1994 Volume 29 Issue 4 Pages 196-205
Rain water samples from initial and latter rainfalls were acidified to 0.2 M HCl, or untreated, and filtrated through a membrane filter with a pore size of 0.45μm, or centrifuged at 3000 rpm. The untreated and treated samples were subjected to fluorometric determination of dissolved aluminum (Ald) at pH 4.5 with 8-hydroxyquinoline-5-sulfonic acid. The total aluminum (Alt) was determined after hydrofluoric acid decomposition of the sample in order to obtain the undissolved aluminum (Alu) from Alt-Ald. Ald in the untreated sample decreased with increasing rain precipitation (P); e. g., 200nm ml-1 in the initial rainfall (P= 0.5mm) and 5ng ml-1in the latter rainfall (P>5mm). The acidification caused increase of Ald by the dissolution of Al from solid particles in the samples. The filtration or centrifugation at pH 4 gave negligible decrease of Ald, while these treatments at pH 5 gave much more decreases up to 48%. Polystyrene bottle was best suitable for the sample storage because of negligible loss of Ald. During the storage, Ald increased for most of the untreated samples. The filtration or centrifugation removed about 90% or more of Alu from the samples in the ixtitial rainfalls, which could be stored for 3 days without significant change of Ald. In the latter rainfalls, the removals of Alu were 30 to 80%, and residual particles caused increase of Ald during the storage. The inductivelycoupled plasma atomic emission spectrometry gave higher Ald than the fluorometry. The change in Ald by the sample treatment and storage is discussed based on the adsorption of aluminum on the filter and particles and the dissolution of the particles. The fluorometry used is recommended for the rapid determination of Ald down to 1ng ml-1 without any pretreatment and storage.
