Biological mechanisms of piping erosion reduction of organic soils

The purpose of this study is to develop an understanding of the biological mechanisms governing piping erosion resistance in organic soils. Our previous investigations demonstrated the ability of organic soils such as peat and compost to effectively decrease piping erosion progression when mixed with otherwise highly erodible silty sands. However, degradation of important geomechanical properties after the addition of the organic soils limits the applicability of this bioabatement method. To better understand the processes of the erosion reduction and the geomechanical detriments, two additional phases of research are performed. First, the possible influence of the unique shape and texture of the botanically derived organic constituents is eliminated in order to more precisely focus on the biological aspects. Results substantiate the hypothesis that the presence of extracellular polymeric substances (EPS) can affect piping erosion behavior. The second phase further investigates this hypothesis by quantifying total biomass and two EPSs, polysaccharides and a glycoprotein called glomalin, in various organic and nonorganic soils. Results of the analyses indicate positive correlations between the presence of both EPSs, total microbial populations, and erosion reduction. The presence of both microbially and synthetically derived polysaccharides contribute to a reduction in piping erosion progression.