FRACTIONATION OF TRACE-METALS IN SURFACE-WATER WITH SCREEN FILTERS

Size fractionation of solid particulate phases serving as carriers of trace elements (e.g. Al, Cd, Cu, Fe, Mn and Zn) in surface waters was conducted by pressure filtration using screen filters with defined por e sizes in the range 5-0.015 mum. The particle size distribution in so lution was determined by Photon Correlation Spectroscopy. The accumula tion of solids on the filter surface was demonstrated, leading to a su ccessive reduction of the efficient pore size ('clogging'). Thus, filt ers with a defined pore size of 0.40 mum and a diameter of 47 mm had a n apparent separation efficiency corresponding to a pore size of 0.015 mum after filtration of 100 ml containing approximately 100 mg/l of s uspended solids. Aluminium and iron were almost exclusively present in the particle size range 5-0.20 mum. Copper and manganese were retaine d to 45% and zinc and cadmium to 30% by the 0.015-mum pore size filter .