Browsing by Author "Taylor, A"
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- ItemComplementarity of SANS,TEM and APT for the study of NbC and MnS precipitates in a direct strip cast steel(Australian Microscopy and Microanalysis Society, 2016-02-04) Dorin, T; Wood, K; Stanford, N; Taylor, A; Hodgson, PDOne of the main alloy design strategies to provide strengthening to low alloy steels is the deliberate addition of strong carbide forming elements such as Nb or Ti to form nano-precipitates with a carbide or carbo-nitride chemistry 1 . The addition of Mn is also common commercial practice to remove free sulphur from the steel. Thus, low alloy steels contain at least two chemically distinct precipitate populations, coarse manganese sulphides and fine carbo-nitrides. When steel alloys are processed by thin slab or direct strip casting (DSC), a significant decrease in the size of the sulphides is observed 2 and this is a direct consequence of the higher cooling rates experienced in these processes 3 . Since DSC is a relatively new processing technology 4 , the precise measurement of these nano-sulphides has not before been required, and very little information on this topic is available in the open literature. Small angle neutron scattering (SANS), atom probe tomography and electron microscopy have been used to investigate the MnS and Nb(C,N) precipitate populations in a low alloy steel processed by direct strip casting. Rapid cooling refined the sulphides, and both the SANS and atom probe tomography data indicate that sulphur is retained in solid solution after rapid cooling. A similar result is observed for the Nb-carbonitrides. The rapid cooling supresses precipitate formation, and only small Nb and N enriched clusters are able to form. These NbN clusters have a low volume fraction compared to the equilibrium condition in which classical Nb(C,N) precipitation is complete. Finally, we present a method to extract precipitate chemistry from the SANS data in order to validate the atom probe measurements on a statistically robust specimen volume.
- ItemFine-particle Mn and other metals linked to the introduction of MMT into gasoline in Sydney, Australia: results of a natural experiment.(Elsevier, 2005-11-01) Cohen, DD; Gulson, B; Davis, JM; Stelcer, E; Garton, D; Hawas, O; Taylor, AUsing a combination of accelerator-based ion beam methods we have analysed PM2.5 particulates for a suite of 21 species (H, C, Na, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Br, Pb) to evaluate the contribution to Sydney (New South Wales, Australia) air associated with the introduction of MMT as a replacement for lead. MMT was discontinued in 2004. Teflon filters representing continuous sampling for a 7 year period from 1998 to 2004 were analysed from two sites: one from Mascot, a suburb close to the Central Business District [CBD (n=718)] and a high trafficked area, and the other, a relatively rural (background) setting at Richmond, 20 km west of the CBD (n=730). Manganese concentrations in air at the background site increased from a mean of 1.5–1.6 ng m−3 to less than 2 ng m−3 at the time of greatest MMT use whereas those at Mascot increased from about 2 to 5 ng m−3. From the maximum values, the Mn showed a steady decrease at both sites concomitant with the decreasing use of MMT. Lead concentrations in air at both sites decreased from 1998 onwards, concomitant with the phase out of leaded gasoline, attained in 2002. Employing previously determined elemental signatures it was possible to adjust effects from season along with auto emissions and soil. A high correlation was obtained for the relationship between Mn in air and lead replacement gasoline use (R2 0.83) and an improved correlation for Mn/ Al+Si+K and lead replacement gasoline use (R2 0.93). In addition, using Mn concentrations normalized to background values of Al+Si+K or Ti to account for the lithogenically derived Mn, the proportion of anthropogenic Mn was approximately 70%. The changes for Mn and Pb detected in the particulates are attributed to the before-during-after use of MMT and decreasing use of lead in gasoline. The values measured in Sydney air are well below the reference concentration of 50 ng Mn m−3. The incremental increases in air, however, are larger than expected given the limited use of MMT only in lead replacement gasoline and high quality monitoring should be undertaken in countries where MMT is used in all gasoline. © 2005, Elsevier Ltd.
- ItemGroundwater recharge at the eastern intake beds of the Great Artesian Basin using multi-isotope studies(National Centre for Groundwater Research And Training, & Australian Chapter International Association Of Hydrogeologists, 2019-11-25) Sucknow, A; Deslandes, A; Gerber, C; Taylor, A; Raiber, M; Barrett, D; Meredith, KTObjectives: Large sedimentary basins with multiple aquifer systems, such as the Great Artesian Basin (GAB) in Australia, are difficult to study because of the very large time scales associated with groundwater flow. The GAB is the world’s largest and deepest artesian groundwater basin and has become increasingly stressed due to demand from multiple competing industries (agriculture, oil, coal and gas). Quantifying groundwater recharge is crucial for understanding the water balance for this economically and culturally important multi-aquifer system. The complexity of the GAB can only be dealt with by applying multiple lines of evidence including environmental isotopes, supported by hydrochemical, sedimentological, and geophysical observations. Design and Methodology: Three studies on the recharge areas of the GAB investigated recharge to the Hutton Sandstone and the Precipice Sandstone (QLD) and the Pilliga Sandstone (NSW). Multiple environmental tracers (major ion chemistry, 18O, 2H, 3H, 13C, 14C, 36Cl, 87Sr/86Sr, 85Kr, 81Kr, noble gases) were measured. Recharge rates were derived from tracer concentration profiles and aquifer cross-sections with porosity derived from previous studies. Conclusions: Tracer results in the Precipice Sandstone are consistent with pumping test data and re-injection of coal seam gas produced water, suggesting high hydraulic conductivities. They provided the first estimate of average long-term annual recharge to this deep confined aquifer, which is of a similar order of magnitude as today’s industrial re-injection of CSG water. © The Authors
- ItemHistory of metal contamination in Lake Illawarra, NSW, Australia(Elsevier, 2015-01-01) Schneider, L; Maher, W; Potts, J; Gruber, B; Batley, GE; Taylor, A; Chariton, AA; Krikowa, F; Zawadzki, A; Heijnis, HLake Illawarra has a long history of sediment contamination, particularly by metals, as a result of past and current industrial operations and land uses within the catchment. In this study, we examined the history of metal contamination in sediments using metal analysis and 210Pb and 137Cs dating. The distributions of copper, zinc, arsenic, selenium, cadmium and lead concentrations within sediment cores were in agreement with historical events in the lake, and indicated that metal contamination had been occurring since the start of industrial activities in Port Kembla in the late 1800s. Most metal contamination, however, has occurred since the 1960s. Sedimentation rates were found to be 0.2 cm year−1 in Griffins Bay and 0.3 cm year−1 in the centre of the lake. Inputs from creeks bringing metals from Port Kembla in the northeast of the lake and a copper slag emplacement from a former copper refinery on the Windang Peninsula were the main sources of metal inputs to Lake Illawarra. The metals of highest concern were zinc and copper, which exceeded the Australian and New Zealand sediment quality guideline values at some sites. Results showed that while historical contamination persists, current management practices have resulted in reduced metal concentrations in surface sediments in the depositional zones in the centre of the lake.© 2015, Elsevier Ltd.
- ItemMulti-isotope studies investigating recharge and inter-aquifer connectivity in coal seam gas areas (Qld, NSW) and shale gas areas (NT)(CSIRO Publishing, 2020-05-15) Suckow, A; Deslandes, A; Gerber, C; Lamontagne, S; Mallants, D; Davies, P; Taylor, A; Wilske, C; Smith, S; Raiber, M; Meredith, KT; Rachakonda, PK; Larcher, A; Wilkes, P; Prommer, H; Siade, A; Barrett, DLarge sedimentary basins with multiple aquifer systems like the Great Artesian Basin and the Beetaloo Sub-Basin are associated with large time and spatial scales for regional groundwater flow and mixing effects from inter-aquifer exchange. This makes them difficult to study using traditional hydrogeological investigation techniques. In continental onshore Australia, such sedimentary aquifer systems can also be important freshwater resources. These resources have become increasingly stressed because of growing demand and use of groundwater by multiple industries (e.g. stock, irrigation, mining, oil and gas). The social licence to operate for extractive oil and gas industries increasingly requires robust and reliable scientific evidence on the degree to which the target formations are vertically and laterally hydraulically separated from the aquifers supplying fresh water for stock and agricultural use. The complexity of such groundwater interactions can only be interpreted by applying multiple lines of evidence including environmental isotopes, hydrochemistry, hydrogeological and geophysical observations. We present an overview of multi-tracer studies from coal seam gas areas (Queensland and New South Wales) or areas targeted for shale gas development (Northern Territory). The focus was to investigate recharge to surficial karst and deep confined aquifer systems before industrial extraction on time scales of decades up to one million years and aquifer inter-connectivity at the formation scale. A systematic and consistent methodology is applied for the different case study areas aimed at building robust conceptual hydrogeological models that inform groundwater management and groundwater modelling. The tracer studies provided (i) in all areas increased confidence around recharge estimates, (ii) evidence for a dual-porosity flow system in the Hutton Sandstone (Queensland) and (iii) new insights into the connectivity, or lack thereof, of flow systems. © CSIRO 2020
- ItemRecent history of sediment metal contamination in Lake Macquarie, Australia, and an assessment of ash handling procedure effectiveness in mitigating metal contamination from coal-fired power stations(Elsevier, 2014-08-15) Schneider, L; Maher, W; Potts, J; Gruber, B; Batley, GE; Taylor, A; Chariton, AA; Krikowa, F; Zawadzki, A; Heijnis, HThis study assessed historical changes in metal concentrations in sediments of southern Lake Macquarie resulting from the activities of coal-fired power stations, using a multi-proxy approach which combines 210Pb, 137Cs and metal concentrations in sediment cores. Metal concentrations in the lake were on average, Zn: 67 mg/kg, Cu: 15 mg/kg, As: 8 mg/kg, Se: 2 mg/kg, Cd: 1.5 mg/kg, Pb: 8 mg/kg with a maximum of Zn: 280 mg/kg, Cu: 80 mg/kg, As: 21 mg/kg, Se: 5 mg/kg, Cd: 4 mg/kg, Pb: 48 mg/kg. The ratios of measured concentrations in sediment cores to their sediment guidelines were Cd 1.8, As 1.0, Cu 0.5, Pb 0.2 and Zn 0.2, with the highest concern being for cadmium. Of special interest was assessment of the effects of changes in ash handling procedures by the Vales Point power station on the metal concentrations in the sediments. Comparing sediment layers before and after ash handling procedures were implemented, zinc concentrations have decreased 10%, arsenic 37%, selenium 20%, cadmium 38% and lead 14%. An analysis of contaminant depth profiles showed that, after implementation of new ash handling procedures in 1995, selenium and cadmium, the main contaminants in Australian black coal had decreased significantly in this estuary. © 2014, Elsevier B.V.