Browsing by Author "Roach, R"
Now showing 1 - 6 of 6
Results Per Page
Sort Options
- ItemCave drip water solutes in south-eastern Australia: constraining sources, sinks and processes(Elsevier, 2019-02-15) Tadros, CV; Treble, PC; Baker, AA; Hankin, SI; Roach, RConstraining sources and site-specific processes of trace elements in speleothem geochemical records is key to an informed interpretation. This paper examines a 10-year data set of drip water solutes from Harrie Wood Cave, south-eastern Australia, and identifies the processes that control their response to El Niño-Southern Oscillation events which varies the site water balance. The contributions of aerosol and bedrock end-members are quantified via hydrochemical mass balance modelling. The parent bedrock is the main source for the drip water solutes: Mg, Sr, K and trace elements (Ba, Al, V, Cr, Mn, Ni, Co, Cu, Pb and U), while atmospheric aerosol inputs also contribute significantly to drip water trace elements and Na, K and Zn. A laboratory investigation evaluating water-soluble fractions of metals in soil samples and soil enrichment factors provided a basis for understanding metal retainment and release to solution and transport from the soil zone. These results identified the role of the soil as a sink for: trace metals, Na and K, and a secondary source for Zn. Further, soil processes including: cation exchange, K-fixation, metal adsorption to colloids and the release of Zn associated with organic matter degradation further modify the chemical composition of the resultant drip waters. This research is significant for the south-eastern Australian region, as well as other sites in a karst setting with clay-rich soil. In particular these results reveal that the response of drip water chemistry to hydroclimatic forcing is non-linear, with the greatest response observed when the long-term gradient in the cumulative water balance reverses. This longer-term drip water monitoring dataset is significant because it provides the pivotal framework required to reliably identify suitable trace element proxies for interpretation in geochemical speleothem records on multi-decadal timescales. © 2018 Crown Copyright © 2018 Published by Elsevier B.V.
- ItemChemical characterisation and source identification of atmospheric aerosols in the Snowy Mountains, south-eastern Australia(Elsevier, 2018-07-15) Tadros, CV; Crawford, J; Treble, PC; Baker, AA; Cohen, DD; Atanacio, AJ; Hankin, SI; Roach, RCharacterisation of atmospheric aerosols is of major importance for: climate, the hydrological cycle, human health and policymaking, biogeochemical and palaeo-climatological studies. In this study, the chemical composition and source apportionment of PM2.5 (particulate matter with aerodynamic diameters less than 2.5 μm) at Yarrangobilly, in the Snowy Mountains, SE Australia are examined and quantified. A new aerosol monitoring network was deployed in June 2013 and aerosol samples collected during the period July 2013 to July 2017 were analysed for 22 trace elements and black carbon by ion beam analysis techniques. Positive matrix factorisation and back trajectory analysis and trajectory clustering methods were employed for source apportionment and to isolate source areas and air mass travel pathways, respectively. This study identified the mean atmospheric PM2.5 mass concentration for the study period was (3.3 ± 2.5) μg m−3. It is shown that automobile (44.9 ± 0.8)%, secondary sulfate (21.4 ± 0.9)%, smoke (12.3 ± 0.6)%, soil (11.3 ± 0.5)% and aged sea salt (10.1 ± 0.4)% were the five PM2.5 source types, each with its own distinctive trends. The automobile and smoke sources were ascribed to a significant local influence from the road network and bushfire and hazard reduction burns, respectively. Long-range transport are the dominant sources for secondary sulfate from coal-fired power stations, windblown soil from the inland saline regions of the Lake Eyre and Murray-Darling Basins, and aged sea salt from the Southern Ocean to the remote alpine study site. The impact of recent climate change was recognised, as elevated smoke and windblown soil events correlated with drought and El Niño periods. Finally, the overall implications including potential aerosol derived proxies for interpreting palaeo-archives are discussed. To our knowledge, this is the first long-term detailed temporal and spatial characterisation of PM2.5 aerosols for the region and provides a crucial dataset for a range of multidisciplinary research. Crown Copyright © 2018 Published by Elsevier B.V.
- ItemENSO–cave drip water hydrochemical relationship: a 7-year dataset from south-eastern Australia(2020-05-26) Tadros, CV; Treble, PC; Baker, AA; Fairchild, IJ; Hankin, SI; Roach, R; Markowska, M; McDonald, JSpeleothems (cave deposits), used for palaeoenvironmental reconstructions, are deposited from cave drip water. Differentiating climate and karst processes within a drip-water signal is fundamental for the correct identification of palaeoenvironmental proxies and ultimately their interpretation within speleothem records. We investigate the potential use of trace element and stable oxygen-isotope (δ18O) variations in cave drip water as palaeorainfall proxies in an Australian alpine karst site. This paper presents the first extensive hydrochemical and δ18O dataset from Harrie Wood Cave, in the Snowy Mountains, south-eastern (SE) Australia. Using a 7-year long rainfall δ18O and drip-water Ca, Cl, Mg / Ca, Sr / Ca and δ18O datasets from three drip sites, we determined that the processes of mixing, dilution, flow path change, carbonate mineral dissolution and prior calcite precipitation (PCP) accounted for the observed variations in the drip-water geochemical composition. We identify that the three monitored drip sites are fed by fracture flow from a well-mixed epikarst storage reservoir, supplied by variable concentrations of dissolved ions from soil and bedrock dissolution. We constrained the influence of multiple processes and controls on drip-water composition in a region dominated by El Niño–Southern Oscillation (ENSO). During the El Niño and dry periods, enhanced PCP, a flow path change and dissolution due to increased soil CO2 production occurred in response to warmer than average temperatures in contrast to the La Niña phase, where dilution dominated and reduced PCP were observed. We present a conceptual model, illustrating the key processes impacting the drip-water chemistry. We identified a robust relationship between ENSO and drip-water trace element concentrations and propose that variations in speleothem Mg / Ca and Sr / Ca ratios may be interpreted to reflect palaeorainfall conditions. These findings inform palaeorainfall reconstruction from speleothems regionally and provide a basis for palaeoclimate studies globally, in regions where there is intermittent recharge variability. © Author(s) 2016.
- ItemReconstructing past environmental change at Yarrangobilly Caves(Sydney Speleological Society, 2016-01-01) Treble, PC; Markowska, M; Tadros, CV; Jex, CN; Coleborn, K; Dredge, J; Baker, AA; Roach, R; Spate, ANot available
- ItemUnsaturated zone hydrology and cave drip discharge water response: implications for speleothem paleoclimate record variability(Elsevier, 2015-10-01) Markowska, M; Baker, AA; Treble, PC; Andersen, MS; Hankin, SI; Jex, CN; Tadros, CV; Roach, RHigh-frequency, spatially-dense discharge monitoring was conducted over fifteen months to characterise unsaturated zone flow at Harrie Wood Cave (HWC), in the Snowy Mountains, Yarrangobilly (SE Australia). The cave was formed in the Late Silurian Yarrangobilly Limestone, a fractured rock associated with very low primary porosity due to past diagenesis. Over our monitoring period we simultaneously measured rainfall, soil moisture saturation and drip discharge rate at fourteen sites to characterise infiltration–discharge relationships. All drip discharge sites exhibited non-Gaussian distributions, indicating long periods where low discharge predominates, punctuated by short infrequent periods of high discharge. However, there was significant variability in discharge between sites and consequently no spatial correlation in the cave. We investigated the depth–discharge relationship at HWC and found a moderate relationship between depth and drip discharge lag (response) times to soil moisture content, but only weak relationships between depth and mean and maximum discharge. This highlights that the karst architecture plays an important role in controlling drip discharge dynamics. Principal Component Analysis (PCA) and Agglomerative Hierarchal Clustering (AHC) were used to classify similar drip types, revealing five unique drip regimes. Two-phase flow and non-linear response to recharge behaviour were observed, suggesting secondary porosity is controlling unsaturated zone flow in mature limestone environments with low primary porosity. Using the data presented here, the first coupled conceptual and box hydrological flow model was developed. This study highlights the heterogeneous nature of hydrological flow in karst and the need to understand unsaturated zone hydrology at the individual drip discharge level, to inform speleothem studies for high-resolution paleoclimate reconstruction. © 2015, Elsevier B.V.
- ItemUnsaturated zone hydrology and implications for paleo-climate speleothem reconstructions(Australian Government Department of Environment and Bureau of Meterology, 2014-06-26) Markowska, M; Treble, PC; Baker, AA; Andersen, MS; Jex, CN; Tadros, CV; Roach, R; Hankin, SISpeleothem growth relies on the supply of water which percolates from the surface, through the unsaturated zone and discharges into cavernous voids. The flow path of water feeding individual speleothems varies considerably depending on the karst architecture e.g. micro-fractures, solution pipes, structural voids in the karst, storage reservoirs, etc., all of which may alter the composition of drip waters over the flow route. By monitoring drip waters, we can determine: 1) unsaturated zone flow regimes; 2) connectivity between the surface and cave discharge zone; and 3) thresholds for groundwater recharge. This information can be used to identify suitable speleothems in caves for reconstruction of past climatic and hydrologic variability, at least over the last few thousand years of similar mean climate state. High-frequency, spatially-dense monitoring was conducted in Harrie Wood Cave, Yarrangobilly, Snowy Mountains over a 15 month period to characterise the flow regimes at 14 sites along a depth profile within the cave. Sites were monitored using acoustic drip loggers (stalagmates®). Discharge rates and response to significant rainfall events were highly variable between sites. A moderate relationship was found between decreasing discharge rates and increasing depth (r2 = 0.40). We suggest unsaturated zone storage and mixing, unrelated to depth, also have a significant impact on flow regimes. Using a statistical approach, five different drip types, which often had no spatial commonality, were identified. This information was used to inform the choice of speleothems for paleo-climate reconstruction, using stalagmites with differing hydrological regimes feeding growth, of which the preliminary data 18 will be presented here. The study highlights the need to understand unsaturated zone hydrology at the individual drip discharge level, prior to any speleothem study for paleo-climate, to truly appreciate the drip water signal it is recording. Copyright (C) The Authors.