Depletion of Selenium in Soil Solution due to its Enhanced Sorption in the Rhizosphere of Soybean |
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Authors: | Y Nakamaru K Tagami S Uchida |
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Institution: | (1) Office of Biospheric Assessment for Waste Disposal, National Institute of Radiological Sciences, Anagawa 4-9-1, Inage, 263-8555 Chiba City, Japan |
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Abstract: | The effect of plant roots on selenium (Se) mobility in soil was studied by a large-scale pot experiment in order to understand
the environmental behavior of Se in agricultural soils under plant growth conditions. Soybean plants (Glycine max (L.) Merrill) were grown in a greenhouse for 84 d. The concentrations of Se and major elements (K, Ca, Mg, Na, and Al) in
the soil solutions and in the plants were measured at different growth periods. Concentrations of Se and major cations in
soil solution decreased as the soybean plants grew, while the concentrations of Al increased. It was assumed that the soybean
roots released H+ with the uptake of cations; consequently, due to the acidification of the rhizosphere, Al3+ was released starting from the soil solid phase. The decreased Se concentration in the soil solution should be due to the
enhancement of Se sorption onto the soil solid phase. The increase of Se sorption level in the rhizosphere was examined in
a small-scale pot experiment. The soil–soil solution distribution coefficient of Se (K
d-Se) was observed as an index of Se sorption level. K
d-Se clearly increased in the rhizosphere soil after cultivation. The effects of pH and Al3+ in the rhizosphere on Se sorption were assessed by K
d-Se measurements at different levels of HCl and AlCl3. In this third experiment, a decrease in pH increased K
d-Se values, but no specific effect was observed on Se sorption due to increased Al3+. These results show that the Se mobility in agricultural soil could be decreased by plant roots under plant growth conditions
due to enhanced Se sorption in the rhizosphere. |
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Keywords: | acidification exchangeable aluminum rhizosphere selenium soil solution |
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