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Less ice, more salt: The environmental cost of deicing

The widespread practice of deicing roads, a crucial safety measure in icy conditions, is causing an unintended environmental crisis: the increasing salinization of soil, air, and water. 

Researchers from Virginia Tech and the University of Maryland set out to better understand and possibly help mitigate this growing issue.

Environmental toll 

Rock salt, commonly used for deicing, plays a vital role in ensuring the safety of pedestrians and motorists during winter. However, the study highlights the environmental toll of this practice.

The team found that the act of deicing roads is making the Earth’s air, soil, and freshwater increasingly salty, a trend that poses a significant existential threat.

A slowly building crisis

Megan Rippy, an assistant professor in Civil and Environmental Engineering, describes the situation as a “slow-moving train wreck.” 

“It’s playing out so slowly that it’s easy to overlook that our streams, lakes, and drinking water resources are becoming progressively saltier.”  

Disrupting the salt cycle

Salts are naturally occurring. They are made up of positively charged cations and negatively charged anions like calcium, magnesium, potassium, and sulfate ions.

Human activities such as mining, land development, agriculture, construction, and industrial processes are rapidly accelerating the natural salt cycle, leading to environmental degradation. This human-induced salinization harms biodiversity and, in severe cases, makes drinking water unsafe.

Potential impacts

“Ecosystems are finely tuned to a certain level of salinity, and as that increases over time it can lead to big impacts, for example loss of important species, including fish. That applies to humans too,” said Rippy.

“Too much salt in irrigation water can cause crops to fail, and salt in drinking water supplies has been linked to human health effects like preeclampsia. This is happening in the U.S. and around the world.”

Cascading effects

The study reveals a startling fact: human-caused salinization has affected about 2.5 billion acres of soil globally – an area equivalent to the size of the United States. Furthermore, salt ions in streams and rivers have increased over the past 50 years, in line with the rise in global salt use and production. 

The intrusion of salt into the air, particularly through the aerosolization of road salts, is causing a decline in air quality, detrimental to wildlife and crops.

This research has established for the first time that humans affect the concentration and cycling of salt on a global, interconnected scale. 

Sustainable solutions

Stanley Grant, the director of the Occoquan Watershed Monitoring Laboratory, emphasizes the substantial impact of road salts in the U.S., which produces 44 billion pounds annually. These salts account for a significant portion of the total dissolved solids in U.S. waterways. 

Alternative deicing methods, like the use of beet juice in Washington, D.C., and other cities, offer a promising yet challenging solution, given the balance between environmental safety and effective road maintenance.

Study implications 

“There’s a lot of interest in how we can change the way roads are maintained in the winter to reduce road salt use and its impacts on ecosystems and drinking water supplies,” said Bhide. “It’s a tricky issue, because deicing roads also reduces traffic accidents and saves lives.” 

Salinization is also associated with cascading effects, noted the researchers. For example, saline dust accelerates the melting of snow, which can harm communities that rely on snow for water supplies. 

“History is littered with ancient civilizations that collapsed because they couldn’t balance their salt budget. I’m hoping this article will raise awareness and lead to action on this issue, so that history doesn’t repeat itself,” said Grant.

The study is published in the journal Nature Reviews Earth & Environment.

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