Winter’s Hidden Cost: Effects of De-icing Agents on Dissolved Oxygen Levels in Freshwater

Every year, Winnipeg spreads 26,000 tonnes of road salt, which doesn't just melt ice - it also harms our water. When road salt enters freshwater, it sinks to the bottom, creating a dead zone where there is very little or no oxygen circulation. In this project, I tested 4 de-icing agents - Road Salt, Beetroot Juice, Abrasive Gravel, and Biochar, to see which had the most effects on dissolved oxygen levels in freshwater.

My results showed that road salt created the most stratification by causing a 22.11% oxygen decrease compared to the control, followed by beetroot juice with a 23.99% decrease. Gravel however showed minimal changes, and biochar showed great oxygen circulation, and proved that this eco-friendly & cost effective alternative has the ability to both let our local lakes stay undisturbed, and have our snow melted in no time. So it’s time to stop the salt and start saving our water. I’m Ramneek Rai, and this is the future of de-icing.

The Problem: The increasing amount of runoff from road salt and other de-icing agents is causing the chemistry of freshwater bodies to be at risk.

Here in Winnipeg, we spread approximately 26,000 tonnes of road salts annually, along with 45,000 tonnes of sand on our roads (Lyons, 2023), without knowing the immense harm behind it. As we spread these de-icing agents on our roads, sidewalks, and driveways, we open many harmful doors to freshwater bodies, which have the potential to lead to the extinction of a whole aquatic system.

When these runoff materials enter freshwater, they create a denser layer of water, which later sinks to the bottom of the water body (the benthic zone), leading to immense stratification. When this happens, the stratified water blocks the circulation of oxygen. Without oxygen, a water body is unable to survive, and can immediately end an aquatic system altogether, known as hypoxia (NOAA, n.d.). Not only do aquatic organisms need oxygen to thrive, but the whole freshwater body also needs an oxygen measurement of more than 6.5mg/L. If this oxygen is not available to the water body, it chemically and physically ruins the water body; it causes a massive decrease in aquatic biodiversity, prevents aquatic vegetation from thriving, and typically turns a healthy water body into sterile, lifeless dead zones.

Research Question:

Which de-icing agent affects the oxygen movement the most in a freshwater body?

Whether organic biochar can be a cost-effective & eco-friendly alternative for this crisis.

Phase 1: Creating water columns replicating Lake Winnipeg's conditions

6 clear rigid PVC pipes (water columns) were cut to a measurement of 2 ½" x 30”

3 holes (¼") were drilled into each water column at each depth: 11.25", 18.25", and 24.25".

In each hole, a small piece of flexible PVC pipe was inserted (for dissolved oxygen measurements); the pipe was then covered with a silicone hole plug.

Each water column was covered by an end cap (to prevent any leakage).

Freshwater and subaqueous soil (soil found in freshwater bodies) were bought from the western shore of Lake Winnipeg.

Subaqueous soil was inserted until the 2” mark.

Freshwater was added to the 26” mark.

All columns remained untouched for 2 days (for microbial growth).

Phase 2: Measurement of dissolved oxygen (mg/L) levels

Four de-icing agents were diluted to replicate runoff conditions.

Road Salt (a combination of calcium chloride + sodium chloride)

Road Salt + Traction Sand

Beetroot juice

Biochar

Using a dissolved oxygen (DO) probe, initial dissolved oxygen measurements at the surface level, as well as at the 11.25", 18.25" and 24.25" depths were taken for each water column. The probe was kept in the water until a stable reading was received.

All de-icing agents were added to their respective columns. One control column was also kept, in which no de-icing agents were added.

After 4, 12, and 24 hours, dissolved oxygen measurements were taken at all four depths to observe changes in dissolved oxygen levels over time.

Results:

Temperature & Dissolved Oxygen: Dissolved oxygen (DO) levels varied at different depths, de-icing agents, and trials due to different temperatures and more settlings time for the de-icing agents over time. Temperatures were as follows for the different trials:

Trial 1: 7.0-8.3 °C

Trial 2: 3.0-4.8 °C

Trial 3: 7.1-8.2 °C

Trial 2 consistently showed the highest DO rates, with the control reaching 9.16 mg/L at the surface level, whereas Trials 1 and 2 showed lower maximum values for DO. This pattern, however, is expected, as colder water is capable of holding more dissolved oxygen (Fondriest Environmental, 2013).

Depth & Dissolved Oxygen: Similar to stratified water bodies, the results across all trials showed that Dissolved Oxygen decreased with depth. In the control during Trial 1, DO went from 8.46 mg/L at the water's surface to 7.56 mg/L at depth 4 (24.25"), and from 9.03 mg/L at the surface to 7.96 mg/L at depth 4, proving oxygen wasn't evenly distributed in the column.

De-Icing Agents & Dissolved Oxygen: For comparisons, Trial 3's results were used because it was conducted after 24 hours of inserting the de-icing agents, allowing them to settle and represent longer-term environmental effects.

In Trial 3, road salt drastically reduced dissolved oxygen compared to the control. At the surface, DO was 7.61 mg/L compared to the control's 9.03 mg/L, which is a 16% decrease. At depth 4, there was a 22.11% decrease from 7.96 mg/L (control) to 6.20 mg/L (road salt).

Beetroot juice caused the largest decrease in DO levels. In Test 3, DO levels were 6.96 mg/L at the surface and 6.05 mg/L at depth 4, which is 22.92% and 23.99% percent lower compared to the control. This is likely because of the increased oxygen consumed by beetroot juice.

Biochar had minimal impacts on dissolved oxygen levels, with surface DO levels only decreasing by 7.20%, and depth 4 oxygen levels rising 0.13%. Gravel also showed very little change, with DO levels remaining close to the control. With the surface DO levels being 8.82 mg/L, there was a 2.33% DO decrease compared to the control. At depth 4, DO levels were 2.01%.

At depths 2 (11.25") and 3 (18.25"), DO levels showed similar trends, with road salts and beetroot juice being lower than the control, and the gravel and biochar being close to the control's levels.

Discussion: Overall, the experiment showed how different de-icing agents have very different impacts on dissolved oxygen levels in water. The central finding was that road salt and beetroot juice, which are two of the most commonly used de-icing agents in Winnipeg, caused the largest decreases in DO levels, while both biochar and gravel had less severe effects.

From these results, we learn that sodium-chloride-based road salts can significantly reduce DO levels, especially at deeper levels. Since dissolved oxygen is necessary for healthy aquatic ecosystems, road salt runoff and its consequences can cause severe negative outcomes for our environment. Also, even though beetroot juice is considered an eco-friendly alternative to road salts, it caused a large decrease in DO levels, which shows that not all eco-friendly alternatives are better for oxygen levels.

Even though biochar is not widely used as a road salt, it has been known to have de-icing abilities, and considering it showed very little impact on DO levels, it could be explored as an alternative which impacts DO levels less. Gravel also had a very small effect, but it is normally less effective at melting ice, which makes it less practical.

Applications: To protect freshwater ecosystems, municipal governments can use this research to become more aware of the effects different de-icing agents have on DO levels and consider more eco-friendly alternatives. Being more knowledgeable about these effects can also help us create policies and road salt runoff managing strategies.

Future Plans:

In the future, I plan on expanding on this project by using a broader range of de-icing agents such as acetates, formates and glycols, to increase awareness of the effects of commonly-used road salts. I also plan on discovering more environmentally-friendly alternatives that are successful de-icing agents.

I also hope to test more aspects of water health, such as phosphorus and nitrogen levels which are essential to healthy ecosystems, to gain a more thorough understanding of how different de-icing agents affect the health of waterbodies and life in them.

From driving up to Lake Winnipeg to obtain freshwater, to taking me to stores every other day, this project would've been nowhere without the support of my parents, which I'm very grateful for.

I'm also thankful to the Bison Regional Science Fair team which been a huge support throughout the process and have all been very encouraging!

And lastly, I would like to thank my brother for helping me with a lot of odd tasks, such as photography, practicing my presentation, and helping assemble the water columns!

References:

Bueckert, K. (2023). Reducing road salt use 'not something that can wait' as Ontario lakes see oxygen depletion, researcher says. CBC. https://www.cbc.ca/news/canada/kitchener-waterloo/road-salt-use-ontario-lakes-salinization-waterloo-study-1.7037693

Schneider, C. (2015). Underwater Soils: Classifying and studying subaqueous soils can provide huge benefits for conservation, restoration, ecosystem services, and infrastructure. CSA News, 60(1), 4–10. https://doi.org/10.2134/csa2015-60-1-1

Dissolved oxygen. (2026). Cary Institute of Ecosystem Studies. https://www.caryinstitute.org/news-insights/2-minute-science/dissolved-oxygen

Environment Canada & Health Canada. (2001). Priority Substances List Assessment Report for Road Salts. https://www.canada.ca/en/health-canada/services/environmental-workplace-health/reports-publications/environmental-contaminants/canadian-environmental-protection-act-1999-priority-substances-list-assessment-report-road-salts.html

Tenneti, A. (2022, December 17). Looking into Road Salt Use, Harms, and Alternatives. NiCHE. https://niche-canada.org/2022/12/19/looking-into-road-salt-use-harms-and-alternatives/

Lyons, A. (2023). Deicing’s impact on Lake Winnipeg. https://uniter.ca/view/deicings-impact-on-lake-winnipeg

Radosavljevic, J., Rezanezhad, F., Goucher, N., Ju, J., Rudolph, D., & Cappellen, P. (2023). ‘Forever contaminant’ road salts pose an icy dilemma: Do we protect drivers or our fresh water? The Conversation. https://doi.org/10.64628/aam.xuemw6w5r

Environment and Climate Change Canada. (2020). State of Lake Winnipeg - 2nd Edition. Government of Manitoba. https://www.gov.mb.ca/sd/water/pubs/water/lakes-beaches-rivers/state_lake_wpg_report_tech.pdf

Scott, K. (2025). Lake Winnipeg Research Consortium Inc. Annual Programs Report 2024/2025.

National Oceanic and Atmospheric Administration (NOAA). (n.d.). Low or depleted oxygen in a water body often leads to ’dead zones ’— regions where life cannot be sustained. https://oceanservice.noaa.gov/hazards/hypoxia/

Fondriest Environmental, Inc. (2013). Dissolved Oxygen. Fundamentals of Environmental Measurements. https://www.fondriest.com/environmental-measurements/parameters/water-quality/dissolved-oxygen/

Image Sources:

Kruzman, D. (2022). Road salt is imperiling US waterways. States might have a solution. Grist. https://grist.org/cities/road-salt-is-imperiling-us-waterways-states-might-have-a-solution/

Road salt science is clear, time to take action | Ausable Freshwater Center. (n.d.). https://www.ausableriver.org/blog/road-salt-science-clear-time-take-action

Environment and Climate Change Canada. (2020). State of Lake Winnipeg - 2nd Edition. Government of Manitoba. https://www.gov.mb.ca/sd/water/pubs/water/lakes-beaches-rivers/state_lake_wpg_report_tech.pdf

Self-made

Baljot Rai

Baljot Rai

Self-made graph

Self-made graph

Self-made graph

Dissolved oxygen. (2026). Cary Institute of Ecosystem Studies. https://www.caryinstitute.org/news-insights/2-minute-science/dissolved-oxygen

Marohn, K. (2019, February 12). Are there eco-friendly alternatives to road salt? MPR News. https://www.mprnews.org/story/2019/02/12/are-there-eco-friendly-alternatives-to-road-salt

Brush, S. (2019). Try using a salt alternative at your home this winter and help avoid the harmful effects that road salt can have on our groundwater supplies, local waterways, and rest of our surrounding environment. North Andover News. https://northandoverma.news/2019/01/07/try-using-a-salt-alternative-at-your-home-this-winter-and-help-avoid-the-harmful-effects-that-road-salt-can-have-on-our-groundwater-supplies-local-waterways-and-rest-of-our-surrounding-environment/

Bison Regional Science Fair

Title Picture: Burg, R. (2015). Hypoxia and its Effect on Wildlife. Long Island Sound Partnership. https://lispartnership.org/2013/11/hypoxia-and-its-affect-on-wildlife/