Impact of sea level rise on the thermodynamics and kinetics of binary ion exchange in non-saline East Coast soils
Date
2022
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Publisher
University of Delaware
Abstract
Rising sea levels are a growing problem throughout the United States, as 23 of the 25 most densely populated counties in the United States are in coastal areas in danger of flooding and salinization due to sea level rise. Along the East Coast of the U.S., sea levels are increasing and are predicted to rise to 1 m due to climate change and subsidence. Consequently, historically non-saline soils in these areas are increasingly being affected by salinity, resulting in orphan forests and crop damage. Such occurrence also threatens national security since many military installations lie along coastal areas. It is estimated that a 1 m rise in sea level would impact 128 Department of Defense facilities in the United States. It is unclear how potential changes in the physical and chemical properties of the soils, due to salinity, will impact military operations. An extensive literature exists on saline and sodic soils; however, little is known on how non-saline/sodic soils with different physicochemical and mineralogical properties from saline/sodic soils are impacted by excess salinity due to sea level rise, flooding, and groundwater salinization. In order to predict what may happen, binary thermodynamic exchange and kinetics of ion exchange studies were conducted on two Delaware soils of contrasting particle size and organic matter contents at multiple ionic strengths to mimic the typical soil solution as well as sea water. Exchangeable sodium ratio (ESR), sodium adsorption ratio (SAR), exchangeable sodium percentage (ESP), Vanselow selectivity coefficients (K_v), thermodynamic ion exchange constants (K_ex), and standard Gibbs free energy values (〖∆G〗^°) were determined for Na-Ca and K-Ca exchange on both soils at two ionic strengths. Electrical conductivity (EC), the kinetics of ion exchange, and changes in pH and DOC were also conducted at various ionic strengths. Ion selectivity measurements (K_v), exchange equilibrium constants (K_ex) and standard Gibbs free energy values (〖∆G〗^°) showed that Na and K were both preferred in both soils at both ionic strengths. These findings were ascribed to the chemical composition of the soils, particularly the clay mineralogy. SAR, ESP, EC, pH, and ion exchange kinetics all increased with increasing ionic strength for both soils, indicating that under increasing salinity, the soil chemical and physical characteristics could be altered such that plant growth and cycling of nutrients and contaminants could be adversely impacted.
Description
Keywords
Climate change, East Coast soils, Ion exchange, Kaolinite, Non-saline soils, Sea level rise