Freshwater salinization syndrome on a continental scale

Area of Science:

• Environmental Chemistry
• Hydrology
• Ecology

Background:

• Freshwater ecosystems are experiencing significant shifts in major ion composition due to human activities.
• Increasing salinization and alkalinization are widespread phenomena across North America.

Purpose of the Study:

• To introduce and define the "freshwater salinization syndrome" linking salinization and alkalinization.
• To describe the trends, causes, and consequences of this syndrome in North American fresh waters.

Main Methods:

• Analysis of long-term monitoring data from United States Geological Survey (USGS) sites.
• Identification of concurrent trends in specific conductance, pH, alkalinity, and base cations.

Main Results:

• Freshwater salinization syndrome affects large areas of the contiguous United States (37% salinization, 90% alkalinization).
• 66% of monitored stream and river sites show statistically significant increases in pH.
• The syndrome is most pronounced in densely populated eastern and midwestern regions.

Conclusions:

• The freshwater salinization syndrome is driven by diverse anthropogenic sources including road salt, agricultural runoff, and urbanization.
• This syndrome poses risks to infrastructure, contaminant mobilization, and coastal ecosystems.
• Effective regulation and management are crucial to mitigate impacts on ecosystem services like drinking water and biodiversity.