The effects of increasing salinity on exchange processes in coastal lowland acid sulfate soils

10 coastal lowland acid sulfate soils (CLASS) from floodplains in eastern Australia were subjected to increasing seawater concentrations to determine the effects of exchange processes on metal desorption due to increasing ionic strength. Soils were subjected to one of six treatments; 0%, 10%, 20%, 50%, 80% or 100% seawater diluted in deionised water. pH decreased with increasing seawater concentration. In general, concentrations of Al, Cd, Fe2+ and Mn increased in soils sampled from levees, organic and mineral sulfuric horizons with increasing salinity. Increasing trace metal concentrations with increasing seawater concentration is attributed to both exchange processes and pH effects. The increasing ionic strength of the seawater treatments displaced trace metals and protons adsorbed on sediments. These processes have implications for rapid water quality changes in CLASS environments when subjected to seawater inundation.