Simulation of the effects of low-volatility organic compounds on aerosol number concentrations in Europe

Abstract

Abstract. PMCAMx-UF, a three-dimensional chemical transport model focusing on the simulation of the ultrafine particle size distribution and composition has been extended with the addition of reactions of chemical aging of semivolatile anthropogenic organic vapors, the emissions and chemical aging of intermediate-volatility organic compounds (IVOCs), and the production of extremely low-volatility organic compounds (ELVOCs) by monoterpenes. The model is applied in Europe to quantify the effect of these processes on particle number concentrations. The model predictions are evaluated against both ground measurements collected during the PEGASOS 2012 summer campaign across many stations in Europe and airborne observations by a zeppelin measuring above Po Valley, Italy. PMCAMx-UF reproduces the ground level daily average concentrations of particles with a diameter larger than 100 nm (N100) with normalized mean error (NME) of 45 % and normalized mean bias (NMB) close to 10 %. For the same simulation, PMCAMx-UF tends to overestimate the concentration of particles with a diameter larger than 10 nm (N10) with a daily NMB of 23 % and a daily NME of 63 %. The model was able to reproduce more than 75 % of the N10 and N100 airborne observations (zeppelin) within a factor of 2. According to the PMCAMx-UF predictions, the ELVOC production by monoterpenes leads to surprisingly small changes of the average number concentrations over Europe. The total number concentration decreased due to the ELVOC formation by 0.2 %, N10 decreased by 1.1 %, N50 (particles with a diameter larger than 50 nm) increased by 3 %, and N100 increased by 4 % due to this new secondary organic aerosol (SOA) source. This small change is due to the nonlinearity of the system, with increases predicted in some areas and decreases in others, but also the cancelation of the effects of the various processes like accelerated growth and accelerated coagulation. Locally, the effects can be significant. For example, an increase in N100 by 20 %–50 % is predicted over Scandinavia and significant increases (10 %–20 %) are predicted over some parts of central Europe. The ELVOCs contributed on average around 0.5 µg m−3 and accounted for 10 %–15 % of the PM2.5 OA. The addition of IVOC emissions and their aging reactions led to a surprising reduction of the total number of particles (Ntot) and N10 by 10 %–15 % and 5 %–10 %, respectively, and to an increase in the concentration of N100 by 5 %–10 %. These were due to the accelerated coagulation and reduced nucleation rates.

New Particle Formation Events Can Reduce Cloud Droplets in Boundary Layer Clouds at the Continental Scale

“…PMCAMx‐UF (Information about the model features can be found in the Supporting Information ) is applied over Europe for summer and spring periods for which it has been extensively evaluated (Fountoukis et al., 2012; Patoulias & Pandis, 2022; Patoulias et al., 2018) to ensure that the simulations represent a broad range of conditions during which NPF takes place. From the simulated aerosol fields, we compute the CCN concentrations and potential CDN (i.e., the droplets that are activated when clouds form) as a function of time and space, for two fixed characteristic levels of cloud‐scale updraft velocity values—one that corresponds to stratiform clouds (with a vertical velocity spectral dispersion, σ w , equal to 0.3 m s −1 ) and one for more convective conditions (σ w = 0.6 m s −1 ; see Supporting Information ).…”

“…The effects of growing, pre‐existing particles and water vapor supersaturation changes in clouds affected by NPF needs to be considered to fully capture the impacts on CCN and CDN. Here we address this question using the state‐of‐the‐art chemical transport model PMCAMx‐UF (Fountoukis et al., 2012; Jung et al., 2010; Patoulias & Pandis, 2022; Patoulias et al., 2018) with explicit two‐moment bin microphysics to simulate the generation of new particles by nucleation, their subsequent growth, transport and their interaction with pre‐existing particles. These interactions shape the CCN distributions and are coupled with a state‐of‐the‐art droplet formation module which determines how NPF impacts CDN throughout Europe and for a variety of cloud formation conditions.…”

J-GAIN v1.0: A flexible tool to incorporate aerosol formation rates obtained by molecular models into large-scale models

“…To further take into account possible differences in the particle formation rates due to different amines, an option is to estimate the contributions of individual species to the lumped concentration based on available measurements (Schade and Crutzen, 1995). Oxidized organic species can be treated in a similar manner through a representative highly oxidized, ultra/extremely low-volatile compound (generally referred to as HOM or ULVOC/ELVOC; Kirkby et al, 2016;Schervish and Donahue, 2021), which is already included in some transport models (Gordon et al, 2017;Julin et al, 2018;Patoulias and Pandis, 2022).…”

J-GAIN v1.1: a flexible tool to incorporate aerosol formation rates obtained by molecular models into large-scale models

“…To take into account possible differences in the particle formation rates due to different amines, an option is to estimate the contributions of individual species based on available measurements (Schade and Crutzen, 1995). Oxidized organic species can be treated in a similar manner through a representative highly oxidized, ultra/extremely low-volatile compound (generally referred to as HOM or ULVOC/ELVOC; Kirkby et al, 2016;Schervish and Donahue, 2021), which is already included in some transport models (Gordon et al, 2017;Julin et al, 2018;Patoulias and Pandis, 2022).…”