The ice melting efficacy and environmental impact of alternative de-icers
Abstract
The application of sodium chloride (NaCl) to maintain safe, passable transportation and infrastructure in Canada can adversely impact the environment, including salinization of freshwater resources and mobilization of heavy metals from soil, thereby motivating efforts to assess alternative salts. This thesis aims to provide a holistic overview of conventional and innovative de-icers, namely calcium chloride (CaCl2), magnesium chloride (MgCl2), potassium chloride (KCl), sodium acetate (NaOAc), calcium magnesium acetate (CMA), chloride free brine (CFB), and sugar brine (SB), for their ice melting efficacy and environmental impact. The ice-melting and ice-penetration ability of these alternative de-icers were examined in the laboratory following standardized procedures from the Strategic Highway Research Program (SHRP) test methods and in the field at a non-trafficked parking lot. A comprehensive suite of batch tests was performed to investigate the mobilization of 10 metals from a common roadside soil when exposed to various concentrations of each alternative de-icer. Results from this thesis showed that all de-icers experienced at least a 49% reduction in their ice-melting capacity when the temperature decreased from -6.7°C to -17.7°C. MgCl2 exhibited the highest ice-melting ability of all de-icers and was the only effective de-icer below -12.2°C. In terms of metal mobilization, the de-icers releasing the highest number of different metals (in decreasing order) were: (1) CaCl2 and SB, (2) KCl and MgCl2, (3) CMA, (4) NaCl, (5) CFB, and (6) NaOAc. The findings from this study can provide policy makers, municipalities, and other road salt users with more knowledge on the performance of alternative de-icers to allow them to make informed decisions on road salt application in Canada.