ADHESION OF WATER-BORNE PARTICULATES ON FRESH-WATER BIOTA

The retention of suspended particles transported by river flow on surf aces of freshwater plants is a potentially important process in the co ntamination of aquatic biota. Field experiments have been performed to test the role of benthic algae (periphyton) in trapping inorganic sus pended solids transported by the river water and to discriminate betwe en the caesium content of periphyton caused by the adherence of inorga nic solids and by the active uptake inside the organisms. The contribu tion of caesium of suspended solids adhering to biotic surfaces was es timated by determining the scandium content (scandium method). The sca ndium method was used because this element is geologically ubiquitous in soils and it is not taken up actively by plants and other organisms . The mass of suspended particles retained on the surfaces of microorg anisms growing on submerged substrates were determined by comparing th e scandium content of suspended material with that in algal communitie s. Neutron activation analysis was used as the analytical method for d etermination for both scandium, and caesium. The results indicate that the suspended particle fraction can contribute up to 80% of the caesi um contamination of periphyton samples. Active caesium uptake and accu mulation by aquatic biota represents the remaining 20% of the total ca esium contamination. (C) 1998 Elsevier Science B.V. All rights reserve d.