Abstract View
The Impacts of Aerosol Mixing State on N2O5 Uptake Coefficient
YICEN LIU, Yu Yao, Jeffrey H. Curtis, Matthew West, Nicole Riemer, University of Illinois at Urbana-Champaign
Abstract Number: 706
Working Group: Aerosol Chemistry
Abstract
Dinitrogen pentoxide (N2O5) is an important nighttime reservoir for NOx. The heterogeneous hydrolysis on aerosol particles is considered as the main loss pathway for N2O5, removing NOx from the atmosphere. Current models use the bulk composition of the particle population to calculate the N2O5 uptake coefficient (γ). While this is appropriate when the aerosol is internally mixed, it remains an open question how large the error is when the aerosol has a more complex mixing state, which is common in the real atmosphere. To better understand the role of mixing state in calculating γ, the stochastic particle-resolved model PartMC-MOSAIC was used to generate 100 scenarios with different input parameters, including primary gas and aerosol emissions, as well as meteorological parameters. Each scenario was simulated for 24 hours with hourly output, yielding a total of 2,500 populations with different aerosol compositions and mixing states. For each population, the uptake coefficient γPR was first calculated using the particle-resolved composition data and the parameterization of N2O5 hydrolysis from Riemer et al (2008), which is a function of the per-particle sulfate and nitrate content and the organic coating thickness. We then compared γPR for each population with the corresponding value γmix which we obtained by assuming that the population was internally mixed. Preliminary results show that for 25% of the populations the error in the uptake coefficient was larger than +/- 20%. We present a detailed process analysis that explains the reasons for this over or underestimation and shows the impacts on the predictions of ozone and aerosol nitrate concentrations.