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Updated: Aug 24, 2026

Combined Size and Density Fractionation of Soils for Investigations of Organo-Mineral Interactions
Published on: February 15, 2019
Effect of fluoride on pH, organic matter and solubility of elements in soils
1Department of Agronomy, Colorado State University, Fort Collins, Colorado 80523, USA.
Abstract:
The effect of NaF addition on pH, organic matter and the solubilities of fifteen elements was investigated on twenty-eight surface soil samples. Four concentrations of NaF were added: 0, 10(-2.7), 10(-1.7) and 10(-1.0)m F in solution. Addition of NaF increased the pH and the solubility of organic matter for all soils. The magnitude of these increases was higher for acid than for alkaline soils. Aluminum, Fe and Ca showed the greatest increases in solubility while Mg, K, Mn and P showed intermediate increases. The elements Cd, Cr, Ni, Cu, Zn, B, Mo and Ba showed only slight increases in solubility. Another experiment was conducted to test whether the effects of NaF on pH, organic matter and the solubilities of various elements were due to F or Na. Four levels of NaCl similar to those for NaF were added to three acid and two alkaline soils. The results confirmed the effects of F on soil pH, organic matter and the solubilities of all elements investigated except those of K, Ca and Mg. Addition of Na as NaF resulted in release of K, Ca and Mg from the exchange sites on solid surfaces into solution.
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A solution is a homogeneous mixture composed of a solvent, the major component, and a solute, the minor component. The physical state of a solution—solid, liquid, or gas—is typically the same as that of the solvent. Solute concentrations are often described with qualitative terms such as dilute (of relatively low concentration) and concentrated (of relatively high concentration).
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