Acid Sulfate Soils in the Murray-Darling Basin

Transcription

1 Acid Sulfate Soils in the Murray-Darling Basin Dean Ansell Murray-Darling Basin Authority September 2009

2 WARNING The following presentation contains images and acronyms that may offend

3 Overview Overview of acid sulfate soils (ASS) ASS in the Murray-Darling Basin MDB ASS Risk Assessment Project Management options Key challenges

4 Overview of acid sulfate soils Acid sulfate soils (ASS) are soils affected by sulfide minerals ASS include soils that contain sulfuric acid, or have the potential to produce acid, release contaminants and cause deoxygenation following oxidation ASS types: Sulfuric; sulfidic, monosulfidic black ooze

5 Overview of acid sulfate soils water column surface water anoxic sulfidic sediments sulfate organic carbon bacteria sulfide volatile sulfides monosulfides e.g. FeS (black ooze) native sediments metals disulfides e.g. Fes 2 (pyrite) groundwater D. Baldwin - MDFRC

6 Overview of acid sulfate soils odors exposed sulfidic sediments sulfides oxygen bacteria ACID odors native sediments anoxic sulfidic sediments D. Baldwin - MDFRC

7 Overview of acid sulfate soils water column acidic sediments surface water buffering buffering ACID sulfate reduction ACID + oxidized iron floc native sediments anoxic sulfidic sediments D. Baldwin - MDFRC

8 Risks of ASS Disturbance introduces risk Acidification Mobilisation of metals and metalloids Deoxygenation Noxious odours

9 ASS in the MDB Only recently discovered in inland aquatic systems High sulfate and carbon input Highly regulated system Drought = disturbance

10 ASS in the MDB

11 Recent ASS issues ASS in the Lower Lakes

12 Recent ASS issues

13 Recent ASS issues Photo: MWWG Acidification of wetlands on the Murray River Bottle Bend Lagoon

14 Recent ASS issues Photo: MWWG Acidification of wetlands on the Murray River Bottle Bend Lagoon

15 Recent ASS issues Photo: CSIRO L&W Acidification of wetlands on the Murray River

16 MDB Ministerial Council established a $5m assessment of threats to wetlands Project objective Assess the spatial extent of, and risk posed by, acid sulfate soils at priority wetlands in the River Murray system, Ramsar wetlands and other key environmental sites in the MDB and identify management options.

17 Project Infrastructure ASS Risk Assessment Advisory Panel Five Governments Scientists ASS Scientific Reference Panel CSIRO Land and Water Murray-Darling Freshwater Research Centre Southern Cross University QLD Dept Natural Resources and Water NSW Dept Environment and Climate Change

18 Overview of Project Strategy Identification of wetlands for assessment Desktop assessment Rapid assessment Detailed assessment Assess risk and identify management/mitigation options

19 Identification of wetlands for assessment Agreed categories of wetlands Based on environmental significance and threats to surrounding waters Ramsar and DIWA wetlands Murray River regulated flow wetlands Proximity to water offtakes Creeks receiving irrigation return water Database development >15,000 records

20 Desktop assessment Purpose: establish shortlist of wetlands for on-ground rapid assessment Criteria developed by SRP Receive irrigation return water Intercept saline groundwater Receive waste water EC >1500 Assessment completed by regional managers Approx wetlands identified

21 Rapid assessment Purpose: identify wetlands with high likelihood of ASS presence Method developed by SRP Sediment and water ph Sediment and water EC Samples collected for sulfate concentration and ph incubation

22 Rapid assessment field guide and recording sheet

23 Rapid assessment extranet

24 Rapid assessment extranet

25 Rapid assessment

26 Rapid assessment: Screening criteria to progress to detailed assessment stage Parameter Trigger value ph soil* < 4 # > 5.5 ph water < 5.5 # EC soil (1:5) EC water Sulfate soil Sulfate water > 6.5 > 1000 EC > 400 EC < 400 EC > 5000 EC > 1750 EC < 1750 EC > 500 mg/l > 100 mg/l < 100 mg/l > 50 mg/l > 10 mg/l < 10 mg/l Action required Priority Detailed assessment Detailed assessment No further assessment Detailed assessment Detailed assessment No further assessment Detailed assessment Detailed assessment No further assessment Detailed assessment Detailed assessment No further assessment Detailed assessment Detailed assessment No further assessment Detailed assessment Detailed assessment No further assessment Extreme Moderate N/A High Moderate N/A High Moderate N/A High Moderate N/A High Moderate N/A High Moderate N/A

27 Reporting of rapid assessment results

28 Rapid assessment: Jurisdictional Prioritisation Process Is the wetland adjacent (<100m downstream or <2km upstream) to a water supply offtake? No Is there a reliance on the wetland for stock and domestic water supplies? Yes Yes HIGH PRIORITY Document and inform MDBA of changed priority level No Is the wetland of high environmental significance (including Ramsar and DIWA wetlands and those with threatened species)? Does the wetland receive water at regulated flow level? No No Yes Yes Is the hydrology of the wetland currently altered or disturbed or is the wetland facing hydrological disturbance (eg. drought, No Yes MODERATE PRIORITY LOWER PRIORITY Is the jurisdiction aware of any other information that would alter the priority level? Yes No Proceed with detailed assessment according to identified priority level

29 Detailed assessment Purpose: determine the presence, nature and extent of acid sulfate soils and associated risks Requires field and laboratory expertise Priority wetlands proceed straight to this stage Two phase process

30 Detailed assessment Phase 1 Confirm presence of ASS Soil description and sampling Avge 80 samples/wetland (4 depths, 20 sample sites) Water quality (ph, SEC, Eh, DO, alkalinity, turbidity) Lab analyses: PH ageing Sulfur Suite Acid Base Accounting: SCr, phkcl, and Titratable Actual Acidity, Acid Neutralising Capacity Water-extractable SO 4

31 Detailed assessment Phase 2 Detailed risk assessment of ASS materials Samples collected in Phase 1 Analyses rapid metal release contaminant and metalloid dynamics MBO formation potential mineralogy by XRD and major and trace elements by XRF surface water and groundwater chemical and nutrient analyses

32 Progress to date Desktop assessment complete at 19,000 wetlands Rapid assessment completed at 1466 wetlands Detailed assessment completed at: 15 Ramsar sites > 80 wetlands in the Lower Murray (SA) Currency/Finniss Rv (SA) Loddon River (Vic)

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34 Status of ASS assessments in the MDB # Jurisdiction Desktop assessment complete Rapid assessment complete Pending further analysis Detailed assessment recommended~ SA NSW Vic Qld 17, ^ TOTAL 19,094 1, ,188 5 No further assessment recommended # Current as at 24 th August ^ A refined method of desktop assessment was applied in Queensland, which resulted in the identification of an initial 200 wetlands for rapid assessment. ~ Detailed assessment is recommended where one or more thresholds in the SRP Expert Screening Criteria were exceeded.

35 Loddon River, Victoria - Dec ph 3.8 (Source: CSIRO Land and Water)

36 WAKOOL Un-named wetland, Wakool system - Dec ,000 μs/cm, soil ph 4.5 (Source: NSW DECCW)

37 ph 3 on incubation Big Toolunka Flat, SA- Nov ,000 μs/cm, water ph 6, soil ph (Source: SA MDBNRMB)

38 Irrigation channel, Qld Sept ph , 18,000 μs/cm, high sulfate concentration, MBOs (Source: Qld DERM)

39 Management options Avoidance

40 Management options Neutralise - liming

41 Management options Neutralise fill and contain River Murray NS 2 NS 5 NS 12 NS 13 NS 14 NS 15 6 ph /3/09 6/4/09 20/4/09 4/5/09 18/5/09 1/6/09 15/6/09 29/6/09 Date River Murray MWREN bh N1 sand 15 cm N2 sand 80 cm N4 clay 15 cm N3 clay 80 cm 6 ph /3/09 6/4/09 20/4/09 4/5/09 18/5/09 1/6/09 15/6/09 29/6/09 Date

42 Management options Neutralise - bioremediation

43 Key challenges Lack of information on wetlands Incomplete/inadequate wetland mapping Resources time, budget, scientists Defining hazard vs risk Management and mitigation options poorly understood Skepticism regarding the level of risk

44 Summary ASS pose an unquantified and potentially significant risk to the environment, water supplies and human health in the MDB Risks are broader than acidification On-going water and land management issue in the MDB ASS another factor to consider in wetland management