APPENDIX E Preliminary characterisation of Acid Sulfate Soils in

part of the Barker Inlet/ Gillman area Coastal Acid Sulfate Soils Program Demonstrating amelioration of Acid Sulfate Soils, Barker Inlet / Gillman area, South Australia

1Rob Fitzpatrick, 1Brett Thomas, 1Phil Davies and 1Richard Merry 1CSIRO Land & Water, Private Bag No. 2, Glen Osmond, South Australia, 5064

July 2001

Preliminary characterization of Acid Sulfate Soils in part of the Barker Inlet/ Gillman area

Contents 1. Introduction 3 2. Steps toward producing an ASS map of the Gillman area 3 2.1 Review published map information from which ASS can be inferred 3 2.1.1 Surficial geological and hydrological data 3 2.1.2 Vegetation 4 2.1.3 Digital aerial orthophotographs 4 2.2 Review published map information from which ASS has been identified 4 2.2.1 Potential Acid Sulfate Soils (PASS) or sulfidic materials 4 2.2.2 Actual Acid Sulfate Soils (ASS) or sulfuric horizons 5 2.3 New survey and soil profile data 6 2.4 Construction of ASS map 6 3 Conclusions 4. Acknowledgements 7 5. References 7 Consortium Members CSIRO Land and Water City of Port Adelaide Enfield Department of Environment and Heritage Land Management Corporation Penrice Soda Products Pty Ltd Salisbury Council St. Kilda Mangrove Trail and Interpretation Centre Torrens Catchment Water Management Board Northern Adelaide & Barossa Catchment Water Management Board

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1. Introduction

The full extent of the distribution of the various types of Potential and Actual Acid Sulfate soil that will generate problems if badly managed has not been evaluated in the Gillman area (Appendix B). Workers in CSIRO Land & Water have made preliminary estimates that there are 12 km2 of potential ASS (sulfidic materials at or the near the surface) and at least 2.5 km2 of actual ASS (sulfuric horizons present). These estimates require better definition and, importantly, an understanding of the thickness, or depth of the ASS layers. The total “size” of the potential problem needs to be evaluated in more detail. The lack of detailed information on ASS prompted characterisation and mapping to determine the extent of the deposition of ASS deposits in the small geographic area of Gillman (Figure 1). This can be achieved by conducting:

• more specific field soil investigations (profile descriptions and pedological interpretations),

• more detailed analyses on selected samples (chemical, mineralogical and physical),

• specific soil surveys to demarcate soil boundaries on orthophotographs to produce comprehensive soil maps, which can be overlain and correlated with the existing maps of sub-facies within the "Mangrove Facies and the Supratidal Marsh Facies" (Belperio and Rice, 1989).

This information will provide better definition and characterization of ASS, so as to develop strategies to deal with these materials in the future planning of the site. Location and characterization of the sulfuric horizons and sulfidic materials will enable better and most economical approaches to remediation to be developed and advice to be given on interception or neutralization actions that may be instituted to prevent movement of mobilized heavy metals and toxic materials to sensitive areas. 2. Steps towards producing an ASS map of the Gillman area

The following stages or steps were used to produce a detailed map of ASS in the small geographic area of Gillman (Figure 1). 2.1 Review published map information from which ASS can be inferred

2.1.1 Surficial geological and hydrological data

In the Gillman area Belperio and Rice (1989) have produced maps showing the extent

and thickness of both the "mangrove facies and supratidal marsh sediments" (Figure 1). These facies approximately coincide with the extent of the Potential Acid Sulfate Soils. However, some buried peaty layers are not confined to the "Mangrove Facies". These surficial facies, however, are mapped separately and were not interpreted to persist beneath some surface features such as deep stranded dune systems and certain landfills. Despite these anomalies, the coverage of the unit mapped as “Holocene Marine” sediments by Belperio and Rice (1989) currently provides the best “risk map” for the

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occurrence of potential acid sulfate soils within coastal areas of Adelaide. These maps give no reference to the presence of actual ASS. Bore water (Pavelic and Dillon, 1993a) and surface water (Harbison, 1986) acidity can also be used to indicate acidic hotspots or Actual ASS. 2.1.2 Vegetation

The location, potency and thickness of sulfidic materials is dependent on the type of organic matter being supplied to saturated / anoxic soils that are subject to tidal flushing (van Breemen, 1993). The correlation between intertidal vegetation and sulfidic materials can be used to infer the extent and reactivity of PASS and actual ASS using vegetation (Fotheringham 1994) and topographic maps in addition to soil profile/chemistry data. High concentrations of pyrite have built up in the tidal mangrove (Avicennia marina) swamps and samphire areas where slow sedimentation rates occur. Mangrove areas indicate thick sapric dominated sulfidic horizons occurring from the surface while samphires form thinner sulfidic horizons dominated by more fibric-like organic material and usually form a partly oxidized surface soil.

Mangrove dieback and elevated levels of hydrogen sulfide gas (H2S) (Coleman, 2001) in the area may be linked to the development of intense reducing conditions in the PASS (low redox potentials), which may be caused by eutrophication of the estuary. The strongly reducing conditions damage the pneumatophores of Avicennia marina, restricting their radial root systems and effecting their stability (Coleman personal communication). These soil processes need to be better understood and the current project intends to monitor redox and soil solutions in degraded areas. 2.1.3 Digital aerial orthophotographs

The distinction between vegetation types can be distinguished on aerial photographs. Digital aerial orthophotographs supplied by the GIS group at Port Adelaide Enfield Council were used to assist in the production of the ASS map below (Figure 6). Other techniques such as remote sensing (e.g. IR and Radar), which are enhanced by field mapping of vegetation will be used to improve the accuracy of the map. 2.2 Review published map information from which ASS has been identified 2.2.1 Potential Acid Sulfate Soils (PASS) or sulfidic materials The morphological, chemical and mineralogical properties of soils occurring in the tidal mangrove swamps at Gillman and St. Kilda are given by Fitzpatrick (1992) and Fitzpatrick et al. (1993; 1992). These organic soils contain more than 20% organic carbon and has a histic epipedon (diagnostic surface horizon) and hence classifies as a Histosol (Soil Survey Staff, 1999). These soils are formed in modern intertidal mangrove swamp deposits (Plate 1) and are underlain by unconsolidated Holocene

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coastal marine sediments (St. Kilda Formation), which consist of saturated, light grey, shelly and often silty or clayey sands. These Histosols contain sulfidic materials, because after aging in the laboratory for 8 weeks they dropped in pH by more than 0.5 pH unit to a pH of < 4 (determined in 1:1 by weight in water, or in a minimum of water to permit measurement - Soil Survey Staff, 1999). The organic carbon consisted dominantly of sapric organic material (i.e. highly decomposed organic matter). Consequently, these soils classify as Terric Sulfisaprists (Soil Survey Staff, 1999). Fitzpatrick et al. (1992, 1993) identified for the first time the presence of sapric material in sulfidic materials in these mangrove swamps and proposed the new subgroup "Terric Sulfisaprists". This proposal was accepted by USDA and included in the Keys to Soil Taxonomy (Soil Survey Staff, 1994; 1999). The “sapric” material is more finely divided and reactive than the coarser, “fibric” materials observed in tropical areas where decomposition rates are much faster. It is thought that the "sapric" materials in these soils form from input of detritus from seagrass and mangroves in the low energy environments of the Gulf St Vincent. It is also believed that intense reducing conditions (i.e. very low redox potential or Eh values -600 mv) occurring in the St Kilda area (Fitzpatrick et al. 1996) is caused by of increased nutrient loads (P. Coleman - personal communication).

More recently, the morphological, chemical and mineralogical properties of soils occurring in the supra-tidal salt-flat/ samphire area between the intertidal mangrove system on Garden Island was characterized (Fitzpatrick 2001 - Appendix C). The sulfidic material is strongly reducing (Eh is –120 to -200 mv) and contains fine grained pyrite, which oxidizes rapidly to form sulfuric acid when exposed to air. These Potential ASS represent stages in the geomorphic development of the estuarine system. The sulfidic material is currently forming and is in equilibrium because there is active tidal influence. These Potential ASS classify as Haplic Sulfaquents (Soil Survey Staff, 1996) and Sapric Histic-sulfidic Intertidal Hydrosol (Isbell 1996). 2.2.2 Actual Acid Sulfate Soils (ASS) or sulfuric horizons

In several parts of the Barker Inlet / Gillman area bunds were constructed across mangrove swamps nearly 50 years ago to cut off tidal flushing, which effectively drained areas (Figure 6). In these areas once the original potential ASS or Sulfisaprists were drained and oxidized, the organic carbon content declined and sulfuric acid was produced to form a wide range of actual Acid Sulfate soils (Fitzpatrick et al., 1992; 1996; Fitzpatrick and Mao 1997; Fitzpatrick and Self 1997). These actual Acid Sulfate soils have sulfuric horizons (pH <3.5) with bright yellow straw-coloured (2.5Y 8/6) mottles in the Btgj1 horizons, which is indicative of the presence of the mineral jarosite [KFe3(OH)6(SO4)2]. The presence of jarosite was confirmed using scanning electron microscopy, powder x-ray diffraction and DTA (Fitzpatrick et al. 1996). Samples also contained more than 0.75% sulfur with some samples containing over 5% sulfur. Although these soils have reduced levels of organic carbon, they still qualify as Histosols with dominantly of sapric organic material. Consequently, these soils classify as Terric Sulfosaprists (Soil Survey Staff, 1999), which Fitzpatrick (1992) identified for the first time and proposed new subgroup.

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A wide range of different types of Actual ASS has been identified in the bunded area (Fitzpatrick 1992; Fitzpatrick et al., 1992; 1993; 1996; Fitzpatrick and Mao 1997). The inherent risk of forming actual ASS is related to thickness of the underlying sulfidic material and its proximity to the surface and watertable, and the type of organic matter that they contain (potency). The transect C-B (location of cores shown in Figure 1) illustrates the location, depth and thickness of sulfidic materials and sulfuric horizons, and height of the water table (Figure 2; Table 1). Profile No. 1 has low organic carbon contents and consequently does not have a histic epipedon and classifies as a Hydraquentic Sulfaquepts (Soil Survey Staff, 1999). Profiles 2-6 and 9-18 all have sulfuric and salic horizons and are Salidic Sulfaquepts. Profiles 7 and 8 have sulfidic materials at depth, with 5-6 % carbon and are Haplic Sulfaquents. Profiles 19-21 have both Calcic and Petrocalcic horizons and are either Petrocalcic Xerochrepts or Petrocalcic Halaquepts.

The schematic cross-section (Figure 2) also illustrates the occurrence of carbonate-rich soils (Petrocalcic Xerochrepts) that are currently being dissolved by the development of immediately adjacent acid sulfate soils (Sulfaquepts). The Ca remaining after dissolution of the carbonates is retained in the system as gypsum crystals (Fitzpatrick et al., 1996; Fitzpatrick and Merry 1999).

The frequency of sulfidic materials and sulfuric horizons occurring below deep sands and dredged fill (>1m) is shown in the soil map (Figure 3). Table 1 indicates how these soil map units correlate with the geological data from Belperio and others. Dredged fill (up to three meters thick) from the Port Adelaide River and North Arm have provided foundation for developing industrial areas, levees and motorcycle tracks in the area (Figure 3).

2.3 New survey and soil profile data

Seven soil cores were taken and described across the survey site to extend the previously characterised transect shown in Figure 2. The location of cores and cross section (A-B) is shown in Figure 1 and extends the cross section (C-B) of Fitzpatrick et al. 1996. The core descriptions were used to construct a cross-sectional diagram (Figure 4) with the same legend as in Figure 2. The distribution of sulfidic materials and sulfuric horizons identified and mapped across this cross section correlate to those demarcated in cross section (C-B) and the facies mapped by Belperio and Rice (1989). 2.4 Construction of ASS map

The above information was combined to synthesized to produce mapping units (legend in Figure 6 and Tables 1 and 2). The map units were demarcated on the digital aerial orthophotograph (Figure 5). The boundaries were digitized and refined using "tonal pattern recognition" within a GIS framework (Figure 6). However, it is intended that this map will develop along with its legend from continued field and detailed laboratory characterization of soils.

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3. Conclusions

This map indicates that a range of acid sulfate and related soils occur in this relatively small geographic area because of the complex geomorphic framework, disturbed or drained areas; and different vegetation and landuses. The two transect diagrams confirm this and also illustrate the depth of ASS and the wide variety of soils encountered. This demonstrates that these Acid sulfate soils are not evenly distributed across the bunded area. Although not as severely affected, evidence of acid discharge can be found in discharge/overflow from windmills (Plate 2), creeks and drains (Plate 3) with evidence of iron precipitates and a low pH during periods of low flow. Sophisticated ASS management and site remediation plan for the entire bunded area is needed to reduce the environmental impact.

In conclusion, the Gillman site is one of many coastal areas in Australia and indeed the world, where past inappropriate practices undertaken through ignorance, have resulted in the formation of actual acid sulfate soils that are an ongoing environmental hazard. The challenge now is for local and state governments, industry and the community to implement the new National Strategy for the Management of Coastal ASS to allow for sustainable coastal development and primary industries while ensuring proper management of acid sulfate soils.

4. Acknowledgments

The authors would like to extend their gratitude to all consortium members who kindly donated their time and resources to locate and provide reference materials. In particular, we would like to thank Peri Coleman for fruitful discussions. Thanks to Shanti Ditter and the GIS group in Port Adelaide Enfield for providing the digital aerial orthophotograph (Figure 5). 5. References Belperio A. P. and Rice R. L. 1989. Stratigraphic Investigation of the Gillman

Development Site, Port Adelaide Estuary. Geological Survey. Department of Mines and Energy Geological Survey South Australia. Report Book 89/62.

Coleman, P. S. J. and Coleman, F. S., 2001. Effects of Anthropogenic (man-made)

Changes. Delta Environmental Consulting Report. Fitzpatrick R.W. (1992). Preliminary assessment of the properties and development of

saline acid sulfate soils at the Gillman MFP Australia site. Confidential Report to PPK Consultants. 9p.

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Fitzpatrick R.W. and P.G. Self (1997). Iron oxyhydroxides, sulfides and oxyhydroxysulfates as indicators of acid sulfate surface weathering environment. In: K. Auerswald, H. Stanjek and J.M. Bigham (eds.). Soils and Environment: Soil Processes from Mineral to Landscape Scale. Advances in GeoEcology 30: 227-240.

Fitzpatrick R.W. and R.H. Merry (1999). Pedogenic Carbonate Pools and Climate

Change in Australia p.105-119. In: R. Lal, J.M. Kimble, H. Eswaran and B.A. Stewart (eds.). “Global Climate Change and Pedogenic Carbonates”. CRC Press Lewis Publishers. Boco Raton. FL Proceedings of the International Workshop on Global Climate Change and Pedogenic Carbonates. Tunis, Tunisia. 13-17 October, 1997.

Fitzpatrick R.W., R.H. Merry, J. Williams, I. White, G. Bowman and G. Taylor (1998).

Acid Sulfate Soil Assessment: Coastal, Inland and Mine spoil Conditions. National Land and Water Resources Audit Methods Paper. p.18.

Fitzpatrick R.W., W.H. Hudnall, D.J. Lowe, D.J., Maschmedt and R.H. Merry (1992)

Proposed changes in the classification of Histosols, Alfisols, Andosols, Aridisols, Inceptisols, Mollisols, Entisols and Spodosols in South Australia. CSIRO Div. Soils Tech Report No. 51/1992. p.17.

Fitzpatrick R.W., W.H. Hudnall, P.G. Self and R. Naidu (1993). Origin and properties of

inland and tidal saline acid sulfate soils in South Australia. Selected papers of the Ho Chi Minh City Symposium on Acid Sulfate Soils (eds. D. L. Dent and M. E. F. van Mensvoort). International Inst. Land Reclamation and Development Publication 53, 71 - 80.

Fitzpatrick, R.W. and Mao R. (1997). Assessment of soils for landscaping of the Gillman

urban development site (Project No. V002-94-522M): MFP Southern boundary landscape structure plan. CSIRO Land and Water Consultancy Report 97-69.

Fitzpatrick, R.W., Cass, A. and Davies. P.J., 1996. Assessment of soils and fill materials

for landscaping Phase 1 of the Gillman Urban Development Site (Project No. V002-94-522M) Confidential Report to MFP Australia. CSIRO Div. Soils Tech Report No. 36/1996. 62p

Fotheringham, D., December 1994. A Vegetation Survey of Barker Inlet- Gulf St Vincent

South Australia. Management Issues and Recommendations. Harbison P., January 1986. An Assessment of the Pollution Status of the Ponding Basin

Area in the Vicinity of Magazine Creek and the North Arm. Department of Geology University of Adelaide.

Isbell, R.F. 1996. The Australian Soil Classification. CSIRO Publishing, Melbourne, 143

pp.

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Pavelic P. and Dillon P. J., December 1993a. Gillman – Dry Creek Groundwater Study, Volume 1. Final Report to MFP Australia. Centre for Groundwater Studies Report No. 54. Collaborating Organizations: CSIRO, Flinders University, Department of Mines and Energy and Water Supply Department. Unpublished report prepared for MFP Australia.

Soil Survey Staff, 1992. Keys to Soil Taxonomy, Fifth Edition. United States

Department of Agriculture, Soil Conservation Service, USA Soil Survey Staff, 1994. Keys to Soil Taxonomy, Sixth Edition. United States

Department of Agriculture, Soil Conservation Service, USA. Soil Survey Staff, 1996. Keys to Soil Taxonomy, Seventh Edition. United States

Department of Agriculture, Soil Conservation Service, USA Soil Survey Staff, 1998. Keys to Soil Taxonomy, Eighth Edition. United States

Department of Agriculture, Soil Conservation Service, USA Soil Survey Staff, 1999. Soil Taxonomy - a basic system of soil classification for making

and interpreting soil surveys, Second Edition. United States Department of Agriculture, Natural Resources Conservation Service, USA Agriculture Handbook No. 436 pp 869.

van Breemen, N. 1993. Environmental aspects of acid sulfate soils. In: Dent, D.L. and

van Mensvoort, M.E.F. (eds), Selected Papers of the Ho Chi Minh City Symposium on Acid Sulfate Soils, Mar. 1992, I.R.I. Pub. No. 53. pp. 391-402. Internat. Instit. For Land Reclam. and Imp. Wageningen.

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Table 1: Classification of materials found in cross section B-C shown in Figure 2

according to soil morphology, acidity and potential acidity, Soil Taxonomy (Soil Survey Staff, 1994) and Belperio and Rice (1989) (from Fitzpatrick et al. 1996)

Classification of materials/

soils layers according to acidity, potential acidity and morphology

Classification of horizons/ materials according to: Soil Taxonomy Belperio & Rice

Chemical, physical & mineralogical criteria

Pit No. Classification of soils according to Soil Taxonomy

1 No surface A1 and/or E horizons

Scalped for sand mining

Bare surface and salt effloresces

10, 13, 17, 18

2 Surface A1 horizon Ochric epipedon Supratidal marsh facies

pH >4 after aging for 8 weeks (i.e. no change); Sandy clay loam

1-9, 11, 12, 14-16, 19-21

3 Bleached E (or A2) horizon E horizon Supratidal sandy shoreface facies

pH >4 after aging for 8 weeks Sand - loamy sand

1-9, 11-18, 20, 21

4 Acid Sulfate Materials

Sulfuric horizon Supratidal Mangrove Facies

pH < 3.5; n-value > 0.7; jarosite mottles

1 Hydraquentic Sulfaquepts

5 Acid Sulfate Materials with severe salinity

Sulfuric and salic horizons Supratidal Mangrove Facies

pH < 3.5 EC 1:1 >30dS/m jarosite mottles

3, 5, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, Salidic Sulfaquepts

6 Acid Sulfate Materials with gypsum crystals, red mottles, shell fragments and severe salinity

Sulfuric and salic horizons Supratidal Mangrove Facies

pH 3.5 - 4.5 EC 1:1 >30dS/m, jarosite mottles, gypsum crystals

2, 4, 6 Salidic Sulfaquepts

7 Potential Acid Sulfate Materials

Sulfidic materials Supratidal Mangrove Facies

pH < 4 after aging for 8 weeks. pyrite framboids

7, 8 Haplic Sulfaquents

8 Soft carbonate (with no Acid Sulphate or Potential Acid Sulphate materials)

Calcic horizon Bk horizon Glanville Formation: Sandy Foreshore Facies

pH >4 after aging for 8 weeks (i.e. remains alkaline). carbonate-rich.

19, 20, 21 Petrocalcic Xerochrepts Petrocalcic Halaquepts

9 Calcrete (with no Acid Sulphate or Potential Acid Sulphate Materials)

Petrocalcic horizon Bkm horizon As above (Bakara calcrete)

Hard calcite 19, 20, 21 (as above)

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Gleyed clayey sand with fluctuating saline ground water table

Depth July, 1996 (1.2-2.6m) Supratidal sandy shoreface facies

Salinity (>10dS/m) 1-21 (ALL)

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Legend

Thickness of the mangrove facies

Soil Survey Sites at Gillman

0

A

B

C

ScaleFigure 1 (after Belperio & Rice, 1989) 1000m750500250

Not Present 0 – 0.5 m 0.5 – 1.0 m 1.0 – 1.5 m 1.5 – 2.0 m

Constructed Freshwater Wetlands

Saltwater Wetlands

Core Samples, this report (refer to cross-section A-B, figure 4) Core Samples, Fitzpatrick & Mao (1997) (refer to figure 3 and Table 1) Core Samples, Fitzpatrick et al, (1996) (refer to cross-section B-C, figure 2)

Figure 2

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Figure

3 Map showing soil pit localities and distribution of soil types in a portion of the Gillman area (for section location refer to Figure 1 and classification of soils refer to Table ) (from Fitzpatrick and Mao 1997).

Table 2 Classification of materials according to morphology, acidity and potential acidity, Soil

Taxonomy (Soil Survey Staff, 1996). The samples show the occurrence of ASS and PASS within the Mangrove Facies of Belperio and Rice, (1989) across a small area in the southwest of the Gillman study site (Fitzpatrick and Mao, 1997). Refer to Figures 1 and 3 for location of sample sites.

Pit No.

Soil layer classification: (Appendix 1) based in acidity, potential acidity and morphology

Soil Horizon classification : (Soil Taxonomy, 1996)

Chemical, physical & mineralogical criteria

Soil profile classification (Soil Taxonomy, 1996)

Geological profile classification (Belperio & Rice)

Layers with Acid Sulphate or Potential Acid Sulphate Materials: 7 Acid Sulfate Material

with severe salinity, gypsum crystals, red mottles & shell fragments

Sulfuric and salic horizon

pH 3.5 - 4.5 EC 1:1 >30dS/m, jarosite mottles, gypsum crystals

Salidic Sulfaquept Supratidal Mangrove Facies

1-9 Potential Acid Sulfate Material

Sulfidic material

pH < 4 after aging for 8 weeks. pyrite framboids

Haplic Sulfaquent Sulfic Endoaquent Sulfic Fluvaquent

Supratidal Mangrove Facies

No Layers with Acid Sulphate or Potential Acid Sulphate Materials: 1,3, 7,8, 8

Surface layer (with abundant organic matter and roots)

A horizon or Ochric epipedon

pH >4 after aging for 8 weeks (i.e. no change); Sandy clay loam

Supratidal marsh facies

6, 7 Subsurface bleached layer

E horizon (or A2)

pH >4 after aging for 8 weeks Sand - loamy sand

Supratidal sandy shoreface facies

6 Stripped surface & subsurface bleached layers because of sand mining

Scalped for sand mining

Bare surface and salt effloresces

1-5 8,9

Soft carbonate (with no Acid Sulphate or Potential Acid Sulphate materials)

Calcic horizon Bk horizon

pH >4 after aging for 8 weeks (i.e. remains alkaline). carbonate-rich.

Aquic Xerofluvent

Glanville Formation: Sandy Foreshore Facies

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A Soil Profile (Drill hole)

1.0 --

0.8 --

0.6 --

0.4 --

0.2 --

0 - -

-0.2 - -

-0.4 --

-0.6 --

-0.8 --

-1.0 --

-1.2 --

-1.4 --

-1.6 --

-1.8 --

-2.0 --

-2.2 --

-2.4 --

-2.6 --

-2.8 --

-3.0 -

B

4

3

Schematic cGillman St

showing the dis(A-B

Surface A Bleached Sulfuric a gypsum shells a Sulfuric h with ja Sulfidic m (Potent Gleyed cl Stranded (Light Light bro (Glanv Surface w Core Sam Core Sam

Depth

(m AH

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Distance (m)0 200 400 600 800 1000 m

ross-section of the udy Site,Adelaide tribution of soil layers, figure 1)

1 horizon (organic)

E1 horizon

nd Salic horizons with jarosite, , ferrihydrite-rich red mottles,

nd severe salinity

orizon (pH<3.5) rosite-rich yellow mottles

aterial ial Acid Sulfate Soil)

ayey sand (grey)

Sandy Foreshore Facies brown, clean sand)

wn/grey, stiff clay ille Formation)

ater Watertable (May 2001)

ple: this report

ple: Fitzpatrick et al. (1996)

Figure 4

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Plate 1. Potential Acid Sulfate soil formed in modern intertidal mangrove (Avicennia marina) swamp sediments. Sulfidic material is shown in the core. The organic carbon consists dominantly of sapric organic material (i.e. highly decomposed organic matter). Consequently, these soils classify as Terric Sulfisaprists (Soil Survey Staff, 1999).

Plate 2. Evidence of iron oxide minerals (ferrihydrite) precipitating from acidic groundwater discharging from sulfidic material through windmill outlets in the Range freshwater artificial wetlands constructed in Acid Sulfate Soils.

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Plate 3. Sulfidic material (black muds) oxidising and producing iron oxide mineral (ferrihydrite) precipitates and low pH water in drains and creeks during periods of low flow.

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