Anion Adsorption Capacity Research Articles

Contrasting nitrate adsorption in Andisols of two coffee plantations in Costa Rica.

Fertilizer use in coffee plantations is a suspected cause of rising ground water nitrate concentrations in the ground water-dependent Central Valley of Costa Rica. Nitrate adsorption was evaluated beneath two coffee (Coffea arabica L.) plantations in the Central Valley. Previous work at one site had identified unsaturated zone nitrate retardation relative to a tritium tracer. Differences in nitrate adsorption were assessed in cores to 4 m depth in Andisols at this and one other plantation using differences in KCl- and water-extractable nitrate as an index. Significant adsorption was confirmed at the site of the previous tracer test, but not at the second site. Anion exchange capacity, X-ray diffraction data, extractable Al and Si, and soil pH in NaF corroborated that differences in adsorption characteristics were related to subtle differences in clay mineralogy. Soils at the site with significant nitrate adsorption showed an Al-rich allophane clay content compared with a more weathered, Si-rich allophane and halloysite clay mineral content at the site with negligible adsorption. At the site with significant nitrate adsorption, nitrate occupied less than 10% of the total anion adsorption capacity, suggesting that adsorption may provide long-term potential for mitigation or delay of nitrate leaching. Evaluation of nitrate sorption potential of soil at local and landscape scales would be useful in development of nitrogen management practices to reduce nitrate leaching to ground water.

A new method for the determination of the anionic adsorption capacity of bottom deposits with particular reference to the adsorption of anionic detergents

After a short discussion of the scarce and incomplete literature on anionic adsorption properties of soils and sediments, a new technique based on the adsorption of manoxol to soils, sediments and pure humic acid is described.

Methyl bromide for increasing I 131 uptake by Pine trees

Soil sterilization by methyl bromide greatly increases the uptake by pine trees of I 131 which has been introduced into the soil. This effect seems to be due to (1) destruction of differentially permeable cytoplasmic membranes of pine roots in treated soil, (2) destruction of soil microorganisms which biologically absorb minerals in the rhizosphere, and (3) prior occupation of the small but significant anion adsorption capacity of soil by bromine compounds. Under these conditions, iodine remains mobile in the soil solution and is “swept” into the transpiration stream. For other isotopes, soil sterilants with different characteristics might be more effective.