Three‐dimensional modeling of the mixing state of particles over Greater Paris

Abstract

A size-composition resolved aerosol model (SCRAM) is coupled to the Polyphemus air quality platform and evaluated over Greater Paris. SCRAM simulates the particle mixing state and solves the aerosol dynamic evolution taking into account the processes of coagulation, condensation/evaporation, and nucleation. Both the size and mass fractions of chemical components of particles are discretized. The performance of SCRAM to model air quality over Greater Paris is evaluated by comparison to PM 2.5 , PM 10 , and Aerosol Optical Depth (AOD) measurements. Because air quality models usually assume that particles are internally mixed, the impact of the mixing state on aerosols formation, composition, optical properties, and their ability to be activated as cloud condensation nuclei (CCN) is investigated. The simulation results show that more than half (up to 80% during rush hours) of black carbon particles are barely mixed at the urban site of Paris, while they are more mixed with organic species at a rural site. The comparisons between the internal-mixing simulation and the mixing state-resolved simulation show that the internal-mixing assumption leads to lower nitrate and higher ammonium concentrations in the particulate phase. Moreover, the internal-mixing assumption leads to lower single scattering albedo, and the difference of aerosol optical depth caused by the mixing state assumption can be as high as 72.5%. Furthermore, the internal-mixing assumption leads to lower CCN activation percentage at low supersaturation, but higher CCN activation percentage at high supersaturation.

Effectiveness of ammonia reduction on control of fine particle nitrate

“…3.2). Although a recent modeling study has suggested that ambient NH 3 concentration can be decreased by as much as 31 % in winter and 67 % in summer in the US, due to the reactive uptake of NH 3 by secondary carbonyl compounds (Zhu et al, 2018), this process does not appear to have an impact on NH 3 -NH + 4 partitioning and predicted pH for the locations in this study. For the winter haze conditions in Beijing, which had the highest pH among the sampling sites, including organic acids (i.e., oxalate) in the model calculation of pH is reported to only reduce pH by at most 0.07 (Song et al, 2018).…”

A single-column particle-resolved model for simulating the vertical distribution of aerosol mixing state: WRF-PartMC-MOSAIC-SCM v1.0

“…Future applications of the model include quantifying the impact of aerosol mixing state on secondary aerosol formation and on climate-relevant aerosol properties, such as aerosol absorption and CCN concentration, and comparing these findings to existing studies (Matsui et al, 2013;Zhang et al, 2014;Zhu et al, 2016a).…”

“…Building on previous two-dimensional sectional frameworks, the MOSAIC-MIX model (Ching et al, 2016) adds an additional dimension to represent hygroscopicity and shows that this optimizes the calculations of CCN concentrations and aerosol optical properties. The SCRAM model (Zhu et al, 2015(Zhu et al, , 2016a, also a two-dimensional sectional model, uses an alternative discretization based on both size and composition where composition is tracked by mass fractions of different chemical groups such as inorganic hydrophilic, organic hydrophilic, organic hydrophobic, black carbon, and dust.…”

“…While some chemical transport models focus on representing black carbon mixing state (Matsui et al, 2013;Matsui, 2016), other models have allowed for more general mixing state representations (Zhang et al, 2014;Zhu et al, 2016a). However, further extension of aerosol bin schemes to include additional dimensions to capture greater mixing state detail eventually becomes computationally prohibitive.…”

Modelling organic aerosol over Europe in summer conditions with the VBS-GECKO parameterization: sensitivity to secondary organic compound properties and IVOC emissions

“…The aging of these three compounds with OH leads to hydrophobic species with a lower volatility. No gaseous oxidation is considered for these hydrophylic and hydrophobic species in H 2 O. H 2 O has been evaluated over Europe (Couvidat et al, 2012 and the 10 Paris area (Couvidat et al, 2013;Zhu et al, 2016aZhu et al, , 2016b. The H 2 O reference mechanism is presented in table S1 of supplementary material.…”