The role of neutral salts in the ion exchange between acid precipitation and soil

• Published in: Geoderma Vol. 14; no. 2; pp. 93 - 105
• Main Author: Wiklander, Lambert
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.1975
• ISSN: 0016-7061; 1872-6259
• DOI: 10.1016/0016-7061(75)90068-3

Theory and experimental results have shown that neutral salts in the precipitation or supplied to the ground by other means reduce the acidification of soils by acid precipitation. This salt effect is caused by the cation exchange occurring after the entry of the rain water into the soil. The acid components of precipitation consist of H 2SO 4, HNO 3 and HCl and of NH 4 + after nitrification in the soil. The magnitude of the salt effect depends on the relative bonding energy of H 3O + and of Ca 2+, Mg 2+, Na +, K +, NH 4 + in the soil as well as on the concentrations of H 3O + and the above cations in the precipitation. The salt effect may be considerable in very acid soils. It decreases with rising pH to become very small or negligible in neutral soils, chiefly due to the increasing bonding energy of H 3O + in this direction. The adverse effect of acid precipitation, therefore, is likely to be less in very acid soils, such as podsols, than in slightly acid and neutral soils with low buffering capacity against pH change. Soil texture and calcite content are very important factors in this respect as fine material and calcite increase the buffering.