Abstract
Despite the considerable environmental importance of mercury (Hg), given its high toxicity and ability to contaminate large areas via atmospheric deposition, little is known about its activity in soils, especially tropical soils, in comparison with other heavy metals. This lack of information about Hg arises because analytical methods for determination of Hg are more laborious and expensive compared to methods for other heavy metals. The situation is even more precarious regarding speciation of Hg in soils since sequential extraction methods are also inefficient for this metal. The aim of this paper is to present a technique of thermal desorption associated with atomic absorption spectrometry, TDAAS, as an efficient tool for quantitative determination of Hg in soils. The method consists of the release of Hg by heating, followed by its quantification by atomic absorption spectrometry. It was developed by constructing calibration curves in different soil samples based on increasing volumes of standard Hg2+ solutions. Performance, accuracy, precision, and quantification and detection limit parameters were evaluated. No matrix interference was detected. Certified reference samples and comparison with a Direct Mercury Analyzer, DMA (another highly recognized technique), were used in validation of the method, which proved to be accurate and precise.
Highlights
RESUMO: Quantificação de Mercúrio em Solos por Termodessorção Acoplada à Espectrometria de Absorção Atômica: Proposição de um Método Alternativo de Análise
Hg mass and the area of each standard are shown in table 3, and the thermograms of each calibration curve are shown in figure 2
The proposed method based on the thermal desorption atomic absorption spectrometry (TDAAS) technique proved to be accurate and precise from evaluation of certified reference materials
Summary
RESUMO: Quantificação de Mercúrio em Solos por Termodessorção Acoplada à Espectrometria de Absorção Atômica: Proposição de um Método Alternativo de Análise. Objetivou-se com este trabalho apresentar a técnica de termodessorção associada à espectrometria de absorção atômica, TDAAS, como ferramenta eficiente para a determinação quantitativa de Hg em amostras de solos. O método consiste na liberação de Hg, por aquecimento, seguido da quantificação desse por espectrometria de absorção atômica, e foi desenvolvido construindo-se curvas de calibração em diferentes matrizes de solo, a partir de soluções-padrão de Hg2+. As amostras de referência certificadas e a comparação com a determinação direta de Hg, DMA, outra técnica consagrada, foram utilizadas na validação do método, que se evidenciou exato e preciso. Despite the ban on Hg use in mining, there are many contaminated soils in Minas Gerais, which is among the states with the largest number of operational gold mines in Brazil (DNPM, 2010). Durão Júnior et al (2009), studying soil samples from that area, identified samples with total Hg concentrations ranging from 0.0371 to 161 μg g-1, In addition to metallic Hg that surfaced, they identified large quantities of Hg2+, showing Hg0 oxidation in the soil
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