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Priestley, S. C., Payne, T. E., Harrison, J. J., Post, V. E. A., Shand, P., Love, A. J., et al. (2018). Use of U-isotopes in exploring groundwater flow and inter-aquifer leakage in the south-western margin of the Great Artesian Basin and Arckaringa Basin, central Australia. Applied Geochemistry, 98, 331–344.
Abstract: The distribution of uranium isotopes (238U and 234U) in groundwaters of the south-western margin of the Great Artesian Basin (GAB), Australia, and underlying Arckaringa Basin were examined using groundwater samples and a sequential extraction of aquifer sediments. Rock weathering, the geochemical environment and α-recoil of daughter products control the 238U and 234U isotope distributions giving rise to large spatial variations. Generally, the shallowest aquifer (J aquifer) contains groundwater with higher 238U activity concentrations and 234U/238U activity ratios close to secular equilibrium. However, the source input of uranium is spatially variable as intermittent recharge from ephemeral rivers passes through rocks that have already undergone extensive weathering and contain low 238U activity concentrations. Other locations in the J aquifer that receive little or no recharge contain higher 238U activity concentrations because uranium from localised uranium-rich rocks have been leached into solution and the geochemical environment allows the uranium to be kept in solution. The geochemical conditions of the deeper aquifers generally result in lower 238U activity concentrations in the groundwater accompanied by higher 234U/238U activity ratios. The sequential extraction of aquifer sediments showed that α-recoil of 234U from the solid mineral phases into the groundwater, rather than dissolution of, or exchange with the groundwater accessible minerals in the aquifer, caused enrichment of groundwater 234U/238U activity ratios in the Boorthanna Formation. Decay of 238U in uranium-rich coatings on J aquifer sediments caused resistant phase 234U/238U activity ratio enrichment. The groundwater 234U/238U activity ratio is dependent on groundwater residence time or flow rate, depending on the flow path trajectory. Thus, uranium isotope variations confirmed earlier groundwater flow interpretations based on other tracers; however, spatial heterogeneity, and the lack of clear regional correlations, made it difficult to identify recharge and inter-aquifer leakage.
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Remmington, G. (2018). Transforming tradition: The aflaj and changing role of traditional knowledge systems for collective water management. Journal of Arid Environments, 151, 134–140.
Abstract: Living in a harsh, desert climate, Omani rural communities have developed locally-appropriate knowledge to deal with water scarcity. Similar to the qanat, the aflaj taps into the natural water table and uses a gravity system to channel water through underground channels to villages. Traditional techniques of water management, such as the aflaj, represents a way of adapting to and coping with difficult climates which have persisted for millennia. However, knowledge systems have often ‘decayed’ with the onset of modernity. These management systems, which developed concurrently with early Omani date palm cultivation, have defined customary and hereditary water rights which are in decline. This article uses Ostrom’s Common Pool Resource (CPR) framework, which prioritises the collective management of shared resources to maximise the benefit for all involved and avoid diminishing benefits that are created by the pursuit of individual goals. Using this framework, this article’s evaluation of the literature found that traditional aflaj management systems have a great capacity to evolve and, therefore, the aflaj represents both a dying system, and a potential for climate adaptation. Historically, aflaj have been managed by ancient water users associations, which provide social controls and govern usage norms. The findings of this review are that the aflaj system’s ability to respond to pressures of modernity from competing institutions, including markets, and embedded social capital mechanisms will influence its capacity to mitigate uncertain hydrology and climate. This article suggests ways in which the management of the aflaj can adapt to a multiple institutional framework to ‘transform’ collective water management.
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Nijsten, G. - J., Christelis, G., Villholth, K. G., Braune, E., & Gaye, C. B. (2018). Transboundary aquifers of Africa: Review of the current state of knowledge and progress towards sustainable development and management. Journal of Hydrology: Regional Studies, 20, 21–34.
Abstract: Study region Transboundary aquifers (TBAs) of Africa. Study focus Review of work on TBAs in Africa, including an overview of assessments and management efforts that have taken place over the last half century. New hydrological insights Seventy-two TBAs have been mapped in Africa. They underlie 40% of the continent, where 33% of the population lives, often in arid or semi-arid regions. TBA inventories have progressed since 2000 and remain work in progress. Despite their importance only eleven TBAs have been subjected to more detailed studies. Cooperation has been formalised for seven TBAs. Most of these TBAs are in North Africa and the Sahel. The recent global Transboundary Waters Assessment Programme compiled information at the national level to describe TBAs in terms of key indicators related to the water resource, socio-economic, and legal and institutional conditions. Availability of data at national level is low, hampering regional assessment. Comparing indicators, from questionnaire surveys, with those from a global water-use model showed variable levels of agreement, calling for further research. Reports on agreements scoping TBA management, indicate that this may be dealt with within international river/lake agreements, but reported inconsistencies between TBA sharing countries also indicate that implementation is limited. Increasing awareness and support to joint TBA management is noticeable amongst international organisations. However, such cooperation requires long-term commitment to produce impacts at the local level.
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Ardelt, G., Külls, C., & Hellbrück, H. (2018). Towards intrinsic molecular communication using isotopic isomerism. Open Journal of Internet Of Things (OJIOT), 4(1), 135–143.
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Li, X., Shen, K., Li, Q., Deng, Y., Zhu, P., & Wang, D. (2018). Roll-over behavior in current-voltage curve introduced by an energy barrier at the front contact in thin film CdTe solar cell. Solar Energy, 165, 27–34.
Abstract: Roll-over phenomenon in the current–voltage (J–V) curve is often observed in a CdTe thin film solar cell. The roll-over phenomenon, which is occurred near the open-circuit voltage in a light J–V curve, is due to Schottky energy barrier formed at the CdTe/metal interface in a CdTe solar cell back contact. In this study we report a J–V roll-over phenomenon which is induced by an energy barrier at the front contact of a CdTe solar cell. Two kinds of oxides, namely, Al2O3 and SnO2, were deposited as high-resistance transparent (HRT) layer between the window layer CdS and the fluorine doped tin oxide (FTO) front electrode in CdTe solar cells. These two oxides present much different electronic band alignment with FTO and CdS. SnO2 formed almost no energy barrier with CdS, this allowed smooth transport for photo-generated electrons from CdTe to CdS and FTO. However, Al2O3 formed a high energy barrier with CdS. The rather high energy barrier with a value of 3.43 eV at the CdS/Al2O3 interface induced a J–V roll-over phenomenon in a CdTe thin film solar cell, which dramatically led to a quick decrease for the cell device efficiency. The electron transport at the FTO/Al2O3/CdS interface is governed by tunneling effect. The results presented in this study demonstrate that the band structure at the front electrode plays an important role for the performance of a CdTe thin film solar cell.
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