Measurement of bromide ion used as a solute-transport monitor via epithermal neutron activation analysis |
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Authors: | H V Kazemi J S Morris S H Anderson C J Gantzer G A Buyanovsky |
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Institution: | (1) Department of Soil and Atmospheric Sciences, University of Missouri-Columbia, Columbia, MO, USA;(2) Research Reactor Center, University of Missouri, Columbia, MO, USA |
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Abstract: | In soil science (ca. 1970), bromide ion (Br−) in various forms (e.g., KBr, NaBr, SrBr2) was introduced as a non-reactive stable tracer in solute transport studies normally moving freely with the flux of water
without substantial chemical or physical interactions with the soil. Typically, Br− is extracted from soil and quantified using either a bromide selective electrode (sensitivity is ≈10μg/ml) or by high-performance
liquid chromatography (sensitivity is ≈0.010 μg/ml). Where the sensitivity is adequate, the selective conductivity method,
which is simple, affordable and fast, is preferred. More recently (ca. 1990), workers have reported that 20% of Br− tracers, at low groundwater pH, may be adsorbed by iron oxides and kaolinite when present in the alluvial aquifer. We investigated
the use of Epithermal Neutron Activation Analysis (ENAA) as a means of measuring Br− directly in soil samples without an extraction. ENAA was chosen because of its high theoretical advantage factor over aluminum
(i.e. ≈20), the principal interfering soil constituent, calculated for the79Br(n,γ)80Br reaction compared to27Al(n, γ)28Al. Br− was measured (sensitivity is ≈0.050 μg/g) in one gram soil samples from a 5 s irradiation (φepi=2.5·1012 n·cm-2·s-1) using a BN capsule. |
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