Nucleation and Growth of Nanoparticles in the Atmosphere Renyi Zhang,* Alexei Khalizov, Lin Wang, Min Hu, and Wen Xu Department of Atmospheric Sciences andDepartment of Chemistry, Center for Atmospheric Chemistry and Environment, Texas A&M University, College Station, Texas 77843, United States Department of Environmental Science & Engineering and Institute of Global Environment Change Research, Fudan University, Shanghai 200433, China State Key Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China

Nucleation and Growth of Nanoparticles in the Atmosphere

[1] An initial evaluation of the Models-3 Community Multiscale Air Quality (CMAQ) model aerosol component reveals CMAQ's varying ability to simulate observed visibility indices and aerosol species concentrations. The visibility evaluation, using National Weather Service observations from 139 airports for 11–15 July 1995, shows that CMAQ reasonably captured the general spatial and temporal patterns of visibility degradation, including major gradients, maxima and minima. However, CMAQ's two visibility prediction methods, Mie theory approximation and mass reconstruction, both underpredict visibility degradation (i.e., overpredict visibility). The mean bias, normalized mean bias (NMB), mean error and normalized mean error (NME) for the Mie calculations are −5.9 dv, −21.7%, 7.0 dv and 25.4%, respectively. For the reconstruction simulations, these statistics are −9.8 dv, −35.5%, 10.0 dv and 36.2%, respectively. Most simulated values (∼90% Mie and ∼85% reconstruction) fall within a factor of two of the observations, although r2 = 0.25 (Mie) and r2 = 0.24 (reconstruction). The speciated aerosol evaluation uses observations of sulfate, nitrate, PM2.5, PM10 and organic carbon obtained from 18 stations of the Interagency Monitoring of Protected Visual Environments (IMPROVE) network in June 1995. This evaluation reveals that, with the exception of sulfate (mean bias: 0.15 μg/m3, NMB: 3.1%), the model consistently underpredicts aerosol concentrations of nitrate (−0.10 μg/m3, −33.1%), PM2.5 (−3.9 μg/m3, −30.1%), PM10 (−5.66 μg/m3, −29.2%) and organic carbon (−0.78 μg/m3, −33.7%). Sulfate was simulated best by the model (r2 = 0.63, mean error = 1.75 μg/m3, NME = 36.2%), followed by PM2.5 (0.55, 5.00 μg/m3, 38.5%), organic carbon (0.25, 0.94 μg/m3, 40.6%), PM10 (0.13, 9.85 μg/m3, 50.8%) and nitrate (0.01, 0.33 μg/m3, 104.3%). Except for nitrate, 75–80% of simulated concentrations fall within a factor of two of the IMPROVE observations.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2001JD001409

Models‐3 Community Multiscale Air Quality (CMAQ) model aerosol component 1. Model description

Recently, it has been proposed that organic aerosol particles in the atmosphere can exist in an amorphous semi-solid or solid (i.e. glassy) state. In this perspective, we analyse and discuss the formation and properties of amorphous semi-solids and glasses from organic liquids. Based on a systematic survey of a wide range of organic compounds, we present estimates for the glass forming properties of atmospheric secondary organic aerosol (SOA). In particular we investigate the dependence of the glass transition temperature Tg upon various molecular properties such as the compounds' melting temperature, their molar mass, and their atomic oxygen-to-carbon ratios (O : C ratios). Also the effects of mixing different compounds and the effects of hygroscopic water uptake depending on ambient relative humidity are investigated. In addition to the effects of temperature, we suggest that molar mass and water content are much more important than the O : C ratio for characterizing whether an organic aerosol particle is in a liquid, semi-solid, or glassy state. Moreover, we show how the viscosity in liquid, semi-solid and glassy states affect the diffusivity of those molecules constituting the organic matrix as well as that of guest molecules such as water or oxidants, and we discuss the implications for atmospheric multi-phase processes. Finally, we assess the current state of knowledge and the level of scientific understanding, and we propose avenues for future studies to resolve existing uncertainties.

Glass transition and phase state of organic compounds: dependency on molecular properties and implications for secondary organic aerosols in the atmosphere.

[1] Mole fraction based equations for aqueous phase activities, together with equilibrium constants for the formation of gases and solids, have been combined with a Gibbs free energy minimization algorithm to create equilibrium phase partitioning models of inorganic atmospheric aerosols. The water content, phase state (solid or liquid), and gas/aerosol partitioning are predicted for known ionic composition, relative humidity, and temperature. The models are valid from <200 to 328 K for the subsystems (H+-SO42−-NO3−-Cl−-Br−-H2O) and (H+-NH4+-SO42−-NO3−-H2O), and 298.15 K only for (H+-NH4+-Na+-SO42−-NO3−-Cl−-H2O). The models involve no simplifying assumptions and include all solid phases identified in bulk experiments, including hydrated and double salt forms not treated in most other studies. The Henry's law constant of H2SO4 is derived as a function of temperature, based upon available data, and the model treatment of the solubility of HBr in aqueous H2SO4 is revised. Phase diagrams are calculated for the (NH4)2SO4/H2SO4/H2O system to low temperature. The models are also used to explore the importance of the double salts in urban inorganic aerosols. These Aerosol Inorganics Model (AIM) models can be run on the Web for a variety of problem types at http://mae.ucdavis.edu/wexler/aim.html and http://www.uea.ac.uk/∼e770/aim.html, and their use is summarized here.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2001JD000451

Atmospheric aerosol models for systems including the ions H+, NH4+, Na+, SO42−, NO3−, Cl−, Br−, and H2O

https://support.olisystems.com/documents/papers/mse-2002fluidphaseeq141.pdf

T. R. Rubin

Papers

The Thermodynamic Properties of Aqueous Sulfuric Acid Solutions and Hydrates from 15 to 300°K.1

Additions and Corrections-The Thermodynamic Properties of Aqueous Sulfuric Acid Solutions and Hydrates from 15 to 300 degrees K