ORCID Profile
0000-0002-7151-9788
Current Organisations
University of South Australia
,
Australian Council of Environmental Deans and Directors
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Publisher: Elsevier BV
Date: 07-2022
Publisher: Informa UK Limited
Date: 27-02-2023
Publisher: Elsevier
Date: 2013
Publisher: EDP Sciences
Date: 06-2023
DOI: 10.1051/0004-6361/202243511
Abstract: Context. The motion of stars has been used to reveal details of the complex history of the Milky Way, in constant interaction with its environment. Nevertheless, to reconstruct the Galactic history puzzle in its entirety, the chemo-physical characterisation of stars is essential. Previous Gaia data releases were supported by a smaller, heterogeneous, and spatially biased mixture of chemical data from ground-based observations. Aims. Gaia Data Release 3 opens a new era of all-sky spectral analysis of stellar populations thanks to the nearly 5.6 million stars observed by the Radial Velocity Spectrometer (RVS) and parametrised by the GSP-Spec module. In this work, we aim to demonstrate the scientific quality of Gaia ’s Milky Way chemical cartography through a chemo-dynamical analysis of disc and halo populations. Methods. Stellar atmospheric parameters and chemical abundances provided by Gaia DR3 spectroscopy are combined with DR3 radial velocities and EDR3 astrometry to analyse the relationships between chemistry and Milky Way structure, stellar kinematics, and orbital parameters. Results. The all-sky Gaia chemical cartography allows a powerful and precise chemo-dynamical view of the Milky Way with unprecedented spatial coverage and statistical robustness. First, it reveals the strong vertical symmetry of the Galaxy and the flared structure of the disc. Second, the observed kinematic disturbances of the disc – seen as phase space correlations – and kinematic or orbital substructures are associated with chemical patterns that favour stars with enhanced metallicities and lower [ α /Fe] abundance ratios compared to the median values in the radial distributions. This is detected both for young objects that trace the spiral arms and older populations. Several α , iron-peak elements and at least one heavy element trace the thin and thick disc properties in the solar cylinder. Third, young disc stars show a recent chemical impoverishment in several elements. Fourth, the largest chemo-dynamical s le of open clusters analysed so far shows a steepening of the radial metallicity gradient with age, which is also observed in the young field population. Finally, the Gaia chemical data have the required coverage and precision to unveil galaxy accretion debris and heated disc stars on halo orbits through their [ α /Fe] ratio, and to allow the study of the chemo-dynamical properties of globular clusters. Conclusions. Gaia DR3 chemo-dynamical diagnostics open new horizons before the era of ground-based wide-field spectroscopic surveys. They unveil a complex Milky Way that is the outcome of an eventful evolution, shaping it to the present day.
Publisher: Elsevier BV
Date: 2016
DOI: 10.1016/J.SCITOTENV.2015.08.124
Abstract: Complementary medicines have associated risks which include toxic heavy metal(loid) and pesticide contamination. The objective of this study was to examine the speciation and bioavailability of lead (Pb) in selected complementary medicines. Six herbal and six ayurvedic medicines were analysed for: (i) total heavy metal(loid) contents including arsenic (As), cadmium (Cd), Pb and mercury (Hg) (ii) speciation of Pb using sequential fractionation and extended x-ray absorption fine structure (EXAFS) techniques and (iii) bioavailability of Pb using a physiologically-based in vitro extraction test (PBET). The daily intake of Pb through the uptake of these medicines was compared with the safety guidelines for Pb. The results indicated that generally ayurvedic medicines contained higher levels of heavy metal(loid)s than herbal medicines with the amount of Pb much higher than the other metal(loid)s. Sequential fractionation indicated that while organic-bound Pb species dominated the herbal medicines, inorganic-bound Pb species dominated the ayurvedic medicines. EXAFS data indicated the presence of various Pb species in ayurvedic medicines. This implies that Pb is derived from plant uptake and inorganic mineral input in herbal and ayurvedic medicines, respectively. Bioavailability of Pb was higher in ayurvedic than herbal medicines, indicating that Pb added as a mineral therapeutic input is more bioavailable than that derived from plant uptake. There was a positive relationship between soluble Pb fraction and bioavailability indicating that solubility is an important factor controlling bioavailability. The daily intake values for Pb as estimated by total and bioavailable metal(loid) contents are likely to exceed the safe threshold level in certain ayurvedic medicines. This research demonstrated that Pb toxicity is likely to result from the regular intake of these medicines which requires further investigation.
Publisher: Elsevier BV
Date: 12-2016
DOI: 10.1016/J.SCITOTENV.2016.07.123
Abstract: The chemical characteristics of water in the Oratunga Area, Central Flinders Ranges, South Australia have been used to evaluate and determine the processes controlling water chemistry in addition to the sources of ions. The isotopic analysis results show that the groundwater is mainly meteoric. Based on the rock and water chemistry, ionic ratios, hydrochemical facies and saturation indices, the chemical evolution has been studied. The chemistry of groundwater revealed two types of water. Thus, in high topographic areas, low TDS, bicarbonate and mixed water types are dominated and support a rapid and direct recharge. While in the low topographic areas, high TDS and chloride compositions are the most common attributed to the accumulation of ions and groundwater evolution. Analysis of the ion concentration, head data and saturation indices shows a compositional trend that can be studied as an evolutionary system. The ionic ratios and hydrogeochemical modelling using NETPATH was used to quantify and verify the different hydrochemical processes. The resulting data shows that calcite dissolution recipitation and cation exchange reactions are the major processes affecting groundwater chemical evolution of the groundwater in the basin. This study has provided a basis for a better understanding of the hydrogeologic setting in areas of a little data.
Publisher: Springer Science and Business Media LLC
Date: 29-01-2016
Publisher: Informa UK Limited
Date: 12-02-2015
Publisher: Emerald
Date: 04-2014
DOI: 10.1108/IJSHE-09-2012-0079
Abstract: – This study investigated whether a course which focused on raising students' awareness of sustainability, from a balanced perspective, that is, one which gives equal consideration to the social and economic aspects as well as the environmental would produce graduates with the knowledge and commitment required to drive the sustainability agenda forward. The paper aims to discuss these issues. – An analysis of students' final entries in their reflective journal was used to explore whether their views on sustainability reflected a balanced view. – The findings of this research confirmed previous studies showed that initially students do have an enviro-centric bias. It also showed that despite experiencing a pedagogical approach which challenged views by encouraging discussion, debate, and reflection and which provided what was considered to be a balanced view of sustainability, many of the students still leaned towards an environmentally focused perspective of sustainability. – The conclusions are based on one data set but are supported by other data described in the paper. – The finding led the authors to conclude that a concerted holistic effort within and across courses is needed within tertiary institutions if students' views about sustainability are to be challenged. – The outcomes demonstrate that students' reflective journals can be used to gather information about the change in students' perceptions about sustainability.
Publisher: Elsevier BV
Date: 09-2014
DOI: 10.1016/J.BIORTECH.2014.02.123
Abstract: Several maturity indices were evaluated for in-vessel co-composting of chicken manure and pine sawdust with three different biochars. All the seven mixtures (piles) contained chicken manure and sawdust. Six of these piles contained biochar each biochar was added at two rates, 5% and 10% wet weight. The maturity of composts was assessed by C/N, dissolved organic carbon (DOC), seed germination, NO3(-)-N/NH4(+)-N, and the Solvita test. The C/N values of finished composts were from 31.5 to 35.7, which were much higher than the optimum value of 21 for matured compost. Nevertheless, the rest of the parameters indicated that the composts were matured. The C/N values were high because of the high amount of recalcitrant carbon present in the feedstocks: biochar and sawdust. Biochar treated piles showed higher respiration as well as decomposition of DOC indicating higher microbial activity. Use of biochar in composting may reduce NH3 emission and nitrate leaching.
Publisher: Elsevier BV
Date: 2016
DOI: 10.1016/J.CHEMOSPHERE.2015.05.065
Abstract: Two experiments were conducted where three biochars, made from macadamia nutshell (MS), hardwood shaving (WS) and chicken litter (CL), were co-composted with chicken manure and sawdust, and also incubated with a chicken litter based commercial compost. Biochars were added at the rates of 5% and 10% in the co-composting and 10% and 20% in the incubation experiment. The rates of biochar had no consistent effect on the change in element contents of composted- or incubated-biochars. The biochar C demonstrated recalcitrance in both composting and incubation systems. Composting increased the CEC of biochars probably due to thermophilic oxidation. The increases in CEC of WS and CL were 6.5 and 2.2 times, respectively, for composting. Translocation of elements, between biochar and compost medium, occurred in both directions. In most cases, biochars gained elements under the influence of positive difference of concentrations (i.e., when compost medium had higher concentration of elements than biochar), while in some cases they lost elements despite a positive difference. Biochar lost some elements (WS: B CL: B, Mg and S) under the influence of negative difference of concentrations. Some biochars showed strong affinity for B, C, N and S: the concentration of these elements gained by biochars surpassed the concentration in the respective composting medium. The material difference in the biochars did not have influence on N retention: all three netbag-biochars increased their N content. The cost of production of biochar-compost will be lower in co-composting than incubation, which involves two separate processes, i.e., composting and subsequent incubation.
Publisher: MDPI AG
Date: 16-03-2023
DOI: 10.3390/LAND12030698
Abstract: An in idual trace metal present in a soil at its ecological screening value or investigation level (trigger/threshold) is expected to cause phytotoxicity. However, phytotoxicity may be induced by a mixture of multiple metals, each present at a concentration lower than the corresponding investigation level. To investigate the accumulative impact of metals present below their in idual investigation levels, three successive phytotoxicity trials were conducted in a greenhouse using the triticale plant CrackerJack (Triticosecale rimpaui), a cereal crop, in a sandy acidic soil treated jointly with Cd, Cu, and Zn at various rates. Seed germination and seedling growth were monitored. The metal rates in the first two trials were either too toxic or nontoxic. In the third trial, it was found that the mixture of Cd, Cu, and Zn at rates of 2.5, 97.5, and 188 mg kg−1, respectively, did not affect seed germination, but caused a slight reduction in plant growth. Although metal concentrations used were lower than the Australian Ecological Investigation Level (Urban) for Cd, Cu, and Zn, which are 3.0, 100, and 200 mg kg−1, respectively, the reduction occurred due to synergy. It was concluded that, to enhance the usefulness of environmental investigation limits, the synergistic effects of multiple metals present at levels slightly below the established limits must be considered.
Publisher: Springer Science and Business Media LLC
Date: 21-07-2020
Location: Australia
No related grants have been discovered for Ian Clark.