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This paper presents X-ray diffraction and SEM evidence for the formation of alunite, and possibly small quantities of natroalunite, within opal-A stalactites formed on quartz sandstone near Sydney in south-eastern, Australia. Alunite has been reported as a speleogenetic mineral from sediments within a number of caves around the world, but this is believed to be the first report of speleothemic alunite in opaline silica speleothems. Individual alunite crystals have not been visually identified, but SEM X-ray element mapping suggests the alunite has formed amongst kaolinite clay. Sedimentary alunite and natroalunite formation is usually associated with the reaction of sulphuric acid on illite, smectite and kaolinite clay materials. In this location groundwater sulphate levels are not high, but evaporative concentration of stalactite drip-water containing small amounts of sulphuric acid generated by oxidization of pyrite might lower the pH to a level sufficiently acidic for conversion of kaolinite or illite to alunite. The ferrolysis of hydrous Fe2+-oxides, or the biochemical activities of bacteria or other micro-organisms, also provide conceivable pathways for the generation of pH sufficiently low to contribute to alunite formation. The occurrence of alunite in these silica stalactites, whilst unusual, is consistent with the normal silica stalactite-forming process in this region, and in accord with observations of the authigenic formation of alunite and groundwater opal in weathering profiles elsewhere. INSET: 1. [ABSTRACT FROM AUTHOR]

Abstract: The waste intermodal station of Clyde, in the city of Sydney, Australia, is in the heart of a complex network of terminals connected by road and rail to transport urban waste from its first collection to its final disposal. The amount of waste the network is projected to handle in 2015 will increase from about 340,000tonnes/year in 2006 up to about 1.5million tonnes/year, following population and consumption raise. The paper proposes a discrete-event model to represent Clyde Transfer Station (TS) and its relations with the other terminals. Such a model allows one to evaluate the effects of different expansion plans of the station structures as well as different policies of the collection service. The results show that, as often happens, a careful consideration of management alternatives can decrease the necessity of structural enlargement, which is normally much more expensive, if at all possible. [Copyright &y& Elsevier]

Rainwater is a traditional but under-utilized water resource that has today had a resurgence due to the worldwide water crisis. This paper demonstrates the outcomes of research on the feasibility of rainwater use in high-rise residential envelopes for four Australian cities of Melbourne, Sydney, Perth and Darwin. Different climate patterns and various levels of water demand management were established for determination of storage dimensions; annual tank water use; reduction in both imported water flow and stormwater disposal; and water spillage from tanks. High level water demand management was a profoundly effective tool for reducing potable water supply, especially in combination with rainwater use. The economic feasibility of rainwater use systems were estimated; with Sydney having the shortest payback period compared to other cities either both with 3A rated appliances (8.6 years) or 5A ones installed (10.4 years). That was due to the higher and more consistent rainfall in Sydney. An outcome of this study was that Sydney was likely most suited to rainwater use, followed by Perth, Darwin, and then Melbourne. The objective of this study was to fill in the gap in estimating feasibility of rainwater use in various Australian cities. This investigation endeavors to provide assistance to water authorities and urban planners of Australian cities with the consideration of the potential of rainwater harvesting. [Copyright &y& Elsevier]