Performance of constructed evaporation ponds for disposal of smelter waster water: a case study at Portland Aluminum, Victoria, Australia

The construction of evaporative ponds and wetlands for the disposal of waste water high in ionic concentrations is a waste disposal strategy currently considered by many industries. However, the design, construction and management of these ponds and wetlands are not straightforward as complex chemical interactions result in both spatial and temporal changes in water quality. The effects of evaporation and drainage on the water quality in two constructed ponds, an adjacent man-made wetland and local groundwater at Portland Aluminium were investigated. The minimum volume of water entering the ponds during the study period was 0.96±0.16 ML per month. The predicted theoretical evaporative capacity of the two ponds was calculated to be 0.30±0.07 ML per month. More water enters the ponds than it is theoretically possible to evaporate under the ambient weather conditions at Portland, yet the ponds do not overflow, suggesting percolation through the pond lining. No spatial differences in solute concentrations (fluoride, sulphate, bicarbonate, carbonate, sodium, potassium, calcium, and magnesium ions) were found within the waters of either pond, although temporal differences were apparent. The results support the conclusion that the ponds are not impermeable, and that much of the waste water entering the ponds is being lost through seepage. The impacts on local groundwater chemistry of this seepage are addressed. Significant correlations exist between solute presence within and between the ponds, wetland and groundwater. Fluoride and sulphate concentrations were significantly higher in pond waters throughout the duration of the experiment. Pond sediments revealed a high degree of spatial and temporal heterogeneity in the concentration of all monitored ions resulting from the chemical heterogeneity of the material making up the pond linings. Adsorption isotherms for fluoride indicate that the adsorption capacity of the pond linings remains high for this ion. Implications for the management of waste water by this strategy are discussed.

Young children learning about evaporation: a longitudinal perspective

This paper traces the learning pathways over a 4-year period of 12 children learning about evaporation. The findings show the complexity and dependence on context of children's understandings. Detailed transcripts for 2 children are used to demonstrate how understandings of phenomena are framed within a network of personal narratives of self that reflect children's different subjectivities as learners and school children, It is argued that the longitudinal methodology opens up a more complex and nuanced view of children's conceptual learning in school settings than is afforded by cross-sectional studies and that the focus on individuals over time compels a very different construction of the learner than is represented in mainstream conceptual-change literature. [ABSTRACT FROM AUTHOR]

Picturing evaporation : learning science literacy through a particle representation

Evaporation is mostly taught in primary schools through a water cycle representation. This has its limitations in explaining mechanisms and local effects such as drops drying in a closed room, condensation on cold surfaces, or how we smell liquids. In this paper the authors describe a classroom sequence of activities for Grade 5 students that explored the use of a particle model in conjunction with a range of representational modes, to explain evaporation phenomena. In interviews the authors explored with students their visual and verbal accounts of particles, modelling a process of teacher-mediated negotiation of multiple representations. From the evidence, the authors argue that difficulties in understanding evaporation are inherently representational, and that by engaging with the multiple literacies of science teachers can support significant advances in conceptual learning.

Representation and learning about evaporation

While there has been considerable research on children's understanding of evaporation, the representational issues entailed in this understanding have not been investigated in depth. This study explored students' engagement with evaporation phenomena through various representational modes. Primary school classroom sequences and structured interviews shortly after, and a year later, indicated significant advances in learning flowing from negotiation of meaning around particle representations. A case study of one child's learning is used to demonstrate how a molecular distribution representation can offer the possibility of significant advances in children's thinking about evaporation. The findings suggest that teacher-mediated negotiation of representational issues can support enriched student learning

Representational issues in students learning about evaporation

This study draws on recent research on the central role of representation in learning. While there has been considerable research on students’ understanding of evaporation, the representational issues entailed in this understanding have not been investigated in depth. The study explored students’ engagement with evaporation phenomena through various representational modes. The study indicates how a focus on representation can provide fresh insights into the conceptual task involved in learning science through an investigation of students’ responses to a structured classroom sequence and subsequent interviews over a year. A case study of one child’s learning demonstrates the way conceptual advances are integrally connected with the development of representational modes. The findings suggest that teacher-mediated negotiation of representational issues as students construct different modal accounts can support enriched learning by enabling both (a) richer conceptual understanding by students, and (b) enhanced teacher insights into students’ thinking.

Multiple representation in learning about evaporation

This study draws on recent research on the central role of representation in learning. While there has been considerable research on Children’s understanding of evaporation, the representational issues entailed in this understanding have not been investigated in depth. The study explored students’ engagement with science concepts relating to evaporation through various representational modes such as diagrams, verbal accounts, gestures, and captioned drawings. This engagement entails students a) clarifying their thinking through exploring representational resources, b) developing understanding of what these representations signify and c) learning how to construct and interpret the representational aspects of scientific explanation. The study indicates how a focus on representation can provide fresh insights into the conceptual task involved in learning science. Primary school classroom sequences and structured interviews with 12 children indicated a range of learning potentialities flowing from this focus. The findings suggest that teacher-mediated negotiation of representational issues as students construct different modal accounts can support enriched learning by enabling both a) richer conceptual understanding by students and b) enhanced teacher insights into students’ thinking.

Multiple representation in learning about evaporation

There has been extensive research on children's understanding of evaporation, but representational issues entailed in this understanding have not been investigated in depth. This study explored three students' engagement with science concepts relating to evaporation through various representational modes, such as diagrams, verbal accounts, gestures, and captioned drawings. This engagement entailed students (a) clarifying their thinking through exploring representational resources; (b) developing understanding of what these representations signify; and (c) learning how to construct representational aspects of scientific explanation. The study involved a sequence of classroom lessons on evaporation and structured interviews with nine children, and found that a focus on representational challenges provided fresh insights into the conceptual task involved in learning science. The findings suggest that teacher-mediated negotiation of representational issues as students construct different modal accounts can support enriched learning by enabling both (a) richer conceptual understanding by students; and (b) enhanced teacher insights into students' thinking.

Anomalous evaporation behavior of ZnO powder milled mechanically under high-energy conditions

ZnO powder showed anomalous evaporation behavior after its mechanical milling treatment under high-energy conditions. The amount of generated vapor is about 10 times higher in the first 15 min of annealing at 1300 °C than that of unmilled ZnO powders. The strong ball impacts are responsible for the greatly enhanced evaporation ability. Low-energy ball milling involving shearing actions and rare weak impacts leads only to a small evaporation rate enhancement. The possible explanation of the high evaporation rate of the heavily milled material is the existence of large fraction of weakly bonded atoms in grain boundaries, surface defects and strained areas.

There's a black boy dead and a migloo holding a gun : death, Aboriginality and history in Australian adolescent literature

This essay is concerned with the extent to which the attitudes and ideologies of colonial discourse continue to influence contemporary signifying practices in Australian adolescent historical fiction. Under scrutiny are three novels which take issue with the violent aspects of colonisation when so many members of the Indigenous population either died or were forcibly displaced: Melissa Lucashenko’s Killing Darcy, Gary Crew’s No Such Country and Mark Svendsen’s Poison Under Their Lips. Although these texts share a desire to interrogate monolithic versions of Australia’s history, it is argued that such motivations offer no guarantee that the implied audience is positioned to come to an understanding of perspectives belonging to ex-centric Others.

In-situ confocal Raman monitoring of evaporation process during protein crystallization

We have introduced an in-situ Raman monitoring technique to investigate the crystallization process inside protein drops. In addition to a conventional vapour-diffusion process, a novel procedure which actively stimulates the evaporation from a protein drop during crystallization was also evaluated, with lysozyme as a model protein. In contrast to the conventional vapour-diffusion condition, the evaporation-stimulated growth of crystals was initiated in a simple dehydration scheme and completed within a significantly shorter time. To gain an understanding of crystallization behaviours under the conditions with and without such evaporation stimulation, confocal Raman spectroscopy combined with linear regression analysis was used to monitor both lysozyme and HEPES buffer concentrations in real time. The confocal measurements having a high spatial resolution and good linear response revealed areas of local inhomogeneity in protein concentration when the crystallization started. The acquired concentration profiles indicated that (1)ÿthe evaporation-stimulated crystallization proceeded with protein concentrations lower than those under conventional vapour diffusion, and (2)ÿcrystals under the evaporation-stimulated condition were noticeable within an early stage of crystallization before the protein concentration approached its maximum value. The HEPES concentration profiles, on the other hand, increased steadily towards the end of the process regardless of the conditions used for crystallization. In particular, the observed local inhomogeneities specific to protein distribution suggested an accumulation mechanism of protein molecules that initiates the nucleation of crystals.

Stability of aqueous films between bubbles. Part 2. Effects of trace impurities and evaporation

The stability of water films has been investigated with a Mysels-Scheludko type film balance. Minor trace impurities in water do not affect the lifetime of water films under vapor saturation, but significantly influence the stability in free evaporation. Trace amounts of positively adsorbed contaminants induce Marangoni-driven flow that destabilizes films under evaporation conditions whereas negatively adsorbed electrolytes actually prolong stability by reversing interfacial tension gradients and driving a steady circulation within the film. At high thinning rates, pure-water films develop exotic-appearing flow patterns and break due to a strong coupling between hydrodynamic and interfacial tensiongradient adsorption stresses. The most dominant factor of transient film stabilization in dynamic conditions under evaporation is a surface tension gradient created in the film. We discuss surface tension gradients in transient films created by temperature differences, impurity concentration, and expansion of the films.