ERRITA XU
she/her | age 16 | Toronto, ON
Bronze Medal, Canada Wide Science Fair 2023 | Gold Medal, Toronto Science Fair 2023 | UTSC Department of Environmental Sciences Award | University of Toronto Chapter of Sigma Xi Award | National Winner, Ingenious+ Youth Innovation Challenge 2023
Edited by Mitchell Jeffs
Recognition of the environmental and physical implications caused by the widespread and growing use of road salts has sparked urgency amongst civilians, scientists, and governments globally. From freshwater acidification to vegetation loss, the widespread use of road salts is further damaging and degrading urban ecosystems. To determine the best alternative, beet juice, corn juice, and grape skin agro-based deicers were tested in comparison to the predominant traditional road salt, sodium chloride (NaCl). 14 treatments were formulated, and the deicing ability and environmental impact on vegetation were experimentally assessed. It was concluded that beet juice was the most effective and least environmentally toxic agro-based deicer, as well as being the most affordable, accessible, and socially feasible.
INTRODUCTION
With thousands of centimetres of snow falling in Canada annually, dependence on road salt to manage winters and maintain social order has increased over time. This alarming number has hovered between 1.5 to 5 million tons since 2004. In the U.S., road salt use has doubled since 1975 with 2017 numbers at over 25 million metric tons (Findlay et al., 2019).
The predominant road salt used is halite, also known as sodium chloride (NaCl). By weight, it contains roughly 40% sodium and 60% chloride. It works to melt ice by decreasing the freezing point of water through the process of freezing point depression. Freezing point depression is a colligative property, meaning that a solution’s freezing point depends on the amount of solute particles the solution contains. In fact, a solution’s freezing point continues to decrease until the solubility limit is reached. The freezing point of pure water is 0°C, but upon creating a 10% salt solution, the melting point decreases to -6°C, and for a 20% solution, it further decreases to -16°C. Figure 1 depicts this process where salt (orange) impedes the ability of water (blue) to form solid ice crystals. However, despite the great effectiveness and low cost of sodium chloride, widespread use especially in urban regions, has presented many environmental and physical concerns particularly due to runoff.
Figure 1: Depiction of how salt (orange) prevents water molecules from solidifying into ice crystals at 0°C (Pollack, 2019).
Freshwater Pollution
The use of road salt has a strong influence on the geochemistry of water. An overall increase in chloride concentrations is a key indicator of salt’s impact. There are higher observed chloride concentrations in urban and residential regions like Toronto, Mississauga, and Hamilton, which demonstrate the exacerbated patterns that urban regions experience. The aftermath of road salt use and high chloride levels is fated as runoff to local waters. Statistical evidence has illustrated the impact of anthropogenic factors and the disparities between urban and rural regions. Ontario’s chloride concentrations have increased from 38.64 mg/L to 54.97 mg/L, with a particular spike from 110.96 mg/L in the 1970s to 272.71 mg/L in the 2010s in urban sites (Sorichettia et al., 2022). Increases in chloride concentrations pose significant implications for aquatic organisms and biogeochemistry of freshwater lakes.
Soil Disintegration
The transfer of NaCl into soil typically occurs through salt splashing, the unintentional transfer of salt water onto roads and streams off-road. Statistics estimate that 45% of chlorides are removed annually by surface runoff in Canada while the rest remain in soil and groundwater (Howard & Haynes, 1993). High concentrations of Ca2+, Mg2+, and Na+ are often observed in roadside soils after salting operations. The faster movement of Na+ in the soil makes ions less available to plants, but more available to aquatic systems (Durickovic, 2019). Furthermore, the physicochemical properties of road salts enhance the release of heavy metals from soil to groundwater, resulting in pollution and decreasing soil quality. Other effects include increased pH levels, crusting, erosion, dispersion, and nutrient deficiencies (Durickovic, 2019).
Stress on Vegetation
Road salts pose not only a threat to the soil but also to the vegetation hosted. Soils that experience nutrient imbalances (under/over-accumulation of ions) impede vegetation growth. Other effects include necrosis, defoliation, and the inability to perform photosynthesis (Durickovic, 2019). Transfer of road salts can also occur through the air when road salts are stirred up and atomized by rapidly moving vehicles, disrupting the wetting and drying cycles of roadside plants. Plants respond to salt-induced stress by altering their biochemical and physiological properties–however, prolonged exposure and forced adaptation result in weakened defence mechanisms. Furthermore, excessive accumulation of Na+ and Cl− on leaf tissue causes direct toxicity in metabolic processes (Łuczak, et al., 2021).
Road/Pavement Damage
Road salts also have detrimental physical implications. They can cause accelerated deterioration, cracking, corrosion, and disruption to the thaw-freeze cycles of roads. The effects on asphalt appear three-fold:
Chemical interactions with cement hydration products and the formation of byproducts
The interaction with abrasives like gravel and sand, which are used to increase road friction.
The physical damage and internal cracks caused by the crystallization of deicing salts cause byproduct formation (Al-Rahim, et al., 2022). The increase in deterioration, corrosion, and infrastructure damage has strained financial and construction resources, as well as increased the occurrence of injuries and car crashes.
Rationale
Road salts and deicers play an integral role in northern cities. However, growing awareness of the environmental and physical harms caused by the widespread use of traditional road salts has sparked interest amongst scientists and city managers globally. The exploration and experimentation of agro-based products is a new emergence and only recently have scientific papers explored its plausibility. Some examples of such agro-based products include beet juice, corn juice, grape extract, apple peels, wine/beer waste, wheat-based starches, coffee grounds, and fireplace ashes. Though some studies have shown reductions in corrosive properties and their effectiveness as deicers, others have shown promise in terms of their environmental implications.
The goal of this study was to develop a sustainable and effective way of managing snow by implementing a comprehensive comparative analysis of different agro-based deicers explored in literature, evaluating its deicing effectiveness, environmental impact, and social feasibility.
METHODS
The three agro-based products chosen for this study include beet juice, corn juice, and grape skin. The experiments used treatments of NaCl, brine mixtures of NaCl and each agro-based product, and the agro-based products alone.
Formulating Treatments
To prepare beet juice, raw red beets were washed using tap water and peeled to remove any potential impurities. The washed and peeled beets were blended to create a uniform product. The product was then strained using a cheese filter to yield pure beet juice separate from its pulp.
To prepare corn juice, plain corn kernels were soaked and steeped in tap water for 24 hours. For every 4 cups of kernels, 1.5 cups of water were added to the blender, where the mixture was blended until a uniform product was created. The product was then strained using a cheese filter.
To create the grape skin solution, 100% red grape skin powder was purchased from North of 49. This product was chosen due to its uniformity and high sugar content from fermentation. Because it was a powder, a 1:3 ratio between grape skin powder (g) and water (mL) was created. The amount of water to add after the cube was melted was adjusted by subtracting the amount of solvent in the treatment cube.
10 mL aliquots of each agro-based juice were reserved and frozen. For the controls and dilutions, distilled water was used to best mimic melted snow. All treatments were created before experimentation by thawing aliquots for at least 2 hours, adding NaCl if part of the treatment, and diluting with distilled water. Experiments were done in an in-door laboratory setting to mitigate fluctuations in temperature, wind, and light.
Deicing Experiment
The first experiment conducted focused on testing the deicing abilities of the developed agro-based deicers to determine ice melting capacity. To maintain statistical significance, each treatment had 3 trials and the experiment was conducted in a clean lab environment to mitigate the presence of confounding externalities, such as wind and temperature when done outdoors.
Before the experiment, 6 mL distilled water ice cubes were made. 40 mL of each treatment was transferred to separately labelled beakers, an ice cube was added to each beaker and a stopwatch commenced. The beakers were stirred 4 cycles every 2 minutes to ensure treatment homogeneity and to check the size of the ice cube. When the ice was fully melted, the time was recorded. Freezing point depression is the decrease in temperature that occurs when a solvent (water) with a solute (treatment) has a lower freezing point, compared to pure solvent (water) alone.
Figure 2: Treatment composition for the deicing experiment (40mL per treatment).
Vegetation and Soil Experiment
The vegetation used for this experiment was radish and kale, both of which are fast-growing and abundant. Additionally, radish being salt-sensitive and kale being salt-tolerant provided a basis for comparison. Control groups for each plant were used to produce a baseline and all seeds were potted a week before experimentation to ensure the seeds could at least germinate.
The concentration of salt and agro-juices used for this experiment was lower than the concentrations displayed in Figure 3 compared to the deicing experiment treatments in Figure 2 to mimic dilution from melted snow. Each pot contained 6 seeds equally placed in 2 cups of soil. Over the 14-day experimentation period, each pot was watered Monday through Friday. On Mondays, Wednesdays, and Fridays, 40 mL of each treatment listed in Figure 6 was given to its respective pot, while 40 mL of distilled water was given on Tuesdays and Thursdays. This was an effort to mitigate overwhelming the newly germinated plants with high concentrations of the treatment. The pots were kept in a laboratory light garden to maintain a controlled environment and provide equal sunlight to each group. Each day, the number of seeds that broke the soil and the height (mm) of each grew was recorded.
The data collected was stored in Google Sheets. The height of each plant was measured prior to the experimentation to provide a baseline. On Mondays, Wednesdays, and Fridays prior to giving each pot treatment, the heights were measured and recorded. After the 30-day experiment period, data graphs were created.
Figure 3: Treatment composition for the vegetation experiment (40mL per pot).
RESULTS
Deicing Experiment
Figure 4: Time required for each deicer treatment to fully melt ice.
Freezing point depression occurs when salt ions react with water, creating a thin layer of salty water. The reaction hinders the formation of ice crystals as salt and water’s ion-dipole intermolecular forces are stronger than water’s dipole-dipole intermolecular forces. Figure 4 displays the results from the deicing experiment where ice melting capacity was measured. It was observed that 10% beet juice performed the best of all agro-based deicers, however, the 10% corn juice brine performed the best and the NaCl brines–on average–were still more effective. Grape skin deicers performed the worst when comparing the averaged results, though this was likely due to a significant lack of homogeneity as grape skin powder sunk to the bottom of the treatment. Further testing should be implemented to verify freezing point depression in a cold room setting. A more robust test determining freezing point depressing and ice melting capacity should be implemented to validate results.
Vegetation Experiment
Figure 5: Average radish height upon adding deicer treatment.
Figure 6: Average kale height upon adding deicer treatment.
Figures 5 and 6 display the height of radish and kale subjects based on added deicers. A control pot was used to allow for comparing height growth. A decrease in height indicated the increasing prevalence of growth failure. As observed in both Figures 5 and 6, height was the least inhibited by the treatments that didn’t contain NaCl – particularly 5% beet juice, 10% beet juice, 5% corn juice, 10% corn juice, and 10% grape skin. As expected, pots that received NaCl treatments showed demonstrated a greater negative response.
Figure 7: Percent of radish plants dead in each treatment’s pot.
Figure 8: Percent of kale plants dead in each treatment’s pot.
Figures 7 and 8 display the proportion of the 6 plants per pot that died during each observation day. The greater the death rate, the more vulnerable the plant subjects were to the deicing treatment. In these experiments, it was observed that the treatments with the highest concentrations of salt caused higher rapid death rates, while most pots containing no amount of salt resulted in little to no death.
DISCUSSION
Effectiveness of Deicers
The term “agro-based deicers” refers to combining traditional road salts with an agro-based additive that enhances deicing capabilities, reduces corrosivity, minimizes harsh chemical by-products, and promotes greater environmental sustainability. The research conducted by Abbas et al. (2021) concluded that beet juice is a highly effective deicer due to its high sucrose content, which possesses a complex chemical structure. Similarly, corn juice was chosen as many studies have studied effective corn-derived poly deicers. In contrast, grape skin deicers have only been evaluated in a study conducted by Nazari & Shi (2019) and it was concluded that its rich source of tartaric acid–a natural acid and preservative–as well as organic compounds, such as polyphenols, exhibit strong deicing properties. After conducting multiple trials with varying concentrations, it is deemed that beet juice is the most effective deicing agent, with an average time of 825.83 seconds, outperforming corn juice and grape skin treatments by 39.93 and 219.67 seconds respectively. These results align with literature and all agro-based deicers performed better than NaCl brines.
Deicers and the Environment
In the vegetation experiment, average growth and death were calculated for each pot containing either radish or kale. Using the raw data, overarching treatment types (i.e. NaCl, beet, corn, or grape skin) were analyzed as groups. Both growth and death are critical characteristics as they indicate the extent of stress, fatality associated, and the overall environmental impact posed by each treatment. These findings are significant for the scientific community as they contribute to our understanding of salt tolerance and plant development, with roadside vegetation particularly vulnerable. Observing the average death and height of radish and kale upon introduction to each treatment, it was concluded that beet deicers were the least environmentally degrading. Plant growth was the least inhibited and plant loss was the least prevalent in beet juice deicer pots. Additionally, all agro-based deicers demonstrated significantly better environmental-friendliness than their NaCl brine counterparts.
Social Feaibility
Finally, the last critical component to assess is social feasibility: which deicer is practical to use? As novel as agro-based deicers are, having an agro-based product cannot directly result in the assumption of effectiveness, sustainability, and adoptability. The cost of agro-based deicers is still unknown as they have mostly been tested in laboratory settings and have yet to be adopted. However, it is hypothesized that beet juice deicers are the least expensive as corn juice and grape skin deicers require significant chemical and physical degradation. This is because of the lack of high concentrations of carbohydrates–which make for a great freezing point depressant–while sugar beets contain high contents of carbohydrates. Furthermore, sugar beet production is widespread across all northern counties–the very countries that heavily rely on road salts during the winter season–unlike the geographic production distribution of corn and grapes. Thus, it is deemed that beet juice deicers are the most socially feasible.
CONCLUSION
In this research study, the deicing abilities, environmental impact, and social feasibility of 14 treatments containing road salt, beet juice, corn juice, and/or grape skin were analyzed. Upon statistical evaluation of implemented experiments and scholarly research, it was concluded that beet juice is the most optimal agro-based additive. Future research should aim to bolster this conclusion by analyzing other characteristics like solubility, phase change, environmental impact on freshwater, physical impacts on metal, asphalt staining, and more. Other recommended changes include using a freezing point depression osmometer to confirm deicing abilities, a centrifuge to help ensure treatment uniformity, and performing chemical and physical degradation more accurately on the agro-products. Connecting with city managers, scientists, corporations, and civilians will garner further feedback and analysis on feasibility. With accelerating rates of climate change and growing dependence on road salts, future works should innovate the social, economic, and environmental well-being of northern communities.
ACKNOWLEDGEMENTS
Thank you to all my mentors, family, and friends who have supported this research study. From advice to connecting me with expertise, this project would not have been possible without their unwavering support. Special thanks to Dr. Amanda G. Tescuiba (Havergal College, Toronto) who guided me throughout the planning process, coordinated materials/equipment, and provided lab space; Emily Xu who assisted throughout experimentation; scientists who took time out of their days to answer my inquiries about their research papers and showed interest in my findings.
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ABOUT THE AUTHOR
Errita Xu
Errita is currently a grade 12 student at Havergal College in Toronto. Her passions lie in environmental science and engineering, and exploring their intersections with other disciplines like technology and business. She was honoured to represent Team Toronto at the 2023 Canada-Wide Science Fair and is currently continuing her research studies into agro-based deicers. As a climate leader, she enjoys finding ways to leverage her scientific urgency for addressing climate change through community events. Outside academics, Errita loves walking in her local trail, cooking, and listening to music.