Seasonal cycle and temperature dependence of pinene oxidation products, dicarboxylic acids and nitrophenols in fine and coarse air particulate matter

Y Y Zhang,U Pöschl,L Müller,G K Moortgat,R Winterhalter,T Hoffmann

doi:10.5194/acp-10-7859-2010

Abstract

Abstract. Filter samples of fine and coarse air particulate matter (PM) collected over a period of one year in central Europe (Mainz, Germany) were analyzed for water-soluble organic compounds (WSOCs), including the α- and β-pinene oxidation products pinic acid, pinonic acid and 3-methyl-1,2,3-butanetricarboxylic acid (3-MBTCA), as well as a variety of dicarboxylic acids and nitrophenols. Seasonal variations and other characteristic features in fine, coarse, and total PM (TSP) are discussed with regard to aerosol sources and sinks in comparison to data from other studies and regions. The ratios of adipic acid and phthalic acid to azelaic acid indicate that the investigated aerosol samples were mainly influenced by biogenic sources. A strong Arrhenius-type correlation was found between the 3-MBTCA concentration and inverse temperature (R2 = 0.79, n = 52, Ea = 126 ± 10 kJ mol−1, temperature range 275–300 K). Model calculations suggest that the temperature dependence observed for 3-MBTCA can be explained by enhanced photochemical production due to an increase of hydroxyl radical (OH) concentration with increasing temperature, whereas the influence of gas-particle partitioning appears to play a minor role. The results indicate that the OH-initiated oxidation of pinonic acid is the rate-limiting step in the formation of 3-MBTCA, and that 3-MBTCA may be a suitable tracer for the chemical aging of biogenic secondary organic aerosol (SOA) by OH radicals. An Arrhenius-type temperature dependence was also observed for the concentration of pinic acid (R2 = 0.60, n = 56, Ea = 84 ± 9 kJ mol−1); it can be tentatively explained by the temperature dependence of biogenic pinene emission as the rate-limiting step of pinic acid formation.

Highlights

Water-soluble organic compounds (WSOCs) are major components of atmospheric aerosols, accounting for up to ∼ 50% of the organic fraction of particulate matter
The results indicate that the OHinitiated oxidation of pinonic acid is the rate-limiting step in the formation of 3-MBTCA, and that 3-MBTCA may be a suitable tracer for the chemical aging of biogenic secondary organic aerosol (SOA) by OH radicals
With regard to total suspended particles (TSP = fine plus coarse particulate matter), the mean concentrations observed in Mainz (0.14–5.71 ng m−3) were higher than values reported from Arctic regions (0.06–0.9 ng m−3), similar to values reported from Philadelphia, USA (PM10, 0.5–3.5 ng m−3), and generally lower than the values reported from Tokyo, Japan, and Melpitz, Germany (PM10, n.d. −25.8 ng m−3)

Summary

Introduction

Water-soluble organic compounds (WSOCs) are major components of atmospheric aerosols, accounting for up to ∼ 50% of the organic fraction of particulate matter. Organic acids are a prominent group of WSOCs and were found in urban, rural, marine and polar aerosols in various regions around the world as detailed below (Kawamura and Ikushima, 1993; Kawamura et al, 1996b; Kawamura and Usukura, 1993). This group includes monocarboxylic acids, dicarboxylic acids, oxocarboxylic acids and tricarboxylic acids. Primary sources include motor exhaust (Kawamura and Kaplan, 1987), biomass combustion

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