Interactions between salinity, acidity, and geochemistry of acidic lakes in the Wheatbel

100 Pages·2007·0.93 MB·English

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Interactions between salinity, acidity, and
geochemistry of acidic lakes in the Wheatbelt
and Goldfields regions.

Geoff Abbott
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Environmental Engineering Project Dissertation
October 2007

Supervisor: Assoc. Prof. Carolyn Oldham
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Abstract

In this project three natural acid-saline lakes in the Goldfields and Wheatbelt regions of Western
Australia were analysed to determine the similarities and differences in chemical processes
occurring in the water bodies. Extensive research has been performed on both natural and
anthropogenic acid-saline lakes throughout the world, however research into the inland lakes of
Western Australia has been limited, focusing only on a few large playa lakes. A preliminary
investigation was made into the chemical composition and interactions in Lake Gilmore – a large
acid-saline playa lake – and two smaller lakes of similar pH and salinity, Kondinin Lake and
Green Lake. This investigation was conducted by performing a desktop assessment of previous
literature, and the collation and analysis of field data collected in September 2006.

Due to being a preliminary investigation, a limited number of samples were collected which
prevented detailed statistical testing. Instead analysis was performed on parameters such as pH,
dissolved ion concentrations and solid phase composition using graphical analysis. The
proportions of major ions in solution were investigated using Piper Plots and also by determining
the order of ionic dominance. For each parameter and method of analysis, comparisons were
made between the three lakes to detect whether significant similarities or differences were
observed.

Macroscopic influences such as origin of solutes, acidity generated by groundwater iron levels,
and the evolution of the lake water by evaporation and precipitation processes, were found to be
the same across the three lakes. However, differences were found in the smaller scale chemical
properties and interactions in the lakes such as the order of ionic dominance, saturation indices,
and pH influence on ion concentrations. Further testing is required in order to confirm these
differences, due to the extremely limited number of samples collected at Kondinin Lake and
Green Lake. It was also recommended that research into the soil types and bedrock material of
the region is conducted in order to understand their effect on the lakes. Overall it was concluded
from this preliminary investigation that the chemical processes and interactions are not identical
in the three lakes investigated.

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Acknowledgements

I would like to thank a number of people for their support and contributions, for without them
this dissertation would not have been possible.

Firstly, many thanks must go to my supervisor, Associate Professor Carolyn Oldham, for her
guidance and assistance throughout the course of this project, and also her efforts in the
collection of field data.

I would also like to thank Ursula Salmon and Stefan Peiffer for their contributions in the field
and the subsequent sample testing and analysis.

Finally, I would like to acknowledge my family and friends for their help.

- Mum for your support, advice and proofreading
- Claire for proofreading, and also your patient support and understanding
- Dad for dispensing advice
- Chris for your technical support with computer issues
- Dan and Mike for proofreading

Without all of your assistance this paper would not have eventuated, and I hope to somehow
return the favour one day. Thank you.

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Contents

List of Figures .............................................................................................................................. viii 
List of Tables ................................................................................................................................... ix 
List of Equations .............................................................................................................................. x 
Glossary ............................................................................................................................................ 1 
1  Introduction .............................................................................................................................. 2 
1.1  Chemical interactions and controls in Lake Gilmore, Kondinin Lake, and Green Lake .. 2 
1.2  Aim .................................................................................................................................... 3 
1.3  Objectives .......................................................................................................................... 3 
2  Literature review ...................................................................................................................... 5 
2.1  Background region ............................................................................................................ 5 
2.2  Salinity in lakes ................................................................................................................. 7 
2.3  Acid generation processes ............................................................................................... 12 
2.4  Influence of pH on water chemistry ................................................................................ 14 
2.5  Missing information ........................................................................................................ 15 
2.6  Study Sites ....................................................................................................................... 17 
2.6.1  Lake Gilmore ............................................................................................................ 17 
2.6.2  Green Lake ............................................................................................................... 19 
2.6.3  Kondinin Lake .......................................................................................................... 19 
3  Methodology .......................................................................................................................... 20 
3.1  Fieldwork ......................................................................................................................... 20 
3.2  Data organisation and analysis ........................................................................................ 20 
3.2.1  Saturation Indices ..................................................................................................... 20 
3.2.2  Graphical Analysis ................................................................................................... 21 
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3.2.3  Ionic Dominance ...................................................................................................... 21 
3.2.4  Piper Plots ................................................................................................................ 21 
4  Results .................................................................................................................................... 25 
4.1  Solid phase ....................................................................................................................... 25 
4.2  Saturation Index ............................................................................................................... 26 
4.3  Ionic dominance .............................................................................................................. 28 
4.4  Piper Plots ........................................................................................................................ 28 
4.5  Graphical Analysis .......................................................................................................... 34 
5  Discussion .............................................................................................................................. 39 
5.1  Solid phase and dissolved mineral levels ........................................................................ 39 
5.2  Ionic dominance .............................................................................................................. 41 
5.3  Piper Plots ........................................................................................................................ 43 
5.4  Limitations and errors ...................................................................................................... 46 
6  Conclusions ............................................................................................................................ 47 
7  Recommendations for future investigation ............................................................................ 49 
8  References .............................................................................................................................. 50 
9  Appendices ............................................................................................................................. 54 
9.1  Appendix A - Field notes ................................................................................................. 54 
9.2  Appendix B – Sampling data ........................................................................................... 75 
9.2.1  Water sample test data .............................................................................................. 75 
9.2.2  Laboratory report ...................................................................................................... 86 

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List of Figures

Figure 1. Cross-sectional view of a typical Australian playa lake. (Johanesson 1994) .................. 5
Figure 2. Paleodrainage channels on the Yilgarn Block (Clarke 1994). ........................................ 6
Figure 3. Map demonstrating the abundance of salt lakes in Western Australia (Geddes 1981). .. 9
Figure 4. A simple three end-member EJH model (Radke 2002). ................................................. 10
Figure 5. A more complex chart of E-J-H end-member pathways (Long 1992). ........................... 11
Figure 6. Path of an ion released from the weathering front of bedrock, showing vertical
diffusion and lateral groundwater flow movements through the soil profile (Mann 1983). .......... 13
Figure 8. Map of the region surrounding Lake Gilmore and Green Lake. Green Lake is located
20km to the South of the map (Johanesson 1994). ......................................................................... 17
Figure 7. Rainfall and evaporation data for the Yilgarn Block region of Western Australia (Mann
1983). .............................................................................................................................................. 18
Figure 9. Piper plot diagram for all lakes. .................................................................................... 30
Figure 10. Piper plot diagram for Lake Gilmore. .......................................................................... 31
Figure 11. Piper plot diagram for Green Lake. ............................................................................. 32
Figure 12. Piper plot diagram for Kondinin Lake. ........................................................................ 33
Figure 13. pH and redox potential in lake water and seepage samples. ....................................... 34
Figure 14. Measured concentrations of Al and Si relative to pH. ................................................. 35
Figure 15. Levels of solid phase Al relative to pH. ........................................................................ 36
Figure 16. Levels of solid phase SiO relative to pH. .................................................................... 37
2
Figure 17. Fraction of total Fe which reacted with sodium dithionite. ......................................... 38
Figure 18. Piper Plot chart from a study on Lake Tyrell, Victoria (Herczeg 1991). ..................... 44
Figure 19. Proposed path for water evolution in Lake Tyrell and the three lakes of this project. 45

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List of Tables

Table 1. Constants used in calculating CO 2- and HCO - concentrations in aqueous solution.
3 3
(Nazaroff 2001) .............................................................................................................................. 22
Table 2. Dominant mineral composition guesses made by Stefan Peiffer based on percentage
mineral composition of soil/sediment samples at the three lakes. ................................................. 25
Table 3. Saturation indices closest to zero in each water sample. ................................................. 26
Table 4. Minerals with lowest saturation index values. ................................................................. 27
Table 5. Minerals with highest saturation index values. ................................................................ 27
Table 6. Order of ionic dominance in water samples taken from the three lakes. ......................... 28
Table 7. Calculated concentrations of HCO3- and CO32- in solutions sampled. ......................... 28
Table 8. Converted concentrations (milliequivalents) of ions in solutions sampled.. ................... 29
Table 9. pH, Eh, and Iron testing data on water samples. ............................................................. 76
Table 10. Raw data for ion concentrations in water samples – millimolar units. ......................... 77
Table 11. Ion concentration data converted to milliequivalents. ................................................... 77
Table 12. Milliequivalent ion concentration data reformatted for GW Chart input. ..................... 77
Table 13. Calculated saturation index values for a range of sparingly soluble salts in the water
samples taken. The values which are closest to zero are shown in bold. ....................................... 78
Table 14. Description, location and type of each solid sample collected at the three lakes. ........ 80
Table 15. Details of sample depths, some testing results, and details of which tests were
performed on each sample. ............................................................................................................ 81
Table 16. Data obtained from water content testing of solid samples. .......................................... 82
Table 17. Percentage composition testing results of each solid sample collected, and estimated
dominant minerals. ......................................................................................................................... 84
Table 18. Data and results from various tests performed to determine free iron levels. ............... 85
Table 19. Report sheet for the laboratory test results. ................................................................... 86
Table 20. Report sheet for the laboratory test results (cont’d). ..................................................... 89
Table 21. Report sheet for the laboratory test results (cont’d). ..................................................... 90

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List of Equations

Equation 1. Overall ferrolysis reaction, proposed by Mann to be the cause of groundwater
acidity in the Yilgarn Block (Mann 1983). ..................................................................................... 13
Equation 2. Formula for calculation of carbonic acid concentration in an open system at
equilibrium (Nazaroff 2001). .......................................................................................................... 23
Equation 3. Relationship between pH and concentration of H+ ions in solution. ......................... 23
Equation 4. Dissociation of carbonic acid. .................................................................................... 23
Equation 5. Dissociation of bicarbonate. ....................................................................................... 23
Equation 6. Relationship of equivalents to moles. ......................................................................... 24
Equation 7. Precipitation/dissolution of alunite (Long 1992) ....................................................... 42
Equation 8. Precipitation/dissolution of jarosite (Long 1992) ...................................................... 42

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