Organic acids in continental background aerosols

With a newly developed method aerosol samples from three distinctly differe nt continental sites were analyzed: an urban site (Vienna), a savanna site in South Africa (Nylsvley Nature Reserve, NNR) and a free tropospheric cont inental background site (Sonnblick Observatory, SBO). In all samples a rang e of monocarboxylic acids (MCAs) and dicarboxylic acids (DCAs) has been ide ntified and quantified. The three most abundant MCAs in Vienna were the C18 , C16 and C14 acids with concentrations of 66, 45 and 36 ng m(-3), respecti vely. At the mid tropospheric background site (SBO) the three most abundant MCAs were the C18, C16 and C12 acid. For the DCAs at all three sites oxali c, malonic and succinic acid were the dominant compounds. For some individu al compounds an information about the sources could be obtained. For exampl e the determined unsaturated MCAs in South Africa appear to result from bio genic sources whereas in Vienna those acids are considered to be derived fr om combustion processes. Oxalic and glyoxalic acid appear to have a free tr opospheric air chemical source. The relative high amounts at SBO in compari son to Vienna can only be explained by secondary formation of oxalic acid i n the atmosphere. (C) 1999 Elsevier Science Ltd. All rights reserved.