COPPER MOLLUSCICIDES FOR CONTROL OF SCHISTOSOMIASIS .3. ADSORPTION BY CLAY SUSPENSIONS

Cupric ions in calcium-rich water simulating snail habitats are more strongly adsorbed by kaolinite, bentonite, and montmorillonite at pH 8 than at pH 7. The toxicity of copper-containing clay suspensions toward Biomphalaria glabrata, measured in a flow system depends on (i) the claytype, (ii) the particle size distribution, (iii) the pH of the aqueous medium, and (iv) the rate of release of clay-bound copper as the pH is lowered. The most, toxic system contains kaolinite in fine suspension at pH 8. The ecological significance of the results is discussed, together with the possibility of using clay loaded with copper as part of a controlled release system for limitation of schistosomiasis.