FRACTIONATION AND CONCENTRATION OF SUSPENDED PARTICULATE MATTER IN NATURAL-WATERS

A scheme for the fractionation and concentration of suspended particulate matter (SPM) from natural waters has been tested. This scheme involves the sequential use of three fractionation techniques sieving, continuous flow centrifugation and tangential flow filtration to collect gram amounts of SPM over the entire particulate and colloidal size range. The separation scheme is able to process large samples (ca. 100 l), within reasonable times (ca. 1 day) and the apparatus is portable. Reproducibility and potential artifacts introducing during the fractionation and concentration of SPM, particularly when tangential flow filtration is used, are discussed. It has been shown that there is a systematic increase in the content of organic carbon, Mg, Ca, Na, K, Cu and Zn with decreasing particle size, highlighting the importance of the colloidal < 1 mum) fraction.