Bromine and bromide content in soils: analytical approach from total reflection X-ray fluorescence spectrometry

Abstract

Monitoring total bromine and bromide concentrations in soils is significant in many environmental studies. Thus fast analytical methodologies that entail simple sample preparation and low-cost analyses are desired. In the present work, the possibilities and drawbacks of low-power total reflection X-ray fluorescence spectrometry (TXRF) for the determination of total bromine and bromide contents in soils were evaluated. The direct analysis of a solid suspension using 20 mg of fine ground soil (<63 µm) gave a 3.7 mg kg-1 limit of detection for bromine which, in most cases, was suitable for monitoring total bromine content in soils (Br content range in soils = 5-40 mg kg-1). Information about bromide determination in soils is also possible by analyzing the Br content in water soil extracts. In this case, the TXRF analysis can be directly performed by depositing 10 µL of the internal standardized soil extract sample on a quartz glass reflector in a measuring time of 1500 s. The bromide limit of detection by this approach was 10 µg L-1. Good agreement was obtained between the TXRF results for the total bromine and bromide determinations in soils and those obtained by other popular analytical techniques, e.g. energy dispersive X-ray fluorescence spectrometry (total bromine) and ionic chromatography (bromide). As a study case, the TXRF method was applied to study bromine accumulation in two agricultural soils fumigated with a methyl bromide pesticide and irrigated with regenerated waste water.