Chemical and biological relationships relevant to the effect of acid rainfall on the soil-plant system

Abstract

This paper deals with problems of measuring acidity in rainfall and the interpretation of these measurements in terms of effects on the soil-plant system. Theoretical relationships of the carbon-dioxide-bicarbonate equalibria and its effect on rainfall acidity measurements are given. The relationship of a cation-anion balance model of acidity in rainfall to plant nutrient uptake processes is considered. It was concluded that average H⁺ concentration calculated from pH measurements is not a satisfactory method of determining H⁺ loading from rainfall unless the rain is consistently acid. Cation-anion balance or titration methods should be more reliable. The flux of H⁺ ions in soil systems due to plant uptake processes and sulfur and nitrogen cycling is considered. H⁺ is produced by oxidation of reduced sulfur and nitrogen compounds mineralized during decomposition of organic matter. Plant uptake processes may result in production of either H⁺ or O H^- ions. Fluxes of H⁺ from these processes are much greater than rainfall H⁺ inputs, complicating measurement and interpretation of rainfall effects. The soil acidifying potential due to the oxidation of the NH₄⁺ in rainfall is examined, with the conclusion that acidity from this source is of a similar magnitude to direct H⁺ inputs common in rainfall.

Parent Publication

• Proceedings of the first international symposium on acid precipitation and the forest ecosystem

Citation

null 1976. Chemical and biological relationships relevant to the effect of acid rainfall on the soil-plant system. In: Dochinger, L. S.; Seliga, T. A., eds. Proceedings of the first international symposium on acid precipitation and the forest ecosystem; Gen. Tech. Rep. NE-23. Upper Darby, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. 791-813