ORCID Profile
0000-0002-8013-1793
Current Organisation
University of Adelaide
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Publisher: Elsevier BV
Date: 06-2014
DOI: 10.1016/J.JCONHYD.2014.03.003
Abstract: A severe drought from 2007 to 2010 resulted in the lowest river levels (1.75 m decline from average) in over 90 years of records at the end of the Murray-Darling Basin in South Australia. Due to the low river level and inability to apply irrigation, the groundwater depth on the adjacent agricultural flood plain also declined substantially (1-1.5 m) and the alluvial clay subsoils dried and cracked. Sulfidic material (pH>4, predominantly in the form of pyrite, FeS2) in these subsoils oxidised to form sulfuric material (pH<4) over an estimated 3300 ha on 13 floodplains. Much of the acidity in the deeply cracked contaminated soil layers was in available form (in pore water and on cation exchange sites), with some layers having retained acidity (iron oxyhydroxysulfate mineral jarosite). Post drought, the rapid raising of surface and ground water levels mobilised acidity in acid sulfate soil profiles to the floodplain drainage channels and this was transported back to the river via pumping. The drainage water exhibited low pH (2-5) with high soluble metal (Al, Co, Mn, Fe, Mn, Ni, and Zn) concentrations, in exceedance of guidelines for ecosystem protection. Irrigation increased the short-term transport of acidity, however loads were generally greater in the non-irrigation (winter) season when rainfall is highest (0.0026 tonnes acidity/ha/day) than in the irrigation (spring-summer) season (0.0013 tonnes acidity/ha/day). Measured reductions in groundwater acidity and increases in pH have been observed over time but severe acidification persisted in floodplain sediments and waters for over two years post-drought. Results from 2-dimensional modelling of the river-floodplain hydrological processes were consistent with field measurements during the drying phase and illustrated how the declining river levels led to floodplain acidification. A modelled management scenario demonstrated how river level stabilisation and limited irrigation could have prevented, or greatly lessened the severity of the acidification.
Publisher: Springer Science and Business Media LLC
Date: 27-07-2012
Publisher: Elsevier BV
Date: 07-2014
DOI: 10.1016/J.SCITOTENV.2014.03.063
Abstract: Acid sulfate soils with sulfuric material (pH 4) underlying this former floodplain occurred due to falling river and groundwater levels during the 2006-2010 extreme "millennium" drought. A low pH ( 3 years) following a return to pre-drought water levels.
Publisher: Elsevier BV
Date: 07-2022
DOI: 10.1016/J.CHEMOSPHERE.2022.134383
Abstract: Climate change is leading to global sea level rise. Storm surges and higher tides will generate short-term 'pulses' of seawater into freshwater systems, often for the first time in over 3000 years. The effect of increased seawater inundation upon soil geochemistry is poorly understood. We identified 12 sites in South Australia which are predicted to be inundated by seawater storm surges in the next 20 years. Within these 12 sites are three distinct environments fresh water streams and lakes, hypersaline saltmarsh and mangroves, and acid sulfate soils. Soils were inundated with seawater under laboratory conditions to replicate a short-term (two weeks) inundation by a storm surge. Lowering of redox potential and dissolution of high concentrations of reactive Mn and Fe in freshwater environments lead to the release of dissolved Fe and Mn in the soils from freshwater environments. Soils also released As, Cu, Ni, Cd and Co, while Zn and Pb were less mobilised. Concentrations of metals released exceeded water quality guidelines to protect freshwater aquatic ecosystems in most cases. By comparison, hypersaline soils only released minor amounts of Mn, Fe, Cd and Ni, and only in some of the soils. The moderately acidic acid sulfate soil (pH 5.41) reductively dissolved Mn and Fe releasing significant amount of Fe and Mn as well as As, Cu, Ni, Cd and Co, whereas almost all metal species decreased in the porewaters of the strongly acidic acid sulfate soil (pH 2.77). The response to short-term seawater inundation in acid sulfate soils was dependent upon the baseline soil acidification status. This study highlights the need for further research on seawater inundation of coastal soils as sea levels rise and storm surges penetrate further inland.
Publisher: Elsevier BV
Date: 04-2023
Publisher: Elsevier BV
Date: 12-2021
Publisher: Springer Science and Business Media LLC
Date: 23-11-2011
Publisher: Elsevier BV
Date: 06-2016
DOI: 10.1016/J.JCONHYD.2016.03.008
Abstract: An extreme hydrological drought in the Lower Lakes of the Murray-Darling Basin (Ramsar listed site) resulted in exposure of large areas of lake bed (25% of pre-drought lake area), containing the reduced iron (Fe) sulfide mineral pyrite. The pyrite oxidised and the resulting acidification (pH<4) posed risks of acid and metals entering shallow groundwater and potentially discharging to the remaining lake water body. Piezometer transects were installed at four locations and monitoring of the groundwater levels and quality was undertaken for six years from 2009 (drought) to 2014 (4years post-reinundation). Acidic (pH3-5) groundwater was recorded at three of the four piezometer locations and included sites close to the lake water. The acidic groundwater (0.5-2m below lake bed) at these sites is likely to have originated from the transport of acid from the upper oxidised sediment layer formed during the drought. High soluble metal (Fe, Al, Mn) levels were also recorded at acidic locations. Acidic shallow groundwater has persisted at many sites for over 4years following reinundation post-drought, and is likely due to slow diffusion and limited sulfate reduction. Increases in dissolved Fe and Mn with decreases in redox potential suggest that reductive dissolution of Fe and Mn hydrous oxides and Fe oxy-hydroxysulfate minerals (e.g. jarosite) occurred post-drought. Groundwater hydraulic head gradients were low, indicating there was limited potential for groundwater to discharge to the lake. The hydraulic gradients at all locations were dynamic with complex relationships along the near-shore environment. The results highlight the long lasting and severe effects on groundwater that can occur following hydrological drought in aquatic environments with sulfidic sediments.
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