Modeling black carbon aging with PartMC-1D

Description

The chemical reactivity, cloud condensation nuclei activity, radiative properties, and health impacts of black-carbon-containing particles depend crucially on the aerosol mixing state. The recently developed stochastic particle-resolving aerosol box model PartMC-MOSAIC has allowed unique insight into the evolution of aerosol mixing state as it tracks per-particle evolution for an aerosol population undergoing coagulation, condensation, dilution, and emission in a Lagrangian air parcel.

We developed this model further by coupling it with the single-column version of the Weather Research and Forecast (WRF) model. The resulting spatially resolved model PartMC-1D predicts the per-particle size and composition as well as transport processes driven by local meteorology to provide detail about the spatial distribution of particles and further insight into the evolution of the aerosol mixing state.

Here we present spatially and particle-resolved simulation results of black carbon aging in a polluted boundary layer. While the bulk concentration of black carbon was well-mixed in the boundary layer during the day, there was a strong dependence of black carbon mixing state on height with fresh black carbon particles existing in only the lowest layers. Maximum surface concentrations were found in the early morning hours due to an increase in gasoline vehicle emissions at a time of low atmospheric mixing. Based on these results we quantify the implications for cloud condensation nucleation activity and optical properties of black-carbon-containing particles.