Determination of water-insoluble light absorbing matter in rainwater using polycarbonate membrane filters and photometric detection

摘要

A method for determination of water-insoluble light absorbing matter inrainwater has been developed. After collection the rainwater samples werefiltered using polycarbonate membrane filter in the laboratory. After dryingthe filter in filtered air, the amount of water-insoluble light absorbingmatter (soot) on the filters was determined with photometry at a wavelengthof 555 nm. The precision for the method was better than 10% calculated asrelative standard deviation. The overall loss of soot due to adsorptionduring collection and filtration was 22±2%. The detection limit wasestimated to 0.025 in optical density, or 2 ng/ml expressed as aconcentration assuming a filtration volume of 30 ml. Analysis ofenvironmental samples have been successfully performed with the describedmethod at the Maldives Climate Observatory Hanimaadhoo and Nepal ClimateObservatory. At Maldives the average soot concentration in rain was0.048 μg/ml and at the Nepal obseravtory 0.086 μg/ml.