While previous studies have focused on how road salt affects water quality and vegetation, limited research has characterized road salt distribution through soil and the resulting impacts. The potential for sodium (Na+) to be retained and impact soil physical and chemical properties is likely to vary depending on the soil's parent material, and more specifically on the extent of base saturation on the cation exchange complex. This thesis contrasted Na+ retention, impacts, and mobility in roadside soils in two different parent materials within southern Ontario. Soils were sampled (pits and deep cores) during fall 2013 and spring 2014 from two sites along highways within base-poor, Precambrian Shield soil and base-rich soil, respectively. Batch experiments were subsequently performed to investigate the influence of parent material and the effect of co-applied Ca2+-enriched grit on the longevity of Na+ retention in soils. Less Na+ is adsorbed upon the co-application of Ca2+, suggesting grit has a protective effect on soil by increasing cation exchange competition. Positive correlations between Na+ and pH, and negative correlations between Na+ and soil organic matter, % clay and base cations within Shield soils suggest that they are more vulnerable to Na+ impacts than calcareous soils due to less cation exchange competition. However, Na+ is more readily released from calcareous roadside soils, suggesting there is greater potential for Na+ transfer to waterways in regions dominated by calcareous soils.
Author Keywords: cation exchange, parent material, road salt, sodium retention, urban soil