32 research outputs found
Review of trace toxic elements (Pb, Cd, Hg, As, Sb, Bi, Se, Te) and their deportment in gold processing. Part 1: Mineralogy, aqueous chemistry and toxicity
A literature review on the deportment of trace toxic elements (Pb, Cd, Hg, As, Sb, Bi, Se, and Te) in gold processing by cyanidation is presented which compiles the current knowledge in this area and highlights the gaps. This review, together with further research on the gaps in the thermodynamics and kinetics of these systems, aims to support the development of computer models to predict the chemical speciation and deportment of these elements through the various stages of the gold cyanidation process. The first part of this review is a collation of the relevant information on trace element mineralogy, aqueous chemistry and toxicity, together with a comparison of two available software packages (JESS and OLI) for thermodynamic modelling. Chemical speciation modelling can assist in understanding the chemistry of the trace toxic elements in gold cyanidation solutions which remains largely unexplored. Many significant differences exist between the predicted speciation of these trace elements for different types of modelling software due to differences in the thermodynamic data used, the paucity of data that exists under appropriate non-ideal conditions, and the methods used by the software packages to estimate thermodynamic parameters under these conditions. The toxicity and environmental guidelines of the chosen trace element species that exist in aqueous solutions are discussed to better understand the health and environmental risks associated with the presence of these elements in gold ores
Identification of regulatory variants associated with genetic susceptibility to meningococcal disease
Non-coding genetic variants play an important role in driving susceptibility to complex diseases but their characterization remains challenging. Here, we employed a novel approach to interrogate the genetic risk of such polymorphisms in a more systematic way by targeting specific regulatory regions relevant for the phenotype studied. We applied this method to meningococcal disease susceptibility, using the DNA binding pattern of RELA - a NF-kB subunit, master regulator of the response to infection - under bacterial stimuli in nasopharyngeal epithelial cells. We designed a custom panel to cover these RELA binding sites and used it for targeted sequencing in cases and controls. Variant calling and association analysis were performed followed by validation of candidate polymorphisms by genotyping in three independent cohorts. We identified two new polymorphisms, rs4823231 and rs11913168, showing signs of association with meningococcal disease susceptibility. In addition, using our genomic data as well as publicly available resources, we found evidences for these SNPs to have potential regulatory effects on ATXN10 and LIF genes respectively. The variants and related candidate genes are relevant for infectious diseases and may have important contribution for meningococcal disease pathology. Finally, we described a novel genetic association approach that could be applied to other phenotypes
Review of trace toxic elements (Pb, Cd, Hg, As, Sb, Bi, Se, Te) and their deportment in gold processing: Part II: Deportment in gold ore processing by cyanidation
The second part of a literature review on the deportment of trace toxic elements in gold processing by cyanidation is presented. Part 1 of this review collated the relevant information on trace element mineralogy, aqueous solution chemistry and toxicity for lead, cadmium, mercury, arsenic, antimony, bismuth, selenium, and tellurium. This paper reviews the deportment of these elements during gold ore cyanidation (including carbon adsorption and elution) and tailings disposal. It also captures related information from the treatment of industrial wastes and wastewaters, including fixation and encapsulation processes that may be applicable to tailings generated from gold ore processing.
The main findings were that only lead, cadmium and mercury form cyano complexes ranging from very weak (Pb) through moderate (Cd) to the strong mercuro complexes. The neutral cyano-complexes of cadmium and mercury strongly adsorb onto activated carbon and thus potentially deport to the gold recovery circuit and carbon regeneration kiln. The strong mercury cyano complexes will persist in tailings storage environments. Arsenic, antimony and bismuth do not form cyanide complexes. The less metallic of these (As and Sb) may form oxyanions and/or thioanions that consume oxygen and retard or prevent gold dissolution. They can be present in solution, including tailings solutions, at relatively high concentrations. Bismuth, being more metallic, remains in the solid phase as a sulfide or oxide during cyanidation. Depending on the redox potential in solution, selenium and tellurium form the oxyanions selenite and tellurite or selenate and tellurate in cyanide solutions. Selenium may form selenocyanate (SeCN-) in cyanide solutions, which is thermodynamically more stable than the oxyanions selenite and selenate. Tellurocyanate is unstable and does not form. The potential for adsorption of selenium or tellurium onto activated carbon is unknown, as is their persistence in tailings storage facilities.
Lead, cadmium and mercury are best removed from wastewaters by precipitation as sulfides or adsorption onto activated carbon or iron or aluminium oxides. Arsenic and antimony in acidic tailings and mine drainage waters are also attenuated by precipitation onto iron oxides, or by precipitation as scorodite (FeAsO4.2H2O) or senarmontite (Sb2O3). Selenite in wastewater efficiently adsorbs on to both iron and manganese oxides but selenate does not. Tellurium is less soluble in the aqueous phase than selenium and adsorbs more strongly onto iron oxides
MarsTwin: an M-mission to Mars with two geophysical laboratories
Mars-Twin - a mission proposed for the running ESA cosmic vision M call - if selected it will be the first European mission to focus on interior processes and the early evolution of Mars, providing essential constraints for models of the thermal, geochemical, and geologic evolution of Mars and for a better understanding of SNC meteorites and future samples from Mars. Our fundamental understanding of the interior of the Earth comes from geophysics, geodesy, geochemistry, geomagnetism, and petrology. For geophysics, seismology, geodesy, magnetic field measurements, and surface heat flow have revealed the basic internal layering of the Earth, its thermal structure, its gross compositional stratification, as well as significant lateral variations in these quantities. The landers will also provide meteorological stations to monitor the Martian meteorology and climate and to obtain new measurements in the Martian boundary layer. The Mars-Twin mission will fill a longstanding gap in the scientific exploration of the solar system by performing an in-situ investigation of the interior of an Earth-like planet other than our own. Mars-Twin will provide unique and critical information about the fundamental processes of terrestrial planet formation and evolution. This investigation has been ranked as a high priority in virtually every set of European, US and international high-level planetary science recommendations for the past 30 years, and the objectives for the Mars-Twin mission are derived directly from these recommendations. In addition to geophysics, the mission will provide important constraints for the Astrobiology of Mars by helping to understand why Mars fails to have a magnetic field, by helping to understand the evolution of the climate, and by providing a limit to the chemoautrophic biosphere through a measurement of the heat flow. The paper will also address the synergy between the lander instruments and the possible orbiter instruments
Spatial Market Efficiency and Policy Regime Change: Seemingly Unrelated Error Correction Model Estimation
We investigate the degree to which the wheat markets of France, Germany, and the United Kingdom are in spatial equilibrium and how reforms to the CAP affect the speed of convergence to the longrun relationship. Due to the interrelationship among these markets and the nonstationarity of our data we introduce a seemingly unrelated regression-augmented Dickey-Fuller and error correction methodology. We argue this methodology is more efficient than ordinary cointegration and error correction models. Empirically we find strong evidence of efficient spatial markets and conformity to the law of one price. Market liberalization reforms in the EU increased the comovement of domestic and world wheat prices; our post-Uruguay Round price transmission elasticity was 0.183. Copyright 2002, Oxford University Press.
Isotopic labeling study of oxygen diffusion in amorphous LaScO3 high-k films on Si(100) and its effects on the electrical characteristics
The influence of post-deposition oxygen anneals on the properties of amorphous LaScO3 films on Si(100) is reported. The use of an isotopically (O-18(2)) enriched atmosphere allowed to investigate the O-16-O-18 exchange and the oxygen diffusion across the dielectric layer. Such effects are connected to the formation of an interfacial layer. Oxygen annealing leads to nearly ideal capacitance-voltage curves, lower leakage currents and interface trap densities, as well as to kappa-values up to 33 for the LaScO3 films. These results are attributed to the suppression of oxygen-related trap centers and the achievement of a stoichiometric oxygen content