Thesis advisor: Rudolph Hon / Road de-icing salts (predominantly NaCl, CaCl2, and MgCl2) are applied each winter in the northern US, northern Europe, and Canada to maintain safe driving conditions. It is widely recognized that road salt enters the environment through runoff and infiltration (Williams et al., 2000; Ostendorf, et al., 2001; J. Marsalek, 2003), resulting in salinization of freshwater (Godwin et al., 2003; Kaushal et al., 2005; Kelly et al., 2012). The chloride concentration (a proxy for deicers) has doubled in the last 20 years in the groundwater Norwell, MA, the primary public water supply for the town’s residents, and often exceeds the EPA secondary drinking water standard for chloride. The annual budget TDLCl¬ of Third Herring Brook in Norwell, MA is estimated using specific conductance and discharge datasets to determine the retention of dissolved deicers in the watershed during the study period. The estimated retention rate is between 59% and 78%. / Thesis (MS) — Boston College, 2015. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.