The use of polymers and coal combustion by-products for amelioration of crusting in disturbed soils

Sedimentation of surface waters leads to decreases in biotic diversity, stress on water control structures, and declines in aesthetic values of natural resources. Agricultural erosion is no longer the predominant source of sedimentation in many areas due to increasing urban and suburban development and the success of agronomic soil conservation practices. Recent technological advances in both pollution control and polymer chemistry have produced materials which can be applied to soil to reduce the formation of surface crusts. Crusting increases stormwater runoff, erosion, and sedimentation. By-products from the electrical utility industry, namely, fly-ash (FA) and flue-gas desulfurization gypsum (FDG), and the synthetic organic polymer, polyacrylamide (PAM), were applied to soil and exposed to simulated rainfall in order to evaluate the potential use of each amendment for stabilization of disturbed soils. Manipulation of extrinsic soil erodibility factors such as initial water content and aggregate size were also evaluated to determine their role in the crusting process. Both factors were found to interact with each other to improve aggregate stability under rainfall. Fly-ash and FDG were found to improve rainfall infiltration; however, FA was found to pose an undue risk to surface water when applied on the soil surface, due to its high potential for off-site transport (i.e., its erodibility), and due to the dissolution of trace metals inherent in the material. The FDG material evaluated here posed little risk since it was relatively pure and since little was transported from the surface during the one-hour simulated storm events. PAM was found to be extremely effective, increasing infiltration percentage to 85% of rainfall in many cases. Erosion was also decreased greatly under rainfall simulation, warranting further testing of the material. PAM application to field plots at 30 Mg ha{dollar}sp{lcub}-1{rcub}{dollar} greatly reduced runoff and erosion. Treated soils withstood more than 2 months of natural rainfall (16 cm of precipitation) before crusts were formed. The material also improved ground cover establishment and applied fertilizer retention on site.