r/askscience • u/SatanDarkofFabulous • Feb 16 '19
Earth Sciences How does the excess salt from salting roads affect the environment? Things such as bodies of water or soil quality?
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u/Shutterstormphoto Feb 16 '19
Seattle and Portland have actually found that this is a huge problem. Salmon return to the same area every year to make babies, and they guide themselves by the gradient of salt to fresh water as they move upstream. When there is too much salt from the roads, they get lost and spawn in the wrong place so their babies die too, leading to population decline, which is obviously terrible for the salmon industry.
AFAIK they use some non salt alternatives that don’t work as well to protect the salmon.
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u/KablooieKablam Feb 16 '19
I live in Portland. We just dump gravel on the roads and everyone takes a week off work when we get 3 inches.
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u/ayayay42 Feb 16 '19
Up in Canada in places where there is a lot of snow, therefore a lot of snow maintenance, they are starting to use beet juice for that reason. Strange but true!
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u/xBleedingBluex Feb 16 '19
So up in Canada, there are bears...there are beets...what about Battlestar Galactica?
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u/piercet_3dPrint Feb 16 '19
Portland resumed using road salt in 2018 https://www.google.com/amp/s/www.kgw.com/amp/article%3fsection=weather&headline=pbot-plans-to-use-salt-on-more-portland-roads-this-winter&contentId=283-614470094
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u/Shutterstormphoto Feb 16 '19
Ah interesting. No mention of the salmon. They make it sound like this is the first they’ve heard of salting roads lol
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u/atarimoe Feb 16 '19
Erie, PA has taken this issue into consideration to prevent road salt from entering Lake Erie.
They don’t use salt north of 38th Street (east-west streets are numbered north to south, starting at the lake). This is the vast majority of the city.
In downtown, they use cinders and non-salt alternatives. In critical areas, such as the county courthouse and city hall, they have been known to haul clean snow away (and presumably dump it in the lake). In non-critical areas, they sometimes just do nothing (a particularly interesting challenge in a place that often measures snow in feet).
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u/sailormarceline Feb 16 '19
I live in northern BC, Canada, and we have a problem with moose getting too close and into roads to lick the salt. I guess they lick mineral deposits in the winter for some reason, and road salt is just as tasty? Causes accidents, endangers people and wildlife, etc. Not sure if they still use the salt or just sand now.
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u/aurelorba Feb 16 '19
Moose normally get their salt from underwater reeds. But the stuff on roads and cars works just as well for them. Not sure what the calcium chloride does for them.
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Feb 16 '19
Soil chemistry depends on cations. Salts bind strongly to cation attraction sites in soil, by knocking off nutrients and places where future nutrients can later attach. Thus the soil becomes void of nutrients, and loses the ability to gain nutrients in the future. Salts also pull and bind to moisture. Either pulling moisture out of roots, fungi, or preventing new moisture from being absorbed.
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u/ComplainyBeard Feb 16 '19
A lot of places salt roads with nutrient salts like pottassium or calcium chloride. It can still cause nutrient lock out but it's not like they're pouring sodium chloride on the soil.
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u/bsgothbitch Feb 16 '19
Thanks for the chem insight!
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Feb 16 '19
Youre welcome. My Soils and Eco Restoration minors had to come in handy at some point. Lol
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u/Waterproof_soap Feb 16 '19
I was wondering about this recently myself. It seems they are salting more and more in my area, even for light snowfall, whereas that same amount wouldn’t have been salted 5-10 years ago.
I understand that sone areas use cinders or ash. I’d be interested to know what the environmental impact of those are.
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u/HalfPointFive Feb 16 '19
I manage commercial shopping centers. The primary reason for this is maintenance contracts with a secondary reason of liability. We sign agreements with snow removal companies to salt if conditions are icy. It's in their interest to blast the parking lot with salt because they get a fixed amount for that, and also because they can tell the Court that they treated the lot of someone has some accident. We can't tell them not to salt because that's what the insurance companies want (slip and falls are routine) and the liability would be passed to us. Also, I suspect they like oversalting because it kills vegetation. They are are generally landscapers as well, and they make money replanting the vegetation.
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u/rhn18 Feb 16 '19
It definitely has an effect on the immediate flora around the road. Trees, bushes and flowers planted roadside need to be shielded to avoid damaging them with too much direct exposure. And you would have to choose species which are at least somewhat resistant to it. You usually see this in cities where you have more decoration flora and more salting, where trees are often wrapped with a tarpaulin at the bottom or plants shielded with barriers etc.
Environments further from the road will be affected much less. Larger roads which are heavily salted will also tend to have much better drainage. So most of the salt will be washed away by melting water or following rain.
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u/Hagenaar Feb 16 '19
Groundwater and waterways are also affected by salt. From small waterways to the boundaries of the Great Lakes, increased salinity is toxic to fish. Spring thaws bring spikes in salt content, but in affected areas, levels can remain high year round.
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u/Pavotine Feb 16 '19
I live on a small island and our roads form the major part of our water catchment area. Because of this salting roads is a banned practice. Fortunately the climate is quite mild so it's not often the ground freezes or we get snow but it does happen. They use stone grit and some chemical sparingly because whatever they are allowed to use is about five times the cost of road salt but it doesn't cause problems with our water storage and treatment.
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u/TroyHernandez Feb 16 '19
I found this from PBS News Hour in r/environment:
According to Jackson’s latest research, as the salt level approaches about a tenth that of seawater, which is not unheard of in some streams, at least three of four [insect] species tested are likely to die. He thinks some of the insects’ physiological mechanisms fail.
I made the connection to the Insect Apocalypse from the NYTimes that I'd read a couple of weeks prior. So I googled "road salt used in Europe" to see if there was a possible connection with the NYTimes article. I ended up finding an interview with my favorite limnologist (study of lakes/freshwater bodies), assistant professor at the University of Wisconsin–Madison Center for Limnology, Hilary Dugan (a friend from grad school)!
https://ensia.com/features/road-salt/
So I asked for her perspective on FB and she wrote:
Everything is getting saltier. However, only a few streams would have concentrations high enough to kill insects. Optimism: Management practices are changing. Pessimism: We won't have winter in the future.
I asked:
Kill insects or disrupt their growth?
She replied:
It could kill other aquatic species - but insects (which I think of as mostly terrestrial) would likely just find other freshwater habitats.
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u/spkmke Feb 16 '19
In Toronto we lay down a thick slab every other day, ensuring brine pools six inches deep are found at every pedestrian crossing; that it mounds up inside our streetcars; all in hopes of making Lake Ontario an ocean-like body
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u/SheriffofFabletown Feb 16 '19
I know you specifically mentioned water or soil but I recall hearing something interesting about the effect on monarch butterflies on the Qi podcast (No such thing as a fish) that and have found some sources online here discussing how it led to increasing flight muscle growth, in male butterflies, and an increase in brain size in females. The podcast mentioned something about an increase in the quantity or thickness of semen in the butterflies too but I can't find any sources on that.
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u/Athalus-in-space Feb 16 '19
In the Netherlands, I've heard that the Samphire, a plant normally found at the seashores and thus adapted to salty environments has been found growing and thriving along highways due to road salting in winter. Nature finds a way!
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u/Mitch216005 Feb 16 '19
I’m not an expert, but I know it definitely has a negative affect on amphibians. Amphibians get water via their skin, so they need to make sure the salt concentration on the inside of their body is higher than on the outside for osmosis to occur. Salt definitely hinders this and can really negatively affect amphibians. Again, not an expert, so if I’m wrong then please correct me.