Possible Errors During Field Evaluations of Sediment Size Distributions

FIELD analyses of size distributions of sediment from aggregated soils necessarily involve conditions that may adversely affect the resulting data. Most of these conditions can cause inaccurate sieving and pipetting, so wet sieving and pipette withdrawal techniques are described that help minimize errors. Experiments were conducted to evaluate the effects of air and water temperature variations, different sediment sample sizes, variable pipette withdrawal depths, and vibrations from pumps and motors. For the range of such conditions encountered during field research, only insufficient sediment in the runoff samples that caused very low sediment concentrations for the pipette analyses showed evidence of seriously affecting the resulting sediment size distributions.