Humans are disrupting natural 'salt cycle' on a global scale, new study shows

 The planet's demand for salt comes at a cost to the environment and human health, according to a new scientific review led by University of Maryland Geology Professor Sujay Kaushal. Published in the journal Nature Reviews Earth & Environment, the paper revealed that human activities are making Earth's air, soil and freshwater saltier, which could pose an "existential threat" if current trends continue.

Geologic and hydrologic processes bring salts to Earth's surface over time, but human activities such as mining and land development are rapidly accelerating the natural "salt cycle." Agriculture, construction, water and road treatment, and other industrial activities can also intensify salinization, which harms biodiversity and makes drinking water unsafe in extreme cases.

"If you think of the planet as a living organism, when you accumulate so much salt it could affect the functioning of vital organs or ecosystems," said Kaushal, who holds a joint appointment in UMD's Earth System Science Interdisciplinary Center. "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."

Kaushal and his co-authors described these disturbances as an "anthropogenic salt cycle," establishing for the first time that humans affect the concentration and cycling of salt on a global, interconnected scale.

"Twenty years ago, all we had were case studies. We could say surface waters were salty here in New York or in Baltimore's drinking water supply," said study co-author Gene Likens, an ecologist at the University of Connecticut and the Cary Institute of Ecosystem Studies. "We now show that it's a cycle -- from the deep Earth to the atmosphere -- that's been significantly perturbed by human activities."

The new study considered a variety of salt ions that are found underground and in surface water. Salts are compounds with positively charged cations and negatively charged anions, with some of the most abundant ones being calcium, magnesium, potassium and sulfate ions.

"When people think of salt, they tend to think of sodium chloride, but our work over the years has shown that we've disturbed other types of salts, including ones related to limestone, gypsum and calcium sulfate," Kaushal said.

sources:science daily