Salting the Earth: Road Salt and Irrigation Threaten US Groundwater

  Alarming increases in groundwater salinity across the United States are linked to road salting and irrigation, and pose threats to aquatic life, infrastructure and human health through elements such as radium, according to research by the U.S. Geological Survey (USGS). For more than three decades, U.S. Geological Survey (USGS) scientists have been tracking groundwater quality in wells across the United States. Their work focuses on detecting potentially harmful chemicals that could negatively impact ecosystems or human health.

  In total, the crew measured up to 500 chemical compounds, including major ions, metals, pesticides, volatile organic compounds, fertilizers and radionuclides.

  Among these components are significantly increased levels of sodium, chloride ions, and dissolved solids, all of which are related to salinity. Details and trends found in this multi-year study were recently presented at the Geological Society of America’s “GSAConnects 2023” conference.

  This research, currently part of the U.S. National Water Quality Network, is a continuation of work begun in 1992 as part of the U.S. National Water Quality Assessment Project. “The initial goal was to assess water quality conditions across the country, including groundwater, surface water and ecological health,” said Bruce Lindsay, a hydrologist with the U.S. Geological Survey. “Over time, they focused on some areas that might ingredients that produce long-term harmful effects.”

  The U.S. Geological Survey Groundwater Quality Decadal Change Program map shows how concentrations of pesticides, nutrients, metals, and organic contaminants in groundwater across the United States have changed over a ten-year period.

  The researchers sampled wells in three different network types: residential, urban and agricultural areas. Domestic wells or private wells not regulated by the Environmental Protection Agency or local municipalities represent intermediate depth aquifers and drinking water. Wells in urban and agricultural areas are shallow, usually about 9 to 15 meters deep. The purpose of “sampling” these wells is to understand conditions and trends at the shallowest water levels, Lindsay explained. It can be said that these shallow wells are “sentinels for possible changes deep in the aquifer.”

  The team identified 82 water networks, each with 20 to 30 wells, and identified 28 worrisome ingredients that needed to be tracked. The water is sampled every 10 years to track changes in chemical concentrations. These compositions and sampling results can be seen on the U.S. Geological Survey’s interactive groundwater map, which shows changes over a decade.

Increased salinity and its effects

  ”If we look at 28 ingredients across all 82 networks, dissolved solids, chloride and sodium are statistically increasing more frequently than other ingredients on our list,” Lindsay said. “If you look at the map, The pattern was immediately discovered. Especially in areas around cities where the weather is cold and there is a lot of road salt. We obtained data on road salting and found that there was a relationship between the increase in chloride, sodium and dissolved solids and the rate of road salting. Correlation”.

  But another area that also has elevated levels of sodium, chloride ions and dissolved solids is the arid regions of the United States, especially the Southwest. Soil salinity in these areas is already high, but irrigation compounds the problem.

  ”When you irrigate agriculture in arid areas, there’s a lot of evaporation,” Lindsay explains. “So if the irrigation water has relatively low salinity, but a large portion of it is evaporated, the salinity levels can become very high. ”

environmental and health impacts

  Rising levels of sodium, chloride ions and dissolved solids can lead to a variety of problems, the first of which is environmental. Many streams are fed from groundwater, and higher concentrations of chlorine in the water can disrupt the natural balance of aquatic life habits. “It can take two to three decades for rising levels to develop, which means if there are changes in the management of salinity sources, it could also take that long to recover,” Lindsay said.

  Dissolved salt ions can also cause damage to infrastructure . Come to question. Corrosivity also becomes a problem as groundwater salinity increases. Corrosive groundwater, if left untreated, can dissolve lead and other metals in pipes and other components in your home’s plumbing.

  Finally, Lindsay and his colleagues also identified a unique problem related to rising salinity, in a sandy aquifer in southern New Jersey where they found low-pH water mixed with high-salinity groundwater will produce more salt.

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