Road Salt Contaminates U.S. Waterways in Northern States Year Round
By Brian Bienkowski
As winter sets in across the northern U.S., the road salt that keeps people out of ditches is flowing into rivers at levels that could harm fish and other creatures.
With billions of pounds of salt spread on U.S. roads every year, waterways in the nation’s wintry cities are getting saltier. And, according to new research, the salt—or sodium chloride—in rivers remains toxic not just in winter, but throughout two-thirds of the year.
Photo courtesy of Shutterstock
In icy Wisconsin, where salt is liberally dumped on roads, the Menomonee and the Kinnickinnic have chloride levels in late winter and early spring 10 to 15 times higher than a federal level set to protect fish, amphibians and tiny crustaceans. Toxic concentrations also have been found in rivers, streams and lakes in New York, Maryland, Minnesota, Missouri and several other states.
“It’s likely that many of the organisms in rivers that are sensitive to chloride are simply no longer there,” said Steve Corsi, a research hydrologist with the U.S. Geological Survey (USGS).
Seven of 20 U.S. rivers—four in Wisconsin, one in Ohio and two in Illinois—have average chloride levels that approach or exceed the U.S. Environmental Protection Agency’s guideline for protecting aquatic life, according to the USGS study, which is not yet published. All seven rivers exceeded it on more days in 2006 than in 1991.
The salt stays in rivers and groundwater for years after it’s tossed on roads, said Sujay Kaushal, an associate professor at the University of Maryland who studies road salt in Northeast U.S. streams.
In addition to posing a threat to wildlife, the salt can leach into groundwater, contaminating drinking water supplies.“Even if they quit applying salt now, it would take decades for it to be removed from the system,” Kaushal said.
Yet road salt is considered a necessity in northern states. It is the most efficient and economical way to keep people safe in the winter, said Morton Satin, a vice president at the Salt Institute, a non-profit trade association that advocates for salt.
“We have chosen to live in a northern climate, where we want the same safety in the winter that we have in the summer,” Satin said. “Amazon has to deliver the same packages even when the roads are bad.”
More than 116,000 people in the U.S. are injured and more than 1,300 killed on snowy or icy pavement each year, according to the U.S. Department of Transportation. Road salt reduces snow-induced crashes by about 88 percent, says a Marquette University study.
Salt lowers the freezing point of water, preventing ice and snow from sticking to roads. In addition, cyanide compounds, which also can be toxic, are often added to road salt to prevent it from caking.
The volumes used on U.S. roads have increased each decade since the 1940s. About 617 million pounds were sold per year in the 1940s, and now roughly 35 billion pounds per year.
Some cities, including Madison and Milwaukee, have experimented with beet juice, sand and other “greener” ways to keep ice off roads. But most deicers still contain some chloride, Corsi said. “You may not need to apply as much of them, but they’re way more expensive.”
In Minnesota, the salinity of 39 lakes has mirrored the upward trend of the state’s purchase of road salt. If this trend continues, salinity will double in these lakes in about 50 years, according to University of Minnesota scientists.
In the new USGS research, the rivers were saltiest in the late winter. But the Menomonee and the Kinnickinnic had high concentrations in the summer, too, Corsi said.
“Chloride is very soluble and it’s easy for it to infiltrate the groundwater, the source of the river flow,” said Corsi, who was lead author of the study.
The new findings build on previous USGS research that found that more than half of sites tested in 13 U.S. cities exceeded the EPA’s chloride guideline of 230 parts per million, according to a 2010 USGS study. That guideline is based on chronic exposure levels that reduced the survival of water fleas, rainbow trout and fathead minnows.
Streams tested in Maryland, New York and New Hampshire were “well beyond” the toxicity guideline, Kaushal said. In Missouri, an urban stream, Hinkson Creek, had high levels of chloride linked to reproductive and survival problems for water fleas.
Some of the creatures most sensitive to chloride are amphibians, which are declining worldwide from a variety of environmental threats.
"Road-side aquatic ecosystems in North America are annually polluted with millions of tons of road deicing salts, which threaten the survival of amphibians which live and breed in these habitats,” Utah State University researchers wrote in a study published earlier this year.
Newts exposed in the Utah laboratory to amounts of salt commonly found in roadside streams had severe developmental deformities– bent tails, bent bodies, cysts, missing tails and gills, two heads and shrunken heads.
Also, salamander eggs develop abnormally when exposed. They cannot retain the water needed to avoid freezing and disease.
Wisconsin does not regulate road salt use, and the levels showing up in the state’s rivers are concerning, said Tim Asplund, a monitoring section chief with the Wisconsin Department of Natural Resources.
The state agency, which has been monitoring 42 river sites since the 1980, has found increasing chloride concentrations.
“There are other contributors to chloride concentrations … wastewater treatment facilities, industrial discharges,” Asplund said. “But it’s very likely due to road salt.”
Satin said the salt industry has long known its “biggest long-term problem would be chloride running off into water.”
There are ways to minimize the runoff impact, he said.
“We encourage people to only use the lowest amount they need,” Satin said. “Also, as a country we have not re-engineered our road system in 50 years, we need to take runoff into account in our road design.”
Kaushal agreed, saying that ensuring protection of wetlands and vegetation “provides some line of defense before things get into the river.”
“We need to ask ourselves if we should really be putting more highways, parking lots and houses right on top of rivers,” Kaushal said.
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If weather is your mood, climate is your personality. That's an analogy some scientists use to help explain the difference between two words people often get mixed up.
Size Matters<p>Climates are a bit like woven tapestries. The big picture is important, no question. But so are all the seemingly minor details found inside the larger whole.</p><p><a href="https://research-information.bris.ac.uk/en/persons/tommaso-jucker" target="_blank">Tommaso Jucker</a> is an environmental scientist at the University of Bristol. In an email, Jucker says he'd define the term microclimate as "the suite of climatic conditions (temperature, rainfall, humidity, solar radiation) measured in localized areas, typically near the ground and at spatial scales that are directly relevant to ecological processes."</p><p>We'll talk about that last bit in a minute. But first, there's another criteria to discuss. According to some researchers, a microclimate — by definition — must differ from the larger area that surrounds it.</p><p><a href="https://www.cfc.umt.edu/research/paleoecologylab/publications/Davis_et_al_2019_Ecography.pdf" target="_blank">Forests</a> provide us with some great examples. "The climate near the ground in a tropical rainforest is dramatically different from the climate in the canopy 50 meters [164 feet] above," says University of Montana ecologist <a href="https://www.cfc.umt.edu/personnel/details.php?ID=1110" target="_blank">Solomon Dobrowski</a> in an email. "This vertical gradient among other factors allows for the staggering biodiversity we see in the tropics."</p><p>Likewise, scientists observed that a 2015 partial <a href="https://animals.howstuffworks.com/insects/bees-stopped-buzzing-during-2017-solar-eclipse.htm" target="_blank">solar eclipse</a> caused the air temperature of an Eastern European meadow to <a href="https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/wea.2802" target="_blank">change more dramatically</a> than it did in a nearby forest. That's because trees provide not only shade, but their leaves also reflect solar radiation. At the same time, forests tend to reduce wind speeds.</p><p>All those factors add up. A 2019 review of 98 wooded places — spread out across five continents — found that forests are 7.2 degrees Fahrenheit (4 degrees Celsius) <a href="https://natureecoevocommunity.nature.com/posts/47363-forests-protect-animals-and-plants-against-warming" target="_blank">cooler on average</a> than the areas outside them.</p><p>Now if you hate the cold, don't worry; there's a cozy exception to the rule. According to that same study, forests are usually 1.8 degrees Fahrenheit (1 degree Celsius) warmer than the external environment during the wintertime. Pretty cool.</p>
A Bug's Life<p>When does a microclimate stop being, well, micro? In other words, is there a maximum size we should be aware of when discussing them?</p><p>Depends on who you ask. "In terms of horizontal scale, some have defined 'microclimate' as anything that is less than 100 meters [328 feet] in range," Jucker says. "I'm personally less prescriptive about this."</p><p>Instead, he says the "scale at which we want to measure [a particular] microclimate" ought to be "dictated" by the questions we're trying to answer.</p><p>"If I want to know how temperature affects the photosynthesis of a leaf, I should be measuring temperature at centimeter scale," Jucker explains. "If I want to know if and how temperature affects the habitat preference of a large, mobile mammal, it's probably more relevant to capture temperature variation across [tens to hundreds] of meters."</p><p>For instance, solitary plants have the power to generate itty-bitty microclimates. Just ask <a href="https://www.colorado.edu/geography/peter-blanken-0" target="_blank">Peter Blanken</a>, a geography professor at the University of Colorado, Boulder and the co-author of the 2016 book, "<a href="https://amzn.to/2XN6FT8" target="_blank">Microclimate and Local Climate</a>."</p>
The urban heat island effect is a good example of how microclimates work. NOAA
Microclimates on a Grand Scale<p>It's no secret that our planet is going through some rough times at the macro level. The global temperature is <a href="https://climate.nasa.gov/vital-signs/global-temperature/" target="_blank">climbing</a>; nine out of the <a href="https://www.noaa.gov/news/2019-was-2nd-hottest-year-on-record-for-earth-say-noaa-nasa" target="_blank">10 hottest years on record</a> have occurred since 2005. And by one recent estimate, roughly 1 million species around the world are <a href="https://ipbes.net/sites/default/files/2020-02/ipbes_global_assessment_report_summary_for_policymakers_en.pdf" target="_blank">facing extinction</a> due to human activities.</p><p>"One of the big questions that ecologists and environmental scientists are trying to answer right now is how will individual species and whole ecosystems respond to rapid climate change and habitat loss," says Jucker. "...To me, [microclimates are] a key component of this research — if we don't measure and understand climate at the appropriate scale, then predicting how things will change in the future becomes a lot harder."</p><p>Developers have long understood the impact small-scale climates have on our daily lives. <a href="https://science.howstuffworks.com/environmental/green-science/urban-heat-island.htm#pt0" target="_blank">Urban heat islands</a> are cities that have higher temperatures than neighboring rural areas.</p><p>Plants release vapors that can moderate local climates. But in cities, natural greenery is often scarce. To make matters worse, plenty of our roads and buildings have a bad habit of absorbing or re-emitting heat from the sun. <a href="https://www.google.com/books/edition/Microclimate_and_Local_Climate/LHUZDAAAQBAJ?hl=en&gbpv=1&bsq=urban%20heat%20island" target="_blank">Vehicle emissions</a> don't exactly help the situation.</p><p>Still, it's not like Boston or Beijing are thermal monoliths. Sometimes, the documented temperatures <a href="https://e360.yale.edu/features/can-we-turn-down-the-temperature-on-urban-heat-islands" target="_blank">within a single city</a> vary by 15 to 20 degrees Fahrenheit (8.3 to 11.1 degrees Celsius).</p><p>That's where metro parks and city trees come in. They have nice cooling effects on nearby neighborhoods. "Several cities around the world have developed programs to increase urban green spaces," says Blanken. "Tree planting programs and green roof programs, have been shown to lower surface temperatures, decrease air pollution and decrease surface water runoff (urban flash-flooding) in urban areas."</p>
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Bricks are a preferred building tool for their durability and resilience against heat and frost since they do not shrink, expand or warp in a way that compromises infrastructure. They are also reusable. What was unknown, until now, is that they can be altered to store electrical energy, according to a new study published in Nature Communications.
The scientists behind the study figured out a way to modify bricks in order to use their iconic red hue, which comes from hematite, an iron oxide, to store enough electricity to power devices, Gizmodo reported. To do that, the researchers filled bricks' pores with a nanofiber made from a conducting plastic that can store an electrical charge.
The first bricks they modified stored enough of a charge to power a small light. They can be charged in just 13 minutes and hold 10,000 charges, but the challenge is getting them to hold a much larger charge, making the technology a distant proposition.
If the capacity can be increased, researchers believe bricks can be used as a cheap alternative to lithium ion batteries — the same batteries used in laptops, phones and tablets.
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