UNDISPERSED SEDIMENT PARTICLE SIZE DISTRIBUTION DETERMINED BY FIELD AND LABORATORY SAMPLES PROCESSI

Abstract

Size and density of sediment particles determines its transportability by erosive agents. This work was conducted with the objective of to evaluate the sediment particle size distribution of runoff samples originated from two different surface flow types, processed at the field and in laboratory, and to evaluate the effect of the laboratory samples storage time and the oscillation time during the wet sieving on the sediment particle size distribution. From two field experiments two kinds of runoff samples were collected, the first from rill concentrated flow without rainfall and the second from broad sheet flow under simulated rainfall. In the two cases, a freshly tilled Paleudult sandy loam soil was used. The sediment particles were splited into eight size classes and a median size was determined by the D index. For the samples originated by rill concentrated flow, the Ds, index from samples sieved at field was greater than the Ds, index from samples sieved in the laboratory (0.509 and 0.305 mm, respectively) and there was no effect for the laboratory samples time storage and time oscillation during the wet sieving. For the runoff samples originated by broad sheet flow under simulated rainfall, there was no difference in the median particle size among all different treatments.