The formation, properties and impact of secondary organic aerosol: current and emerging issues

Abstract

Abstract. Secondary organic aerosol (SOA) accounts for a significant fraction of ambient tropospheric aerosol and a detailed knowledge of the formation, properties and transformation of SOA is therefore required to evaluate its impact on atmospheric processes, climate and human health. The chemical and physical processes associated with SOA formation are complex and varied, and, despite considerable progress in recent years, a quantitative and predictive understanding of SOA formation does not exist and therefore represents a major research challenge in atmospheric science. This review begins with a description of the current state of knowledge on the global SOA budget and the atmospheric degradation mechanisms for SOA precursors. The topic of gas-particle partitioning theory is followed by an account of the analytical techniques used to determine the chemical composition of SOA. A survey of recent laboratory, field and modeling studies is also presented. The following topical and emerging issues are highlighted and discussed in detail; molecular characterization of biogenic SOA constituents, condensed phase reactions and oligomerization, the interaction of atmospheric organic components with sulfuric acid, the chemical and photochemical processing of organics in the atmospheric aqueous phase, aerosol formation from real plant emissions, interaction of atmospheric organic components with water, thermodynamics and mixtures in atmospheric models. Finally, the major challenges ahead in laboratory, field and modeling studies of SOA are discussed and recommendations for future research directions are proposed.

SOA Formation Potential of Emissions from Soil and Leaf Litter

“…The most prevalent SOA precursors on a global scale are terpenoid compounds emitted from vegetation. 14 Much effort has gone toward developing parametrizations of VOC emissions from vegetation sources, such as those contained in the model of emissions of gases and aerosols from nature (MEGAN). 15,16 While not considered a major global source of terpenoid emissions, soil and leaf litter still contribute significantly to VOCs in the atmosphere, particularly in spring and fall.…”

Experimental data on SOA formation from mixtures of anthropogenic and biogenic organic compounds

“…Knowledge of the processes that involve SOA formation has significantly increased over the last few years (Hallquist et al, 2009). The most studied and probably the most important mechanism of SOA formation is the oxidation of volatile organic compounds (VOCs), frequently produced through the reaction with OH radicals, forming products of lower volatility that subsequently partition into the condensed phase (Kroll and Seinfeld, 2008).…”

“…A recent publication on the current and emerging issues related to SOA suggests that more complex mixtures than just one or two VOCs should be investigated in laboratories studies, in order to describe their effect on SOA formation (Hallquist et al, 2009). In Vivanco et al (2011) we presented the results of ten photooxidation experiments performed in the European Photorreactor (EUPHORE) outdoor chamber (CEAM, Valencia, Spain) in order to study SOA formation under different VOCs initial conditions.…”

Towards On-Line 14C Analysis of Carbonaceous Aerosol Fractions

“…Therefore, the picture has been conventionally simplified by dividing the total carbon (TC) of the carbonaceous particulate matter into 2 subfractions: organic carbon (OC) made of lighter, weakly refractory and non-light-absorbing compounds, and elemental carbon (EC) consisting of strongly refractory, light-absorbing, highly polymerized compounds (Pöschl 2005). While EC is mainly emitted as a primary product of combustion processes, OC stems from combustion, industrial, biological, or geological processes when formed primarily (Pöschl 2005) or can result as a secondary product from the condensation of low-vapor compounds produced during the photo-oxidation of volatile organic compounds (Hallquist et al 2009). …”