Modelling of organic aerosols over Europe (2002–2007) using a volatility basis set (VBS) framework: application of different assumptions regarding the formation of secondary organic aerosol

R. Bergström,A. S. H. Prévôt,D. Simpson,K. E. Yttri,H. A. C. Denier van der Gon

doi:10.5194/acp-12-8499-2012

Abstract

Abstract. A new organic aerosol module has been implemented into the EMEP chemical transport model. Four different volatility basis set (VBS) schemes have been tested in long-term simulations for Europe, covering the six years 2002–2007. Different assumptions regarding partitioning of primary organic aerosol and aging of primary semi-volatile and intermediate volatility organic carbon (S/IVOC) species and secondary organic aerosol (SOA) have been explored. Model results are compared to filter measurements, aerosol mass spectrometry (AMS) data and source apportionment studies, as well as to other model studies. The present study indicates that many different sources contribute significantly to organic aerosol in Europe. Biogenic and anthropogenic SOA, residential wood combustion and vegetation fire emissions may all contribute more than 10% each over substantial parts of Europe. This study shows smaller contributions from biogenic SOA to organic aerosol in Europe than earlier work, but relatively greater anthropogenic SOA. Simple VBS based organic aerosol models can give reasonably good results for summer conditions but more observational studies are needed to constrain the VBS parameterisations and to help improve emission inventories. The volatility distribution of primary emissions is one important issue for further work. Emissions of volatile organic compounds from biogenic sources are also highly uncertain and need further validation. We can not reproduce winter levels of organic aerosol in Europe, and there are many indications that the present emission inventories substantially underestimate emissions from residential wood combustion in large parts of Europe.

Highlights

During the last 10–15 yr carbonaceous aerosol has become one of the most intensively studied fields within the atmospheric sciences
A large number of new measurements has become available recently, e.g. through the EUCAARI (Kulmala et al, 2011) and other projects (e.g. Lanz et al, 2010; Aas et al, 2012). These data mainly consist of relatively short-term campaigns, but with very high time resolution and multiple instruments. These will be analysed in a subsequent paper; the main focus of this paper is to provide an initial assessment of the different volatility basis set (VBS) schemes against long-term observations, and especially for sites where some source apportionment results are already available
The EMEP MSC-W chemical transport model for Europe has been extended with a new scheme for treatment of organic aerosol by the volatility basis set (VBS) approach

Summary

Introduction

During the last 10–15 yr carbonaceous aerosol has become one of the most intensively studied fields within the atmospheric sciences. This can be attributed to its postulated impacts on global climate (Novakov and Penner, 1993; Kanakidou et al, 2005), and on human health (McDonald et al, 2004). Particulate carbonaceous matter (PCM) contributes around 10–40 % (mean 30 %) to the total concentration of particulate matter (PM) with diameter less than 10 μm (PM10) at rural and natural background sites in Europe (Yttri et al, 2007; Putaud et al, 2004). The sum of EC and OC is referred to as total carbon (TC).

Results

Discussion

Conclusion