ABSTRACT
The objective of this study is to explore the hypothesis that the presence of Se associated with the colloidal fraction could explain the presence of unknown selenium species highlighted in soil extracts (ultrapure water and sodium hydroxide extracts) used for selenium speciation determination in the studied soils. First, selenium speciation was carried out in the soil using the two specic extractants. The results were analyzed in terms of species distribution and mass balance calculations as well as in terms of selenium mobility assessment. Two different and complementary analytical techniques were used to characterize this colloidal fraction, the analytical
CONTENTS
7.1 Introduction ................................................................................................ 216 7.1.1 Case Study ...................................................................................... 218
7.2 Approach ..................................................................................................... 218 7.2.1 Selenium Parallel Single-Extraction Methodology ................... 219 7.2.2 Analytical Procedure for Selenium Determination .................. 219
7.2.2.1 Total Se .............................................................................. 219 7.2.2.2 Selenium Speciation ....................................................... 220
7.2.3 Instrumentation for Selenium Size Fractionation ..................... 220 7.2.4 Analytical Conditions for Selenium Size Fractionation ........... 221 7.2.5 Quantication of Selenium Associated with the Colloidal
Populations .....................................................................................222 7.3 Findings .......................................................................................................222
