Interactions between anthropogenic sulphate and marine salts in the Bs horizons of acidic soils in Scotland

In laboratory adsorption experiments, the comparison of podzol Bs horizons from coastal and inland moderately-impacted catchments with those from a severely-acidified inland region has demonstrated the effect of marine inputs on SO 4 2- -retention. Moderate sea-salt inputs and low acid deposition leads to the retention of most of the SO 4 2- and the release of soluble Mg 2+ ; increasing the marine salt loading causes the development of a selectivity towards retention of acidic SO 4 2- and the retention of Mg 2+ . In the highly-impacted soil, the marine input caused a decrease in SO 4 2- retention in open moorland soils. The opposite occurred under forest, due to the ion-exchange of marine Mg 2+ for soil Al 3+ , increasing soil acidity towards the pH 0 (Gillman and Uehara, 1980), which is depressed below that of its moorland equivalent