Capillary zone electrophoresis to study the humic fraction in organic soils and its relationship with radiocaesium mobility

Abstract

Humic acids and associated radionuclides were extracted from several soil samples with a significant organic matter content, such as peaty soils and forest soil layers. Extractions were made using two alkaline solutions (Na₄P₂O₇ 0.1 mol·1⁻¹ and NaOH 0.1 mol·1⁻¹ under N₂). The humic acid content in the extract was determined by the capillary zone electrophoresis technique (CZE) and associated radiocaseium was determined by gamma spectrometry. After analizing a large number of samples and studying the relationship between humic acid and organic matter content it was possible to conclude that the CZE technique may be a good alternative to classical techniques in humic acid determinations, with NaOH extractions leading to higher results than Na₄P₂O₇. Furthermore, the quantification of the radiocaseium desorbed by applying different extractant reagents (NaOH, Na₄P₂O₇, NH₄AcO and CaCl₂) showed that there may be some organic matter-radionuclide interations, other than those originated by humic acids. which may govern radionuclide retention in soils with a high content of organic matter.