Freshwater Salinization Syndrome: An Emerging Environmental Problem

The physical and chemical properties of inland waters necessary to support aquatic life, grow food, provide energy, and supply drinking water have significantly changed over the past century. We synthesize causes and consequences of increasing water temperatures, salinity, alkalinity, and pH in inland waters of the United States and elsewhere. These synergistic changes in water quality have far-reaching impacts on ecosystems, infrastructure, and environmental processes related to ion exchange, chemical weathering rates, contaminant toxicity, corrosion potential, solubility of dissolved gases (including dissolved oxygen), and biodiversity of aquatic life. As a case study, we show how freshwater salinization with different ions causes changes in acid-base properties, contaminant mobilization, and can exacerbate water quality issues such as eutrophication and impact stream and river restoration efforts. These emerging environmental symptoms are known as the Freshwater Salinization Syndrome. Freshwater Salinization Syndrome has increasingly been recognized as an environmental problem impacting the ecosystem services of major freshwater supplies in regions of the United States, Europe, and elsewhere. We analyze long-term trends in water quality. We also analyze high-frequency sensor data along with experimental data to illustrate some impacts of the Freshwater Salinization Syndrome. Our synthesis shows seasonal interactions between salt mixtures and nutrients and metals (particularly during winter months), which can significantly enhance chemical transport in watersheds. We illustrate a conceptual model explaining how the Freshwater Salinization Syndrome can influence hydrologic transport of different 'chemical cocktails' or distinct chemical mixtures from watersheds. Freshwater Salinization Syndrome can impact transport and transformation of many chemicals synergistically and will continue to contribute to increasingly interconnected water quality problems in the future, unless managed at local and regional scales.