Global Salt Cycle Disturbance: A Rising Concern from Human Activities

Recent research underscores the alarming increase in global salinity due to human interventions, posing grave implications for both biodiversity and human health. This study emphasizes the far-reaching impacts of human-induced changes on salt levels in the environment, spanning soil, water, and air. It underscores the urgent need for policies to curtail salt consumption and set international benchmarks for sustainable salt use.

The University of Maryland’s research group, led by Geology Professor Sujay Kaushal, indicates that the spike in salt content in water bodies poses a profound risk.

The extensive use and demand for salt by human activities take a toll on ecological systems and human health. Kaushal’s paper, published in Nature Reviews Earth & Environment, suggests that human actions are leading to a rise in salinity across Earth’s mediums, which might be a significant threat if unchecked.

Speeding up the Natural Salt Cycle

While geologic and hydrologic events naturally introduce salts to the Earth’s surface over extended periods, human actions, including mining and infrastructure development, are fast-tracking this natural salt cycle. Such acceleration, compounded by agricultural, constructional, and industrial pursuits, can lead to severe environmental salinization, threatening biodiversity and jeopardizing drinking water safety.

This salt movement, naturally encompassing the elevation of salts and their eventual transport to oceans, is amplified by human interventions like mining, which also leads to greater saline dust release into the atmosphere.

Kaushal likens the Earth to a living entity, suggesting that excess salt can jeopardize its integral ecosystems. He notes that desalinating water is not only energy-consuming but also costly. The resulting brine is even saltier than seawater, presenting significant disposal challenges.

The Human-Induced Salt Cycle

The disruptions caused by these activities are termed as the “anthropogenic salt cycle,” signifying for the first time that human actions have a pronounced influence on global salt concentration and its movement. Gene Likens, a co-author of the study and an ecologist at the University of Connecticut, emphasizes that their findings indicate a global-scale disturbance of the salt cycle by human actions, far more extensive than previously localized case studies suggested.

Salt: Beyond Sodium Chloride

The study considers various salt ions found both underground and in surface waters. Contrary to the common association of salt with sodium chloride, the research underscores disturbances to other salt types, including those linked to limestone and gypsum. When released in elevated quantities, these ions can lead to environmental challenges. The study reveals that human-induced salinization impacts an area equivalent to the size of the United States. Additionally, there has been a marked increase in salt ions in water bodies in the past half-century, parallel to the global surge in salt usage and production.

Salinity’s Broad Environmental Ramifications

Salinization has now permeated the atmosphere. In some regions, drying lakes emit saline dust plumes. Areas with snowy conditions witness aerosolization of road salts, leading to particulate matter. Furthermore, salinization leads to ripple effects: saline dust can hasten snow melt, affecting areas reliant on snow for water. Due to their structure, salt ions can combine with contaminants, resulting in harmful environmental “chemical cocktails.”

Road Salts: A Significant Contributor

In the U.S., the use of road salts, essential for deicing, is a major contributor to salinity. Between 2013 and 2017, road salts made up 44% of U.S. salt consumption, contributing to nearly 14% of total dissolved solids in the country’s water bodies. Kaushal suggests policies to limit such salts or adopt alternatives. Some U.S. cities, like Washington, D.C., have begun using beet juice as an alternative, which achieves the desired outcome with much less salt content.

However, Kaushal stresses the need to balance the immediate safety provided by road salts and the long-term health risks associated with increased salinity in water.

Regulatory Impediments and Ecological Warnings

The research team also proposes the establishment of global benchmarks for salt use, similar to those set for carbon dioxide to curb climate change. While regulating salt levels is theoretically feasible, Kaushal notes the challenges, especially since salt isn’t deemed a primary drinking water contaminant in the U.S. However, he firmly believes that the escalating levels of salt in the environment could be harmful.

Reference: “The anthropogenic salt cycle” by Sujay S. Kaushal et al., 31 October 2023, Nature Reviews Earth & Environment. DOI: 10.1038/s43017-023-00485-y

Support for this research came from the National Science Foundation, Maryland Sea Grant, and the Washington Metropolitan Council of Governments.

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More about salinization

• University of Maryland Geology Department
• Nature Reviews Earth & Environment Journal
• National Science Foundation
• Maryland Sea Grant
• Cary Institute of Ecosystem Studies
• Washington Metropolitan Council of Governments