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Role of Redox Potential in Chemical Transformations of Selenium in Soils
Author(s) -
Jayaweera Gamani R.,
Biggar James W.
Publication year - 1996
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1996.03615995006000040014x
Subject(s) - anoxic waters , redox , selenide , soil water , chemistry , selenium , environmental chemistry , dissolution , groundwater , inorganic chemistry , soil science , geology , organic chemistry , geotechnical engineering
Irrigated agricultural areas with high levels of soil Se face the dilemma of elevated Se levels in drainage and groundwater systems, which will adversely affect the environment and the wildlife. The release of Se from soils to water systems is dependent on the speciation of Se, which is primarily governed by the redox potential. This study describes the dynamics of redox transformations of naturally occurring Se in a soil matrix as a continuous function of time during a sequence of oxic‐anoxic‐oxic transition. An experimental setup where a solution stream is continuously passed through a soil column in a closed loop to reach an equilibrium between the soil and the solution was used. The pH and redox potential (Eh) were recorded and the solution was analyzed over time for various Se forms and Mn 2+ . During soil reduction, the total soluble Se and SeO 2− 4 decreased, while the SeO 2− 3 and other Se forms (organic Se, elemental Se, and selenide) increased initially, then decreased. Both soluble Se and SeO 2− 4 decreased during the anoxic phase, slowly at first, then more rapidly, and were characterized by first‐order rate constants. During reoxidation, the total soluble Se and SeO 2− 4 increased, SeO 2− 3 initially increased followed by a decrease, and other Se forms decreased. Decrease in SeO 2− 3 during reduction may be partly due to the precipitation of MnSeO 3 . This study showed that the soil Eh plays an important role in mobilizing Se into water systems.