Browsing by Author "McGowan, HA"

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    Atmospheric pollutants in alpine peat bogs record a detailed chronology of industrial and agricultural development on the Australian continent
    (Elsevier, 2010-05-01) Marx, SK; Kamber, BS; McGowan, HA; Zawadzki, A
    Two peat bogs from remote alpine sites in Australia were found to contain detailed and coherent histories of atmospheric metal pollution for Pb, Zn, Cu, Mo, Ag, As, Cd, Sb, Zn, In, Cr, Ni, Tl and V. Dramatic increases in metal deposition in the post-1850 AD portion of the cores coincide with the onset of mining in Australia. Using both Pb isotopes and metals, pollutants were ascribed to the main atmospheric pollution emitting sources in Australia, namely mining and smelting, coal combustion and agriculture. Results imply mining and metal production are the major source of atmospheric metal pollution, although coal combustion may account for up to 30% of metal pollutants. A novel finding of this study is the increase in the otherwise near-constant Y/Ho ratio after 1900 AD. We link this change to widespread and increased application of marine phosphate fertiliser in Australia's main agricultural area (the Murray Darling Basin). Detailed records of atmospheric metal pollution accumulation in Australia are presented and are shown to trace the industrial and agricultural development of the continent. © 2010, Elsevier Ltd.
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    Coherent patterns of environmental change at multiple organic spring sites in northwest Australia: evidence of Indonesian-Australian summer monsoon variability over the last 14,500 years
    (Elsevier, 2018-09-15) Field, E; Tyler, JJ; Gadd, PS; Moss, PT; McGowan, HA; Marx, SK
    At present, knowledge of late Quaternary variability of the Indonesian-Australian summer monsoon in the Australian tropics is limited. Organic spring deposits, which occur throughout the Kimberley region of northwest Australia, are valuable archives that contain records spanning the past ∼14,500 years. In this study we compare multiple proxies from three organic springs. Principal Components Analyses demonstrates similar patterns of change in the elemental and non-pollen palynomorph (NPP) datasets between the springs, implying regional drivers are responsible for changes in these proxies. By comparison, the pollen records differ between each of the springs, with the assemblage at each thought to be influenced by spring recharge and evolution rather than climate variability. In order to empirically and objectively assess the synchronicity of changes, we applied Monte Carlo empirical orthogonal function (MCEOF) analysis to one variable in each μXRF and NPP dataset (Si/Ti ratios and Pseudoschizaea accumulation rates, as these proxies are expected to reflect hydrological conditions in springs) to assess regional patterns of change in site moisture. This analysis revealed periods of increased monsoonal precipitation from ∼14,500–7500 cal. yr BP corresponding with deglacial sea level rise, high orbital tilt coupled with warmer sea surface temperatures, and with possible links to a southward migration of the Inter Tropical Convergence Zone (ITCZ) during the Younger Dryas. Monsoonal precipitation was reduced from 7500 cal. yr BP coinciding with the culmination of deglacial sea level rise and a possible northward shift in the mean position of the ITCZ, in addition to between 2600 and 1000 cal. yr BP corresponding with increased moderate-to-strong ENSO events. ©2018 Elsevier Ltd
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    Evidence of wet-dry cycles and mega-droughts in the Eemian climate of southeast Australia
    (Springer Nature, 2020-10-22) McGowan, HA; Campbell, M; Callow, JN; Lowry, A; Wong, HKY
    Understanding past climate variability is critical to informing debate of likely impacts of global warming on weather and climate, and water resources. Here we present a near annual resolution reconstruction of climate developed from a speleothem that spans the Eemian [Marine Isotope Stage 5e (MIS 5e)] from 117,500 to 123,500 years BP—the most recent period in the Earth’s history when temperatures were similar to those of today. Using 25 Mg, 88Sr, and 137Ba as proxies, we show the first indication of solar and teleconnection cyclic forcing of Eemian climate in southeast Australia, a region at present often affected by severe drought and bushfires. We find evidence for multi-centennial dry periods interpreted as mega-droughts, and highlight the importance of understanding the causes of these in the context of a rapidly warming world, where temperatures are now, or projected to exceed those of the Eemian. © The Author(s) 2020
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    A landscape-scale approach to examining the fate of atmospherically derived industrial metals in the surficial environment
    (Elsevier, 2015-02-01) Heijnis, H; Stromsoe, N; Marx, SK; McGowan, HA; Callow, JN; Zawadzki, A
    Industrial metals are now ubiquitous within the atmosphere and their deposition represents a potential source of contamination to surficial environments. Few studies, however, have examined the environmental fate of atmospheric industrial metals within different surface environments. In this study, patterns of accumulation of atmospherically transported industrial metals were investigated within the surface environments of the Snowy Mountains, Australia. Metals, including Pb, Sb, Cr and Mo, were enriched in aerosols collected in the Snowy Mountains by 3.5–50 times pre-industrial concentrations. In sedimentary environments (soils, lakes and reservoirs) metals showed varying degrees of enrichment. Differences were attributed to the relative degree of atmospheric input, metal sensitivity to enrichment, catchment area and metal behaviour following deposition. In settings where atmospheric deposition dominated (ombrotrophic peat mires in the upper parts of catchments), metal enrichment patterns most closely resembled those in collected aerosols. However, even in these environments significant dilution (by 5–7 times) occurred. The most sensitive industrial metals (those with the lowest natural concentration; Cd, Ag, Sb and Mo) were enriched throughout the studied environments. However, in alpine tarn-lakes no other metals were enriched, due to the dilution of pollutant-metals by catchment derived sediment. In reservoirs, which were located lower within catchments, industrial metals exhibited more complex patterns. Particle reactive metals (e.g. Pb) displayed little enrichment, implying that they were retained up catchment, whereas more soluble metals (e.g., Cu and Zn) showed evidence of concentration. These same metals (Cu and Zn) were depleted in soils, implying that they are preferentially transported through catchments. Enrichment of other metals (e.g. Cd) varied between reservoirs as a function of contributing catchment area. Overall this study showed that the fate of atmospherically derived metals is complex, and depends upon metal behaviour and geomorphic processes operating at landscape scales. © 2014 Elsevier B.V.