The History of Salt
It is that time of year where the weather is getting colder and with this cold weather also comes the potential for ice development on our roads, driveways and sidewalks. Throughout time we have been using the compound NaCl or commonly known as salt or rock salt is what people most commonly use to try and combat this Icey conditions. The truth is, “The rock salt used on roads is the same salt that is used on your dinner table. The larger salt pieces are typically ground down to finer crystals before being placed on your supermarket shelves. Salt is collected by underground salt mines and then processed, packaged and distributed. The largest salt mining company in the United States, American Rock Salt, produces 10,000 to 18,000 tons of salt each day” (Tuthill para 2).
Now that we have discussed what salt is the next topic of discussion is what its true purpose of the current process of deicing our roadways and sidewalks. The purpose of the salt is that it lowers the freezing point of moisture on the surfaces below the regular liquid freezing point of 32 degrees. Based on a Study that was completed by Harvard University, “in order for salt can become effective, the salt needs to be crushed by vehicles or pedestrian traffic and requires heat from pavement before the salt to dissolve” (Sexton pg 3). Only after the salt then dissolves it creates a brine where it prevents the ice from developing.
The effectiveness of the salt does not depend on the air temperatures but the temperatures of the pavement. The colder the pavement is, the longer time period it would take for the salt to deice. The main issue that can occur from using salt to deice is the process of refreeze. Refreeze occurs when the broken-down molecule of salt is weakened by the moisture that it causes that previous freezing point of the salt brine to be the same as the pavement temperature. At that point, the salt will not work and allows the water on the surface to refreeze if the temperatures of the pavement are declining. So if the pavement temperatures are too low for the salt to work, is it really worth it?
Salt and the Environment
In the past there has been many forms of documentations and publications that have investigated on lakes, streams and rivers have been contaminated by salt which breaks down into chloride and sodium. In fact, “Fifty pounds of salt, the equivalent to one large bag, can pollute 10,000 gallons of water” (Tuthill). Just a fifty-pound bag alone can contribute to over 10,000 gallons of water, just imagine with the amount of water that could be contaminated that we in the United States produce in the salt mines in just a single day.
In the research according to the Harvard University study, “Chloride (Cl) contamination in surface waters can be toxic to many forms of fresh water aquatic life including fish, macro invertebrates, insects and amphibians. Contaminants from salt used for winter management enter fresh water resources by infiltration to groundwater, non-point source runoff to surface waters and storm drains (Sexton pg 10). So not only does the brine from the rock salts infiltrate our lakes, rivers and streams from all that are listed above but are hurting the aquatic life in those areas. According to the New Hampshire Department of Environment, “Water contaminated with NaCl creates a higher water density and will settle at the deepest part of the water body where current velocities are low such as in ponds and lakes. This can lead to a chemical stratification which can impede turnover and mixing, preventing the dissolved oxygen within the upper layers of the water from reaching the bottom layers and nutrients within the bottom layers from reaching the top layers. This leads to the bottom layer of the water body becoming void of oxygen and unable to support aquatic life” (des.nh.gov).
The aquatic life these highly salted areas are being highly affected with the amount of salt that is contributed to winter management to deice our roadways and our sidewalks. Another interesting fact that was stated by the Department of Environment in the state of New Hampshire was that “During winter and spring and during times of low flow in the summer and fall, chloride levels can exceed 800mg/L, while natural background levels fall within the range of 1-10mg/L. The accumulation and persistence of chloride poses a risk to the water quality and the plants, animals, and humans who depend upon it” (des.nh.gov). The amounts of chloride that are measured based on the winter and spring months are dramatically and potentially dangerously high for any form of life that really depends on that source of water in order to survive. So the only question that I have is, is this right to do to the forms of life that depend on these waters in order to survive?
Salt and You
In the current way that we live, salt is all around us. From the salt that we put on our driveways, roads and our sidewalks to even to our foods that we eat. No matter how you look at it, salt is salt. The same salt that we have to enjoy French fries with is the same salt that is put on our streets to attempt to deice the roads. The only real difference in the two are the sizes of them. The salt that we use at our kitchens are just broken down into finer crystal-like form.
So, how does it negatively affect us? Well the answer for that actually comes from the sodium that is in the salt. “Sodium in drinking water is a health concern for individuals restricted to low-sodium diets due to hypertension (high blood pressure). Therefore, the US Environmental Protection Agency (EPA) now requires drinking water to be monitored for sodium and public water suppliers to report to local health authorities any concentration above 20 mg sodium per liter of water (20mg/l)4. Chloride is not toxic to human health at low levels but does pose taste and odor issues at concentrations exceeding 250 mg/l. In New Hampshire from 1983 to 2003 the NHDOT replaced more than 424 private wells contaminated by road salt at a cost of $3.2 million. Several public water supply wells have also been abandoned due to contamination” (des.nh.gov).
Not only does this pose a health issue in relation to high blood pressure but we are spending millions of dollars in order to replace these water supply wells because of the fact that the salt that we use for our driveways and roads contaminated our water pipelines. If this is the amount that has occurred in New Hampshire, just imagine what it is like in our state of Wisconsin. In the idea of your blood pressure, it is known that intaking a large amount of salt will higher your blood pressure, which all can lead to heart attacks, strokes, dementia and kidney disease, all of which that are all bad for us. Anything that can potentially either temporarily or permanently affect our hearts is something vital for us. If we had to choose between something that can ultimately affect our lives, I would want to do whatever I can to prevent anything like that occur to me. So if we do not want this happening to us, the question remains is what do we use instead of this salt to help deice our road and sidewalks?
Alternatives to Road Salt
In all of the other blogs that were posted we have discussed the history, the negative effects on the environment and most importantly how it ultimately affects us, but the one last topic of discussion remains, what are some alternatives that we can use in the replacement of Salt? There are currently a few different things that are being tested to look for a more environmentally friendly solution.
One of the ideas that was brought forward and being tested by engineers is the idea of having solar panel road ways. With using solar panel road ways this would allow for the usage of heating water pipes under the roads that would be able to melt all the snow and ice that accumulate on the roads. Another suggestion that has been thrown out there was beet wastewater or also known as the left-over sugar beet processing. According to CNN, “The carbohydrates or sugars in beet wastewater make it more effective at lower temperatures than salt water or brine alone, lowering the melting point of the ice to below -20℃ from -10℃ — and reducing the amount of chloride applied to the road” (Summers).
With this all-in mind, this solution especially in more of the colder regions on the United States like Wisconsin would be able to deice the roads even in the colder weathers where rock salt would not be able to clear the road. Another proven alternative that is out there is using sand. In some areas in the state of Wisconsin, some winter management organizations have replaced rock salt with sand. The difference with sand Is that it is more of an abrasive material and so from that what sand does is provide traction even in the coldest of temperatures. The only way it would work though is if the sand is on the surface of the ice. So with all these different more environmentally friendly alternatives, why not make a switch?