Rising Concern: Updated Studies Indicate Increasing Salinity in U.S. Groundwater

Research by the United States Geological Survey (USGS) discloses a worrisome uptick in the salinity of groundwater across the United States, attributed to road salt application and irrigation practices. This heightened salinity has potential repercussions for aquatic ecosystems, human health, and infrastructure, including issues related to radioactive elements like radium.

Table of Contents

Background and Objectives of the Study

For more than three decades, scientists at the U.S. Geological Survey have been monitoring the chemical composition of the nation’s groundwater wells. The aim has been to identify any substances or chemicals that could be detrimental to either ecological systems or human health. In total, the researchers have analyzed approximately 500 different chemical components, comprising major ions, metals, pesticides, volatile organic compounds, fertilizers, and radionuclides.

Detailed Findings on Salinity

Among these myriad components, noteworthy escalations have been observed in sodium (Na) and chloride (Cl) ions as well as dissolved solids—all related to the phenomenon of salinity. The latest data and trends from this multi-decade research were formally presented at the Geological Society of America’s GSA Connects 2023 conference.

The ongoing study is integrated into the National Water Quality Network, a continuation of the National Water Quality Assessment Project initiated in 1992. Bruce Lindsey, a hydrologist with the USGS, stated, “The original objective was to scrutinize the quality of water nationwide, which includes groundwater, surface water, and the health of ecosystems.” Over the years, the research concentrated on specific components that might have long-term detrimental impacts.

Sampling Strategy and Methodological Approach

The investigative team utilized wells from three distinct network types: domestic zones, urban sectors, and agricultural regions. The domestic wells, which are not subject to regulations by the Environmental Protection Agency or local governments, represent medium-depth aquifers and sources of drinking water. Wells in urban and agricultural areas are generally shallower, with depths ranging between 30 to 50 feet. Lindsey elucidated, “The rationale behind sampling these wells was to comprehend the current conditions and trends in the shallowest layers of water.” These shallower wells serve as indicators for potential changes that may percolate deeper into the aquifers.

The research encompassed 82 distinct networks, each consisting of 20 to 30 wells, and isolated 28 chemical constituents for tracking that raised levels of concern. Sampling occurred every decade to monitor shifts in chemical concentrations. These constituents and their sampling outcomes are available on the USGS’s interactive map, illustrating decadal fluctuations.

Salinity Escalation and Its Implications

According to Lindsey, when evaluating all 28 components across the 82 networks, “Dissolved solids, chloride, and sodium demonstrated statistically significant increases more frequently than any other components under observation.” Geographic patterns also emerged, particularly in the Northeastern and Upper Midwest regions around urban zones that experience colder climates and higher road salt applications. Correlations were established between these rises in salinity and the rates of road salt usage.

However, arid regions, particularly in the southwestern United States, also exhibited elevated levels of salinity. Lindsey explained, “During the irrigation process in these dry areas, evaporation is high, and thus, if the initial salinity of irrigation water is low but subject to high evaporation, salinity levels can become significant.”

Environmental and Health Ramifications

Increased levels of sodium, chloride, and dissolved solids pose multiple challenges. Elevated salinity impacts streams that are fed by groundwater, disrupting the natural equilibrium to which aquatic life has adapted. Infrastructure is also vulnerable, as higher salinity enhances corrosive properties, potentially leaching lead and other metals from plumbing systems.

Additionally, Lindsey and his team discovered specific human health risks associated with increased salinity. In a sandy aquifer located in southern New Jersey, they found that the combination of low pH and high salinity mobilized radium, a radioactive element detrimental to human health.

Lindsey indicated growing awareness surrounding the ecological impact of road salt. Measures like reduced salt applications or utilization of lower-concentration brine solutions are being adopted. He hopes that their findings will shed light on the multifaceted issues arising from elevated groundwater salinity, including environmental degradation, infrastructure erosion, and emerging human health risks.

Reference: “Increasing Salinization of Groundwater in the United States” by Bruce Lindsey, 18 October 2023, GSA Connects 2023.
DOI: 10.1130/abs/2023AM-391692

Frequently Asked Questions (FAQs) about Rising groundwater salinity

What is the primary focus of the USGS research discussed in the article?

The primary focus of the research conducted by the United States Geological Survey (USGS) is the rising levels of salinity in groundwater across the United States. The study aims to identify the chemical constituents that are increasing in concentration and assess their implications for aquatic ecosystems, human health, and infrastructure.

Who conducted the research and where were the findings presented?

The research was carried out by scientists at the U.S. Geological Survey (USGS). The latest data and trends from this multi-decade study were formally presented at the Geological Society of America’s GSA Connects 2023 conference.

What was the methodology of the study?

The study sampled wells in three different types of networks: domestic areas, urban sectors, and agricultural regions. Researchers identified 82 networks, each with 20 to 30 wells, and isolated 28 chemical constituents to track. Sampling occurred every decade, and the results are available on the USGS’s interactive groundwater map.

Which areas in the United States are most affected by rising groundwater salinity?

The Northeastern and Upper Midwest regions of the United States are particularly affected, especially around urban areas that experience cold weather and have high road salt application rates. Additionally, arid regions in the southwestern United States also showed elevated levels of salinity, exacerbated by irrigation practices.

What are the environmental implications of the rising salinity?

Increased salinity affects aquatic ecosystems by disrupting the natural balance of streams fed by groundwater. The elevated levels of chloride can have long-term impacts, taking decades to develop and similarly long periods to recover.

What are the ramifications for human health?

One specific human health concern identified by the study is the mobilization of radium in groundwater, a radioactive element harmful to humans. This issue was discovered in a sandy aquifer in southern New Jersey and is related to the combination of low pH and high salinity levels.

What is being done to mitigate the effects of rising salinity?

There is a growing awareness about the ecological effects of road salt, leading to some municipalities adopting measures like reduced salt application or using lower-concentration brine solutions. However, more widespread and comprehensive strategies need to be developed to mitigate the rising salinity and its multifaceted implications.