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- van Hullebusch, Eric D., et al.
(författare)
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Methodological approaches for fractionation and speciation to estimate trace element bioavailability in engineered anaerobic digestion ecosystems: An overview
- 2016
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Ingår i: Critical reviews in environmental science and technology. - : TAYLOR & FRANCIS INC. - 1064-3389 .- 1547-6537. ; 46:16, s. 1324-1366
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Forskningsöversikt (refereegranskat)abstract
- Optimal supply of trace elements (TE) is a prerequisite for microbial growth and activity in anaerobic digestion (AD) bioprocesses. However, the required concentrations and ratios of essential TE for AD biotechnologies strongly depend on prevailing operating conditions as well as feedstock composition. Furthermore, TE in AD bioreactors undergo complex physicochemical reactions and may be present as free ions, complex bound or as precipitates depending on pH, or on the presence of sulfur compounds or organic macromolecules. To overcome TE deficiency, various commercial mineral products are typically applied to AD processes. The addition of heavy metals poses the risk of overdosing operating systems, which may be toxic to microbial consortia and ultimately the environment. Adequate supplementation, therefore, requires appropriate knowledge not only about the composition, but also on the speciation and bioavailability of TE. However, very little is yet fully understood on this specific issue. Evaluations of TE typically only include the measurement of total TE concentrations but do not consider the chemical forms in which TE exist. Thus detailed information on bioavailability and potential toxicity cannot be provided. This review provides an overview of the state of the art in approaches to determine bioavailable TE in anaerobic bioprocesses, including sequential fractionation and speciation techniques. Critical aspects and considerations, including with respect to sampling and analytical procedures, as well as mathematical modeling, are examined. The approaches discussed in this review are based on our experiences and on previously published studies in the context of the COST Action 1302: European Network on Ecological Roles of Trace Metals in Anaerobic Biotechnologies.
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- Zaccarini, Frederica, et al.
(författare)
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Chromite and platinum group elements mineralization in the Santa Elena Ultramafic Nappe (Costa Rica) : Geodynamic implications
- 2011
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Ingår i: Geologica Acta. - 1695-6133 .- 1696-5728. ; 9:3-4, s. 407-423
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Tidskriftsartikel (refereegranskat)abstract
- Chromitites associated with strongly altered peridotite from six distinct localities in the Santa Elena ultramaficnappe (Costa Rica) have been investigated for the first time. Santa Elena chromitites commonly display acompositional variation from extremely chromiferous (Cr/(Cr+Al)=0.81) to intermediate and aluminous(Cr/(Cr+Al)=0.54). This composition varies along a continuous trend, corresponding to calculated parental liquidswhich may have been derived from the differentiation of a single batch of boninitic magma with Cr-rich and(Al, Ti)-poor initial composition. Fractional precipitation of chromite probably occurred during differentiation ofthe boninitic melt and progressive metasomatic reaction with mantle peridotite. The distribution of platinum groupelements (PGE) displays the high (Os+Ir+Ru)/(Rh+Pt+Pd) ratio typical of ophiolitic chromitites and, consistently,the platinum group minerals (PGM) encountered are mainly Ru-Os-Ir sulfides and arsenides. Textural relations ofmost of the platinum group elements suggest crystallization at magmatic temperatures, possibly under relativelyhigh sulfur fugacity as indicated by the apparent lack of primary Os-Ir-Ru alloys.The chemical and mineralogical characteristics of chromitites from the Santa Elena ultramafic nappe have astrong affinity to podiform chromitites in the mantle section of supra-subduction-zone ophiolites. Calculatedparental melts of the chromitites are consistent with the differentiation of arc-related magmas, and do not supportthe oceanic spreading center geodynamic setting previously proposed by some authors.
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