USE OF WET SIEVING TO IMPROVE THE ACCURACY OF SEDIMENT AND SEDIMENT-ASSOCIATED CONSTITUENT CONCENTRATIONS IN WHOLE- WATER SAMPLES

Abstract: Sand-size particles (greater than 63 microns) in urban runoff have the potential to produce substantial bias and/or poor precision both during sample splitting and laboratory analysis. New techniques were evaluated in an effort to overcome some of the limitations associated with sample splitting and analyzing whole-water samples containing sand-size particles. Wet sieving physically separates sand-size particles from a whole-water sample. Once separated, both the sieved solids and the remaining aqueous samples were analyzed for total recoverable metals using a modified version of EPA method 200.7 which digests the entire sample, rather than an aliquot, of the sample container. Using a total recoverable acid digestion on the entire contents of the sieved solid and aqueous samples improved the accuracy of sediment-associated constituent concentration. However, heterogeneities associated with coarser particle sizes may contribute to increased variability in concentration results