In some ways, road salt is miraculous. An easy way to reduce ice formation in winter, which can help prevent accidents, slips and falls, and avoid countless injuries? That’s great! But too often we forget that all that salt has to go somewhere, and that the massive amounts that are often seen on streets are damaging our freshwater ecosystems.
What does road salt do to freshwater?
Once chloride – the Cl part of the NaCl formula for sodium chloride (salt) – enters the water column from salt washing off of our roads, it can be quite persistent. It doesn’t biodegrade, nor is it readily absorbed by sediment or other organic surfaces. This can result in high chloride concentrations in the stream long after the initial introduction.
Toxicity caused by sodium chloride entering a freshwater ecosystem can be either chronic or acute, depending on the concentration. At or above chronic levels (120mg/L), long-term exposure to chloride can cause harm to organisms living in the ecosystem, with amphibian, fish and invertebrate species being particularly at risk. Acute toxicity instead means that chloride levels are high enough (640 mg/L) that even a one-time exposure can damage the ecosystem. With these two thresholds in mind, last year Ottawa Riverkeeper launched a community based monitoring program to detect the levels of chloride in our streams.
The results were staggering.
While we expected there to be high levels of chloride in the winter months, corresponding to the use of road salt, the heights of contamination of our streams shocked us. All the creeks we measured exhibited chloride levels well above the chronic and acute thresholds on numerous occasions. On average, chloride concentrations were almost 10 times the chronic threshold! These levels are incredibly concerning, and constitute a massive threat to the health of our freshwater ecosystems.
Last year’s results were so telling that this year we are not just continuing the monitoring project, we are expanding it! In 2019-2020, we had four dedicated volunteers. That number has increased to twelve (including an additional coordinator for the program) for this new round of monitoring. Furthermore, we have increased the number of sites to 17 across Ottawa, Gatineau and the Chelsea/Wakefield area. Additionally, we are collaborating with new partners, including the Agence de Bassin Versant des 7, to expand this initiative on the Quebec side of the river.
All things in moderation
What can you do? The first step is to start using less salt. Alternative strategies for dealing with snow and ice abound, as do the reasons not to use salt.
For example, road salt becomes ineffective at temperatures lower than -10 °C, and our watershed regularly sees temperatures much lower than that. When it is that cold outside, skip the salt and try an alternative, such as gravel, sand, ashes, or even cat litter. Or just keep up to date with the shoveling to prevent ice buildup!
Sometimes you have to use a bit of salt, but in that case keep in mind the simple rule that a coffee mug full is about enough for a standard driveway. If you want even more simple rules on how much salt to use for surfaces, we created a whole quiz to help you!
However, while individual changes in use will help, the greatest impact can come from an institutional and cultural shift away from the dependence we see on road salt in our cities. To that end, the other thing you can do is help us raise awareness about its harmful consequences.
We are asking the public to send in photos of themselves using alternatives, or if they need to use salt, doing so responsibly. Send in a photo of yourself being a Salt Hero! Alternatively, let everyone know when you spot over-use of salt. You can share the photos on social media (try using #LessSalty), or send them to us to share on your behalf.
The bigger picture
This year we are combining our monitoring results with your voices and photos to make the case to municipalities, companies, and institutions that they too need to step up their game in addressing the issue of road salt.
We will be promoting the type of training and education that these larger institutions need to get a grip on salt over-use. One example is Smart About Salt, a training program that teaches responsible use of road salt. Keep an eye out for ways to get involved in these conversations, as an individual or on behalf of your organization, group, or company.
What comes next? As we push for these changes we will continue the monitoring begun in 2019. Over time we hope to see noticeable decline in chloride concentrations in our local waterways. For the sake of our freshwater ecosystems, we will be doing our best to make it happen – with your help.