Thesis advisor: Rudolph Hon / Road salt deicers are necessary for road safety, yet pose a risk to wildlife and public water supplies by increasing major ion loads above EPA limits. To better understand the fate of deicers after application, we need to know the migration routes and subsurface pathways that deicers take from their sources to points of discharge. This project used sediment core analysis and major ion chemistry analysis of water quality to evaluate the pathways of NaCl and CaCl2 through the subsurface of a shallow glacial aquifer in south east New England. Assessment of sediment cores revealed a heterogeneous subsurface with great variation in hydraulic conductivity. Analysis of major ion concentrations and ion ratios showed both short, direct pathways and deeper, longer pathways indicative of yearly salt retention in the aquifer. Ion chemistry also revealed deicer sources by their variable NaCl to CaCl2 ratios. / Thesis (MS) — Boston College, 2015. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

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.

Thesis advisor: Rudolph Hon / The application of road de-icers has lead to increasing solute concentrations in surface and ground water across the northern US, Canada, and northern Europe. In a public water supply well field in southeastern Massachusetts, USA, chloride concentrations in ground water from an unconfined aquifer have steadily risen for the past twenty years. The objectives of this study are to understand spatial and temporal trends in road salt concentrations in order to identify contamination sources and fate. To this end, the methods of this project include field and lab work. Water samples were collected from surface, near-surface, and ground water from March 2012 to March 2013. The other major field data are specific conductance measurements from probes located in three piezometers. In the lab, all samples were analyzed for major ions with ion chromatography analysis. Additionally, trace elements were measured by inductively coupled plasma analysis on a subset of samples. The results of these hydrogeochemical procedures showed several important trends. First, the highest concentrations of sodium and chloride from near-surface samples were located near to roadways. Second, ground water samples taken from glacial sediments contained relatively high concentrations throughout the water column, whereas ground water samples from wetlands had high concentrations only near the surface. Third, there was no clear relationship between pH and cation concentrations. Finally, specific conductance data showed strong seasonal trends near to the surface, whereas values taken from deeper in the aquifer were steadily increasing. Based on these results, it is highly probable that road salt application is the dominate contamination source. The pathways of road salt in the watershed include runoff into surface water and infiltration into the vadose zone and ground water. Road salt appears to preferentially travel through glacial features rather than floodplain features. It is possible that sodium from road salt is sorbed to aquifer sediment and displaces other cations. However, the low values of trace metals suggest that cation exchange is not mobilizing heavy metals. Finally, the increasing specific conductance values deep in the aquifer suggest that road salt is retained within the aquifer and concentrations will likely increase in the future if the current road salt application procedures are continued. / Thesis (MS) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

Thesis advisor: Rudolph Hon / Over 10 million tons of deicers are applied on impervious surfaces during winter storms in the United States every year to create safer driving and walking conditions. Road salt, or sodium chloride, is the most common deicer due to its low price and wide availability. Increasing concentrations of sodium chloride (NaCl) over the past decades have been measured in surface waters and groundwater throughout North America and it is projected to continue increasing. As there are no cost effective alternatives available to road salt, its potential role as an environmental and drinking water contaminant needs to be investigated. Field measurements from previous studies reveal the homogenization of NaCl in the subsurface through consistent elevated levels year-round. Through the integration of field and laboratory methods, this thesis aims to investigate the role of subsurface processes in the transport and pathways of deicers from the point of deposition to eventual emergence in surface waters and its potential impact on drinking water supplies. To understand the contamination pathways of NaCl that result in the observed surface water concentrations, experimental simulations were designed that indicate that gravitational/convective processes are the most important initial processes influencing deicer transport, but that other processes such as diffusion, surface tension, and dispersion/advection also play important roles. / Thesis (MS) — Boston College, 2020. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

Chloride concentrations at the Greenbrook well field in Kitchener, Ontario, have been steadily increasing over the past several decades and may soon pose a threat to drinking water quality. Drinking water limits at some wells have already been exceeded. The Regional Municipality of Waterloo (RMOW) relies mainly on local groundwater resources for its drinking water supply, and the Greenbrook well field is the oldest of 50 municipal well fields contributing to this supply. Urban growth and the expansion of city limits over the years has surrounded the well field, placing it in a high risk area in need of protection. As such, protection of this water supply is essential until alternative sources can be found. Road salt has been identified as the prime source of the chloride contamination, and various management alternatives and remediation strategies are currently being studied. In order to characterize the behaviour of chloride in the subsurface, an understanding of the mechanisms that control travel of chloride to the water table and through the groundwater system is needed. For the first phase of this work, a 2-D variably-saturated flow and transport model (SWMS-2D) was used to evaluate the effect of seasonal fluctuation in chloride loading to a generic aquifer system. Chloride was applied over the surface of the model in seasonal pulses that correlated with temperature and precipitation. The model showed a dampening of the seasonal response with depth that lead to the conclusion that long-term transport models can neglect seasonal changes in solute loading. For the second phase of this work, a proven 3D finite element transport model (Waterloo Transport Code: WTC) was used to simulate road salt impacts to the well field. Road salt was applied over selected roads throughout the steady-state capture zone via a type 3 (Cauchy) boundary that varies both temporally and spatially with road type and location. After calibrating the model from 1945 to 2002 to chloride concentrations using the weighted average of 5 Greenbrook production wells, the model was run to the year 2041 to assess future implications. Remediation strategies were also investigated via 6 predictive scenarios in which chloride applications were reduced by varying degrees. The results of this phase will be used by the RMOW in cost-benefit analyses of alternative de-icing approaches versus de-chlorination treatment of the well water.

Thesis advisor: Rudolph Hon / Thesis advisor: Yvette Kuiper / Chloride-based deicers (NaCl, CaCl₂, MgCl₂), also referred to as road salt, are the most common substances used in maintaining safe roadway surfaces during the winter months. Upon application, road salt reacts with the accumulated snow or ice to form brine equilibrium solutions along the liquidus line in the salt-water system. Dissolved salts dissociate, leading to increased concentrations of the respective ions in nearby soils, surface water, and groundwater. Of the ions present in road salt, chloride has the advantage of tracking all chloride deicers at the same time and since chloride ions are conservative tracers in soils it stays unaffected by ionic exchange interferences. This study explores the mechanisms of chloride return flows by investigating chloride dissolved loads, chloride concentrations in stream waters, seasonal patterns, and changes over the course of four years in two separate watersheds in Massachusetts with differing degrees of urbanization. The chloride tracking technique used in this study is based on calibrated chloride concentrations obtained from specific conductance signals recorded every 15 minutes by automatic recording systems at two locations, one in rural central Massachusetts and the other in urban eastern Massachusetts. These systems are maintained by the USGS, which also provide the simultaneously recorded stream flow datasets. The dissolved chloride load carried by each river is calculated for each single 15-minute interval by multiplying water volume with the corresponding chloride concentration, resulting in a total of over 34,000 data points per annum per site. Hydrograph separation techniques were used to separate dissolved load transported by each river into two separate flow components, event flow resulting from precipitation events, and baseflow resulting from groundwater discharge. Well defined hydrograph baseflow supported periods yield consistent chloride concentrations independent of the season at either urban or rural study sites. Comparison of direct runoff dissolved chloride loads with the total annual dissolved loads suggests that only a small fraction of the deicers actually removed during the overland runoff events and that a minimum of 60% of the total load discharged each year in both urban and rural systems is transported by groundwater. From groundwater recharge by brines rural watersheds are currently retaining as much as 95% of the total chloride applied to roadways each year while urban and suburban watersheds may only retain 75% of the total chloride applied to roadways each year. The increased retention of chloride in rural areas is likely due to the decreased amount of chloride transported during winter seasons as event flow compared to urban watersheds. / Thesis (MS) — Boston College, 2009. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Geology and Geophysics.

"Abstract. Urbanization has a significant impact on water quality. Urban drainage systems and impervious surfaces accelerate the delivery of pollutants from land areas in watersheds to streams and rivers. The harmful pollutants include sodium and chloride associated with the application of road salts during the winter, metals and oils associated with vehicles and impervious surface. The goal of this project was to access impacts of urbanization on River Meadow Brook and validate a chloride assessment tool. The first phase of this research was a part of a chloride study sponsored by the Massachusetts Department of Environmental Protection (MassDEP). The second phase of the projects included flow and water quality monitoring. The first phase of the project involved the development of a linear regression equation to validate a chloride assessment tool that MassDEP had developed and implemented based on historical data. River Meadow Brook, a Massachusetts stream that flows from a non-urban, rural area with relatively low pollutant concentrations to highly urbanized area in Lowell, MA, was chosen for that purpose because of the area’s large concentration of roadways and highways and historically high concentrations of chloride. Water samples and continuous conductivity data were collected for a 7-month period. Using 24 grab samples analyzed at the United States Environmental Protection Agency (USEPA) laboratory in Chelmsford, MA, the model was validated with 99.37% confidence using a linear regression equation. Therefore, the relationship between conductivity and chloride was validated. Calculated chloride was used to identify chloride violations of ambient water quality standards in River Meadow Brook. In addition to MassDEP study, the relationship between the percent of imperviousness and various trace metals, anions and total suspended solids was developed to show impacts of urbanization on the stream. The research approach included collection of both water samples and flows to calculate daily pollutant loads. Water monitoring included grab samples and unattended continuous conductivity with a 30-minute recording intervals. Discharge monitoring included collection of flows in River Meadow Brook using a brad- crested dam and the area- velocity technique. A wide variety of cations from a sampling of 5 sites along River Meadow Brook were analyzed using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Cl, sulfate and nitrate were analyzed using the Dionex ICS-2100 Ion Chromatography System. Laboratory results of water quality parameters showed that pollutants associated with impervious surface increase as the stream flows from its headwaters to downstream. The result from the Pearson correlation analysis revealed that sodium, chloride, potassium, vanadium, nickel, copper, arsenic, TSs and pH had a positive relationship with imperviousness while DO and nitrate had negative relationship. The combination of laboratory and field analysis helped to assess the impacts of urbanization and checked against ambient water quality standards. "

Winter road maintenance activities are crucial for maintaining the accessibility and traffic safety of the road network at northerly latitudes during winter. Common winter road maintenance activities include snow ploughing and the use of anti-icing agents (e.g. road salt, NaCl). Since the local weather is decisive in creating an increased risk of slippery conditions, understanding the link between local weather and conditions at the road surface is critically important. Sensors are commonly installed along roads to measure road weather conditions and support road maintenance personnel in taking appropriate actions. In order to improve winter road maintenance, more precise information about road surface conditions is essential. In this thesis, different methods for estimation of road weather are developed, discussed and tested. The methods use the principles of infrared thermometry, image analysis and spectroscopy to describe ice formation, snow accumulation and road surface wetness in specific patches or along road sections. In practical applications, the methods could be used for better planning of snow clearing operations, forecasting of ice formation and spreading of road salt. Implementing the proposed methods could lead to lower maintenance costs, increased traffic safety and reduced environmental impact. / <p>QC 20121116</p>

Chloride concentrations at the Greenbrook well field in Kitchener, Ontario, have been steadily increasing over the past several decades and may soon pose a threat to drinking water quality. Drinking water limits at some wells have already been exceeded. The Regional Municipality of Waterloo (RMOW) relies mainly on local groundwater resources for its drinking water supply, and the Greenbrook well field is the oldest of 50 municipal well fields contributing to this supply. Urban growth and the expansion of city limits over the years has surrounded the well field, placing it in a high risk area in need of protection. As such, protection of this water supply is essential until alternative sources can be found. Road salt has been identified as the prime source of the chloride contamination, and various management alternatives and remediation strategies are currently being studied. In order to characterize the behaviour of chloride in the subsurface, an understanding of the mechanisms that control travel of chloride to the water table and through the groundwater system is needed. For the first phase of this work, a 2-D variably-saturated flow and transport model (SWMS-2D) was used to evaluate the effect of seasonal fluctuation in chloride loading to a generic aquifer system. Chloride was applied over the surface of the model in seasonal pulses that correlated with temperature and precipitation. The model showed a dampening of the seasonal response with depth that lead to the conclusion that long-term transport models can neglect seasonal changes in solute loading. For the second phase of this work, a proven 3D finite element transport model (Waterloo Transport Code: WTC) was used to simulate road salt impacts to the well field. Road salt was applied over selected roads throughout the steady-state capture zone via a type 3 (Cauchy) boundary that varies both temporally and spatially with road type and location. After calibrating the model from 1945 to 2002 to chloride concentrations using the weighted average of 5 Greenbrook production wells, the model was run to the year 2041 to assess future implications. Remediation strategies were also investigated via 6 predictive scenarios in which chloride applications were reduced by varying degrees. The results of this phase will be used by the RMOW in cost-benefit analyses of alternative de-icing approaches versus de-chlorination treatment of the well water.

De-icing agents such as road salts is one of the most commonly used winter road management strategies employed in Canada and the United States. However, the use of chloride has caused negative impacts on aquatic habitats and drinking water supplies. The purpose of this study is to develop a methodology using readily available GIS data to identify salt vulnerable areas, through evaluating the impact the application of road salts have on areas of interest and quantifying the vulnerability to the area in order to prioritize implementation of best management practices. The proposed methodology for assigning a vulnerability score to a given watershed has been divided into two receiving receptors; surface water and groundwater recharge. The methodology employs a chloride mass balance approach. The vulnerability assessment was performed on seven sites in four watersheds in the Greater Toronto Area and validated using Hanlon Creek watershed in Guelph, ON.