Sea ice working group (SIP)

The sea ice is a crucial component of the polar climate system, and has an impact on albedo, heat and gas ex- change, primary productivity and car- bon export, atmospheric and ocean circulation, freshwater budget, ocean stratification, and deep water mass for- mation. It is therefore critical that it is correctly specified as a forcing or pre- dicted as a feedback in modeling stud- ies

Adsorption and time dependent fixation of uranium (VI) in synthetic and natural matrices

Disposal of low level radioactive liquid waste to soil is commonly practiced. Therefore, sorption of uranium from aqueous solution and fixation of uranium into soil are processes which are crucial to the attenuation of uranium and protection of groundwater. Exposure of human populations is either by direct water consumption or through crop irrigation and transfer into the food chain. In this study a range of materials, including natural materials (e.g. biochar and the natural zeolites ‘Chabazite and Mordenite’) and the synthetic zeolite ‘Faujasite-X’, were investigated as potential adsorbents for UVI from aqueous solution. A range of experiments were carried out to investigate the efficacy of using these adsorbents to successfully adsorb and fix UVI from aqueous solutions. These included sorption and desorption experiments, quantifying time-dependent fixation of UVI and applying kinetic models of this process and measuring isotopically exchangeable UVI within adsorbent materials when possible. The factors affecting adsorption processes, such as solution pH, initially added UVI concentrations and adsorption contact time, were also investigated. Speciation of U in the solution phase was investigated using the Windermere Humic Aqueous Model (WHAM-VII). Saturation indices of potential solid phases were also configured using known solubility products and the free ion activities predicted from the speciation model, WHAM-VII. Mordenite zeolite showed a poor adsorption affinity for UVI as the solution pH was continuously buffered towards high pH values > 6.5 which favours UVI ion solubilisation as a result of uranyl carbonate complex formation. Uranium (VI) ion adsorption on chabazite at pH 4.7 at 20 oC was found to fit the Freundlich adsorption isotherm but the optimised equation parameters were unique for each contact time of 1, 5, 10, 20 and 30 days. The time-dependent fixation of UVI on chabazite was found to follow an irreversible first-order kinetic equation and an intraparticle diffusion model suggesting slow penetration of chabazite porous structure following initial surface adsorption. Isotopically exchangeable 238UVI (the E-value, UE) adsorbed on chabazite showed that > 65% of initially added UVI remained isotopically exchangeable. Faujasite-X also showed time-dependent fixation of UVI over 35 days of adsorption contact time at pH values 4, 5 and 6. The adsorption kinetics were best described by an irreversible first-order equation and a spherical diffusion model. Desorption trends showed that UVI adsorption into faujasite- X was almost wholly irreversible. Saturation indices calculated from the solubility products and free ion activities of constituent ions showed that the fixation of UVI was not controlled by the precipitation of any solid phase investigated at the studied range of pH values. Bone biochar, a by-product from the production of biofuel and syngas by gasification, was tested as a material for adsorption and fixation of UVI from aqueous solutions. A batch experiment was conducted to study the factors that influence the adsorption and time-dependent fixation on biochar at 20◦C, including pH, initial concentration of UVI and contact time. Uranium (UVI) adsorption was highly dependent on pH. However, it was found that UVI adsorption on biochar was high over a wide range of pH values, from 4.5 to 9.0, and adsorption strength was time-dependent over several days. The experimental data for pH> 7 were most effectively modelled using a Freundlich adsorption isotherm coupled to a reversible first order kinetic equation to describe the time-dependent fixation of UVI within the biochar structure. Desorption experiments showed that UVI was only sparingly desorbable from the biochar with time and isotopic dilution with 233UVI confirmed the low, and time-dependent, lability of adsorbed 238UVI. Below pH 7 the adsorption isotherm trend suggested that precipitation, rather than true adsorption, may occur. Across all pH values (4.5–9) measured saturation indices suggested precipitation was possible: autunite below pH 6.5 and swartzite, liebigite or bayleyite above pH 6.5 Another source of bone biochar with a fraction size of (20x 60 mesh) was investigated as candidate materials for soil remediation. Its ability both to adsorb uranium and to render it non-labile (i.e. chemically inactive) was tested by addition to a wide range of soils recently spiked with 238UVI and incubated under moist conditions. The overall aim was to recommend improved strategies for immobilisation of uranium in soils subject to application of low level radioactive waste solutions. Several measurements were made to assess possible reductions in U availability from biochar addition, including U solubility in 0.01 M Ca(NO3)2, exchangeability in 1 M Mg(NO3)2 solution and isotopic dilution with 233U and 236U. Results showed that 41.3 %, 27.6%, 28.9% and 31.7% were isotopically exchangeable on average for soil amended with 0%, 3%, 5% and 10% loading of biochar, but overall there appeared to be only marginal advantages in adding even large concentrations of biochar to soil. The major factor controlling U solubility, exchangeability and lability was soil pH and the pH value resulting from biochar, rather than the biochar itself. Therefore, while the use of biochar to effectively remove U from water is clear, its role in adsorbing U in the highly buffered soil environment is probably minimal

The effect of multilingual glossaries of meta-cognitive verbs on improving assessment performance: a case study at a South African university of technology

Thesis (MA)--Stellenbosch University, 2018.ENGLISH ABSTRACT: This study was conducted to determine whether first-year students at a university of technology would benefit from the use of multilingual glossaries of metacognitive verbs, and specifically whether such glossaries will improve the students’ understanding of the instructional verbs used in their test and examination papers and other assessments. First-year students at the university of technology often present with low English proficiency due to factors such as an inadequate school system and language-in-education policies which require them to study through means of a language other than their mother tongue. Such students typically find it difficult to cope with English as the sole language of teaching and learning unless they receive additional assistance as regards their English language proficiency. As this university of technology no longer has an English support programme, alternative methods of support are needed. Multilingual glossaries of subject-specific concepts have been developed and are in use in some South African universities, but there is a marked lack of information on multilingual glossaries containing metacognitive verbs. For the purposes of this study, multilingual glossaries were developed using the seven languages most widely spoken on campus and seven of the most commonly misunderstood metacognitive verbs (the latter as identified by lecturers at the university at which the study was conducted). English was used as the control and the words were translated into the other six languages – viz. Afrikaans, French, isiZulu, Sesotho, Sepedi and Tshivenda – giving the metacognitive verb, the meaning of the verb and an application using that verb, in each language. In order to make them easily accessible, the multilingual glossaries were made available on the online learning platform of the university, to which all the university’s students have free access, and as a low data-consuming cellphone application. The study to determine whether first-year students would benefit from the use of these multilingual glossaries was conducted by means of a baseline test to determine prior knowledge of the metacognitive verbs, a series of tutorials to explain the verbs, and activities in which students used the multilingual glossaries and were encouraged to translanguage during their discussions, in order to encourage deeper understanding of the metacognitive verbs. This was followed by a post-test. The results of the baseline test and the post-test were compared and the latter showed a clear improvement. The participants of the study were asked to fill in a questionnaire indicating (a) whether or not they found the multilingual glossaries helpful and (b) what their impressions were of this means of language support. Most of the responses were positive. It was concluded that the multilingual glossaries of metacognitive verbs could successfully be implemented to scaffold student learning, especially as the glossaries could be made easily accessible to students.AFRIKAANSE OPSOMMING: Die doel van hierdie studie is om te bepaal of studente aan ‘n sekere universiteit van tegnologie sou baat vind by die gebruik van veeltalige woordelyste van metakognitiewe werkwoorde en spesifiek of hierdie woordelyste die studente in staat sal stel om die instruksiewerkwoorde wat gebruik word in hulle toetse, eksamenvraestelle en ander assessering beter te verstaan. Eerstejaarstudente toon dikwels lae vaardighede in Engels te wyte aan faktore soos ‘n ondoeltreffende skoolstelsel en die taal-in-opvoedingsbeleid wat van studente vereis om in ‘n taal te leer wat nie hulle moedertaal is nie. Hierdie studente vind dit gewoonlik moeilik om met Engels as die enigste medium van onderrig en leer oor die weg te kom as hulle nie bykomende ondersteuning ontvang nie in terme van hulle Engelse taalvaardighede. Omdat hierdie universiteit van tegnologie nie meer ‘n ondersteuningsprogram in Engels aanbied nie, is ander middele van ondersteuning nodig. Veeltalige woordelyste van vakspesifieke konsepte is al ontwikkel en in gebruik in sommige Suid-Afrikaanse universiteite, maar daar is ‘n ooglopende gebrek aan inligting oor veeltalige woordelyste wat metakognitiewe werkwoorde bevat. Vir die doel van hierdie studie is veeltalige woordelyste ontwikkel deur gebruik te maak van die sewe tale wat die meeste op die betrokke kampus gepraat word, sowel as die sewe mees misverstane metakognitiewe werkwoorde. Hierdie werkwoorde is deur dosente aan die universiteit van tegnologie waar die studie afgelê is, uitgeken. Engels is as die kontroletaal gebruik en die werkwoorde is in die ander ses tale vertaal, nl. Afrikaans, Frans, isiZulu, Sepedi, Sesotho en Tshivenda vertaal; die metakognitiewe werkwoord, die betekenis van die woord en ‘n toepassing van die werkwoord is in elke taal verskaf. Die veeltalige woordelyste is beskikbaar gestel op die aanlyn-leerbestuurstelsel wat deur die universiteit gebruik word (waartoe alle studente aan hierdie universiteit vrye toegang het) asook as ‘n selfoontoepassing met ‘n lae dataverbruik. Die studie om te bepaal of eerstejaarstudente voordeel sal trek uit die gebruik van hierdie veeltalige woordelyste is uitgevoer deur die skryf van ‘n voortoets om aanvangskennis te bepaal, ‘n reeks tutoriaalklasse om die woorde te bespreek, en oefeninge waartydens die studente die veeltalige woordelyste van metakognitiewe werkwoorde gebruik het en aangemoedig is om die besprekings in hulle eie taal te hou om sodoende ‘n dieper begrip van die metakognitiewe werkwoordete verkry. Hierna is ‘n opvolgtoets gedoen. Die uitslae van die eerste toets en die opvolgtoets is met mekaar vergelyk en ‘n merkbare verbetering is in die opvolgtoets getoon. Die deelnemers aan die studie is gevra om ‘n vraelys in te vul om aan te dui (a) of hulle die veeltalige woordelyste nuttig gevind het al dan nie en (b) hulle indrukke omtrent hierdie metode van taalondersteuning. Die oorgrote meerderheid van die antwoorde was positief. Hieruit is afgelei dat die veeltalige woordelyste van metakognitiewe werkwoorde suksesvol aangewend kan word om studentestudie te onderskraag, veral aangesien die woordelyste maklik beskikbaar vir studente gemaak kan word