The Determination of Acid-Volatile Sulphide in Sediments Using Microwave- Assisted Chemical Vapour Generation: An Alternative to the US EPA Method

Author(s): Ricardo E. Santelli, Aline S. Freire, Bernardo F. Braz, Francis A. Meireles, Maria de F.B. de Carvalho, John E.L. Maddock

Journal Name: Current Microwave Chemistry

Volume 4 , Issue 1 , 2017


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Abstract:

Background: Acid-volatile sulphides (AVS) and simultaneously extracted metals (SEM) have been used as sediment quality criteria in both contaminated or non-contaminated sediments. The AVS/SEM model is based on the criterion that metal toxicity is absent when the sum of the acid-labile divalent metal concentrations ([ΣSEM]) is less than the concentration of acid-volatile sulphides ([AVS]) expressed as a molar ratio.

Method: The US EPA-recommended method for AVS extraction and determination uses 6 mol L-1 HCl solution for 1 hour and NaOH solution to absorb the H2S generated in the previous step. Sulphide ions can be determined by different procedures, such as gravimetry, spectrophotometry and ion-selective electrode.

Results: The aim of this work was the use of microwave radiation as a fast alternative for the generation of H2S. For this procedure, a glass apparatus was developed, adapting a digestion tube that is generally used in a focused microwave oven. The chemical extraction conditions were evaluated. A flow injection analysis (FIA) system was applied to the determination of sulphide.

Conclusion: The developed procedure results in a total time for the AVS determination method that is one-tenth of that of the recommended method (12 minutes compared to approximately 2 hours). The results obtained show that AVS was accurately quantified in a range of 1.5 to µ290mol S g-1 sediment (RSD < 13 %). Surficial and core sediment samples from several impacted areas were analysed by both the standard (US EPA) procedure and the developed method, and no significant differences were observed.

Keywords: Acid-volatile sulphides, chemical vapour generation, microwave radiation, sample pre-treatment.

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Article Details

VOLUME: 4
ISSUE: 1
Year: 2017
Published on: 01 December, 2016
Page: [64 - 72]
Pages: 9
DOI: 10.2174/2213335603666151113213822
Price: $25

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