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Papers by Thomas Baumgartl

Water, Jun 9, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

The impacts of high salinity and polymer properties on dewatering and structural characteristics of flocculated high-solids tailings

Journal of Cleaner Production, Mar 1, 2022

How Farmers, Graziers, Miners, and Gas-Industry Personnel See Their Potential for Coexistence in Rural Queensland

SPE Economics & Management, 2014

Summary The rapid expansion of the coal-seam-gas (CSG) sector in Queensland has fueled debate on ... more Summary The rapid expansion of the coal-seam-gas (CSG) sector in Queensland has fueled debate on the sector's contributions to community sustainability in a rural economy dominated by the farming of food and cotton, cattle grazing, coal mining, and a modest level of tourism. For example, will the impacts of CSG extraction on surface and groundwater have sustained negative impacts on the growing of grain, and if so, what should one expect of the CSG industry today? The intensity of debate is accompanied by an array of operating conditions placed on CSG projects by the state government, extensive media coverage, and a focus on what it takes to maintain a “social license to operate.” Such a context is a challenge for resource companies committed to sustainability principles and to contributing to the social, economic, and institutional development of the communities in which they operate as well as to the conservation of biodiversity and integrated approaches to land-use planning. ...

A cellular automata-based run-of model and its application in mined land rehabilitation designs

Paste ..., 2018

Tailings rehabilitation, using soil-like properties with chemical and physical stability, can be ... more Tailings rehabilitation, using soil-like properties with chemical and physical stability, can be influenced by surface forces on a particle scale and microstructure. Non-homogeneous structures, manifesting as particle aggregation, alter the permeability/porosity and improve the balance of aerated and water-filled pores that then favours plant growth. Polymer flocculation in tailings thickeners yields large, weak aggregates that are sheared in beds and on pumping. While low-level residual structure may remain, sizes are small and downstream polymer impacts are minor. However, high polymer dosages added in-pipe to high-solids streams lead to further water recovery on deposition, and while this process is poorly understood, it gives aggregates that are likely denser and stronger. If such structures persist, they could potentially offer closure and rehabilitation benefits in some applications. A high-solids (50 wt%) thickener underflow analogue (kaolin, silt, and fine sand) was treated with anionic polyacrylamide (PAM) polymers at elevated dosages (up to 1,000 g t-1) to establish if aggregate structures created during inline tailings flocculation survive or change over longer-term consolidation. Low and high molecular weight (MW) PAM polymers of fixed anionicity (30%) were tested. Focused beam reflectance measurement (FBRM) provided real-time monitoring of the aggregation state after polymer addition. The compressibility of the inline flocculated tailings was assessed over an eight week period. Variations in the size-density relationship of aggregate structures were determined over this period using an image analysis technique, revealing that the shorter polymer chains produced denser, more compact structures immediately after deposition, whereas the longer chains resulted in a much slower re-conformation of the partially adsorbed polymer, leading to additional densification over time. Eight weeks after deposition, inline flocculated tailings produced with the low MW polymer were characterised by a higher compressive yield stress compared with the high MW polymer, consistent with the formation of smaller, more rigid aggregate structures with the shorter chains. The potential impact of such structures on longer-term rehabilitation properties (e.g. metal/metalloid ion adsorption and surface exchange capacity) of the treated tailings is discussed.

Land Degradation & Development, Mar 8, 2018

Large-scale open cut mining has occurred within the Bowen Basin for over 4 decades, transitioning... more Large-scale open cut mining has occurred within the Bowen Basin for over 4 decades, transitioning from shallow mining depths and limited spoil elevation to increased mining depths, prestripping and increasingly elevated mesa-like landforms. As a result of this evolution, the stabilisation of modern constructed landforms is no longer assured through the establishment of vegetation alone. The selection of resilient fragmental spoil types for the construction of final landform surfaces, and as cladding for stabilising steep erosive batters, is a practical methodology that has the potential to significantly improve rehabilitation outcomes, by increasing surface rock cover, roughness, and infiltration and reducing erodibility. An understanding of the properties and behaviour of individual spoil materials disturbed during mining is required. Relevant information from published literature on the geological origins, lithology, and weathering characteristics of individual strata within the Bowen Basin Coal Measures (and younger overlying weathered strata) has been reviewed, related to natural landforms and applied to the surface stability of major strata types when disturbed by mining. A spoil classification derived from geological characteristics and weathering behaviour of identifiable lithologic components has been reviewed and refined, demonstrating the application of use of geological information. This classification system is a tool for the allocation of spoil types and use of categories that have application in premine feasibility investigations, landform design, and material selection and placement. The logic of classifying materials based on their stability in the natural landscape has wider relevance to other mining areas where elevated landforms of sedimentary material are constructed.

Water, Jun 28, 2023

EroCA: a new tool for simulating constructed landform erosion

Extensive disturbances during the mining and rehabilitation process can include removal of vegeta... more Extensive disturbances during the mining and rehabilitation process can include removal of vegetation, removal and storage of soils hence their modification, changes in topography, and planting of new vegetation. A main goal of mine rehabilitation is to produce a post-mining landscape that is resistant to geotechnical failure and to surface erosion processes. To achieve this, hydrology and erosion models are required to determine erosion rates under alternative landscape designs, including landscape form and cover options. By critical review of the relevant literature, it was found that most previous erosion modelling studies have concentrated on surface hydrology in agricultural, forestry, and other natural systems, while disturbed ecosystems like mining regions have received little attention. Landscape evolution models have been developed for mined landform applications but modelling over long time-scales compromises the temporal and spatial resolution. The main objectives of this research therefore were: Extend an existing plot-scale hydrological model to plot-scale erosion model. To improve knowledge of the errors and uncertainty in applying a high-resolution erosion model to mined landforms and to conclude on the potential applicability and limitations of EroCA. The experimental data used in the research were from a 30 m × 30 m field plot on a mine waste rock dump in the wet tropical environment of the Ranger mine (north-east Australia) from the period 2009 to 2014. The new EroCA model is an extension to the RunCA model, which was developed to provide high resolution simulation of runoff and infiltration in constructed landforms. The extended model uses mass balance principles and established erosion and sediment transport models, covering both suspended and bedload, and solves the equations using the cellular automata approach. Code verification against analytical solutions of runoff and sediment illustrated small errors, which were partly due to approximations used in the analytical solutions. The EroCA model was then applied to the Ranger experimental plot data to assess the suspended and bedload erosion performance. EroCA was able to reasonably represent the observed flows and turbidity profiles. Although an arbitrary reduction in the erodibility parameter value of 20% per year was needed to simulate the bedload depletion.

Hydrological performance of soil and vegetation covers impact in mine rehabilitation: results of a preliminary modelling study

Rehabilitation in the mining context refers to restoring the natural characteristics such as land... more Rehabilitation in the mining context refers to restoring the natural characteristics such as land stability, vegetation, soil functions, biodiversity and hydrological cycle. The main aim of mine rehabilitation is to construct environmentally sustainable landforms and to restore their ecosystem services, either to a site specific stable equilibrium or ideally to its previous state. The objective of this work is to build a predictive and decision making tool using hypothetical modelling to simulate water fluxes for two different scenarios in terms of different soil cover depth including vegetation (grass). Hypothetical hydrological modelling was performed using the HYDRUS-1D with one-dimension water flow modelling based on the Richards equation and hydraulic functions of van Genuchten-Mualem model. The soil and coal hydraulic parameters were derived from laboratory tests using the extended evaporation method. Water flux modelling was performed for 2021 using the climatic data from Latrobe Valley (Victoria, Australia) meteorological station, where the coal and soil samples were collected. Two scenarios were selected which varied in the depth of soil cover and coal layer, both with grass vegetation on top of the soil columns. The first scenario (S1) had 50 cm of soil cover, while the second scenario (S2) had 100 cm of soil cover on top of coal material, respectively. Modelling results revealed that soil water content and fluxes were directly reflecting the precipitation pattern and the most limiting factor in downward water flow was the low permeability of the coal layer. The hydraulic parameters for coal show large water retention capacity at very low hydraulic conductivity. The shallower soil cover in the S1 scenario resulted in higher soil water content during the period of intense rainfall and resulted in larger and faster initiation of surface runoff. The thicker soil cover layer resulted in larger infiltration rate and root water uptake which was however limited when the soil was fully saturated in both scenarios. Interestingly, very similar bottom flux in both scenarios even with two different coal layer depth (i.e., 30 cm vs 80 cm) were recorded. Water balance results indicate increase in potential of storing water in the S1 scenario which has a thicker coal layer due to its high water retention capacity. However, at this point it is not clear to what extent stored water from coal can be available for plants. Beside valuable research insights in terms of soil cover design, hypothetical modelling will assist in preventing experimental design flaws and providing a more efficient, robust controlled experiment performed in a next study phase.

The impact of preferential flow on Temperate Highland Peat Swamps on Sandstone soil hydrology

&lt;p&gt;Temperate Highland Peat Swamps on Sandstone (THPSS) are ecological commu... more &lt;p&gt;Temperate Highland Peat Swamps on Sandstone (THPSS) are ecological communities that consist of either ephemeral or permanent swamps developed in peat overlying Triassic sandstone formations in the Sydney Basin Bioregion of eastern Australia. THPSS with distinctive vegetation play an important role in biodiversity, carbon capture and storage, and the regional hydrological cycle. Some THPSS of Sydney Basin have underlying sandstone with cracks potentially formed over the past decades by human intervention. These cracks may create preferential flow paths that may accelerate the drainage process at the bottom of the swamps and may affect the soil moisture conditions of the swamps with ecological consequences. In order to understand and predict the impact of cracks on the swamps&amp;#8217; soil moisture and provide information to guide the management and restoration of the THPSS, 2D numerical simulations have been carried out using dual-porosity hydraulic models or explicit fast flow paths to represent the preferential flow paths. The models are calibrated and validated against historical soil moisture data and then used to evaluate the effect of cracks on soil moisture.&lt;/p&gt;

Assessing environmental safety of in-pit disposal of tailings in coal mines

Proceedings of the International Conference on Mine Closure, 2021

Rehabilitation intends to provide a safe, stable and sustainable environment. Soil health is ofte... more Rehabilitation intends to provide a safe, stable and sustainable environment. Soil health is often used as a parameter, which describes the success of reclamation, the performance of the soil and its associated soil system functions. Reclaimed and therefore young soils are in general deprived of soil organic carbon. They are not in equilibrium with their environment and undergo changes over time, faster than natural and developed soils. Carbon content as a summarising criterion for soil health status can be used as an indicator as it reflects the performance of important soil processes, like water holding capacity, drainage and aeration potential and nutrient supply and storage. It is well established that carbon content affects soil functions like hydraulic conductivity by creating structural elements through aggregation processes. Increasing carbon content leads to increased water infiltration, reduced surface runoff and erosional risks, and increases the exchange rate of gases and improves aeration and has in general positive consequences for microbiological activity. Results from a study of soil covers of different ages emphasise this consequence. The evaluation of the rehabilitation success in coal mining using carbon content is complicated due to the difficulty distinguishing between carbon forms: organic carbon naturally formed by decomposition vs. carbon originating from coal as coal dust or charred material. Furthermore, the assessment of the performance of rehabilitated soils is strongly affected by climatic conditions, which affect the production, decomposition and translocation of organic matter. Litter and dead organic matter from plants are decomposed on the soil surface and incorporated through organisms into the soil profile. Dissolvable organic constituents may be transported with infiltrating water down the profile. Consequently, carbon is primarily concentrated close to the surface. In semi-arid environments the accumulation depth may only be centimetres as was found from a study on the performance of the carbon pool of rehabilitated soils across sites up to 35 years of age. This has implications for the sampling strategy and the assessment of the performance of soils over time. As the carbon content in soils at coal mines can be affected by precipitation and incorporation of coal dust into the soil, the content of new organic carbon representing soil health status can be misleadingly interpreted. Therefore, separation of carbon fractions is necessary to identify the "green" carbon pool (carbon originating from plant litter and residue) as best as possible and extract the correct fraction to assess the performance of soil development. A method has been developed and is presented which allows the separation between the various carbon pools. From the presented study, the following conclusions were drawn: 1) Soil carbon is an easy to measure indicator for the assessment of the performance of soil health of rehabilitated soils; 2) soil functional properties are affected by carbon content and age and hence change with soil development; 3) only green carbon represents soil health and appropriate methodology has to be in place to exclude other carbon pools; 4) carbon storage in rehabilitated soils of semi-arid environments of Australia is below that of natural soils.

Soil Science Society of America Journal, Jul 1, 2017

Aggregation of tailings is instrumental for developing a physical environment permitting water in... more Aggregation of tailings is instrumental for developing a physical environment permitting water infiltration, aeration, and root penetration. Previous research found that microaggregation of Cu-Pb-Zn tailings was stimulated by amendment of composted sugarcane residues. The present study aimed to identify organic functional groups in humic acids (HA) involved in the aggregation of Cu-Pb-Zn tailings, which were considered to be formed from long-term organic matter decomposition in the engineered tailing-soil. The adsorption of HA by the weathered (WT) and freshly deposited (FT) tailings was evaluated at a range of pH conditions in tailing-HA suspension. Humic acid adsorption decreased with increasing pH from 5.0 to 9.0. The FT was found to contain more oxy-(hydr)oxides, particularly poorly crystalline Fe and Al oxy-(hydr)oxides than the WT, which was one of the factors attributing to FT's higher HA affinity. The Fourier transform infrared spectroscopy analysis of tailing particles before and after HA adsorption indicated that carboxylic and phenolic groups of HA preferentially interacted with tailing mineral particles, probably through ligand exchange, polyvalent cation bridge and electrostatic attraction. The pH-dependent HA adsorption indicated the potential role of functional groups of organic matters in microaggregation of Cu/Pb-Zn tailings. Moreover, the presence of abundant Al/Fe oxyhydroxides promoted organo-mineral interactions. The present findings will contribute toward developing field application to engineer functional Technosols from the tailings by selecting organic matter rich in functional groups. Abbreviations: HA, humic acid; FT, freshly deposited tailings; OM, organic matter; WT, weathered tailings. L arge volumes of soil and cover materials are required to reconstruct root zones and soil profile for tailings rehabilitation at metal mines, leading to huge financial costs associated with the closure and rehabilitation of tailings storage facilities. Developing Technosols from mine tailings by ecological engineering inputs and practices have been advocated as a cost-effective and ecologically sustainable technology for rehabilitating large areas of tailings landforms at mine sites (Huang et al., 2014). While many studies in literature focused on physical development in natural soils, much less is known about aggregation in novel and engineered parent materials like tailings. Rehabilitating physical properties (e.g., aggregates and aggregate stability, development of macropores) in tailings of silty texture is one of the critical challenges when engineering soil formation from mine tailings toward functional technosols with the primary goal of supporting sustainable plant communities (Uzarowicz and Skiba, 2011; Huang et al., 2014). The formation of microaggregates (<250 mm) is a process of solid-phase reaction among organic matter (OM), polyvalent cations and mineral particles of different sizes (Edwards and Bremner, 1967), mainly through organo-mineral interactions (Tisdall and Oades, 1982). These interactions are the foundation of soil

International Journal of Sustainable Development and World Ecology, Jan 4, 2017

Mining development can potentially lead to cumulative impacts on ecosystems and their services ac... more Mining development can potentially lead to cumulative impacts on ecosystems and their services across a range of scales. Site-specific environmental impact assessments are commonly assessed for mining projects; however, large-scale cumulative impacts of multiple mines that aggregate and interact in resources regions have had little attention in the literature and there are few examples where regional-scale mining impacts have been assessed on ecosystem services. The objective of this study is to quantify regional-scale cumulative impacts of mining on sediment retention ecosystem services. We apply the sediment delivery ratio model of Integrated Valuation of Ecosystem Services and Trade-offs to calculate and map the sediment retention and export using a synthetic catchment model and a real case study under different mining scenarios in an Australian mining region. Two impact indices were created to quantify the cumulative impacts associated with a single mine and the interactions between multiple mines. The indices clarified the magnitude of impacts and the positive/negative impacts associated with regional-scale sediment retention and export. We found cumulative impacts associated with multiple mines' interaction occurred but the influence of these interactions was relatively weak. This research demonstrated the potential for utilising ecosystem services modelling for the quantitative assessment of the cumulative impacts. Such research provide decision-makers and planners with a tool for sustainable regional and landscape planning that balances the needs of mining and the provision of ecosystem services.

Ecological Engineering, May 1, 2017

Direct seeding is an effective approach for plant re-establishment and revegetation of post-minin... more Direct seeding is an effective approach for plant re-establishment and revegetation of post-mining areas. However, germination of seeds is influenced by environmental stressors such as soil water conditions and salinity, eventually affecting revegetation success. In this study, we conducted laboratory experiments to evaluate the effect of water stress and salinity on the germination of Atriplex halimus seeds. We exposed seeds to various solutions of NaCl and Polyethylen Glycol (PEG) ranging from soil saturation (0 MPa) to permanent wilting point (−1.5 MPa). We measured the germinability and mean germination time to quantify seed germination. Based on the measured germination data, we estimated the parameters of the hydrotime model, which is a critical tool to predict timing and success of seed emergence. At an osmotic potential of −1.5 MPa, 31% or 3% of the seeds germinated when exposed to PEG or NaCl solution, respectively. This indicates that Atriplex halimus seeds are highly tolerant to water stress, but less tolerant to salinity stress. The results of this study suggest that direct seeding of Atriplex halimus may be an effective path for revegetation of post-mining landscapes where salinity and water stress are predominant features of the environment.

Geoderma, Apr 1, 2017

Saline-sodic soils may be reclaimed through the addition of amendments to alter the soil pore sys... more Saline-sodic soils may be reclaimed through the addition of amendments to alter the soil pore system and hydraulic functions, therefore allowing salts to be leached from the soil. For the purpose of investigating the suitability of specific amendments for improving leaching and reclamation, soil percolation column studies were conducted to assess the influence of amendments on cation exchange, the potential for the release of cations and changes in hydraulic conductivity of the soil. A fine textured saline-sodic soil amended separately with 20% wood chips (wt/wt), 40% fine sand (wt/wt) and 2.5% bentonite (wt/wt) was used for this study as well as a non-amended soil as a control. The impact of amendments was evaluated by continuous leaching of the soil substrates with deionized water until the hydraulic conductivity and leachate chemistry stabilised. The bentonite amended soil had a greater increase (15.9 cmol c kg −1) in exchangeable Ca 2+ and a higher reduction in exchangeable Na + (12.29 cmol c kg −1) after the final leaching due to a greater rate of cation exchange for this soil substrate. The bentonite amended soil also had a greater reduction (92%) in Na + content compared with the other soil substrates. The hydraulic conductivity of all soil substrates improved during leaching although the hydraulic conductivity of bentonite amended soil reduced after three pore volumes of leaching. This study suggests that a slower water movement (an increased percolation time) and a greater rate of cation exchange were associated with the greater leaching efficiency. Therefore, addition of bentonite improves and accelerates the reduction of salinity and sodicity.

Capturing SUbsurface PREferential transport processes in agricultural HILLslope soils: SUPREHILL CZO

Agricultural hillslopes present particular challenges for estimating vadose zone dynamics due to ... more Agricultural hillslopes present particular challenges for estimating vadose zone dynamics due to a variety of processes, such as surface runoff, vertical flow, erosion, subsurface preferential flow affected by soil structure and layering, non-linear chemical behaviour, evapotranspiration, etc. To investigate these processes and complexity, the SUPREHILL critical zone observatory (CZO) was started in 2020, at vineyard hillslope site in Croatia. The observatory is extensively equipped for the soil-water regime and agrochemical fluxes monitoring, and includes an extensive sensor network, lysimeters (weighing and passive wick), suction probes, surface and subsurface flow and precipitation collection instruments. The main objective of the SUPREHILL observatory is to quantify subsurface lateral and local scale preferential flow processes. Local-scale nonlinear processes in eroded agricultural hillslope sites have large significance on water and solute behaviour within the critical zone and thus need to be researched in depth using combined methods and various approaches. First results from the sensor and lysimeter network, soil-water regime monitoring, isotope analysis, and agrochemical concentrations in 2021 supported the hypothesis of the observatory, that the subsurface flow plays a relevant part in the hillslope soil-water dynamics. In the wick lysimeter network, although the highest cumulative outflow values were found at the hilltop, the highest individual measurements were found at the footslope. During high-intensity rainfall events, there were differences in weighing lysimeters, possibly related to subsurface lateral flow. Based on the isotope analysis, wick lysimeters exhibit a greater variation of d-excess values than suction probes. Agrochemical fluxes confirmed the sloping effect on their transport in soil and demonstrated the favourability of Cu transport by subsurface flow. Using the comprehensive database presented herein, future analyses of this hypothesis will be carried out in more detail using model-based analyses.

How do mine rehabilitation strategies affects soil heterogeneity and structure in the long term?

Open-cast or surface mining present a site-specific and a temporary use of land that unavoidably ... more Open-cast or surface mining present a site-specific and a temporary use of land that unavoidably involves the displacement of the fertile topsoil layer and overall environmental change. Following mine closure, rehabilitation of mining areas is essential to build sustainable and stable landforms. Reclamation of soils is particularly challenging as their construction needs to take into account broader land reclamation analysis including soils, water, vegetation, stability and biodiversity effects. The objective of this study was to assess development in soil properties of rehabilitated soils since construction (1980, 1998, 2009, 2016, 2017) focusing on hydraulic and mechanical soil properties. The study was performed at an open-cast lignite coal mine site in south-east Australia (Victoria) in 2021. Soil hydraulic properties (SHP) were determined using the extended evaporation method while the mechanical properties were assessed using in-situ vane shear tests. The study indicated the relevance of a consistent soil cover design and construction. The soil hydraulic properties results showed a shift in soil water retention curve characteristic (1980 vs 2017 site), together with a decrease in saturated hydraulic conductivity (Ks), which can certainly influence soil water dynamics and increase surface runoff. The vane shear test showed large heterogeneity among the sites with rehabilitated sites indicating large internal variation compared to the reference site and generally higher shear resistance. Differences in soil hydraulic conductivity and higher SOC storage over time revealed developments in soil recovery, but the improvement in soil mechanical strength did not show any relation to soil properties affecting soil structural stability. Rather, the change was driven by the large variability in texturally affected pore size distribution among the sites. The observed small-scale heterogeneity of the rehabilitated soils is most likely explained by disturbance due to excavation activities and used rehabilitation methods as well as availability of the soil material. Closer monitoring of rehabilitated areas temporally and spatially as well as in improvement in topsoil cover design is recommended, as such heterogeneity leads to uncertainty in long-term sustainable landscape formation.

Proceedings of the International Conference on Mine Closure, 2022

Since closure of the Hazelwood Power Station in 2017, and the associated Morwell open cut mine, t... more Since closure of the Hazelwood Power Station in 2017, and the associated Morwell open cut mine, the community of the Latrobe Valley have largely come to terms with the coming end of an industry that for almost a century defined their region. However, the capacity for the community to envisage what comes next has been limited. This is in part due to uncertainty of the viability of options for rehabilitation, future ownership and responsibility for the sites, and a challenging policy framework. It is also related to systemic social issues, such as mistrust of both government and energy companies, as well as over-consultation fatigue. We draw here on findings from a recent study, commissioned by AGL Loy Yang, on the community perspectives on the final void forms and future land and water uses of the three Latrobe Valley open cut brown coal mines-and surrounding lands. The data were obtained through a series of focus groups with key stakeholders, including community organisations, environmental groups, government authorities, business groups, primary producers and Traditional Owners; and a web-based survey, completed by over 560 participants. From this we found a common theme concerning a desire to have the land returned to the community and to leave a positive legacy for the sites. Options that were visually attractive and enabled either recreation and/or tourism were preferred to future industrial uses; environmental benefit was also a strong priority. Authentic community consultation necessitates that the community be empowered to make an informed contribution to the discussion, and that they are made aware of how their input will be utilised. The community of the Latrobe Valley are invested in having a positive outcome for their region, which future generations can benefit from. To achieve this, the community must be actively engaged in the process.