Human disruption of the global salt cycle is a looming environmental threat, according to a new study led by Professor Sujay Kaushal of the University of Maryland.
The research has revealed that human activities have a substantial impact on the natural salt cycle, signaling a potential health crisis if the trend persists.
The study authors warn that human endeavors have led to an increased salinity in the Earth’s air, soil, and freshwater systems – a change that could reach existential proportions.
The natural dispersion of salts through geological and hydrological processes has been a slow-moving cycle over millennia. However, human-induced acceleration is now evident through mining, land development, and other industrial activities.
These processes, alongside agricultural practices and water treatment, are leading to an alarming increase in salinization, negatively affecting biodiversity and potentially making drinking water unsafe.
Professor Kaushal, who is also associated with UMD’s Earth System Science Interdisciplinary Center, compared Earth to a living organism.
“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. “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 colleagues use the term “anthropogenic salt cycle” to describe the human influence on the global salt dynamics. Unlike twenty years ago, where evidence was anecdotal and localized, there is now a clear pattern of perturbation globally.
“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.”
This research went beyond just sodium chloride, examining various salt ions like calcium, magnesium, potassium, and sulfate. Such ions, when released in excessive amounts, lead to environmental degradation.
The researchers noted a concerning trend: human-induced salinization has affected approximately 2.5 billion acres of soil and has increased salt ion presence in rivers and streams over the past half-century, corresponding with a surge in global salt use and production.
Salts are not only seeping into the soil and water but also into the air. The study points to regions where drying lakes emit saline dust into the atmosphere and road salts, used for deicing, become airborne particulates, posing risks to human health and environmental stability.
The cascading effects of salinization include accelerated snowmelt and the formation of dangerous “chemical cocktails” as salt ions bind to other contaminants.
The study also sheds light on the significant use of road salts, which are pumped out at a rate of 44 billion pounds per year in the United States. This not only poses an immediate public safety benefit but also raises long-term concerns for water quality.
To mitigate the salinity crisis, Kaushal suggests policies to curb road salt usage and promote alternatives like beet juice treatments for icy roads, currently being implemented in Washington, D.C., and other cities.
The authors propose the establishment of a “planetary boundary for safe and sustainable salt use,” drawing a parallel to carbon dioxide regulation in the context of climate change.
Kaushal said that while it’s theoretically possible to regulate and control salt levels, it comes with unique challenges.
“This is a very complex issue because salt is not considered a primary drinking water contaminant in the U.S., so to regulate it would be a big undertaking. But do I think it’s a substance that is increasing in the environment to harmful levels? Yes.”
The study is published in the journal Nature Reviews Earth & Environment.
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