AMTD Atmospheric Measurement Techniques Discussions AMTD Atmos. Meas. Tech. Discuss. 1867-8610 Göttingen, Germany 10.5194/amtd-2-237-2009 Determination of water-insoluble light absorbing matter in rainwater using polycarbonate membrane filters and photometric detection Engström J. E. 1 Leck C. 1 Department of Meteorology, Arrhenius Laboratory, Stockholm Univ., 10691 Stockholm, Sweden 04 02 2009 2 1 237 264 Copyright: © 2009 J. E. Engström 2009 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://amt.copernicus.org/preprints/2/237/2009/amtd-2-237-2009.html The full text article is available as a PDF file from https://amt.copernicus.org/preprints/2/237/2009/amtd-2-237-2009.pdf

A method for determination of water-insoluble light absorbing matter in rainwater has been developed. After collection the rainwater samples were filtered using polycarbonate membrane filter in the laboratory. After drying the filter in filtered air, the amount of water-insoluble light absorbing matter (soot) on the filters was determined with photometry at a wavelength of 555 nm. The precision for the method was better than 10% calculated as relative standard deviation. The overall loss of soot due to adsorption during collection and filtration was 22±2%. The detection limit was estimated to 0.025 in optical density, or 2 ng/ml expressed as a concentration assuming a filtration volume of 30 ml. Analysis of environmental samples have been successfully performed with the described method at the Maldives Climate Observatory Hanimaadhoo and Nepal Climate Observatory. At Maldives the average soot concentration in rain was 0.048 μg/ml and at the Nepal obseravtory 0.086 μg/ml.

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