Abstract

Effluents of different phosphate plants have been analysed for their Pb-210, Po-210 and Ra-226 content and for general characteristics important for their behaviour in surface water. The effluents of wet process plants were shown to contain large quantities of dispersed gypsum. Dilution of the phosphogypsum effluent with synthetic estuarine water showed that the gypsum dissolves and the major part of Ra-226, Pb-210 and Po-210 is fixed on a small amount of insoluble residue. The enhanced contamination level (>10 kBq.kg-1) of the insoluble residue corresponded with measurements by NIOZ of suspended matter sampled in the river Rhine close to the discharge points. Desorption experiments have shown that Ra-226, Pb-210 and Po-210, contained in the residue, remain alsmost insoluble. The effluents of the thermal industries contained only small amounts of solids. Dilution of the effluent of a thermal plant showed that most of the nuclides dissolve. Contact experiments using a soluble Po-210 salt in synthetic estuarine water with fine -sized sediment or illite, have shown that polonium adsorbs rapidly on suspended matter. Calculated KD values ranged from 20,000 to 60,000 which are in the same order of magnitude as found for water and suspended matter in the Westerscheldt.