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Abstract: The thermodynamic modelling of solid (crystalline) phases forms a central topic within the Calphad approach and a variety of aspects have been discussed at previous Ringberg workshops. At the present Ringberg workshop, modelling of volume and its temperature, pressure and composition dependence formed a major part of the discussions. In addition, modelling of the heat capacity above the (equilibrium) melting temperature, sublattice modelling of complex phases, modelling of ordering and interstitial solutions in the bcc lattice and the effect of magnetism were addressed. [Copyright &y& Elsevier]

The till east of the Liikavaara O¨stra ore deposit in northern Sweden is in some parts rich in Cu and other sulphide-associated metals. Groundwater flowing in this till has higher concentrations of Cu than groundwater in a reference area where the till has low concentrations of Cu and other metals. To understand the processes that release metals from the mineralized till at Liikavaara into the groundwater, the authors performed a detailed study of the <2 mm fraction of a till profile where the highest metal concentrations in the Liikavaara area occur. The geochemistry and mineralogy of the till were determined, and the soil water was sampled by tension lysimeters. The importance of local diffusion of Cu-bearing airborne dust from the adjacent Aitik mine tailings impoundment was quantified and solid speciation of metals in airborne material was performed by sequential extraction. The results from Liikavaara were compared to results from the reference area. Glacial ice picked up sulphide-rich material from the Liikavaara O¨stra Cu ore during its flow. This material was deposited in the till east of the ore body when the ice melted. The sulphides have been dissolved in the <2 mm fraction during 8.7 ka of weathering since the glacial ice retreated. After dissolution of the sulphides, Cu was redistributed and secondarily retained in association with Fe-oxyhydroxides and altered biotite. Other sulphide-associated elements such as Co, Ni and Zn show the same pattern in the till profile as Cu, though the concentrations are much lower. Uptake of Cu2+ in the biotite through ion exchange with K+ may be an important mechanism for Cu-enrichment in biotite at Liikavaara. The airborne dust is not the source of Cu in the till. Although the soil water at Liikavaara has higher concentrations of Cu and other metals than the soil water at the reference area, the Cu-concentration is too low for infiltrating soil water to explain the high Cu-concentrations observed in groundwater. The high metal concentrations in the till, of Cu in particular, cause the increased concentrations in the local groundwater. A fluctuating groundwater table washes out Cu and other metals from the till. It is possible that increased Cu concentration in the local groundwater is caused by dissolved organic complexes, or by colloids (<0.45 μm) rich in organic matter and/or Fe-oxyhydroxides. [Copyright &y& Elsevier]

Pure titanium has an HCP structure and lacks mechanical properties for many industrial purposes. The BCC phase of Ti is required to make alloys with increased strength compared to pure Ti. Iron is the most potent element for stabilising the BCC phase. However, the addition of Fe to Ti causes segregation issues during solidification, which can be avoided by diffusion-driven solid-state alloying. To predict the diffusion kinetics, the interaction mobility parameters of Ti and Fe in the disordered BCC phase of Ti are necessary. In this work, these parameters are optimised based on new experimental data from Ti-Fe diffusion couples produced by the Field Assisted Sintering Technology (FAST). Diffusion couples were held at 1173K and 1273K for one hour. High-resolution Fe concentration profiles are obtained from Electron Probe Micro Analyser (EPMA). Ternary mobility interaction parameters are assessed based on binary endmembers with a DICTRA sub-module, and results are compared to earlier assessments of mobilities of the disordered BCC TiFe system. [ABSTRACT FROM AUTHOR]

Methylation of mercury (Hg) to highly toxic methyl Hg (MeHg), a process known to occur when organic matter (OM) decomposition leads to anoxia, is considered a worldwide threat to aquatic ecosystems and human health. We measured temporal and spatial variations in sediment MeHg, total Hg (THg), and major elements in a freshwater lagoon in Sweden polluted with Hg-laden cellulose fibers. Fiber decomposition, confined to a narrow surface layer, resulted in loss of carbon (C), uptake of nitrogen (N), phosphorus (P), and sulfur (S), and increased MeHg levels. Notably, fiber decomposition and subsequent erosion of fiber residues will cause buried contaminants to gradually come closer to the sediment-water interface. At an adjacent site where decomposed fiber accumulated, there was a gain in C and a loss of S when MeHg increased. As evidenced by correlation patterns and vertical chemical profiles, reduced S may have fueled C-fixation and Hg methylation at this site.