Fixation and Volatilization by Soils of Selenium from Trimethylselenonium1
- O. E. Olson2,
- E. E. Cary and
- W. H. Allaway3
Selenium, an essential element for animals, is now being added to some livestock diets. The trimethylselenonium ion (TMSe+) is an important urinary metabolite of dietary Se. Selenium spillage onto soils is related to its natural cycling and seems important in creating Se excesses or correcting Se deficiencies in soils. Volatilization and fixation of Se from TMSe+ was studied using four soils: a Typic Quartzipsamment, an Aeric Fragiaquept, a Typic Hapludult, and a Glossoboric Hapludalf. For volatilization studies, soils treated with TMSe+ or TM75Se+ were placed in a closed system maintained at room temperature and equipped for aeration and collection of volatile Se or 75Se, which was determined at intervals over a period of several weeks. Volatilization occurred with all soils, but the rates varied widely. Treating the acid Aeric Fragiaquept with CaCO3 increased Se volatilization. Treatment with toluene or autoclaving of the Aeric Fragiaquept or the Glossoboric Hapludalf almost completely prevented the volatilization. A nitrogen atmosphere retarded the volatilization in all but the Aeric Fragiaquept soil. In one experiment, the volatilization and fixation of Se added to soils as Na275SeO4, Na275SeO3, or TM75Se+ were studied. Volatilization was measured by 75Se loss and was observed only when the TM75Se+ was added, being appreciable only with the Typic Hapludult and Glossoboric Hapludalf soils. Fixation was determined by measuring the 75Se not extracted with 0.1 M CaCl2 or with water, and was greatest for the 75Se from the Na2SeO3. Fixation of from TM75Se+ occurred in all soils during a 21-day period to an extent of about 30 to 50% of that added. The data suggest that Se from urinary TMSe+ spilled onto soils would generally be soon lost to the atmosphere or fixed and thus become unavailable to plants.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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