Impacts of Amending Bauxite Residue Sands with Residue Fines for

345 Pages·2009·4.16 MB·English

Impacts of Amending Bauxite Residue Sands with Residue Fines
for the Establishment of
Vegetation on Residue Disposal Areas

Jonathan D. Anderson
BSc Geology
MSc Soil Science

This thesis is presented for the degree of
Doctor of Philosophy
of Murdoch University
2009
Declaration

I declare that this thesis is my own account of my research
and contains, as its main content, work which has not previously been submitted
for a degree at any tertiary institution.

________________________________
Jonathan D Anderson
Abstract
Long term storage of bauxite residue materials requires a capping stratum which
will limit erosion while stabilizing slopes, limit deep infiltration of water into storage
piles, and be aesthetically acceptable to the surrounding community. A diverse native
vegetative community capable of surviving seasonal drought, low plant available water
and nutrient constraints has the best potential of satisfying most, if not all of these
requirements. Current and past rehabilitation of residue disposal areas (RDAs) using
species native to southwest Western Australia has exhibited varying success. Current
practices at Alcoa World Alumina Australia’s (Alcoa) Western Australia refineries have
bauxite residue fines (< 150 µm) stored within impoundments, in which the outer
embankments are constructed with bauxite residue sands (> 150 µm). The residue
sands are also used as the growth media in the capping stratum for vegetation
establishment on the disposal sites. Despite the inherently hostile properties of residue
sand (pH > 10, EC > 4 dS m-1, and ESP > 50), reductions in alkalinity (pH), salinity
(1:5)
(EC) and sodicity (ESP) are corrected, through freshwater leaching, to a greater extent
than is possible with residue fines. Although leaching can reduce the hostile character
of residue sand, additions of phosphogypsum are typically added to expedite the
removal of Na and alkalinity, and inorganic fertilizers are incorporated to improve the
nutrient status of the growth media. However, due to the inconsistencies in vegetation
establishment, which are attributed to poor water retention, inherent nutrient
deficiencies and rapid loss of nutrients within residue sands (because of high hydraulic
conductivity), further amendments are required.
The aim of this study was to determine if amending the residue sand capping
layer with residue fines would enhance its overall growth potential for vegetation
establishment. Additions of fines to residue sands were predicted to increase water
retention, add nutrients and increase the ability of the growth media to retain nutrients.
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Comparisons were made between the treated residue fines (seawater washed,
carbonated, or unaltered) at a series of fines additions (1 - 20 % w/w) and a control
(residue sand) amended with 2 % (w/w) phosphogypsum and inorganic fertilizer.
Comparisons were to determine the differences in 1) water retention, 2) nutrient
concentrations and nutrient retention, and 3) plant growth responses and plant biomass
nutrient concentrations between the growth media treatments. Four experiments were
set up to measure differences in these variables which included: a glasshouse study
involving the growth of Acacia saligna; a germination and emergence study (A.
saligna); a two year field study in Western Australia; and a glasshouse column leaching
study.
Water retention increased with increasing percentage of residue fines addition.
Plant available water (PAW) increased up to 110 %, with a 20 % increase in fines,
representing an increase of 0.026 m3 PAW m-3 residue growth media, when compared
to the residue sand only. This increase in PAW was attributed to changes in pore space
distributions, due to the increasing fines contents altering the sandy texture to loamy
sand texture class. However, initially much of this increase in PAW may not be
realized, due to estimated temporary increases in osmotic potential associated with the
high salt contents of residue sand and fines. Fines materials have much greater salt
contents, and thus need to be leached to a greater extent than sands to remove the
associated osmotic potential effects.
Essential plant nutrients (P, K, S, Ca, Mg, and B) were increased with additions
of residue fines in the glasshouse studies, although many nutrients (Mg, Zn, Mn and B)
were still marginal for sustainable plant growth and development. Seawater treated
residue fines additions produced the greatest increases in growth media nutrients with
substantial increases in soluble (> 7 mg L-1) and exchangeable (> 0.10 cmol kg-1) Mg,
c
being up to 400 % greater than all other treatments. Along with these necessary
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nutrients, concentrations of Na were also increased in all fines additions treatments.
Added Na may offset the benefits of fines additions, at least in the short term, due to
inhibitions of cation uptake from Na competition. However, in the column leaching
study soluble and exchangeable Na was lost rapidly from the profile, due to Ca and K
displacement of Na from exchange sites during leaching. Soluble Na was removed
from the profile to < 5 % of initial concentrations, after only three pore volumes of
leaching, and exchangeable Na was removed from charge sites to less than 25 % of the
initial concentration. Fines additions did increase concentrations of Mg and K on
exchange sites, thus reflecting increased nutrient retention capacity relative to that in
residue sand only.
Plant growth responses and plant biomass nutrient concentrations were altered
with the additions of residue fines to residue sands. The germination and emergence
study demonstrated that the emergence of native seedlings was affected by additions of
fines, due to the increased salinity and sodicity of the materials. Acacia saligna
seedling emergence was inhibited by EC > 2 dS m-1, which was highly correlated
(1:5)
with a Na/Ca ratio of > 40, for all treatments, except the seawater fines additions. Seeds
sown in seawater treatments emerged from growth media with EC as high as 3.33 dS
(1:5)
m-1 and appeared to be better correlated with Ca/Mg ratios than any other variable.
Native vegetation growth responses showed mixed results in fines treated residues in
the field. In the greenhouse study, plant growth tended to decrease with fines additions.
Poor plant growth with increasing fines additions occurred despite the increased water
retention and increased nutrients. This was attributed to the addition of Na associated
with the residue fines, as increases in Na, EC and ESP in fines treatments all appear to
have limited growth of Acacia saligna in the glasshouse over three months. Seawater
fines additions had elevated Mg and B concentrations in plant biomass, and performed
better than the carbonated or unaltered fines treatments, but still had reduced growth
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compared to the residue sand, which contained lower Na concentrations. Additional
plant growth limitations may have occurred, due to possible plant nutrient deficiencies
including: Mg, Zn, Mn and B and Na toxicity.
Incorporation of residue fines into residue sands did increase water retention,
nutrient concentrations and the nutrient retention capacity, but did not enhance the
overall growth potential for vegetation, at least in the short term. Reductions in
germination and emergence of seedlings and reduced plant growth were attributed to
increases in Na concentrations introduced from the fines. Seawater washed residue
fines had lower ESP and greater concentrations of nutrients, thus reducing the negative
impacts from the additional Na introduced, and showed the greatest promise as a fines
amendment. As leaching occurs over the first few initial months of rehabilitation, it is
expected that the majority of the Na will be removed, from a system with an addition of
5 to 10 % fines, and the positive benefits of the fines additions will than be realized.
Findings also illustrate that delaying the planting of vegetation on RDAs, until adequate
leaching has occurred to reduce the Na concentrations, will substantially increase
vegetation emergence and establishment.

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Table of Contents
Abstract.............................................................................................................................i
Table of Contents.............................................................................................................v
List of Tables...................................................................................................................xi
List of Figures..............................................................................................................xvii
Acknowledgements.......................................................................................................xxi
Chapter 1 Introduction.........................................................................................1
1.1 Need for study...............................................................................................3
1.2 Aims of study................................................................................................5
1.3 Literature review and background.................................................................7
Chapter 2 Materials and Methods......................................................................17
2.1 Introduction.................................................................................................17
2.2 Experiment 1. Chemical and physical properties of residue fines treatments
using Acacia saligna as a biological indicator: Acacia saligna glasshouse study.....18
2.3 Purpose and background..............................................................................18
2.4 Glasshouse experiment................................................................................18
2.4.1 Material preparation.............................................................................18
2.4.2 Column preparation.............................................................................19
2.4.3 Vegetation monitoring.........................................................................20
2.4.3.1 Aboveground biomass.....................................................................21
2.4.3.2 Belowground biomass......................................................................21
2.4.4 Growth media characterization............................................................22
2.4.4.1 Chemical properties.........................................................................22
2.4.4.1.1 Initial growth media conditions..................................................22
2.4.4.1.2 Final growth media conditions...................................................22
2.4.4.2 Particle size analysis........................................................................23
2.4.4.3 Water retention characteristics.........................................................24
2.4.4.4 Water retention curves.....................................................................26
2.5 Experiment 2. Field sites at Alcoa World Alumina’s Kwinana and Pinjarra
residue disposal areas, Western Australia................................................................27
2.6 Purpose and background..............................................................................27
2.7 Set up and development of field experimental sites......................................27
2.7.1 Field site description............................................................................27
2.7.2 Additions of residue fines and phosphogypsum...................................29
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2.7.2.1 Preparations of fines and transport...................................................30
2.7.2.2 Incorporation techniques..................................................................30
2.7.3 Surface preparations.............................................................................32
2.7.3.1 Fertilizer incorporation.....................................................................32
2.7.3.2 Broadcast seed application and species composition.........................32
2.7.3.3 Mulch application............................................................................33
2.7.3.4 Vegetation plots map and tubestock plantings..................................34
2.7.3.5 Dates of plantings/replantings..........................................................35
2.7.4 Growth media sampling.......................................................................35
2.7.4.1 Timing and techniques.....................................................................36
2.7.4.2 Initial sampling of construction materials.........................................36
2.7.4.3 Pre fertilizer vs. post fertilizer sampling...........................................36
2.7.4.4 Yearly sampling...............................................................................37
2.7.5 Vegetation sampling............................................................................37
2.7.5.1 Emergence and survival of broadcast seeds......................................37
2.7.5.2 Survival of tubestock seedlings........................................................38
2.7.5.3 Nutrient concentrations of vegetation...............................................38
2.7.6 Field growth media water content measurements.................................39
2.7.6.1 Installation of access tubes...............................................................40
2.7.6.2 Sampling and data collection............................................................42
2.8 Experiment 3. Germination and emergence of Acacia saligna in altered
bauxite residue materials: part 1 and 2.....................................................................43
2.9 Purpose and background..............................................................................43
2.10 Experimental setup......................................................................................44
2.10.1 Treatments...........................................................................................44
2.10.2 Propagation trays.................................................................................45
2.10.3 Seed handling......................................................................................45
2.10.4 Watering and emergence counts...........................................................45
2.10.5 Categorizing non-emerged seeds..........................................................46
2.10.6 Part 1...................................................................................................46
2.10.7 Part 2...................................................................................................47
2.10.8 Extractable bases (Ca, Mg, K and Na), pH and EC...............................47
2.11 Experiment 4. Mobility of cations (Ca, Mg, K, Na) in altered bauxite residue
fines treatments: column leaching study..................................................................48
2.12 Purpose and background..............................................................................48
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2.13 Column leaching study experimental setup..................................................48
2.13.1 Column preparation.............................................................................48
2.13.1.1 Wetting to field capacity..............................................................49
2.13.1.2 Growth media solution samplers..................................................50
2.13.1.3 Leachate collection......................................................................51
2.13.1.4 Sampling regime..........................................................................51
2.13.2 Extractable and exchangeable base cation extractions..........................52
2.13.2.1 Leaching column rack construction..............................................52
2.13.2.2 Leaching soluble salts and extracting exchangeable bases............53
2.13.3 Soluble cations from saturated paste....................................................54
2.13.4 Electrical conductivity and pH.............................................................55
2.13.4.1 Growth media materials...............................................................55
2.13.4.2 Growth media solution and leachate.............................................55
2.13.5 Water retention characteristics.............................................................55
2.14 Statistics......................................................................................................55
Chapter 3 Plant Available Water.......................................................................57
3.1 Introduction.................................................................................................57
3.2 Materials and methods.................................................................................64
3.2.1 Column field capacity..........................................................................65
3.2.2 Porous plate pressure chamber.............................................................65
3.2.3 Field water content monitoring............................................................66
3.3 Results........................................................................................................66
3.3.1 Particle size analysis............................................................................66
3.3.1.1 Sand ................................................................................................66
3.3.1.2 Fines................................................................................................69
3.3.2 Estimated pore volumes from Experiment 1.........................................74
3.3.3 Pore volume verification from Experiment 4........................................75
3.3.4 Water retention characteristics from pressure plate chamber tests........75
3.3.4.1 Volumetric water contents...............................................................76
3.3.4.2 Retention curves..............................................................................77
3.3.4.3 Plant available water........................................................................80
3.3.4.4 Relationship between fines additions and volumetric water content..81
3.3.4.5 Estimated osmotic potential.............................................................83
3.3.5 Field water content measurements from experiment 2..........................85
3.3.5.1 Total water content..........................................................................85
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3.3.5.2 Water content by depth....................................................................89
3.4 Discussion...................................................................................................93
3.5 Conclusion..................................................................................................98
Chapter 4 Growth Media Nutrients and Nutrient Retention: Part 1 Plant
Available Nutrients and Cation Movement under Field Conditions......................99
4.1 Introduction.................................................................................................99
4.2 Background...............................................................................................101
4.3 Materials and methods...............................................................................102
4.3.1 Experiment 1. Acacia saligna glasshouse experiment.........................103
4.3.2 Experiment 2. Field experiment.........................................................103
4.4 Results.......................................................................................................104
4.4.1 Nutrient concentrations - Acacia saligna glasshouse study 1..............104
4.4.1.1 Initial materials..............................................................................104
4.4.1.2 Fines additions treatments..............................................................107
4.4.2 Nutrient concentrations from Experiment 2: Field study.....................114
4.4.2.1 pH..................................................................................................115
4.4.2.2 Electrical conductivity...................................................................117
4.4.2.3 Calcium.........................................................................................120
4.4.2.4 Magnesium....................................................................................122
4.4.2.5 Potassium.......................................................................................123
4.4.2.6 Sodium..........................................................................................125
4.5 Discussion.................................................................................................128
4.6 Conclusions...............................................................................................132
Chapter 5 Growth Media Nutrients and Nutrient Retention: Part 2 – Leaching,
Movement and Retention of Cations......................................................................135
5.1 Introduction...............................................................................................135
5.2 Background...............................................................................................136
5.3 Materials and methods...............................................................................140
5.4 Results: Concentrations, movement and loss of soluble cations..................142
5.4.1 Initial properties in residue treatments prior to leaching.....................142
5.4.1.1 pH and electrical conductivity........................................................142
5.4.1.2 Water soluble cations.....................................................................142
5.4.1.3 Cation saturation percentage..........................................................143
5.4.2 Leachate............................................................................................144
5.4.2.1 pH..................................................................................................144
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