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Full-Text Articles in Physical Sciences and Mathematics
Assessment And Behaviour Of Secondary Iron(Iii) Minerals In Acid Sulphate Soil Materials, Chamindra Vithana
Assessment And Behaviour Of Secondary Iron(Iii) Minerals In Acid Sulphate Soil Materials, Chamindra Vithana
Chamindra Vithana
This study examined two aspects of acidity generating secondary Fe(III) minerals (i.e. schwertmannite and jarosite) in acid sulfate soils (ASS) environments: i) accurate identification and quantification, and ii) improving our understanding of their behaviour in ASS.The study showed that current assessment methods have a number of limitations and are not reliable for accurate estimation of both minerals in ASS environments. The study also showed that in natural environments, these minerals can behave in a manner different to current conceptual understanding. The broad implication of this study was identification of the need for development of improved management techniques for ASS.
Assessment Of Peroxide Oxidation For Acid Sulfate Soil Analysis. 2. Acidity Determination, Nicholas Ward, Leigh Sullivan, Richard Bush, Chuxia Lin
Assessment Of Peroxide Oxidation For Acid Sulfate Soil Analysis. 2. Acidity Determination, Nicholas Ward, Leigh Sullivan, Richard Bush, Chuxia Lin
Dr Nicholas J Ward
Total sulfidic acidity (TSA) and total potential acidity (TPA) are derived from peroxide oxidation of acid sulfate soil materials (ASS), and are measures of the sulfidic acidity and the net acidity (net acidity = sulfidic acidity + actual acidity – acid neutralising capacity), respectively. The TSA and TPA of 4 ASS materials were determined using a variety of peroxide oxidation procedures and compared with the sulfidic acidity and net acidity derived from the use of an acid–base accounting model. TSA and TPA values both varied greatly with each peroxide oxidation method used, and both measures were found to substantially underestimate …
Assessment Of Peroxide Oxidation For Acid Sulfate Soil Analysis. 1. Reduced Inorganic Sulfur, Nicholas Ward, Leigh Sullivan, Richard Bush, Chuxia Lin
Assessment Of Peroxide Oxidation For Acid Sulfate Soil Analysis. 1. Reduced Inorganic Sulfur, Nicholas Ward, Leigh Sullivan, Richard Bush, Chuxia Lin
Dr Nicholas J Ward
The reduced inorganic sulfur fraction of 4 acid sulfate soil (ASS) materials was quantified using a variety of peroxide oxidation procedures. The temperature and duration of the peroxide oxidation were found to markedly affect the peroxide oxidisable sulfur determination. For 3 ASS materials with low total carbon content (i.e. <2.5% C), peroxide oxidisable sulfur underestimated the reduced inorganic sulfur fraction, with the peroxide oxidisable sulfur determinations being as low as 42% of those determined using chromium reducible sulfur technique. The precipitation of jarosite during peroxide oxidation was a major factor contributing to the underestimation of reduced inorganic sulfur in these materials. Apparent losses of sulfur of approximately 25% on average occurred during peroxide oxidation budget accounting; this also contributed towards the observed underestimation of reduced inorganic sulfur. It is most likely that these unaccounted losses are due to atmospheric losses of sulfur. In a peat ASS, one of the peroxide oxidation methods overestimated the reduced inorganic sulfur fraction and was attributed to the release of a large reserve of organic sulfur in this material by the peroxide. This study shows the peroxide oxidation methods examined here are subject to substantial interferences. Consequently these peroxide oxidation methods are unable to reliably provide accurate measurements of the reduced inorganic sulfur fraction in ASS materials
Arsenic Mobilization And Iron Transformations During Sulfidization Of As(V)-Bearing Jarosite, Scott Johnston, Edward Burton, Annabelle Keene, Britta Planer-Friedrich, Andreas Voegelin, Mark Blackford, Greg Lumpkin
Arsenic Mobilization And Iron Transformations During Sulfidization Of As(V)-Bearing Jarosite, Scott Johnston, Edward Burton, Annabelle Keene, Britta Planer-Friedrich, Andreas Voegelin, Mark Blackford, Greg Lumpkin
Associate Professor Edward D Burton
Jarosite (KFe3(SO4) 2(OH)6) is an important host-phase for As in acid mine drainage (AMD) environments and coastal acid sulfate soils (CASS). In AMD and CASS wetlands, jarosite may encounter S(−II) produced by sulfate reducing bacteria. Here, we examine abiotic sulfidization of As(V)-bearing K-jarosite at pH 4.0, 5.0, 6.5 and 8.0. We quantify the mobilization and speciation of As and identify corresponding Fe mineral transformations. Sulfide-promoted dissolution of jarosite caused release of co-precipitated As and the majority of mobilized As was re-partitioned to a readily exchangeable surface complex (AsEx). In general, maximum As mobilization occurred in the highly sulfidized end-members of …