Dissolution of secondary copper sulphides using complex-forming agents (EDTA,EDA). Part I: Covellite dissolution in EDTA and EDA

Problems of dissolution of the so-called secondary copper sulphides are very important for dynamic as well as percolation leaching of ores. This paper deals with dissolution kinetics of sulphides in an alkaline medium, using complex-forming agents in connection with possibility to leach basic, partially oxidized ores. Natural minerals and their polydispersions were investigated and the so-called geometrical model was used for evaluation. Basic dependences of the dissolution rate on the reagent concentration and pH value of the leaching solution were found and an attempt at their mathematical expression and physical interpretation was made. The first part of this work refers to the systems of covellite-ethylene diamine tetra-acetic acid (EDTA) and covellite-ethylene diamine (EDA). The established dependences are not only of theoretical but also of practical importance.     

Dissolution of secondary copper sulphides using complex-forming agents (EDTA,EDA). Part II: Chalcocite dissolution in EDTA and EDA

This work is immediate continuation of Part I, using an identical method and evaluation for kinetic studies. The systems chalcocite-ethylene diamine tetra-acetic acid and chalcocite-ethylene diamine were studied. It was necessary to refine the geometrical model method for chalcocite in order to establish dissolution kinetics of polydispersions. This work confirms that chalcocite leaching proceeds through covellite even in the medium of complex-forming agents and kinetic equations for both leaching stages were evaluated with an attempt at physical interpretation.     

Embedding reach-scale fluvial dynamics within the CAESAR cellular automaton landscape evolution model

We introduce a new computational model designed to simulate and investigate reach-scale alluvial dynamics within a landscape evolution model. The model is based on the cellular automaton concept, whereby the continued iteration of a series of local process ‘rules’ governs the behaviour of the entire system. The model is a modified version of the CAESAR landscape evolution model, which applies a suite of physically based rules to simulate the entrainment, transport and deposition of sediments. The CAESAR model has been altered to improve the representation of hydraulic and geomorphic processes in an alluvial environment. In-channel and overbank flow, sediment entrainment and deposition, suspended load and bed load transport, lateral erosion and bank failure have all been represented as local cellular automaton rules. Although these rules are relatively simple and straightforward, their combined and repeatedly iterated effect is such that complex, non-linear geomorphological response can be simulated within the model. Examples of such larger-scale, emergent responses include channel incision and aggradation, terrace formation, channel migration and river meandering, formation of meander cutoffs, and transitions between braided and single-thread channel patterns. In the current study, the model is illustrated on a reach of the River Teifi, near Lampeter, Wales, UK.     

Geographies of age: thinking relationally

In contrast to recent treatment of other social identities, geographers' work on age still focuses disproportionately on the social-chronological margins – the very young and (to a far lesser extent) the very old – and rarely connects them directly. We outline the benefits of creating relational geographies of age, in order to build out from the recent explosion of children's geographies, and discuss three helpful concepts: intergenerationality, intersectionality and lifecourse. We suggest that participation provides one epistemological vehicle for getting beyond geographies which are mainly adults'.     

Thinking critically and creatively about focus groups

Focus groups are now widely used by human geographers conducting qualitative research, and are clearly recognised as an established research method within the discipline. Despite this, there is a lack of discussion about the various methodological issues involved in using focus groups. This paper aims to open up discussion by suggesting that there is a need to think critically and creatively about using focus groups in human geography. I draw upon my experience of conducting focus groups with young Muslim men in order to suggest some of the ways in which human geographers might think critically about using focus groups. Some of the issues discussed include group size, location, context and timing, sensitivity of topic, the age of research participants and the positionalities of the researcher.     

Certainty, uncertainty, and the spatiality of disease: a West Nile Virus example

The problem is not uncertainty—proposed here as an inevitable condition—but the chimera of certainty asserted by most contemporary researchers. Problems of data definition, collection, and their use are reviewed in terms of spatial epidemiology and health data with examples drawn from several areas of contemporary health research. The argument is that preconceptions limit data modeled in a manner assuming its completeness. The result, as the West Nile Virus example seeks to demonstrate, may obscure other patterns and limit avenues of research.