ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-4-1759-2004 Optical properties in the UV and visible spectral region of organic acids relevant to tropospheric aerosols Lund Myhre C. E. 1 Nielsen C. J. 1 Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0372 Oslo, Norway 03 09 2004 4 7 1759 1769 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/4/1759/2004/acp-4-1759-2004.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/4/1759/2004/acp-4-1759-2004.pdf

Refractive and absorption indices in the UV and visible region of selected aqueous organic acids relevant to tropospheric aerosols are reported. The acids investigated are the aliphatic dicarboxylic acids oxalic, malonic, tartronic, succinic and glutaric acid. In addition we report data for pyruvic, pinonic, benzoic and phthalic acid. To cover a wide range of conditions we have investigated the aqueous organic acids at different concentrations spanning from highly diluted samples to concentrations close to saturation. The density of the investigated samples is reported and a parameterisation of the absorption and refractive index that allows the calculation of the optical constants of mixed aqueous organic acids at different concentrations is presented. The single scattering albedo is calculated for two size distributions using measured and a synthetic set of optical constants. The results show that tropospheric aerosols consisting of only these organic acids and water have a pure scattering effect.