is simulated using the ISORROPIA-II thermodynamic equilibrium model that considers K+, Ca2+, Mg2+, NH4+, Na+, SO42−, NO3−, Cl−, and H2O aerosol components. Emissions of mineral dust are calculated online by taking into account the soil particle size distribution and chemical composition of different deserts worldwide. Presence of metallic ions can substantially affect the nitrate partitioning into the aerosol phase due to thermodynamic interactions. The model simulates highest fine aerosol nitrate concentration over urban and industrialized areas (1–3 µg m−3), while coarse aerosol nitrate is highest close to deserts (1–4 µg m−3). The influence of mineral dust on nitrate formation extends across southern Europe, western USA, and northeastern China. The tropospheric burden of aerosol nitrate increases by 44 % when considering interactions of nitrate with mineral dust. The calculated global average nitrate aerosol concentration near the surface increases by 36 %, while the coarse- and fine-mode concentrations of nitrate increase by 53 and 21 %, respectively. Other inorganic aerosol components are affected by reactive dust components as well (e.g., the tropospheric burden of chloride increases by 9 %, ammonium decreases by 41 %, and sulfate increases by 7 %). Sensitivity tests show that nitrate aerosol is most sensitive to the chemical composition of the emitted mineral dust, followed by the soil size distribution of dust particles, the magnitude of the mineral dust emissions, and the aerosol state assumption.
Highlights
Atmospheric aerosols from natural and anthropogenic sources adversely affect human health and play an important role in changing the Earth’s climate
The model reproduces the mineral dust cations (K+, Mg2+, Ca2+) measured by the European Monitoring and Evaluation Programme (EMEP) network remarkably well (RMSE ∼ 0.1 μg m−3), indicating that their representation over the Sahara proposed by this study is of the correct magnitude and is suitable to be used to estimate their effect on nitrate aerosol formation over Europe
This study assesses the effect of mineral dust particles on nitrate aerosol formation by using the thermodynamic equilibrium model ISORROPIA-II that takes the thermodynamics of the K+, Ca2+, Mg2+, NH+4, Na+, SO24−, NO−3, Cl−, and H2O components into account
Summary
Atmospheric aerosols from natural and anthropogenic sources adversely affect human health and play an important role in changing the Earth’s climate. Several studies in the past have shown that the simulation of these effects, especially in areas where dust or sea salt comprises a significant portion of total particulate matter, can considerably improve model predictions (Dentener et al, 1996; Gong et al, 1997; Jacobson, 1999; Jacob, 2000; Song and Carmichael, 2001; Moya et al, 2002; Bian and Zender, 2003; Laskin et al, 2005; Hodzic et al, 2006; Kallos et al, 2007; Astitha and Kallos, 2009; Athanasopoulou et al, 2008, 2010; Fountoukis et al, 2009; Karydis et al, 2010, 2011a; Tsyro et al, 2011; Wang et al, 2012; Im, 2013; Trump et al, 2015) According to their findings, including marine and crustal species in models can substantially affect the phase partitioning of nitrate aerosols. The sensitivity of the results to the emitted dust aerosol load, the size distribution of the soil particles, the mineral dust chemical composition, and the aerosol thermodynamic state is discussed
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