David R. Gonzalez, Minnesota Department of Transportation / FlickrTruck spreads salt to melt snow on the road in Minnesota, USADavid R. Gonzalez, Minnesota Department of Transportation / Flickr
Every year, the US spreads 44 million tons of salt—44% of the country’s annual consumption—on roads to melt ice, which increases the salinity of rivers near cities. This and other human activities, such as mining and agriculture, are accelerating the natural salt cycle and spreading salt into the air, soil, and rivers. As well as posing a risk to biodiversity and making it more difficult to obtain fresh drinking water, salt ions can generate harmful compounds when they bind to soil contaminants. A study led by Sujay Kaushal, a geologist from the University of Maryland, USA, concluded that an area roughly the size of the USA has been salinized over the last 50 years. “If you think of the planet as a living organism, accumulating so much salt could affect the functioning of vital organs or ecosystems,” said Kaushal in a National Science Foundation (NSF) press release. “Removing salt from water is energy-intensive and expensive, and the brine byproduct you end up with is saltier than ocean water and can’t be easily disposed of.” (Nature Reviews Earth & Environment, October 31, 2023; NSF Newsletter, January 4).
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