Acid Sulfate Soils

ACID SULFATE SOILS

TANNUM SANDS – GLADSTONE AREA

D J Ross

Department of Natural Resources & Mines Queensland 2004

QNRM04285 ISBN 1 921062 00 2

While all care has been taken in the preparation of this report, neither the Department of Natural Resources and Mines nor its officers or staff accepts any responsibility for any loss or damage that may result from any inaccuracy or omission in the information contained herein.

Department of Natural Resources & Mines PO Box 1762 ROCKHAMPTON QLD 4700

ii Contents

List of figures, tables and maps iv

Summary v

1. Introduction 1

2. Survey area 2

3. Methods 4

4. Description of the soil map units 5

4.1 Actual Acid Sulfate Soils on Relatively Undisturbed Land 5

4.2 Potential Acid Sulfate Soils on Relatively Undisturbed Land 11

4.3 Acid Sulfate on Relatively Undisturbed Land 14

4.4 Acid Sulfate on Disturbed Land 15

4.5 Land with a Low Probability of Acid Sulfate Soil Occurrence 18

5. Discussion 20

6. Acknowledgments 23

7. References 24

APPENDIX Chemical data for selected depth samples 26

iii List of figures

Figure 1. Location of the survey area. 2

Figure 2. Gouge auger sampling, supratidal flat, Calliope River. 6

Figure 3. Geoprobe core sampling, terraced alluvium, Boyne River. 6

Figure 4. Gum-topped box woodland with AASS, Blain Park. 6

Figure 5. Typical bare saltpan with samphire on slightly elevated margins, A0S0 map unit. 10

Figure 6. Greyish brown AASS layer with jarosite, greenish grey PASS layer. 10

Figure 7. Marine couch flat above saltpan west of Calliope River, A1S1 map unit. 10

Figure 8. Mangrove thicket Fishermans Landing, S0 map unit. 12

Figure 9. Supratidal and extratidal areas of S1/S2 map unit, Boat Creek. 12

Figure 10. Extratidal flat along the Calliope River, S2 map unit. 12

Figure 11. Bleached white and brown fine sands, greenish grey PASS layer, SLAN map unit. 16

Figure 12. Sampling in back-channel below high terrace of Boyne River, LP5 map unit. 16

Figure 13. Brown sandy loam, greenish grey PASS layer over non-pyritic river gravels. 16

Figure 14. Auckland Inlet 1996. 17

Figure 15. Auckland Inlet 1959. 17

List of tables

Table 1. Area of map units. 8

Table 2. Retained acidity for selected samples with jarosite. 21

Table 3. Acid sulfate hazard classes. 23

List of maps

Acid Sulfate Soil Sampling Sites (1:50 000 scale).

Acid Sulfate Soils (1:50 000 scale).

Acid Sulfate Hazard (1:50 000 scale).

iv Summary

Mapping of acid sulfate soils has been undertaken for a section of the Central Queensland coast from Tannum Sands to Fishermans Landing, at 1:50 000 scale. The mapping identifies areas of both actual acid sulfate soils and potential acid sulfate soils and their respective depth of occurrence. The majority of land containing acid sulfate soils consists of tidal flats with an elevation of less than 3m Australian Height Datum.

In the Tannum Sands-Gladstone area, there are 3,471 ha of land mapped with acid sulfate soils. Actual acid sulfate soils total 1,466.5 ha in area, and potential acid sulfate soils 2,004.5 ha. A further 1,820 ha of disturbed land is likely to contain acid sulfate soils.

Descriptions of the acid sulfate soil map units are presented in this report. Chemical data for selected depth samples are appended. Sample site location is illustrated on the accompanying Sampling Sites map. The distribution of acid sulfate soils is shown on the Acid Sulfate Soils map.

An additional map presenting acid sulfate soil hazard has also been included. This map is an interpretation of the acid sulfate soil mapping in which land is classified into four classes of acid generation potential. The four classes are very low, low, moderate and high. The distribution of soils with potential for acid generation is shown on the Acid Sulfate Hazard map.

The acid sulfate soils range in texture from fine sands to heavy clays, are seasonally wet or saturated and have a shallow or perched watertable. Potential acid sulfate soils are typically greenish grey to dark grey in colour with decomposed organic fragments.

Eighty-eight percent of the area assessed with actual and potential acid sulfate soils, has acid sulfate soil layers within 0.5m depth of the soil surface. Layers of high acid generation potential occur within 0.5m depth of the soil surface over much of the area.

Oxidisable sulfur levels of up to 6.4% and potential acidities to 4,497 mol H+/t were recorded on an extratidal flat. At slightly lower elevations the supratidal flats had up to 5.5% oxidisable sulfur and potential acidities to 3,914 mol H+/t. Intertidal flats contain up to 5.4% oxidisable sulfur and potential acidities to 3,584 mol H+/t. High levels of sulfur at shallow depth in the intertidal zone are associated with the mangrove genus Rhizophora.

Retained acidity or net acid soluble sulfur levels of up to 2.7% occur in jarosite layers of actual acid sulfate soils. Gum-topped box and ironbark communities were recorded on strongly acid, almost fully oxidised acid sulfate soils.

v 1. Introduction

Acid sulfate soils (ASS) are soils or sediments containing sulfides or an acid producing soil layer as the result of the oxidation of sulfides. They commonly occur on low-lying very poorly drained coastal land at elevations less than 5m AHD (Australian Height Datum). Excavating soil or sediment, extracting groundwater or the filling land may cause disturbance of acid sulfate soils. When exposed to air, sulfides oxidise to produce sulfuric acid. Disturbed land can release acid, aluminium, iron and heavy metals into drainage waters affecting aquatic plants and animals. Concrete and steel infrastructure including pipes, foundations, house slabs and bridges are susceptible to acidic corrosion leading to accelerated structural failure (Ahern et al.1998).

Both actual acid sulfate soils (AASS) and potential acid sulfate soils (PASS) occur throughout the survey area. AASS are soils or sediments containing highly acidic soil horizons or layers caused by the oxidation of soil materials that are rich in iron sulfides, primarily pyrite. This oxidation produces hydrogen ions in excess of the sediments capacity to neutralise the acidity, resulting in soils or sediments of pH 4 or less. PASS are soils or sediment containing iron sulfides or sulfidic material that have not been exposed to air and oxidised. The field pH of these soils or sediment in their undisturbed state is pH 4 or more, and may be neutral or slightly alkaline (Anon. 2002).

The survey area is located at Gladstone on the Central Queensland coast (Figure1). It covers the mainland section of the Curtis Coast from Wild Cattle Creek (south of Tannum Sands) to Fishermans Landing, north of Gladstone. The lower estuary of the Boyne and Calliope Rivers form part of the survey area. The coastline is largely characterised by mangrove mudflats, saltpans and port facilities. Deep-water channels enable international port facilities and support tourism, recreation and commercial fishing. Excluding the low rises and headlands of country rock, the survey area is approximately 7,000 hectares.

A reconnaissance survey of acid sulfate soils along the southern part of the Central Queensland coast (Ross 2002) had identified acid sulfate soils at several locations from Wild Cattle Creek to Fishermans Landing in the current survey area, and that information is used in the map compilation. Prior to the current survey, no acid sulfate soil mapping had been undertaken along the Curtis Coast. This mapping project has been undertaken at a scale of 1:50 000, which represents a medium intensity survey with the suitability of information limited to planning purposes. Map unit description and chemical data from laboratory analyses are presented in this report.

A number of land use activities which could disturb potential acid sulfate soils are present in the Tannum Sands-Gladstone area. These include land reclamation, dredging, pipelaying, housing development, and the construction of roads, bridges and boat ramps. The mapping project was undertaken by the Department of Natural Resources and Mines because of the known occurrence of acid sulfate soils with high acid generation potential and the likelihood of acid sulfate soil disturbance within this rapidly developing area. Disturbance of high risk acid sulfate soils, if they cannot be avoided, may result in very high treatment costs.

2. Survey area

The coastline from Tannum Sands to The Lillies, Boyne Island is largely made up of narrow sandy beaches adjoining country rock or mangrove mudflat. North of The Lillies to Fishermans Landing the coastline consists of mangrove mudflats and saltpans, port facilities and the occasional headland of country rock. Landward of the coastline lie the extensive estuaries of the Boyne River, South Trees Inlet and the Calliope River. Smaller but significant estuaries in area include Auckland Inlet and Wild Cattle Creek. The estuaries are typically clayey mangrove mudflats and saltpans with mangrove lined channels extending into the bare saltpans. Marine couch flats and tea tree wetlands are minor in extent.

2 The primary focus of the acid sulfate soil investigation in this survey are the pyritic sediments that were deposited in the Holocene period, that is, during the last 10,000 years. Experience in coastal stratigraphic mapping shows that similar, but much older pyritic sediments of Pleistocene age can occur, still in a reduced (anaerobic) state, being buried under either cemented sands or old, consolidated alluvium. They are far less common than the Holocene equivalents, and have been found beneath land whose surface is both above and below 5m AHD. Generally, Pleistocene sediments will be found at greater depths below the surface than equivalent Holocene sediments.

In geomorphic terms the estuaries along the Curtis Coast represent a series of drowned valleys submerged with rising sea levels (QHED 1994). Filling of the valleys with sediments from both fluvial and marine sources would have occurred during Holocene (last 10,000 years) sea level rise. The landforms present today of predominantly tidal flats of fine sediment indicate low energy deposition of a marine dominated rather than a fluvial dominated depositional regime. At some locations, for example Callemondah, the change from marine to fluvial sedimentation in low lying areas occurs over very short distances and represents the boundary between acid sulfate soils and non-acid sulfate soils. Deep drilling to 9m depth on Black Harry Island indicates a thickness of the pyritic sediments of up to 6m and non-pyritic sand and gravel sediments below.

Broad scale geological mapping of the survey area has been undertaken by Donchak and Holmes (1981) and updated by Crouch et al. (2001). The local country rock consists mainly of Devonian Carboniferous age mudstone, sandstone and chert of the Curtis Island Group. Sulfide bearing rock is not indicated. Most of the pyritic sediments are contained in Quaternary (Holocene) estuarine mud and sand deposits in mangrove flats and saltpans at elevations <5m AHD. There is a minor occurrence of pyrite at depth in a back-channel within the intermediate terrace (Quaternary alluvia) of the Boyne River. Beach ridge sand deposits generally overlie pyritic sediments with carbonate materials.

The highest astronomical tide (HAT) level or predicted tide level for the port of Gladstone is 2.27m AHD and 2.7m AHD at Boat Creek, The Narrows (QHED 1994). The elevation at which pyritic sediments or acid sulfate soils are likely to occur throughout the survey area is expected to be closely related to HAT, for areas with accommodation for marine deposition during former sea level rise. Accurate elevation, data for the sampling sites is not available, however previous studies and contour data indicate most of the occurrence is below an elevation of 5m AHD. An investigation of acid sulfate soils near Boat Creek by GeoCoastal Australia estimated the upper level of pyritic sediment occurrence to be 2.5m AHD (T. Graham pers. comm.).

Port Curtis (Gladstone Harbour) is the ocean port for the city of Gladstone and nearby urban centres of Boyne Island and Tannum Sands. Port infrastructure on reclaimed land comprises a major land use within the survey area from South Trees Point to Fishermans Landing. Much of the economic activity is industrial processing plants located at Boyne Island, Parsons Point and the Yarwun Industrial Area. Light industries including fabrication, transportation, construction and manufacturing represent a significant land use. Recreational fishing in the streams and channels of the Boyne and Calliope River estuaries is a significant activity.

3 3. Methods

Sites for description and assessment were selected using a free survey technique (Reid 1988) with the aid of 1:25 000 scale colour aerial photographs and orthophoto maps. Boundaries of disturbed lands likely to contain acid sulfate soils were determined from field observation and interpretation of 1959 1:23 800 scale black and white aerial photographs. The accompanying acid sulfate soil map has been compiled at 1:50 000 scale and meets the sampling requirements for medium intensity soil mapping. Areas with actual acid sulfate soils (AASS) and / or potential acid sulfate soils (PASS) at various depths are delineated on the map from field observation and interpretation. Acid sulfate soil information collected during a previous reconnaissance survey (Ross 2002) was used in the compilation. The map reference was adopted from the Queensland Acid Sulfate Soil Investigation Team (QASSIT) with minor modification to suit the survey area results. Site and soil description follows the Australian Soil and Land Survey Field Handbook (McDonald et al. 1990).

Much of the sampling was undertaken using 75mm diameter stainless steel Dormer hand augers. Saturated clays from mangrove flats and saltpans were sampled with a 60mm diameter gouge auger to 1.8m depth or to the depth of hand penetration (Figure 2). Hydraulically driven stainless steel push tubes (75mm diameter) combined with tapered gouge augers (73, 60 and 48mm diameter) and push rods were used to sample sites with clay suitable sediments and vehicle access. Uncontaminated cores were taken at a limited number of sites to depths of up to 9m with the QASSIT track mounted Geoprobe coring machine (Figure 3).

Field pH tests were carried out using a WP81 pH-conductivity meter fitted with an IJ44 pH electrode. Field pH (pHF) and field pH peroxide (pHFOX) measurements were determined at 0.25m intervals to the depth of sampling in accordance with QASSIT guidelines (Ahern et al. 1998). With the exception of calcareous sands and shelly clayey sediments, the pHFOX test was an extremely reliable indicator of potential acid sulfate soils. The presence of oxidisable sulfur in calcareous sands and shelly clayey sediments was usually indicated by an increase in pH after peroxide oxidation (pHFOX > pHF).

Following field pH tests, samples for laboratory analysis were selected at each site from the upper depth of occurrence of the acid sulfate soil layer, for confirmation of the depth category for mapping. The lower depth of occurrence of the ASS layer was also usually sampled at each site. More frequent sampling down the soil profile occurred at Geoprobe cored sites. Selected samples were placed in a portable refrigerator / freezer and packed frozen for dispatch to Brisbane by overnight air express. Shell coarse fragments were manually removed from clayey samples and sieved from dried sandy samples.

Selected soil samples from each site were analysed for peroxide oxidisable sulfur, titratable actual acidity and titratable peroxide acidity using the Suspension Peroxide Oxidation Combined Acidity and Sulfur (SPOCAS) method (Ahern et al. 2004). Laboratory results are given in the Appendix. Thirty-eight samples with jarosite were analysed for retained acidity by the Net Acid Soluble Sulfur (SNAS) method (Ahern et al. 2004).

4 4. Description of the soil map units

The depth to an actual acid sulfate soil (AASS) layer and/or potential acid sulfate soil (PASS) layer on relatively undisturbed land is shown on the accompanying soil map by an alphanumeric code. The alpha component A refers to an AASS layer, the alpha component S to a PASS layer while the numerical component (for example 0,1,2 etc) refers to the depth at which these layers occur. The alphanumeric codes are used separately (for example A0) or combined (for example A0S0) where the map unit contains AASS layers overlying PASS layers. Where there is varying depth to an acid sulfate soil layer within a mapping unit a forward slash is used, for example S1/S2. The acid sulfate soil map units, of relatively undisturbed land, depict varying depths to the acid sulfate soil layer, coloured using shades of red and overlain with yellow dots where AASS is present.

Additional information is provided (by code) for areas of soils with a strongly acid soil layer (for example a1S1) and for those containing carbonate materials (subscript N). Other map units indicate ASS on disturbed lands (SDL) or areas where there was limited assessment due to restricted access (SLA). The distribution of land where there is a low probability of ASS occurring below (LP), or above an elevation of 5m AHD (LP5) is also shown on the map.

There are 3,471 ha of acid sulfate soils mapped within the survey area. This area contains approximately 1,466 ha of land with AASS and 2,004 ha of land with PASS (Table 1). Other map units (SDL, SLA) indicating areas of land where ASS are likely to occur, total 3,485.2 ha.

4.1 Actual Acid Sulfate Soils on Relatively Undisturbed Land

A0 (AASS layer within 0.5m depth, no PASS layer)

This single map unit occurs immediately north-east of the Yarwun Industrial Area and occupies much of the elevated area previously used for motocross. The associated vegetation is narrow-leaved ironbark (Eucalyptus crebra), blue gum (Eucalyptus tereticornis) and paper- barked tea tree (Melaleuca quinquenervia) with a ground cover of dominantly marine couch (Sporobolus virginicus). The soils are typically strongly acid at shallow depth, contain jarosite, and have negligible oxidisable sulfur values (<0.01 to 0.07%), indicating almost complete oxidation of pyritic sediments. Titratable Actual Acidity (TAA) ranges from 0 to 70 moles of hydrogen per tonne of soil (mol H+/t) and Titratable Peroxide Acidity (TPA) from 11 to 122 mol H+/t, which are generally low. Retained acidity (Ahern et al. 2004) of the soil layers containing jarosite ranges from 2 to 127 mol H+/t. These strongly acid layers overlie a cemented gravel layer or country rock which was not penetrable by sampling equipment.

Similar strongly acid soils were recorded at Blain Park on local alluvium with gum-topped box (Eucalyptus moluccana) woodland (Figure 4), in an area formerly susceptible to tidal inundation.

A0S0 (AASS layer and PASS layer within 0.5m depth)

Mapping unit areas with the code A0S0 total 628.1 ha in area and represent 42% of the area of actual acid sulfate soils. The landform is typically an infrequently inundated supratidal flat (bare saltpan) with patches of samphire on the slightly elevated margins (Figure 5). The largest areas occur at Callemondah adjacent to the Calliope River Anabranch, along the western margin of South Trees Inlet and at Parsons Point.

Figure 2. Gouge auger sampling, supratidal flat, Calliope River.

Figure 3. Geoprobe core sampling, terraced alluvium, Boyne River.

Figure 4. Gum-topped box woodland with AASS, Blain Park.

6 Common soil profile features are a thin brown, structured, medium to heavy clay surface horizon grading to a greyish brown clay subsoil with abundant pale yellow jarosite mottles. The lower unoxidised sulfidic layers are dark grey or greenish grey organic enriched silty clays (Figure 6). Pre-Holocene or Pleistocene substrate, where present, is a mottled olive grey heavy clay, moist and of very firm strength, with pyrite at the interface.

Along the western side of the estuary of South Trees Inlet the soils contain variable levels of oxidisable sulfur. Commonly levels are 1 to 1.5% but can range from low (<0.35%) to very high levels (5%). No visible organic materials were evident in the soils with low levels of oxidisable sulfur. TAA of the jarosite layers range from 34 to 140 mol H+/t, and the retained acidity of these layers from 46 to 63 mol H+/t.

An area of saltpan to the north-west at Parsons Point, with restricted tidal influence, generally has moderate levels of oxidisable sulfur (0.29 to 1.1%) and acid generation potential (272 to 980 mol H+/t) in the PASS layers, with one site containing higher levels (2.8% 1,960 mol H+/t). Actual acidity (TAA) levels range from 24 to 185 mol H+/t, and retained acidity from 235 to 1,263 mol H +/t.

The depth to the AASS layers can be very shallow on the saltpan between the Calliope River Anabranch and the Yarwun Industrial Area. Adjacent to Hanson Road, where the tidal flow is restricted jarosite appears on the soil surface with a field pH of 2.7 to 3.2 units. None of the jarositic layers from this area were analysed for existing acidity. The potential acid sulfate soil layers commonly have high amounts of organic materials with oxidisable sulfur values ranging from 0.8 to 2.9% with most above 1.5%.

The unit south of Boat Creek contains similar levels of oxidisable sulfur (1.7 to 2.4%), with lower levels recorded in soils with less organic fragments (0.9-1.3%). Retained acidity was determined on one heavy clay subsoil sample only, with a value of 194 mol H+/t.

A0S0/S0 (Association of AASS and PASS layers within 0.5m depth)

A substantial area (403.9 ha) of tidal flats is situated east of South Trees Inlet, between the low rises of country rock, red mud Dam No1 and sandridges on Boyne Island. These have been mapped as a single unit. The tidal flats are mostly supratidal (bare saltpans) with some intertidal areas (mangrove mudflats). Some of the sites sampled on saltpans did not contain jarosite and the more predictable occurrence of PASS with mangrove areas would indicate the S0 association.

The main features of the dominant soils are a thin brown surface horizon, strongly acid subsoil of similar thickness with jarosite, and a dark grey unoxidised substrate with a high organic content. Greenish grey pre-Holocene substrate is recorded at one site and is pyritic in the upper part.

Actual acidity (TAA) values are high (107 to 162 mol H+/t) throughout the unit. The levels of oxidisable sulfur and peroxide acidities (TPA) are also high, except for one PASS layer with a moderate level, range from 1.4 to 4.4% and 1,116 to 3,261 mol H+/t, respectively.

7 Table 1. Area of map units. Map Unit Map Unit Area Percentage of Area (ha) Assessed (%) Actual acid sulfate soils A0 9.0 0.1 A0S0 628.1 9.0 A0S0/S0 403.9 5.9 A0S1 161.0 2.3 A0S2 44.7 0.6 A1S1 48.3 0.7 A1S2 95.6 1.4 A2S2 75.9 1.1 Total 1466.5 21.1

Potential acid sulfate soils S0 1325.3 19.0 S0/S1 498.9 7.2 S1 79.5 1.1 a1S1 27.4 0.4 S1/S2 53.9 0.8 S2 19.5 0.3 Total 2004.5 28.8

Acid sulfate on undisturbed land SLA 962.5 13.8 SLAN 345.7 5.0 Total 1308.2 18.8

Acid sulfate on disturbed land SDL 1820.8 26.2 Low probability ASS land LP 62.5 0.9 LP5 293.7 4.2 Total 356.2 5.1

Total area 6956.2 100

A0S1 (AASS layer within 0.5m depth, PASS layer 0.5 to 1m depth)

A small area of slightly elevated marine couch flat (extratidal flat) traversed by Hanson Road and a substantially larger area of bare saltpan (supratidal flat) nearby and north of the Yarwun Industrial Area comprise this mapping unit. The soils of the Hanson Road unit have a dark to black, well structured, medium to heavy clay surface horizon overlying greyish brown medium clay subsoils with orange and red mottles, and yellow jarositic mottles. At less than 1m depth the potential acid sulfate soil layers are dark grey silty medium clays with organic fragments and are strongly acid (field pH 3.2 to 4.1). Oxidisable sulfur values in the unoxidised substrate range from 1.7 to 6.49% with corresponding peroxide acidities of 1,154 to 4,497 mol H+/t.

8 The larger nearby unit of saltpan generally has a much darker (black), and finer textured (heavy clay) surface horizon, than occurs on saltpans elsewhere throughout the survey area. Retained acidity measurement of the jarositic layers vary from 4 to 143 mol H+/t, with most measurements above 80 mol H+/t. Oxidisable sulfur values of the dark grey or greenish grey substrate range from 0.33 to 3.5% with peroxide acidities of 382 to 2,252 mol H+/t, respectively. Small amounts of fine shell fragment occur in the soil profile below 1.3m depth at some sites.

A0S2 (AASS layer within 0.5m depth, PASS layer 1 to 2m depth)

These map units are the elevated areas landward of the above saltpan area mapped as A0S1. The associated vegetation is largely low tea tree woodland with marine couch groundcover. The soils are strongly acid throughout (field pH <4), contain a thick layer with jarosite and usually have low levels of actual and peroxide acidity, but high levels of retained acidity. Seasonally wet areas of the map units have soils with a peaty surface horizon.

The grey or dark grey heavy clay subsoils are well structured with bright red, orange and yellow mottles in the upper subsoil grading to weakly structured lower subsoils with some pale yellow jarositic mottles. These are underlain by layers of gravelly, mottled, grey and brown, pre-Holocene sediments of sandy medium clay to heavy clay texture below 1.5m to 2m depth.

Laboratory analysis of the acid sulfate soil layers indicate that most are almost fully oxidised with very low or low levels of oxidisable sulfur (0.01 to 0.11%). Actual and peroxide acidity levels of these oxidised soils are low, and ranged from 24 to 54, and 57 to 83 mol H+/t respectively. Retained acidity measurement of selected layers with jarosite is higher and ranged from 145 to 640 mol H+/t. The infrequent unoxidised layers in the map units had peroxide acidity values (TPA) of 1,142 to 2,242 mol H+/t.

A1S1 (AASS layer and PASS layer 0.5 to 1m depth)

Mapping units are located on Black Harry Island and immediately west of the Calliope River Anabranch (Figure 7). Common features of these areas, other than acid sulfate soil depth, include an extratidal flat landform and a strongly acid soil reaction. The extratidal flat on Black Harry Island, surrounded by mangroves, contains marine couch, samphire and bare areas. Extratidal flats with dominantly marine couch grassland occur west of the Calliope River Anabranch, with one area supporting gum-topped box and ironbark vegetation.

There are essentially two soil types comprising this mapping unit. One is largely unoxidised with significant levels of oxidisable sulfur (0.8 to 1.17%) and acid generation potential (585 to 852 mol H+/t). The other is almost fully oxidised with very high levels of retained acidity within 1m depth of the soil surface, and classed as a PASS layer. Calculated net acidity ranges from 707 to 1,227 mol H+/t.

Figure 5. Typical bare saltpan with samphire on slightly elevated margins, A0S0 map unit.

Figure 6. Greyish brown AASS layer with jarosite, greenish grey PASS layer.

Figure 7. Marine couch flat above saltpan west of Calliope River, A1S1 map unit.

10 A1S2 (AASS layer 0.5 to 1m depth, PASS layer 1 to 2m depth)

Marine couch flats (extratidal flats) with isolated clumps of ironbark and blue gum trees represent this map unit. They adjoin the Calliope River at Byellee and Black Harry Island. The soils are mostly clay with sandy sediment at depth. Deep drilling in the Black Harry Island unit indicates a thickness of 6m of the acid sulfate soil layers or pyritic sediments. These are underlain by a further 3m of non-pyritic sand and river gravels.

Oxidisable sulfur and actual acidity levels of the AASS layers containing jarosite are very low (<0.09% S, TAA <50 mol H+/t). Retained acidity levels are low (74 to 148 mol H+/t). The PASS layers contain low to moderate (0.13 to 0.65%) levels of oxidisable sulfur in the upper substrate increasing to a maximum level of 1.26%, recorded at 6m depth for the Black Harry Island unit.

A2S2 (AASS layer and PASS layer 1 to 2m depth)

These units form part of the tidal, lower section of Clyde Creek between Byellee and Beecher. They are the more elevated areas with marine couch and are situated well below the high alluvial terrace of the Calliope River. The landform of the area locally called the Byellee Wetlands, with borrow pits and ponds is partly man made, previously being used for sand extraction.

The profile of the sediments is generally a soil of alluvial origin, with a sandy or loamy surface, overlying a relatively thin layer of AASS, which in turn is underlain by a relatively thick layer of PASS with some rounded gravels. Oxidisable sulfur levels in the Beecher unit range from 1.3 to 2.52% with peroxide acidities of 706 to 1,432 mol H+/t. PASS layers in the Byellee unit have oxidisable sulfur levels of 0.5 to 1.8% and peroxide acidities of 320 to 1,154 mol H+/t.

4.2 Potential Acid Sulfate Soils on Relatively Undisturbed Land

S0 (PASS layer within 0.5m depth)

The S0 map units are scattered throughout the southern section of the survey area from Pacific Ranch Estate to the Calliope River. North of the Calliope River, the map unit is almost continuous and occupies much of the coastal strip to the northern extent of the survey area. The S0 map units occupy 1,325 ha or 66% of the area of potential acid sulfate soils. They are mostly associated with frequently inundated intertidal flats (locally called mangrove mudflats), with a few units represented by saltpans (supratidal flats). Closed thickets of the mangrove genus Rhizophora are common throughout the map units (Figure 8).

The soils are dark grey, grading to greenish grey, saturated silty clays with a greyish brown surface horizon. Organic materials feature in the surface layer and underlying silty clay sediment. The potential acid sulfate soil layer can occur in or just below the soil surface layer. For example, 0-0.2m depth sample of site CQA632 contains 1.34% oxidisable sulfur and TPA of 929 mol H+/t (Appendix).

Figure 8. Mangrove thicket Fishermans Landing, S0 map unit.

Figure 9. Supratidal and extratidal areas of S1/S2 map unit, Boat Creek.

Figure 10. Extratidal flat along the Calliope River, S2 map unit.

12 Very high levels of pyritic sediments occur at <0.5m depth at several locations, with measured SPOS values of 4.8% at Cattle Creek Inlet, Tannum Sands; 5% Rogers Road, Boyne; 5% South Trees Island; 3.7% Auckland Inlet, Gladstone, and 3.3% at Callemondah. The levels elsewhere range from 0.5% to 2.9% peroxide oxidisable sulfur.

S0/S1 (PASS layer 0 to 1m depth)

This map unit area with varying depth to the PASS layer (0 to 1m), is substantial in size (499 ha) and represents twenty-five percent of the area of potential acid sulfate soils. Much of the area is located at Wild Cattle Creek and on Black Harry Island with a small area situated adjacent to the Calliope River at Byellee. The landform is dominantly intertidal flats with mangrove cover and slightly elevated areas of supratidal flats (saltpan) with samphire. The shallower depth to the PASS layer in the mapping unit areas is often, but not always associated with mangrove cover.

The soils at Wild Cattle Creek have coarse textures with layers of sandy loam overlying layers of fine sandy clay. The levels of oxidisable sulfur and acid generation potential in the 0 to 0.5m and 0.5 to 1m depth categories are moderate (0.6 to 1.27% and 281 to 632 mol H+/t respectively). Fine textured clays on Black Harry Island also generally contain moderate levels of oxidisable sulfur and acid generation potential (0.58 to 1.3%, 381 to 800 mol H+/t) for the same depth categories, with a higher level (2.8%, 2104 mol H+/t) recorded at one sampling site. The small area at Byellee has moderate to high levels of oxidisable sulfur and acid generation potential (0.7 to 2.29% and 424 to 1,458 mol H+/t).

S1 (PASS layer 0.5 to 1m depth)

The largest area of the S1 mapping unit is located at Callemondah adjacent to Black Harry Island. Smaller areas are located along the Boyne and Calliope Rivers, on Black Harry Island and at Tannum Sands. The landform is either a tidal flat or tidal creek and partly covered with mangroves. Vegetation within the unit at Callemondah includes ironbark, blue gum, Moreton Bay ash (Corymbia tessellaris) and quinine berry (Petalostigma pubescens) on small elevated areas of non-pyritic local alluvium.

Oxidisable sulfur and acid generation potential within the unit at Callemondah varies from 0.5 to 3.7% and 263 to 2,524 mol H+/t. The nearby Black Harry Island map unit contains 2.3% oxidisable sulfur and 1,694 moles of acidity in the PASS layer at 0.5 to 1m depth. The levels elsewhere range from 0.33% and 187 mol H+/t in sandy sediments at Tannum Sands, to1.7% and 1,060 mol H+/t in clayey sediments along the Boyne River.

a1S1 (Strongly acid layer and PASS layer 0.5 to 1m depth)

This unit is restricted to the saltpan (supratidal flat) area west of the Boyne Smelters haul road on South Trees Island. It is distinguished by a strongly acid (field pH 4 to 5) layer and PASS layer within 1m depth. Along the northern and eastern margins of the saltpan adjacent to beach ridge sands, the soils have fine sandy surface layers. Elsewhere they are recorded with medium heavy clay surface horizons grading to dark grey and grey silty clays and then to fine sandy clays.

13 The silty clay PASS layers contain between 1.4 and 2.6% oxidisable sulfur and potential acidities of 1,230 to 2,096 mol H+/t. A lower level of oxidisable sulfur and peroxide acidity (1% and 737 mol H+/t) occurs in the underlying fine sandy sediment.

S1/S2 (PASS layer 0.5 to 2 m depth)

The landform of these two mapping units is complex containing a number of elements, hence the variable depth to the PASS layer. The units are located on Tuckers Farm adjacent to South Trees Inlet and near the mouth of Boat Creek at Fishermans Landing. At Tuckers Farm, the landform consists of a dissected alluvial plain with flats and drainage lines previously subject to tidal influence and now protected by pondage banks and a barrage. The Boat Creek unit (Figure 9) contains the following landform elements, a tidal creek, mangrove mudflats (intertidal flats), saltpan (supratidal flats), marine couch grassland (extratidal flats) and low gravelly deposits of local alluvium with ironbark and blue gum vegetation.

The incised drainage line on Tuckers Farm contains high levels of oxidisable sulfur (3.1%) and acid generation potential (1,868 mol H+/t) at 0.8 to 1m depth, in grey non-cracking clays overlying sandy and gravelly sediment. On the adjacent alluvial flats, below brown gradational soils, the levels vary from 1.2 to 3.8% oxidisable sulfur at 1.3 to 1.5m depth.

The acid sulfate soils on the more frequently affected tidal flats at Boat Creek are mostly grey, structure-less medium to heavy clays, with brown or dark structured heavy clays occupying the more elevated marine couch flats. Oxidisable sulfur levels range from 0.7 to 1.5% and acid generation potential from 341 to 1012 mol H+/t in the 0.8 to 1m depth samples, and from1.1 to 1.3% and 812 to 865 mol H+/t in samples from 1m to 2.5m depth.

S2 (PASS layer 1 to 2 m depth)

This single map unit occupies an extratidal flat with marine couch along the Calliope River at West Stowe. Sampling sites are located in the northern part of the unit between the two railway bridges (Figure 10). The soils are mottled, structured medium to heavy clays overlying a dark grey silty clay substrate with some organic fragments, below 1m depth. The levels of oxidisable sulfur and acid generation potential are high from 1.3 to 3m depth, with a moderate level below. Values are 2.4% SPOS with 1,903 moles of acidity at 1.3m, decreasing to 1.5% with 1,070 moles of acidity at 3m depth, and to 1% with 686 moles of acidity below.

4.3 Acid Sulfate on Relatively Undisturbed Land

SLA (Limited field assessment and landform indicating ASS)

The SLA map units total 962.5 ha in area. They represent either intertidal flats or are intertidal in part with mangroves indicating the presence of acid sulfate soils. Limited sampling was undertaken in the complex foreshore area of Boyne Island from Wyndham Park in the south to The Lillies, and on South Trees Island.

14 At Wyndham Park, acid sulfate soils are recorded in fine sandy sediments of a drainage depression at 0.8 to 1m depth. Oxidisable sulfur is 0.44% and acid generation potential is moderate (359 mol H+/t). North of the access track to Lillies Beach, non-acid sulfate soils were found in a beach ridge swale underlain by river gravels, to 1.2m depth. East of the Boyne Smelters plant on an extratidal flat, self-neutralising acid sulfate soils occur. Oxidisable sulfur values from samples from 0.9 to 2.8m depth, in shelly fine sandy sediments, range from 0.13 to 0.43% with no measurable acid generation potential. An intertidal flat, south of The Lillies and adjacent to the Boyne Smelters haul road, contains acid sulfate soils at shallow depth (0.3m). Oxidisable sulfur ranges from 0.22 to 0.99% and peroxide acidity 133 to 647 mol H+/t.

Very limited sampling on South Trees Island also indicates acid sulfate soils are associated with sand deposits and mangrove mudflats. The oxidisable sulfur levels in marine clays underlying sand sediments varied from 0.7 to 1.24%, and acid generation potential from 491 to 859 mol H+/t. The mangrove mudflat had 0.35% oxidisable sulfur at 0.5m depth increasing to 0.87% below 1m depth, with corresponding potential acidities of 214 and 559 mol H+/t.

SLAN (Limited field assessment and landform indicating ASS with carbonate materials)

The SLAN map code indicates limited field assessment in a landscape where there is a reasonable probability of acid sulfate soils occurring, with carbonate materials that may compensate for the potential acidity. The map units located at Canoe Point and beside Wild Cattle Creek comprise an area of 345.7 ha.

Negligible levels of oxidisable sulfur (0.02%) and no acid generation potential were measured in layered sandy sediments with shell fragments, overlying river gravels, in a swale at Canoe Point. Sampling within the much larger, more elevated sand deposit (predominately >5m AHD) beside Wild Cattle Creek indicates self-neutralising acid sulfate soils at >5m depth. The soils are slightly acid, yellowish brown fine sands overlying layers of bleached and brown fine sand to 4m depth. Below 4m depth, the brown grading to dark greenish grey fine sandy sediments (Figure 11) contain very fine shell and some organic fragments. Oxidisable sulfur levels in the dark greenish grey PASS layer range from 0.03 to 0.07% with no measurable acid generation potential. The associated vegetation includes Moreton Bay ash, coastal Banksia (Banksia integrifolia), black wattle (Acacia aulacocarpa) and red ash (Alphitonia excelsa).

4.4 Acid Sulfate on Disturbed Land

SDL (Disturbed land likely to contain acid sulfate soils)

Most SDL map unit boundaries were interpreted from 1:23 800 scale black and white aerial photographs flown in 1959 as part of the Gladstone Aerial Photography Program. This photography pre-dates much of the industrial and urban development throughout the survey area. For example, the Gladstone Power Station, Queensland Alumina Limited red mud dams on Boyne Island, and the urban area of Auckland Inlet were not developed (Figures 14 and 15). The map units mostly represent former mangrove mudflats (intertidal flats) and saltpans (supratidal flats) and total 1,820.8 ha in area. For the period 1941 to 1994, approximately 650 ha of mangroves and 990 ha of coastal saltflats along the Curtis Coast is reported as being lost to clearing and reclamation, mostly around Gladstone (QHED 1994).

Figure 11. Bleached white and brown fine sands, greenish grey PASS layer, SLAN map unit.

Figure 12. Sampling in back-channel below high terrace of Boyne River, LP5 map unit.

Figure 13. Brown sandy loam, greenish grey PASS layer over non-pyritic river gravels.

Figure 14. Auckland Inlet 1996.

Figure 15. Auckland Inlet 1959.

17 Acid sulfate soil sampling on disturbed lands is restricted to a few locations. A small former tidal inlet off the Boyne River at Tannum Sands, which has been filled and now appears as a drainage depression, contains actual acid sulfate soil layers overlying PASS. Oxidisable sulfur levels increase down the soil profile from 0.22 to 1.37% and peroxide acidities from 254 to 928 mol H+/t.

Air photo interpretation and sampling from the intertidal flat below the Queensland Alumina Limited No 4 Ashpond indicate acid sulfate soils would likely underlie this ashpond. The levels of oxidisable sulfur and acid generation potential on the tidal flat are moderate to 1m depth (0.7 to 0.9% and 347 to 617 mol H+/t).

At Barney Point on reclaimed land, low levels of oxidisable sulfur and acid generation potential (0.2% and 96 mol H+/t) were found in dark grey silt loam below layers of yellowish brown clay fill. Much higher levels are recorded for the nearby tidal creek or drain in dark + grey silty clay sediments (1.5% SPOS and 1,150 mol H /t).

Acid sulfate soils at Blain Park, and in a drain below Helen Street with isolated mangroves, indicate they extend upstream of Lake Callemondah on former tidal affected land. The soils are almost fully oxidised with negligible or very low levels of actual and peroxide acidity (0.01 to 0.18% peroxide oxidisable sulfur).

Partly filled land between Alf O’Rourke Drive and Auckland Inlet with layers of grey to reddish brown silt loam and clay, overlying dark grey marine clays, contains acid sulfate soils with high levels of actual and peroxide acidity. Titratable actual acidity levels range from 109 to 161 moles H+/t, and peroxide acidities from 1,138 to 1,736 mol H+/t.

4.5 Land with a Low Probability of Acid Sulfate Soil Occurrence

LP (Land predominantly < 5m AHD with low probability of ASS occurrence)

A low-lying flat below low rises of granitic rocks at Tannum Sands, a slightly elevated plain at Callemondah, and a drainage depression and flat at Boat Creek comprise this mapping unit. Queensland peppermint (Eucalyptus exserta), black wattle and tea tree are the main vegetation species at Tannum Sands. The soil is texture contrast and overlies a cemented siliceous hardpan from 1.4 to 2.5m depth. Below the hardpan is greenish grey saturated sand, which appears to be non-acid sulfate soil from the limited sampling.

The slightly elevated plain at Callemondah is interpreted as Calliope River alluvium and is likely to have had seawater incursion due to its low elevation (<4m AHD) and landscape position. The associated vegetation is Moreton Bay ash, blue gum and black wattle with a ground cover of dominantly marine couch. The soils are slightly acid to neutral, brown to dark non-cracking clays. Depth to olive brown sandy saturated sediment ranges from 1.7 to > 2.5m. Laboratory results indicate very low levels of oxidisable sulfur (0.08%) and acid generation potential (39 mol H+/t) below 2m depth at one sampling site.

18 Isolated clumps of ironbark and blue gum occur within the Boat Creek unit along with marine couch in the drainage depression and on the flat above a previously ponded area. The more elevated area of flat and low ridge was found to contain reddish brown, loamy, non-acid sulfate soils to the depth sampled. Negligible levels of oxidisable sulfur (0.02%) and peroxide acidity (14 mol H+/t) occur in grey structured heavy clays of the drainage depression.

LP5 (Land predominantly > 5m AHD with low probability of ASS occurrence)

Approximately 294 ha of land, predominantly above 5m AHD, is identified to have a low probability of acid sulfate soil occurrence. The land consists of low-lying alluvial deposits of the Boyne and Calliope Rivers, which can have a watertable at depth and may have the potential to contain pyritic materials.

Deep drilling on the levee of the Boyne River below the BITS Club to 7.2m depth indicates non-acid sulfate soils to this depth along the levee. The soil has a black sandy surface with a brown sandy massive subsoil (previously named Boyanda soil type, Ross 1999). It overlies layers of yellowish brown and dark brown single-grain sand to 4.7m depth. The underlying substrate is river gravels with some coarse sand, and a watertable commencing at 6m depth.

To the immediate west, in the adjoining back-channel below 5m AHD (Figure 12), acid sulfate soils were found in dark grey sandy and loamy sediments from 3 to 4m depth. These PASS layers overlie non-PASS layers of grey and greenish grey coarse sand and gravel to 6m depth. Oxidisable sulfur content of the sand sediment is very low (0.03%) with negligible peroxide acidity (16 mol H+/t). Higher levels are associated with the loamy sediment (0.23%) and 155 moles of peroxide acidity (Fig 13). The very narrow back-channel or drainage depression is too small to be shown at 1:50 000 scale mapping.

Deep drilling on the proposed Boyne Island Cemetery site to 6m depth indicates non-acid sulfate soils to this depth in terraced alluvium and its associated drainage depressions. The soils and sediments were sampled in drainage depressions, being the areas of lowest elevation and highest likelihood of pyritic sediments being preserved. The dominant soils for the site have been previously mapped as Harwood and Berrigan. The soils occupying the drainage depressions are more closely associated with Ceduna soil type and overlie saturated coarse sand and river gravels at 4 to 5m depth.

The area occupied by the LP5 map unit on Black Harry Island is indicated on the Gladstone Geology map as Quaternary high terrace alluvium (Crouch et al. 2001). The moderate depth of penetration (2.4m) by Geoprobe coring indicates a clay veneer of alluvium over hard rock or cemented gravel. The dominant vegetation is blue gum and ironbark. The soils are strongly texture contrast and neutral to alkaline in soil reaction. Oxidisable sulfur levels are negligible to very low (0.01 to 0.03%) with no measurable or very low levels of acid generation potential (22 mol H+/t).

19 4. Discussion

Acid sulfate soils recorded in the survey area are almost exclusively associated with tidal lands or the tidal zone. They occur in a limited number of landforms in comparison with other areas of the southern Central Queensland coast (Ross et al. 2000, Ross 2002, 2003), and have a predictable occurrence within the tidal zone. The acid sulfate soils are permanently wet with a shallow watertable, and are classified within the Australian Soil Classification (Isbell, 1996) as Hydrosols. Sulfidic Hydrosols and Histic-Sulfidic Hydrosols (or potential acid sulfate soils) typically occur on the intertidal or mangrove mudflats. Sulfuric Hydrosols, containing both actual and potential acid sulfate soil layers, are mainly associated with supratidal flats (saltpans) or slightly elevated marine couch flats (extratidal flats). The soil orders of the beach ridge sands are either Rudosols or Tenosols overlying potential acid sulfate soils. Other soil orders in the survey area overlying acid sulfate soils with acid generation potential are Anthroposols and Dermosols.

Excluding the beach ridge sands at Canoe Point and at Wild Cattle Creek, few sites were found to contain shell or shell fragments within clayey marine sediment to the depth sampled. Those sites with shell are mostly located on intertidal flats at Tannum Sands, South Trees Inlet and at Parsons Point. There is also one site from a supratidal flat (saltpan) near Boat Creek with shell fragments in the lower substrate. Some soil layers from these sites contain sufficient carbonate to be self-neutralising, have no net acidity and would not require treatment if disturbed. Other layers containing shell, with Net Acidity, would generally require reduced treatment (Dear et al. 2002). The largest shell deposits observed during the survey are located at Parsons Point and in the low, shelly and gravelly ridge and its remnants north of Fishermans Landing.

The new Laboratory Methods Guidelines (Ahern et al. 2004) use an acid base accounting approach for predicting Net Acidity from sulfide oxidation of acid sulfate soils. Net acidity is calculated using the following equation:

Net Acidity = Potential Sulfidic Acidity + Existing Acidity – Acid Neutralising Capacity where: Existing Acidity = Actual Acidity + Retained Acidity; and

Acid Neutralising Capacity (ANC) = measured ANC/Fineness Factor.

The laboratory results of samples analysed by the POCAS and POCASm methods (Ahern et al. 2000) from previous sampling throughout the survey area had indicated low levels of actual acidity (<50 mol H+/t) in acid sulfate soil layers with abundant jarosite. Consequently, retained acidity was not considered to be significant, although a risk of iron and acid contamination was acknowledged. During this survey, the 4M HCl extractable sulfur content was determined on thirty-eight samples containing jarosite. This analysis enables the calculation of Retained Acidity (SNAS), and is additional to the SPOCAS method. The results are listed in Table 2.

In Table 2, it can be seen that most samples fall in the fine texture category (medium clays to heavy clays) used in acid sulfate soil investigations, and a few from the medium texture category (sandy loams to light clays). All samples contain jarosite and have a field pH of 4.3 units or less, before oxidation with hydrogen peroxide. The levels of retained acidity or Net Acid Soluble Sulfur, range from negligible to very high and appear to be unrelated to soil

20 Table 2. Retained acidity for selected samples with jarosite.

1 2 3 4 5 Site No Depth Texture Field pH SNAS s-SNAS a-SNAS (m) Category (%) (%) (mol H+/ t) CQA501 1.0-1.2 Fine 3.3 0.158 0.118 74 CQA502 1.0-1.2 Fine 3.2 0.410 0.307 192 CQA502 1.6-1.8 Fine 3.3 0.246 0.184 115 CQA503 0.6-0.8 Fine 3.6 0.318 0.238 148 CQA509 0.8-1.0 Fine 3.5 0.052 0.039 24 CQA514 0.4-0.5 Fine 3.4 1.469 1.101 687 CQA514 1.6-1.8 Fine 3.3 0.178 0.133 83 CQA518 0.9-1.1 Fine 3.6 0.271 0.203 127 CQA519 0.5-0.6 Fine 3.7 0.005 0.003 2 CQA519 0.8-0.9 Fine 3.8 0.006 0.004 3 CQA520 0.5-0.6 Fine 3.6 2.483 1.862 1161 CQA521 0.8-1.0 Fine 3.8 1.372 1.029 642 CQA521 1.8-2.0 Fine 4.0 0.012 0.009 6 CQA569 1.8-2.0 Fine 3.8 0.241 0.180 113 CQA569 2.8-3.0 Fine 3.2 0.340 0.225 159 CQA577 1.3-1.5 Medium 2.7 0.236 0.177 110 CQA577 1.8-2.0 Medium 2.8 0.306 0.229 143 CQA583 0.8-1.0 Medium 3.0 0.134 0.100 63 CQA586 0.3-0.5 Fine 3.8 0.098 0.073 46 CQA590 0.3-0.5 Medium 3.8 0.007 0.005 3 CQA605 0.1-0.3 Medium 3.7 0.050 0.037 23 CQA609 0.3-0.5 Fine 3.4 0.118 0.088 74 CQA655 2.0-2.2 Fine 3.8 0.012 0.009 5 CQA658 1.8-2.0 Fine 3.7 0.036 0.027 16 CQA659 1.3-1.5 Fine 4.0 0.014 0.010 6 CQA659 2.0-2.2 Fine 3.8 0.216 0.162 101 CQA666 0.3-0.5 Fine 3.5 2.700 2.025 1263 CQA666 0.8-1.0 Fine 3.6 0.503 0.377 235 CQA667 0.3-0.5 Fine 3.9 0.197 0.147 92 CQA668 0.3-0.5 Fine 3.5 0.851 0.638 398 CQA669 0.8-1.0 Fine 3.7 0.363 0.272 169 CQA669 1.3-1.5 Fine 4.3 0.709 0.531 331 CQA670 0.1-0.3 Fine 3.5 0.010 0.007 4 CQA670 0.3-0.5 Fine 3.4 0.306 0.229 143 CQA672 0.2-0.4 Fine 3.6 0.415 0.311 194 CQA673 0.3-0.5 Fine 3.6 0.232 0.174 108 CQA673 0.7-0.9 Fine 3.2 0.175 0.131 81 CQA674 0.3-0.5 Fine 3.2 0.239 0.179 111

1 Ahern et al. (1998). 2 Field pH before oxidation. 3 Net acid soluble Sulfur (Ahern et al. 2004). 4 Equivalent % pyrite Sulfur. 5 Equivalent acidity units.

21 morphology, jarosite content, or soil reaction. The highest levels are from a saltpan at Parsons Point (Site CQA666), and from a marine couch flat at Callemondah (Site CQA520). Actual acidity (Titratable Actual Acidity) measured for these two sample sites are low, 39 and 36 mol H+/t, respectively, and do not provide an indication of the very high levels of retained acidity.

For this survey, net acidity (moles H+/tonne) is calculated as follows and the results are listed in the Appendix: pH KCl ≥ 6.5, Net Acidity = 623.7 x SPOS – (332.7 x CaA – 548.4 x MgA); pH KCl <6.5, Net Acidity = 623.7 x SPOS + TAA + (467.8 x SNAS); pH KCl < 6.5, Net Acidity = 623.7 x SPOS + TAA.

Calculated Net Acidity is generally less than the measured Titratable Peroxide Acidity (TPA) and in some samples the difference is quite substantial. For example, site CQA515 1.6-1.8m depth sample (Appendix) has a measured TPA of 567 mol H+/t greater than the calculated Net Acidity for sulfide oxidation. The complexity of acid sulfate soil chemistry, and reasons why acidity measured by titration methods are not consistent with acidity predicted from sulfur analysis, are outlined in the Acid Sulfate Soil Laboratory Methods Guidelines (Ahern et al. 2004). These differences are possibly due to organic matter and organic acidity effects as acid sulfate soils in the Tannum Sands-Gladstone area are known to have a high organic carbon content (2 to 9%). Because the measured TPA values indicated a higher risk of acid and iron contamination if disturbed, these were used in the description of the map units and not Net Acidity terminology.

The accompanying acid sulfate soils map is essentially a map of depth to the acid sulfate soil layers. An indication of risk, depending on the type and extent of disturbance, can be inferred from the depth to an actual acid sulfate soil and/or potential acid sulfate soil layer. For example, draining land with actual and potential acid sulfate soil layers at very shallow depth (< 0.5m), within the A0S0 mapping units would be considered a high risk activity. However, there is no indication of the level of sulfides, actual acidity or acid generation potential provided at 1:50 000 scale of mapping. Mapping units with the same depth code can contain quite variable levels of sulfides, existing and potential acidity and consequently varying levels of risk.

Acid sulfate soil risk maps which predict the distribution of acid sulfate soils, based on an assessment of the geomorphic environment, have been produced for coastal areas of New South Wales (Flewin et al. 1996). The maps identify the areas at risk and likely depth to the occurrence of acid sulfate soils. Three risk classes are used (High, Low and No Known Occurrence) and these can be related to land use activities that may expose acid sulfate soils, creating an environmental risk. Unlike risk maps, hazard maps are based on more objective criteria with limited interpretation.

The potential acid generation of particular areas of land is illustrated on the accompanying acid sulfate soil hazard map. Four classes of acid generation potential are used (Very Low, Low, Moderate and High) based on the concentration of sulfides (peroxide oxidisable sulfur content, SPOS) and corresponding acid generation potential (titratable peroxide acidity, TPA)

22 or Net Acidity. The criteria used to establish the classes (Table 3) is essentially a revised acid sulfate soil hazard rating scheme applied to laboratory results in a previous survey (Ross 2003).

Table 3. Acid sulfate hazard classes.

Class Criteria + Very Low SPOS < 0.03% and TPA = 18 to 80 mol H /t + SPOS > 0.03% and TPA = 0 to < 18 mol H /t Low probability areas

+ Low SPOS > 0.03% and TPA ≥ 18 to < 200 mol H /t

+ Moderate SPOS > 0.35% and TPA ≥ 200 to < 1000 mol H /t Net Acidity ≥ 200 to < 1000 mol H+/t

+ High SPOS > 1.5% and TPA > 1000 mol H /t Net Acidity > 1000 mol H+/t

Depth to the acid sulfate soil layer is not used in the class criteria because the higher concentrations of sulfides and acid generation potential mostly occur at shallow depth and are associated with clayey sediments. Lower concentrations of sulfides and lower acid generation potential generally occur at greater depth and are often associated with sandy sediments. For convenience of use, the depth to the acid sulfate soil layer with significant potential acidity has been placed on the mapping units of the hazard map. The hazard map should be read in conjunction with the accompanying acid sulfate soil map.

6. Acknowledgments

David Hawton (Queensland Alumina Limited) provided access for sampling at Parsons Point, South Trees Island and on Boyne Island. Peter Lander and Craig Dobson (Boyne Smelters Limited) organised access and assisted with sampling on Boyne Island. Sharlene Gustafson (Gladstone City Council) arranged access for sampling at the Byellee Wetlands. Christine Krebs (Calliope Shire Council) assisted with site selection and access in the Boyne-Tannum area. Col Ahern (QASSIT, NR&M) provided specialised equipment for deep sampling. Geoprobe core sampling was undertaken by Jeremy Manders (QASSIT, NR&M). Ian Grant and Niki Finch (Analytical Services, NR&M) determined most of the laboratory results. Net Acidities were calculated by Dave Lyons (Analytical Services, NR&M). The maps were prepared and produced by John Simpson (Central West GIS Group, NR&M). Don Malcolm (QASSIT, NR&M) and Bruce Forster (NR&M) reviewed and edited the document.

23 7. References

Ahern CR, Ahern MR and Powell B (1998). Guidelines for Sampling and Analysis of Lowland Acid Sulfate Soils (ASS) in Queensland. QASSIT, Department of Natural Resources, Indooroopilly, Queensland.

Ahern CR, McElnea AE, Latham NP and Denny SL (2000). A Modified Acid Sulfate Soil Method for Comparing Net Acid Generation and Potential Sulfide Oxidation-POCASm. In Acid Sulfate Soils: Environmental Issues, Assessment and Management, Technical Papers. Ahern CR, Hey KM, Watling KM and Eldershaw VJ (eds), Brisbane, 20-22 June, 2000. Department of Natural Resources, Queensland.

Ahern CR, McElnea AE and Sullivan LA (2004). Acid Sulfate Soils Laboratory Methods Guidelines. Queensland Department of Natural Resources, Mines and Energy, Indooroopilly, Queensland, Australia.

Anon (2002). State Planning Policy 2/02 Guideline. Planning and Managing Development Involving Acid Sulfate Soils. Department of Local Government and Planning. Department of Natural Resources and Mines, Queensland.

Crouch SBS, Blake PR, Blight RKJ and Roberts CW (2001). Gladstone Special. Department of Natural Resources and Mines, Queensland.

Dear SE, Moore NG, Dobos SK, Watling KM and Ahern CR (2002). Soil Management Guidelines. In: Queensland Acid Sulfate Soil Technical Manual. Department of Natural Resources and Mines, Indooroopilly, Queensland, Australia.

Donchak PJT and Holmes KH (1991). Gladstone Queensland 1:100 000 Geological Map Commentary. Department of Resource Industries, Queensland.

Flewin TC, Naylor GA, Chapman G, Atkinson CL, Murphy MJ, Talau MJ, Milford HB and Morand DT (1996). Maps Make Acid Sulfate Soil Manageable. In: Proceedings the 2nd National Conference on Acid Sulfate Soils. RJ Smith and Associates and ASSMAC, Australia.

Isbell RF (1996). The Australian Soil Classification. CSIRO Publishing, Melbourne.

Mc Donald RC, Isbell RF, Speight JG, Walker J and Hopkins MS (1990). Australian Soil and Land Survey Field Handbook. 2nd edition, Inkata Press, Melbourne.

QHED (1994). Curtis Coast Study Resource Report. Queensland Department of Environment and Heritage, Rockhampton.

Reid RE (1988). Soil Survey Specifications. In: RH Gunn, JA Beattie, RE Reid and RHM van de Graff (editors) Australian Soil and Land Survey Handbook, Guidelines for Conducting Surveys. Inkata Press, Melbourne.

24 Ross DJ (1999). Land Suitability Assessment and Soils of the Calliope and Yeppoon Areas, Queensland. Department of Natural Resources Queensland. Land Resources Bulletin 990066. Ross DJ (2002). Acid Sulfate Soils, Tannum Sands to St Lawrence, Central Queensland Coast. Department of Natural Resources and Mines, Queensland. QNRM02008.

Ross DJ (2003). Acid Sulfate Soils, Keppel Sands-Yeppoon Area, Central Queensland Coast. Department of Natural Resources and Mines, Queensland. QNRM03370.

Ross DJ, Malcolm DT and Hall IR (2000). Pyritic sediments in geological map units of Pleistocene age on the Central Queensland Coast. In Acid Sulfate Soils: Environmental Issues, Assessment and Management, Technical Papers. Ahern CR, Hey KM, Watling KM and Eldershaw VJ (eds), Brisbane, 20-22 June, 2000. Department of Natural Resources, Queensland.

25 APPENDIX

Chemical data for selected depth samples

ABBREVIATIONS

SPOS Peroxide oxidisable sulfur

TAA Titratable actual acidity

TPA Titratable peroxide acidity

26 Site Depth Locality Landform SPOS TAA TPA Net Acidity No m % mol H+/t mol H+/t mol H+/t 492 0.8-1.0 Callemondah Extratidal 2.806 51 2022 1801 1.6-1.8 Flat 2.169 41 1458 1394 493 0.8-1.0 Callemondah Supratidal 0.526 0 263 301 1.3-1.5 Flat 0.505 0 187 248 494 0.4-0.5 Callemondah Supratidal 3.752 17 2524 2357 1.4-1.6 Flat 1.927 0 1142 1170 495 2.3-2.5 Callemondah Plain 0.087 0 39 38 496 0.3-0.5 Callemondah Supratidal 1.616 0 925 951 1.0-1.2 Flat 1.256 0 622 740 497 0.3-0.5 Callemondah Supratidal 1.655 33 1103 1065 1.1-1.3 Flat 1.331 14 794 844 498 0.2-0.3 Callemondah Intertidal 2.083 24 1363 1323 1.5-1.7 Flat 1.900 60 1302 1245 499 0.9-1.0 Black Harry Extratidal 0.801 74 585 573 1.5-1.7 Island Flat 1.172 80 852 810 500 0.6-0.8 Black Harry Supratidal 2.315 76 1694 1520 1.6-1.8 Island Flat 1.287 46 833 843 501 1.0-1.2 Black Harry Extratidal 0.068 23 63 139 1.6-1.8 Island Flat 0.486 39 324 342 502 1.0-1.2 Black Harry Extratidal 0.005 22 31 217 1.6-1.8 Island Flat 0.018 27 43 153 503 0.6-0.8 Black Harry Swamp 0.017 30 38 189 1.6-1.8 Island 0.089 21 68 71 504 0.8-1.0 Black Harry Intertidal 2.849 45 2104 1822 1.6-1.8 Island Flat 3.845 72 2684 2501 505 0.3-0.5 Black Harry Intertidal 1.332 0 712 758 1.6-1.8 Island Flat 2.085 27 1349 1327 506 0.8-1.0 Black Harry Intertidal 0.588 27 381 394 1.6-1.8 Island Flat 1.529 31 990 985 507 0.4-0.5 Black Harry Supratidal 1.143 43 800 756 1.6-1.8 Island Flat 3.014 89 2034 1969 508 0.8-1.0 Black Harry Intertidal 1.156 0 621 664 1.6-1.8 Island Flat 1.308 28 813 844 509 0.8-1.0 Callemondah Extratidal 0.035 41 66 87 1.5-1.7 Flat 6.491 173 4497 4221 510 0.3-0.5 Callemondah Supratidal 0.834 26 516 546 1.3-1.5 Flat 1.240 0 742 778 511 0.3-0.5 Callemondah Supratidal 2.938 44 1954 1875 1.2-1.4 Flat 2.078 10 1279 1306 512 0.6-0.8 Callemondah Supratidal 2.779 44 1881 1777 1.1-1.3 Flat 3.505 25 2252 2211 513 0.4-0.5 Boat Creek Supratidal 1.321 0 784 829 Flat 514 0.4-0.5 Callemondah Extratidal 0.047 42 65 759 1.4-1.6 Flat 0.013 54 57 145 515 0.3-0.5 Boat Creek Intertidal 3.223 100 2547 2110 1.6-1.8 Flat 3.879 99 3085 2518 516 0.4-0.5 Callemondah Supratidal 2.424 59 1875 1571 1.2-1.4 Flat 1.849 20 1272 1173 517 1.4-1.6 Boat Creek Drainage 0.022 0 14 18 Depression 518 0.9-1.1 Callemondah Extratidal 0.075 70 122 244 Flat 519 0.5-0.6 Callemondah Plain 0.010 37 49 46 0.8-0.9 0.009 51 67 59

27 Site Depth Locality Landform SPOS TAA TPA Net Acidity No m % mol H+/t mol H+/t mol H+/t 520 0.5-0.6 Callemondah Extratidal Flat 0.048 36 55 1227 1.1-1.3 0.091 26 84 83 521 0.8-1.0 Callemondah Extratidal Flat 0.047 43 59 707 0.002 33 45 40 529 0.3-0.5 Boyne Island Drainage 0.051 14 0 46 0.8-1.0 Depression 0.442 59 359 322 530 0.6-0.8 Barney Point Made Land <0.01 0 0 0 1.2-1.4 0.202 0 96 126 531 0.1-0.3 Barney Point Tidal Creek 1.560 90 1150 1063 0.8-1.0 1.000 0 434 550 1.4-1.5 1.210 0 642 713 532 0.3-0.5 Callemondah Intertidal Flat 0.851 0 498 530 1.3-1.5 1.020 11 634 647 533 0.5-0.7 Callemondah Supratidal Flat 1.370 68 1030 922 1.0-1.2 1.110 20 722 712 534 0.8-1.0 Callemondah Extratidal Flat 2.970 138 2091 1990 1.5-1.7 1.730 74 1154 1153 536 1.3-1.5 Black Harry Plain 0.030 0 0 0 Island 542 0.3-0.5 Calliope Intertidal Flat 2.050 69 1551 1348 1.6-1.8 River 1.690 116 1232 1170 543 0.3-0.5 Calliope Supratidal Flat 1.180 0 761 736 1.6-1.8 River 1.460 65 1098 976 544 0.3-0.5 Calliope Supratidal Flat 1.320 23 923 846 1.6-1.8 River 0.974 70 753 677 545 0.3-0.5 Auckland Supratidal Flat 1.230 12 787 779 1.6-1.8 Inlet 1.310 0 796 817 546 0.5-0.7 Auckland Made Land 1.890 154 1579 1333 1.6-1.8 Inlet 2.210 140 1736 1518 547 1.0-1.2 Auckland Made Land 1.940 161 1603 1371 1.6-1.8 Inlet 1.440 109 1138 1007 548 0.4-0.6 Auckland Intertidal Flat 0.876 13 550 559 1.6-1.8 Inlet 1.130 57 801 762 549 0.5-0.7 Calliope Tidal Creek 1.410 22 936 901 1.6-1.8 River 2.250 69 1596 1472 550 0.8-1.0 Calliope River Terrace <0.01 0 10 0 1.8-2.0 River 0.013 77 120 85 551 0.3-0.5 Auckland Intertidal Flat 3.710 154 2978 2468 1.3-1.5 Creek 2.660 71 1868 1730 552 0.5-0.7 South Trees Supratidal Flat 0.661 50 499 462 1.6-1.8 1.360 74 1041 922 553 0.2-0.4 South Trees Intertidal Flat 1.770 133 1400 1237 1.0-1.2 0.750 24 474 492 554 0.2-0.4 South Trees Intertidal Flat 0.241 10 159 160 0.8-1.0 1.280 19 829 817 555 0.3-0.5 South Trees Supratidal Flat 4.470 206 3357 2994 1.6-1.8 3.690 123 2607 2424 556 0.8-1.0 South Trees Supratidal Flat 4.250 131 2904 2782 1.4-1.6 1.520 43 1056 991 557 0.2-0.4 South Trees Supratidal Flat 3.530 75 2472 2277 0.8-1.0 5.530 109 3914 3558 1.6-1.8 2.800 76 1938 1822 558 0.2-0.4 South Trees Intertidal Flat 3.710 77 2640 2391 1.6-1.8 2.700 35 1884 1719

28 Site Depth Locality Landform SPOS TAA TPA Net Acidity No m % mol H+/t mol H+/t mol H+/t 568 2.1-2.3 Black Harry Alluvial Plain 0.013 0 22 8 Island 569 1.8-2.0 Black Harry Marine Plain 0.013 78 114 199 2.8-3.0 Island 0.074 77 147 282 3.8-4.0 1.050 67 781 722 4.8-5.0 1.220 45 820 806 5.8-6.0 1.260 42 854 828 6.8-7.0 0.174 0 105 109 8.8-9.0 <0.01 0 0 0 570 0.6-0.8 Callemondah Plain <0.01 0 11 0 2.1-2.3 <0.01 0 12 0 571 2.3-2.5 Boyne Island Drainage <0.01 0 0 0 2.8-3.0 Depression <0.01 0 0 0 3.2-3.4 0.223 0 155 139 3.8-4.0 0.031 0 16 19 5.7-5.9 <0.01 0 0 0 572 7.0-7.2 Boyne Island River Terrace <0.01 0 0 0

573 5.0-5.2 Tannum Sands Beach Ridge 0.017 0 0 0 5.5-5.7 0.073 0 0 0 5.8-6.0 0.037 0 0 0 574 5.0-5.2 Boyne Island Drainage <0.01 0 0 0 5.8-6.0 Depression <0.01 0 0 0 575 3.0-3.2 Boyne Island Drainage <0.01 0 0 0 4.3-4.5 Depression <0.01 0 0 0 576 1.6-1.8 Tannum Sands Drainage <0.01 0 0 0 Depression 577 1.3-1.5 Tannum Sands Drainage 0.226 73 254 324 1.8-2.0 Depression 0.717 109 633 699 2.3-2.5 1.370 70 928 924 578 0.3-0.5 Tannum Sands Intertidal Flat 0.142 0 0 0 1.0-1.2 1.110 0 108 444 1.6-1.8 0.811 0 0 0 579 0.3-0.5 South Trees Intertidal Flat 2.930 90 2054 1917 1.6-1.8 1.930 80 1308 1284 580 0.3-0.5 South Trees Supratidal Flat 2.380 104 1652 1588 1.1-1.3 1.140 20 345 731 581 0.0-0.2 South Trees Tidal Creek 0.504 0 0 221 0.8-1.0 3.070 62 2164 1977 1.6-1.8 2.000 46 1360 1293 582 0.3-0.5 South Trees Intertidal Flat 2.450 36 1608 1564 1.3-1.5 3.010 68 2058 1945 583 0.8-1.0 South Trees Supratidal Flat 4.324 116 3484 3169 1.4-1.6 1.640 32 1136 1055 584 0.4-0.6 South Trees Supratidal Flat 2.420 140 1830 1649 1.0-1.2 2.300 130 1738 1565 1.6-1.8 0.751 12 472 480 585 0.3-0.5 South Trees Intertidal Flat 1.870 104 1342 1270 1.6-1.8 2.700 148 2026 1832 586 0.3-0.5 South Trees Supratidal Flat 0.027 0 17 157 0.8-1.0 0.341 0 173 213 587 0.6-0.8 South Trees Supratidal Flat 0.183 0 32 97 1.3-1.5 0.222 0 72 125 588 0.3-0.5 South Trees Supratidal Flat 1.000 45 658 669 1.6-1.8 1.140 0 548 633

29 Site Depth Locality Landform SPOS TAA TPA Net Acidity No m % mol H+/t mol H+/t mol H+/t 589 0.0-0.2 Tannum Sands Intertidal 0.263 0 126 159 0.4-0.6 Flat 0.758 12 465 485 1.0-1.2 2.550 42 1698 1632 590 0.3-0.5 Tannum Sands Supratidal 0.054 0 24 73 0.8-1.0 Flat <0.01 0 0 0 1.8-2.0 <0.01 0 0 0 591 0.3-0.5 Tannum Sands Supratidal 4.880 184 3546 3288 0.8-1.0 Flat 3.380 106 2268 2214 1.6-1.8 2.280 238 1966 1660 592 0.2-0.4 South Trees Supratidal 1.370 57 942 911 0.9-1.1 Flat 1.320 26 806 849 593 0.2-0.4 South Trees Intertidal 1.160 19 702 742 0.7-0.9 Flat 1.360 19 826 867 594 0.4-0.6 South Trees Supratidal 0.839 21 536 544 0.8-1.0 Flat 1.600 34 1000 1032 595 0.3-0.5 Auckland Intertidal 2.100 99 1482 1409 0.8-1.0 Creek Flat 1.730 66 1178 1145 1.3-1.5 1.250 21 796 801 596 0.3-0.5 Auckland Tidal Creek 0.406 0 237 253 0.8-1.0 Creek 1.590 36 1004 1028 1.6-1.8 1.880 28 1120 1201 597 0.3-0.5 Auckland Supratidal 2.940 136 2104 1970 0.8-1.0 Creek Flat 1.550 103 1102 1070 1.8-2.0 2.050 111 1458 1390 598 0.2-0.4 Auckland Supratidal 1.790 84 1220 1200 1.6-1.8 Creek Flat 1.790 98 1276 1214 599 0.3-0.5 Auckland Stream 0.284 0 107 177 0.8-1.0 Creek Channel 2.360 55 1534 1527 1.6-1.8 1.630 20 950 1037 600 0.4-0.6 Auckland Supratidal 2.090 119 1492 1423 0.8-1.0 Creek Flat 1.990 81 1350 1322 601 0.2-0.4 Auckland Intertidal 1.760 22 1066 1120 0.8-1.0 Creek Flat 1.800 20 1068 1143 1.3-1.5 1.290 24 758 829 602 0.2-0.4 Auckland Intertidal 0.726 0 400 453 1.2-1.4 Creek Flat 2.280 46 1496 1468 603 0.2-0.4 Auckland Intertidal 1.450 26 930 930 0.8-1.0 Creek Flat 5.400 113 3584 3481 1.5-1.7 2.060 112 1336 1397 604 0.8-1.0 Auckland Made Land 0.027 0 0 0 Creek 605 0.1-0.3 Auckland Made Land <0.01 35 69 58 0.8-1.0 Creek 0.045 35 55 63 1.2-1.4 0.013 34 43 42 606 0.8-1.0 Parsons Point Marine Plain <0.01 0 0 0 1.8-2.0 0.062 0 0 39 607 0.3-0.5 Parsons Point Drainage <0.01 28 67 28 0.8-1.0 Depression 0.019 24 56 36 1.8-2.0 0.845 77 639 610 608 0.3-0.5 Parsons Point Marine Plain 0.030 0 0 19 0.8-1.0 <0.01 0 0 0 609 0.3-0.5 Parsons Point Marine Plain 0.926 76 731 709 0.8-1.0 0.607 133 467 512 1.6-1.8 0.479 0 361 299 610 0.3-0.5 Parsons Point Marine Plain 2.750 178 2143 1893 1.3-1.5 1.260 185 753 971

30 Site Depth Locality Landform SPOS TAA TPA Net Acidity No m % mol H+/t mol H+/t mol H+/t 611 0.3-0.5 Boyne Island Supratidal 3.010 107 2308 1984 0.8-1.0 Flat 4.410 142 3261 2893 1.6-1.8 1.490 157 1122 1086 612 0.3-0.5 Boyne Island Supratidal 2.850 132 2144 1910 0.8-1.0 Flat 1.760 123 1398 1221 1.6-1.8 1.900 50 1433 1235 613 0.2-0.4 Boyne Island Supratidal 2.320 83 1728 1530 0.8-1.0 Flat 0.872 148 619 692 614 0.3-0.5 Boyne Island Supratidal 2.870 129 2010 1919 1.0-1.2 Flat 2.040 162 1591 1434 1.6-1.8 1.510 137 1220 1079 615 0.2-0.4 Boyne Island Supratidal 1.400 134 1185 1007 0.8-1.0 Flat 3.300 129 2373 2187 1.6-1.8 1.430 139 1116 1031 616 0.3-0.5 Calliope River Supratidal 2.300 135 1715 1570 1.6-1.8 Flat 0.914 85 639 655 617 0.5-0.7 Calliope River Supratidal 3.900 108 2759 2540 1.0-1.2 Flat 2.940 100 2086 1934 1.4-1.6 1.250 14 747 794 618 0.6-0.8 Calliope River Intertidal 2.580 31 1714 1648 1.6-1.8 Flat 1.280 39 834 829 619 1.3-1.5 Calliope River Extratidal 2.460 175 1903 1709 2.1-2.3 Flat 2.260 50 1509 1460 2.8-3.0 1.530 64 1070 1018 3.6-3.8 1.180 0 686 736 620 0.3-0.5 Calliope River Channel 0.653 0 394 407 1.0-1.2 Bench 1.319 0 836 817 621 0.2-0.4 Calliope River Intertidal 1.350 0 926 842 0.8-1.0 Flat 1.180 0 709 736 1.5-1.7 0.920 0 457 513 622 0.5-0.7 Calliope River Supratidal 0.650 0 399 405 1.0-1.2 Flat 1.140 0 716 711 623 0.8-1.0 Callemondah Extratidal 0.031 0 0 2 4.8-5.0 Flat 0.036 0 10 15 624 1.0-1.2 Callemondah Alluvial 0.013 0 0 8 2.7-2.9 Plain <0.01 0 23 0 625 0.9-1.1 Callemondah Alluvial <0.01 0 0 0 2.8-3.0 Plain <0.01 0 17 0 626 0.2-0.4 South Trees Intertidal 5.010 112 3458 3237 0.8-1.0 Island Flat 3.600 55 2411 2300 1.6-1.8 4.540 126 3125 2958 627 0.5-0.7 South Trees Supratidal 1.480 87 1230 1010 1.0-1.2 Island Flat 2.650 89 2096 1724 1.4-1.6 1.000 52 737 676 628 0.4-0.6 South Trees Intertidal 0.719 42 556 490 0.8-1.0 Inlet Flat 0.907 0 558 528 1.4-1.6 0.761 0 204 335 629 0.3-0.5 South Trees Intertidal 0.751 60 617 528 0.8-1.0 Inlet Flat 0.949 0 347 469 1.6-1.8 0.754 0 12 123 630 0.3-0.5 Fishermans Supratidal 2.460 39 1711 1573 0.8-1.0 Landing Flat 3.090 49 2126 1976 631 0-2-0.4 Fishermans Supratidal 2.140 111 1683 1446 0.8-1.0 Landing Flat 5.020 67 3299 3198 1.2-1.3 0.664 0 415 414

31 Site Depth Locality Landform SPOS TAA TPA Net Acidity No m % mol H+/t mol H+/t mol H+/t 632 0.0-0.2 Fishermans Intertidal Flat 1.340 39 929 875 1.2-1.4 Landing 1.990 66 1426 1307 633 0.2-0.4 Fishermans Intertidal Flat 0.625 0 13 213 0.7-0.8 Landing 0.254 0 44 117 634 0.2-0.4 Fishermans Intertidal Flat 0.759 0 457 449 0.8-1.0 Landing 1.100 42 912 728 635 0.3-0.5 Fishermans Intertidal Flat 1.130 26 762 731 1.0-1.2 Landing 0.559 0 315 363 636 0.4-0.6 Callemondah Supratidal Flat 0.974 34 658 641 1.0-1.2 1.390 47 905 914 637 0.3-0.5 Callemondah Supratidal Flat 0.032 24 39 45 0.7-0.9 0.265 17 230 182 1.6-1.8 1.390 53 971 920 638 0.5-0.7 Boyne Island Made Land 0.011 12 71 19 2.3-2.5 <0.01 0 20 0 639 1.2-1.4 South Trees Swale 0.701 0 491 437 1.6-1.8 Island 1.240 30 859 803 640 0.5-0.7 South Trees Intertidal Flat 0.356 0 214 222 1.1-1.3 Island 0.879 0 559 548 641 0.3-0.5 Boyne Island Intertidal Flat 0.224 0 133 140 0.6-0.8 0.995 18 647 639 642 0.9-1.1 Boyne Island Extratidal Flat 0.135 0 0 0 1.8-2.0 0.436 0 0 42 2.6-2.8 0.279 0 0 17 643 1.0-1.2 Boyne Island Swale <0.01 0 0 0 644 0.2-0.3 Boyne Island Made Land <0.01 0 76 0 0.4-0.6 <0.01 0 55 0 0.7-0.9 <0.01 12 74 12 645 0.7-0.9 Boyne Island Made Land <0.01 0 0 0 1.5-1.7 <0.01 0 44 0 646 0.2-0.4 South Trees Intertidal Flat 1.530 16 1054 970 1.6-1.8 2.380 24 1656 1508 647 0.3-0.5 South Trees Supratidal Flat 0.337 44 283 254 0.8-1.0 0.472 25 343 319 1.6-1.8 0.488 0 265 304 648 0.3-0.5 South Trees Supratidal Flat 1.030 91 806 733 1.6-1.8 1.240 43 828 816 649 0.3-0.5 South Trees Supratidal Flat 1.150 48 766 765 1.5-1.7 1.120 0 608 656 650 2.8-3.0 South Trees Made Land 0.013 0 37 3 651 3.5-3.7 South Trees Made Land <0.01 0 0 0 4.3-4.5 <0.01 0 0 0 652 0.8-1.0 Boat Creek Extratidal Flat <0.01 0 29 0 1.3-1.5 1.150 26 746 743 2.3-2.5 1.320 17 812 840 653 0.8-1.0 Boat Creek Tidal Creek 1.500 0 1012 936 1.6-1.8 1.350 13 865 855 654 0.3-0.5 Boat Creek Tidal Creek 0.087 0 15 33 0.8-1.0 0.723 0 341 451 655 2.0-2.2 Byellee Extratidal Flat 0.030 25 118 49 2.3-2.5 1.350 109 1004 951 2.8-3.0 1.220 111 853 811

32 Site Depth Locality Landform SPOS TAA TPA Net Acidity No m % mol H+/t mol H+/t mol H+/t 656 0.5-0.7 Byellee Supratidal 0.708 10 424 451 1.0-1.2 Flat 2.285 44 1458 1469 1.6-1.8 1.480 23 932 946 657 0.3-0.5 Byellee Tidal 2.920 73 1988 1897 0.7-0.9 Creek 0.485 0 300 302 658 1.3-1.5 Byellee Supratidal 0.013 27 55 35 1.8-2.0 Flat 0.007 23 33 44 2.3-2.5 0.526 10 320 338 659 1.3-1.5 Byellee Swamp 0.025 20 60 42 2.0-2.2 0.113 36 131 208 2.8-3.0 1.230 31 762 798 660 0.2-0.4 Byellee Tidal 0.680 0 392 427 0.8-1.0 Creek 1.500 58 1036 992 1.6-1.8 1.840 17 1154 1163 661 0.2-0.4 Byellee Intertidal 1.060 20 680 679 0.8-1.0 Flat 2.000 12 1186 1257 1.6-1.8 0.765 0 372 422 662 0.2-0.4 Auckland Drainage 0.086 0 0 0 0.8-1.0 Creek Depression 0.187 0 31 100 663 0.2-0.4 Auckland Drainage 0.050 0 0 0 0.6-0.8 Creek Depression 0.087 0 0 38 664 0.0-0.2 Auckland Drainage 0.118 0 0 83 0.7-0.9 Creek Depression 0.049 0 0 30 665 0.3-0.5 Auckland Supratidal 0.940 26 560 613 0.8-1.0 Creek Flat 1.120 0 406 560 1.3-1.5 1.350 0 392 610 1.8-2.0 1.500 0 572 743 2.3-2.5 1.540 0 426 663 2.8-3.0 1.590 0 473 711 666 0.3-0.5 Parsons Supratidal 0.065 39 53 1343 0.8-1.0 Point Flat 0.024 34 41 284 1.6-1.8 0.770 58 544 536 667 0.3-0.5 Parsons Supratidal 0.731 70 531 618 0.8-1.0 Point Flat 2.200 140 1534 1513 1.6-1.8 2.850 111 1960 1888 668 0.3-0.5 Callemondah Supratidal 0.024 44 75 457 1.0-1.2 Flat 1.620 99 1142 1110 1.6-1.8 2.460 51 1524 1582 669 0.8-1.0 Callemondah Extratidal 0.025 46 77 231 1.3-1.5 Flat <0.01 42 91 355 1.8-2.0 3.450 116 2242 2265 670 0.1-0.3 Callemondah Supratidal 0.043 23 68 55 0.3-0.5 Flat 0.062 27 99 208 0.8-1.0 1.140 60 764 772 671 0.3-0.5 Boat Creek Supratidal 1.910 78 1322 1271 0.8-1.0 Flat 1.690 0 1050 1029 672 0.2-0.4 Callemondah Supratidal 0.062 15 0 247 0.6-0.8 Flat 0.923 25 464 601 1.0-1.1 2.992 68 1944 1934 673 0.3-0.5 Callemondah Supratidal 0.075 50 57 200 0.7-0.9 Flat 0.056 34 10 151 1.3-1.5 2.242 60 1284 1458 674 0.3-0.5 Callemondah Supratidal 0.038 35 35 165 0.8-1.0 Flat 0.070 18 19 62 1.2-1.4 1.303 57 883 870

33 Site Depth Locality Landform SPOS TAA TPA Net Acidity No m % mol H+/t mol H+/t mol H+/t 678 0.5-0.7 Boyne Intertidal 1.770 17 1060 1121 1.0-1.2 Island Flat 1.290 0 704 757 1.6-1.8 1.638 0 633 812 679 0.3-0.5 Tannum Intertidal 0.336 0 187 209 0.8-1.0 Sands Flat 0.586 10 412 375 1.6-1.8 0.532 14 382 346 680 0.0-0.2 Parsons Intertidal 0.631 0 327 338 0.6-0.8 Point Flat 1.620 0 14 488 1.6-1.8 1.380 15 801 876