A LABORATORY INVESTIGATION OF PARTICLE-SIZE EFFECTS ON AN OPTICAL BACKSCATTERANCE SENSOR

The effect of particle size on an optical backscatterance sensor's (OBS) response to suspended sediment concentration was investigated in the laboratory. Sieved ground glass was used in place of natural sediments to eliminate mineralogical effects. Highly reliable linear regressions of OBS output versus suspended sediment concentration were obtained for suspensions of constant particle size. Regression analyses were conducted to determine an empirical relationship between OBS gain and particle size; an inverse power law regression best fit the data. A regression based upon Mie's theory also fit within the error bands of the data, suggesting the theory may be applicable to OBS performance. Results indicate that the OBS is most sensitive to particle size changes for particles 100 mum or less.