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Selenite fixation by soil particle‐size separates
Author(s) -
CHRISTENSEN B. T.,
BERTELSEN F.,
GISSELNIELSEN G.
Publication year - 1989
Publication title -
journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 0022-4588
DOI - 10.1111/j.1365-2389.1989.tb01305.x
Subject(s) - silt , soil water , selenium , organic matter , chemistry , clay minerals , hydrogen peroxide , particle size , environmental chemistry , mineralogy , geology , zoology , soil science , biology , paleontology , organic chemistry
SUMMARY The fixation of selenite by clay‐ (< 2 μm), silt‐ (2–20 μm) and sand‐size (20–2000 μm) separates from two arable soils was examined in solutions of 75 Se‐labelled sodium selenite using a Se/sample ratio of 1/10 6 . Size separates were isolated by ultrasonic dispersion and gravity sedimentation. Selenite fixation was determined after equilibration periods ranging from 5 min to 26 h. Hydrogen peroxide‐treated samples were included to examine the effect of organic matter on selenite fixation capacity. The relative distribution of native Se, C, dithionite/citrate‐extractable Fe and Al between size separates was similar. Concentrations in clay were four to nine times higher than in whole soils, silt showing two to five times higher concentrations and sand being very low in Se, C, Fe and Al. After 1 h, clay, silt and sand fixed 64–65%, 45–61% and <5% of the selenite added, respectively. The fixation on whole soils was 14–18%. After 1 day, fixation on clay, silt, sand and whole soil increased to 78–87%, 67–79%, 3–14% and 31–39%, respectively. Hydrogen peroxide‐treatment reduced the selenite fixation capacity of whole soil, silt and sand to very low levels. Fixation on peroxide‐treated clay was in accord with values for pure clay minerals reported in the literature. Generally, the fixation capacity of peroxide‐treated natural clay and pure clay minerals was only half that observed for intact clay‐size separates, demonstrating the importance of organic matter in soil selenite fixation capacity.