Assessment of acid sulfate soil materials (Phase 2) Disher Creek (12254), South Australia

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Shand, Paul; Grocke, Sonia Grocke; Baker, Andrew; Smith, Lester; Fiebiger, Catherine; Cozens, Gillian; Wright, Claire; Smith, Julie; Gouzos, John; Smart, Michelle




An initial Phase 1 acid sulfate soil investigation of the Disher Creek (12254) wetland during April 2010 showed acid sulfate soils to be a priority concern within this wetland complex. Based on Phase 1 recommendations, a Phase 2 investigation was undertaken for the Disher Creek (12254) wetland to determine the nature, severity and the specific risks associated with acid sulfate soil materials. The wetland had dried during previous drought conditions, but had partially rewet at the time of sampling. The 24 hour reactive metals tests were undertaken to determine those metals and metalloids extractable with a moderately strong acid i.e. potentially available from binding sites on soil minerals such as iron (Fe), manganese (Mn) and aluminium (Al) oxides. Although comparisons can be made with soil and sediment quality guidelines, these are defined for total concentrations and not partial extractions. The results showed that concentrations were below the sediment quality guidelines (SQG) and soil ecological investigation levels (EIL) for those elements where guidelines are available. The exception was manganese which was very high in one profile studied. Although most metals and metalloids did not breach sediment quality guidelines and soil ecological investigation level trigger values, the concentrations of some elements were high enough that they may impact water quality if mobilised, particularly for iron (Fe), manganese (Mn) and aluminium (Al) and possibly vanadium (V). The contaminant and metalloid dynamics tests were undertaken to assess the release of metals during a water extraction, and to assess dynamics in response to saturation over time by incubating soil materials for periods of 1, 7, 14 and 35 days. The degree to which metal and metalloid concentrations exceed ANZECC/ARMCANZ guideline values was used to characterise the degree of hazard. For Disher Creek (12254), no metals or metalloids were assigned a moderate or high hazard with concentrations exceeding ANZECC/ARMCANZ environmental protection guidelines by more than 10 or 100 times. However, vanadium was slightly above the guideline value. The Disher Creek (12254) wetland has been classified as medium conservation status by the SA Murray-Darling Basin Natural Resources Management Board (Miles et al. 2010). The wetland was largely full at the time of sampling with one dry and one subaqueous soil studied. The tests undertaken for the subaqueous soil in this wetland are difficult to extrapolate to a case where the soils have dried and oxidised, as the generated acidity depends on a number of complex factors. In addition, it is not possible to predict the potential impacts of metal and metalloid release, as these may be present in reduced minerals such as pyrite and thus not easily released until oxidation occurs. The main hazards considered in this study that may impact on wetland values are acidification, contaminant mobilisation and deoxygenation. The wetland has been allocated a medium risk rating due to acidification and a low contaminant risk rating for soils. For surface waters, the risk is largely dependent on surface and sub-surface hydrology and is thus scenario dependent. Taking into account the range of likely scenarios, from very low flows (highest risk) to very high flows (lowest risk), the risk to surface waters in the wetland has been allocated medium risk rating for acidification and low risk rating for contaminant mobilisation. The risk associated with deoxygenation was determined as medium due to high levels of acid volatile sulfide and good connectivity to the river. In designing a management strategy for dealing with acid sulfate soils in Disher Creek (12254) wetland, other values and uses of the wetland need to be taken into account to ensure that any intervention is compatible with other management plans and objectives for the wetland. The data suggest that management options for acidification and deoxygenation should be consider

Murray-Darling Basin Authority


wetland; acid sulfate soil; Murray-Darling Basin; Water for a Healthy Country Flagship; Healthy Water Ecosystems

Environmental Management

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© Murray-Darling Basin Authority. Graphical and textual information in the work (with the exception of photographs and the MDBA logo) may be stored, retrieved and reproduced in whole or in part, provided the information is not sold or used for commercial benefit and its source is acknowledged. Reproduction for other purposes is prohibited without prior permission of the Murray-Darling Basin Authority, or the copyright holders in the case of photographs.

Water for a Healthy Country Flagship Report series ISSN: 1835-095X


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Shand, Paul; Grocke, Sonia Grocke; Baker, Andrew; Smith, Lester; Fiebiger, Catherine; Cozens, Gillian; Wright, Claire; Smith, Julie; Gouzos, John; Smart, Michelle. Assessment of acid sulfate soil materials (Phase 2) Disher Creek (12254), South Australia. Australia: Murray-Darling Basin Authority; 2011.

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