Particle Size Distribution Analysis of a Mining-Impacted Gravel-Bed Stream in Ohio Using a Hybrid Sediment Sampling Technique

Abstract

As part of a risk assessment study of the Leading Creek Watershed in Ohio, a prior Virginia Tech researcher collected pavement and subpavement sediment samples at 17 sites using the hybrid areal sampling technique with a clay adhesive. The watershed, which is heavily impacted by mining and agricultural activities, suffers from low pH, high concentrations of metals and sediment in the water column, and excessively silted streambeds. The current work presents the results of the particle size analyses performed on the hybrid samples in the context of evaluating the effectiveness of the technique itself and as a tool in future watershed/ecological studies, as well as examining possible relationships between siltation and indicators of ecological health in Leading Creek. By combining clay grid and adhesive sampling methods, the hybrid technique consistently achieved an effective particle size sampling range of 0.05 mm (1.97 x 10-3 in) to over 300 mm (11.8 in), thereby reducing the common problem of trunction. However, the overlap of the clay adhesive and natural sediment distributions and atypical sediment loading from surrounding abandoned and reclaimed mine lands obscured expected trends such as downstream fining and hindered the analysis of materials finer than 0.125 mm (4.93 x 10-3 in). Volumetric conversion of areal samples using the Modified Cube Model with a traditional exponent of -1 for clay was complicated by the large amount of fines in the Leading Creek samples. Further investigation into a more appropriate conversion technique for the evaluation of fine sediment samples is warranted.