Submission note: A thesis submitted in total fulfilment of the requirements for the degree of Doctor of Philosophy [to the] School of Life Sciences, Faculty of Science, Technology and Engineering, La Trobe University, Bundoora.
Acid sulfate soils(ASS) are an important environmental concern. Acidity from the oxidation of these sediments can be flushed into waterways following rainfall events, causing ecological and infrastructure degradation. Until recently, the distribution of ASS was believed to be predominantly coastal, but ASS are now recognised in inland environments. While knowledge of ASS has been growing, little of the published literature has been conducted on a regional scale, and this gap has been highlighted across many areas of Australia, including within the Corangamite Catchment Management Authority (CMA). Four sites were investigated on the Basalt Plains, where drainage patterns have been disrupted by lava flows: two sites are swamps and two sites are smaller depressions. The two swamps are waterlogged for longer periods of time than the smaller depressions; sufficient evaporation within the upper layer of the swamps allows precipitation of carbonate minerals, providing a buffering capacity in excess of any potential acidity generated by the sulfide minerals. The depressions contain no carbonate minerals, but only have very low levels of sulfides, and therefore will not undergo a large acidification. In the Otway Ranges, five sites were investigated: three occur in 'peat swamps' and two within the altered floodplain of the Barwon River. The three sites that occur in ‘peat’ swamps are currently oxidising due to seasonal fluctuation in the watertable [sic] and alteration of nearby creeks. There is a large potential for further oxidation, and analysis of the surface water at one of the ‘peat’ swamp sites (Boundary Creek) shows acid is leaching from the swamp. No carbonate minerals were found, and the sites have no ability to neutralise the acidity in‐situ. The two remaining sites on the altered floodplain of the Barwon River have only low levels of sulfides, and are unlikely to undergo acidification. Mapping of ASS is therefore important in determining areas potentially at risk. The Basalt Plains were excluded from the mapping due to the large buffering capacity within the sediments. Mapping of the Otway Ranges was conducted using LIDAR topography, geology and ecological vegetation maps (EVCs). Areas with slope angles of 0‐4° extracted from the LIDAR overestimated the potential areas for ASS to occur, and were constrained by using the pre‐existing EVC mapping overlaid on the LIDAR topography. The GIS mapping matched known ASS sites, indicating that the method developed for mapping these areas remotely is accurate.
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