Simulation of the size-composition distribution of atmospheric nanoparticles over Europe

David Patoulias,Markku Kulmala,Ilona Riipinen,Spyros N Pandis,Christos Fountoukis,Ari Asmi

doi:10.5194/acp-18-13639-2018

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 the volatility basis set (VBS) approach for the simulation of organic aerosol (OA). The model was applied in Europe to quantify the effect of secondary semi-volatile organic vapors on particle number concentrations. The model predictions were evaluated against field observations collected during the PEGASOS 2012 campaign. The measurements included both ground and airborne measurements, from stations across Europe and a zeppelin measuring above Po Valley. The ground level concentrations of particles with a diameter larger than 100 nm (N100) were reproduced with a daily normalized mean error of 40 % and a daily normalized mean bias of −20 %. PMCAMx-UF tended to overestimate the concentration of particles with a diameter larger than 10 nm (N10) with a daily normalized mean bias of 75 %. The model was able to reproduce, within a factor of 2, 85 % of the N10 and 75 % of the N100 zeppelin measurements above ground. The condensation of organics led to an increase (50 %–120 %) in the N100 concentration mainly in central and northern Europe, while the N10 concentration decreased by 10 %–30 %. Including the VBS in PMCAMx-UF improved its ability to simulate aerosol number concentration compared to simulations neglecting organic condensation on ultrafine particles.

Highlights

New particles are introduced in the atmosphere by two major processes: direct emission from multiple sources and nucleation from low-volatility vapors
We extended the 3-D chemical transport models (CTMs) PMCAMx-UF (Fountoukis et al, 2012; Jung et al, 2010), which originally assumed that ultrafine particles can grow only by condensation of sulfuric acid and ammonia as well as by coagulation
The N50 and N100 concentrations are often used as proxies for cloud condensation nuclei (CCN)-related aerosol number concentrations (Fountoukis et al, 2012)

Summary

Introduction

New particles are introduced in the atmosphere by two major processes: direct emission from multiple sources and nucleation from low-volatility vapors. Nucleation and subsequent growth of new particles have been observed in a variety of environments worldwide (Kulmala et al, 2004), representing a significant source of aerosol number. Field measurements (Eisele and McMurry, 1997; Weber et al, 1998, 1999) and model simulations (Kulmala et al, 2000; Pirjola and Kulmala, 2001; Anttila and Kerminen, 2003) indicated that the condensation of sulfuric acid alone is often not sufficient to justify the observed growth rates of fresh particles (Riipinen et al, 2011). Growth of new particles has been attributed to the condensation of organic species (Kulmala et al, 1998; Anttila and Kerminen, 2003; Kerminen et al, 2000), heterogeneous reactions (Zhang and Wexler, 2002), or ion-enhanced condensation (Laakso et al, 2002)

Objectives

Results

Conclusion