Ratios of Total Suspended Solids to Suspended Sediment Concentrations by Particle Size

Abstract

Wet-sieving sand-sized particles from a whole storm-water sample before splitting the sample into laboratory-prepared containers can reduce bias and improve the precision of suspended-sediment concentrations (SSC). Wet-sieving, however, may alter concentrations of total suspended solids (TSS) because the analytical method used to determine TSS may not have included the sediment retained on the sieves. Measuring TSS is still commonly used by environmental managers as a regulatory metric for solids in storm water. For this reason, a new method of correlating concentrations of TSS and SSC by particle size was used to develop a series of correction factors for SSC as a means to estimate TSS. In general, differences between TSS and SSC increased with greater particle size and higher sand content. Median correction factors to SSC ranged from 0.29 for particles larger than 500 µm to 0.85 for particles measuring from 32 to 63 µm. Great variability was observed in each fraction—a result of varying amounts of organic matter in the samples. Wide variability in organic content could reduce the transferability of the correction factors.