This study presents a comprehensive physically based stochastic dynamic optimization model to assist planners in making decisions concerning mine soil depths and soil mixture ratios required to achieve successful revegetation of mined lands at different probability levels of success, subject to an uncertain weather regime. A perennial grass growth model was modified and validated for predicting vegetation growth in reclaimed mine soils. The plant growth model is based on continuous relationships between plant growth, air temperature, day length, leaf area, photoperiod and plant-soil-moisture stresses. A plant available soil moisture model was adopted to estimate daily soil moisture for mine soils. A general probability model was developed to estimate the probability of successful revegetation in a 5-year bond release period. The probability model considers five possible bond release criteria ir1 mine soil reclamation planning. A stochastic dynamic optimization model (SDOM) was developed to find the optimum combination of soil depth and soil mixture ratios that met the successful vegetation standard under non-irrigated conditions with weather as the only random element of the system. The SDOM was applied for Wise County, Virginia, and the model found that 2:1 sandstone/siltstone soil mixture required the minimum soil depth to achieve successful revegetation. These results were also supported by field data. The developed model allows the planners to better manage lands drastically disturbed by surface mining. / Ph. D.

In the western United States, elevated selenium (Se) levels in soil have resulted in documented cases of ruminant fatalities. This is due to the ingestion of Se-hyperaccumulating vegetation growing on previously reclaimed phosphate mine soils. A field-scale analysis was first conducted to examine Se bioavailability to plants. Soil and plant samples were collected from transects from five study locations in Soda Springs, Idaho. Soils were analyzed for Se speciation and geochemical phases using a sequential extraction procedure (SEP). Additionally, speciation, SEP results, and Se bioavailability in the hyperaccumulator, western aster (Symphyotrichum ascendens (Lindl.)), were related using simple linear regression. Soil speciation and the validity of this SEP were then evaluated using synchrotron-sourced X-ray absorption fine structure (XAFS) spectroscopy for both whole and a sequence of extracted soils. Lastly, competitive adsorption of Se with two dissolved organic carbon (DOC) species, citric and salicylic acid, was examined on an amorphous iron oxide mineral surface. A strong relationship was identified for western aster Se and the first two combined SEP fractions, water-soluble and PO43--extractable Se (R2 = 0.85; P = <0.0001). Results also indicated a strong relationship between selenate and water-soluble Se (R2 = 0.83; P = 0.0002). This suggests that water extracts could be useful Se bioavailability assessment tools in highly contaminated systems. XAFS analyses indicated that elemental and organic Se were the most predominant phases overall in whole soils. The dominant oxidized species present was selenite sorbed onto iron oxides and calcite. Critical SEP evaluations using XAFS also indicate that oxidized Se species were underestimated by the SEP and elemental Se was overestimated. In extracted soils, XAFS results indicated partial recovery of carbonate, iron oxide and organic Se occurred. Therefore, it is suggested that researchers exert caution when employing SEPs. Additionally, sorption analyses demonstrated the highly competitive behavior of citric acid with both selenite (pH 5-8) and selenate (pH 5-6). Little competition was observed in the presence of salicylic acid for both Se species. Competition and subsequent desorption of both sorbed species in the presence of citric acid suggest a possible mechanism for Se solubilization and bioavailability in seleniferous environments. / Ph. D. / Selenium (Se) is a contaminant found in elevated levels in soils and plants in the Western United States due to phosphate mining. This has caused livestock deaths throughout the mining region following ingestion of plants with particularly high Se levels. Soils and plants were sampled from five study locations and used to assess relationships between soils and plant Se uptake. A sequential extraction procedure (SEP) was used to estimate Se in soils related to soluble, exchangeable, bound, organic, and elemental forms of Se. X-ray absorption fine structure (XAFS) spectroscopy was then used to critically evaluate the validity of these phases and the procedure accuracy. Lastly, the competitive effects of organic acids, which are naturally present in soils, on Se sorption was evaluated in a batch reactor system. From the SEP analysis, higher levels of Se were found in organic and elemental fractions, moderate quantities were observed in sorbed fractions, and smaller abundances were observed in soluble and exchangeable fractions. Relationships between soluble Se and selenate, a highly bioavailable form of Se determined from speciation analyses, indicated that simple water extracts could be used to assess Se “hotspots” in order to prevent further livestock fatalities. The critical evaluation of this SEP using XAFS determined that this procedure was under- and over-estimating bound and organic extracted phases of Se. This was possibly due to mineral and organics that were incompletely dissolved during extraction. It was determined that researchers should exert caution prior to using SEPs and have suggested several recommendations. Lastly, the batch reactor analysis indicated a form of DOC, citric acid, was highly competitive for mineral surface sites with selenite and selenate. Competition from salicylic acid was not obvious. Differences in competition were speculated to be linked to differences in molecular structure. This work suggests possible mechanisms for solubilization of both selenite, which is typically strongly bound, and selenate, which is typically soluble, in soil systems. Results offer an explanation for the exceedingly bioavailable nature of Se in the Western US.

Carbon accreditation of forest development projects is essential for sequestering atmospheric CO2 under the provisions of the Kyoto Protocol. The carbon sequestration potential of surface coal-mined lands is not well known. The purpose of this work was to determine how to measure carbon sequestration and estimate the additional amount that could be sequestered using different reforestation methods compared to the common practice of establishing grasslands. I developed a thermal oxidation technique for differentiating sequestered soil carbon from inorganic and fossilized carbon found at high levels in mine soils along with a geospatial and statistical protocol for carbon monitoring and accounting. I used existing tree, litter, and soil carbon data for 14 mined and 8 adjacent, non-mined forests in the Midwestern and Eastern coal regions to determine, and model sequestered carbon across the spectrum of site index and stand age in pine, mixed, and hardwood forest stands. Finally, I developed the framework of a decision support system consisting of the first iteration of a dynamic model to predict carbon sequestration for a 60-year period for three forest types (white pine, hybrid poplar, and native hardwoods) at three levels of management intensity: low (weed control), medium (weed control and tillage) and high (weed control, tillage, and fertilization). On average, the highest amount of ecosystem carbon on mined land was sequestered by pine stands (148 Mg ha-1), followed by hardwood (130 Mg ha-1) and mixed stands (118 Mg ha-1). Non-mined hardwood stands contained 210 Mg C ha-1, which was about 62% higher than the average of all mined stands. After 60 years, the net carbon in ecosystem components, wood products, and landfills ranged from 20 to 235 Mg ha-1 among all scenarios. The highest net amount of carbon was estimated under mixed hardwood vegetation established by the highest intensity treatment. Under this scenario, a surface-mined land of average site quality would sequester net carbon stock at 235 Mg C ha-1, at a rate of 3.9 Mg C ha-1 yr-1, which was 100% greater than a grassland scenario. Reforestation is a logical choice for mined land reclamation if carbon sequestration is a management objective. / Ph. D.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The Northern Cape Province of South Africa has played host to numerous mining activities for over a century. To date, most of the mining activity has ceased, leaving the area laden with derelict mine sites and unlined tailings dumps. One such site is the Spektakel mine situated to the west of the town of Springbok. The unlined copper and sulphide rich tailings at the site have the potential to leach elevated concentrations of copper and acidic water into the Buffels River downslope of the site. This poses a threat to the surrounding communities that rely mainly on the river to supply water for drinking, livestock and irrigation. The soil surrounding the tailings dumps was characterised in terms of its mineralogical and chemical properties. The results indicate that the soil contains elevated concentrations of Cu2+, which is bound in the soil in the form of the secondary copper hydroxy mineral atacamite (Cu2(OH)3Cl). No other secondary copper minerals were identified at the site. Analysis of the solution present on the surface of the tailings dumps indicate that the tailings are the main source of the high Cu2+, Mg2+ and SO42- concentrations observed in the surrounding soils. As this solution migrates through the tailings dumps, into the soil, it accumulates Cl- through halite dissolution. The resulting acidic Cu2+, Mg2+, SO42- and Cl- solution reacts with the calcite in the soil, replacing it with atacamite. To determine why only a copper chloride mineral formed in the sulphate rich environment a synthetic solution with the composition of a solution in equilibrium with the soil was evaporated, both in the presence and absence of calcite. The results indicate that when the solution comes into contact with calcite, atacamite immediately precipitated, removing the Cu2+ from the solution. In the absence of calcite Cu2+ remains conservative, accumulating in the solution without precipitating a copper sulphate mineral. This establishes that the elevated Mg2+ concentration of the solution induces the formation MgSO4 aqueous complexes that reduce the activity of free sulphate, thus restricting copper sulphate mineral formation. The results from the soil characterization indicate that the atacamite stabilization mechanisms (circumneutral pH, high Cl- concentration and calcite) in the soil are diminishing. During sporadic rain events the acidic tailings solutions dissolve the calcite and temporarily reduce the Cl- concentration of the soil. To determine how these decreases will influence Cu2+ mobility in the soil, the stability of atacamite was tested by reducing the pH both in the presence and the absence of chloride. The results indicate that an elevated Cl- concentration and a pH > 6 stabilizes atacamite. A decrease in either of these parameters destabilizes atacamite and favours its dissolution. The study concludes that the current chemical conditions in the soil at Spektakel favour the stability of atacamite. However, continued sporadic rain events will reduce the Cl- concentration in the soil by increasing the SO42- concentration. This acidic solution will dissolve the calcite in the soil, thus reducing the buffering capacity of the soil, leading to the instability of atacamite, resulting in the leaching of large quantities of Cu2+ into the surrounding water bodies. / AFRIKAANSE OPSOMMING: Die mynbou bedryf was die ekonomiese dryfkrag van die Noord-Kaap Provinsie van Suid-Afrika vir meer as ‘n eeu. Die area was die gasheer vir ‘n verskeidenheid mynbou aktiwiteite tot die mynmaatskappye besluit het om mynproduksie te staak en die gebied te verlaat. Die mynmaatskappye het geen rehabilitasie aan die myne en mynhope verrig nie. Die verlate myne lê verspreid in die area met oop mynhope wat koper en ander swaar metale in die grond, sowel as in die water, na omliggende areas kan versprei. Een van dié verlate myne is die Spektakel myn 40 km wes van Springbok. Die mynhope by Spektakel kan moontlik koper en ander swaar metale in die Buffelsrivier, wat langs die myn verby loop, loog. Dit dien as ‘n bedreiging vir die omliggende gemeenskappe wat staatmaak op die water vir drinkwater en besproeiing. Die grond rondom die mynhope was ge-analiseer om te bepaal hoe erg ‘n bedreiging die mynhope vir die omgewing is. Die resultate dui daarop dat die grond hoë konsentrasies Cu2+ bevat wat vasgebind is in die sekondêre koper mineral atakamiet (Cu2(OH)3Cl). Geen ander sekondêre koper minerale is in die grond geïdentifiseer. Die analise van die oplossing wat bo-op die mynhoop aangetref is dui aan dat dié oplossing suur en gekonsentreerd is t.o.v. Cu2+, Mg2+ en SO42-. Terwyl die oplossing deur die mynhoop migreer los dit haliet in die grond op wat Cl- tot die oplossing byvoeg. Wanneer hierdie suur en Cu2+, Mg2+, SO42- en Cl- ryke oplossing met die kalsiet in die grond reageer word die kalsiet vervang met atakamiet (Garrels en Stine, 1948). Om vas te stel waarom slegs 'n koperchloried mineraal vorm in die sulfaat ryke grond was ‘n oplossing, met ‘n samestelling soortgelyk aan 'n oplossing in ewewig met die grond, verdamp in beide die teenwoordigheid en afwesigheid van kalsiet. Die resultate van die eksperiment dui daarop dat wanneer die oplossing in kontak kom met kalsiet atakamiet onmiddellik neerslaan en Cu2+ uit die oplossing verwyder. In die afwesigheid van kalsiet bly Cu2+ konserwatief in die oplossing; die Cu2+ hoop op in die oplossing en slaan nooit neer nie. Daar is vasgestel dat die verhoogde Mg2+ in die grondoplossing MgSO4 water komplekse vorm wat die aktiwiteit van SO42- verlaag en verhoed dat kopersulfaat minerale kan vorm. Verdere navorsing dui aan dat die chemiese meganismes wat atakamiet in die grond stabiliseer besig is om te kwyn. Gedurende sporadiese reën buie word die kalsiet in die grond opgelos deur die suur mynhoop oplossings wat die pH van die grond verlaag. Die mynhoop oplossing verryk ook die grond t.o.v SO42- wat die Cl- konsentrasie verlaag. Om te bepaal hoe hierdie afname in Cl- konsentrasie en pH die migrasie van Cu2+ beïnvloed was atakamiet oplossbaarheid bepaal. Atakamiet was onderskeidelik geplaas in ‘n suiwer water en chloried oplossing tewyl die pH verlaag was om te bepaal hoe atakamiet oplos in elk van die oplossings. Die resultate dui aan dat 'n verhoogde Cl- konsentrasie en pH > 6 atakamiet stabiliseer. Die afname van beide hierdie veranderlikes het veroorsaak dat atakamiet makliker ontbind en Cu2+ vrystel. Die gevolgtrekking van die studie is dat die huidige chemiese toestande in die grond by Spektakel gunstig is vir die stabiliteit van atakamiet. Met sporadiese reën buie neem die Cl- konsentrasie in die grond af en los kalsiet op. Hierdie afname in pH en Cl- konsentrasie maak atakamiet meer onstabiel wat gevolglik Cu2+ in die grond en water rondom Spektakel vrystel.

[Truncated abstract] Many soil properties are involved in supporting the growth of plants and in limiting soil degradation. The present study was carried out to provide a basis for minimising environmental impact by providing a firm understanding of the soil properties that affect plant growth for soils developed from mining waste from the Wesfarmers Premier coalmine at Collie. The purpose of this study was to provide an understanding of the soil materials and to identify the potential interactions between soil properties and plants for soils developed on coalmine materials at the Premier mine, Collie. This research was to identify the nature of the manmade soils so as to determine if soil forming processes are active, to determine soil acidity including pH buffering capacity and the lime requirement of soils, to measure water retention characteristics and soil available water for plant growth, to relate soil properties to possible effects on plant growth, and to identify management strategies to improve soil conditions and overcome plant growth constraints. Seventy-seven manmade horizons from pits in 18 constructed soils, ranging from 9 to 21-years old, were analyzed throughout this study. These samples are classified based on soil depth, layer (topsoil and subsoil), and age of soil since rehabilitation. The methods for doing most of the analyses follow the Australian Soil and Land Survey handbook by Rayment and Higginson (1992). The results are presented quantitatively and soil properties are compared to provide information on pedogenic processes, the extent of soil development, the ability of the soils to resist degradation and to provide an indication of soil parent materials

Soil organic matter (SOM) is highly important for soil quality and the global carbon cycle. SOM content is influenced by a complex interplay of many different factors such as time, climate, parent material, vegetation, and others. The effect of time is often studied using the chronosequence approach using a set of study sites differing in age but comparable in other soil-forming factors. The effect of other factors can be studied by comparing two or more chronosequences. An important assumption of these approaches is that the SOM quantification methods produce comparable results both among sites of each sequence and among different sequences. In this thesis, I explored the key factors in SOM accumulation and dealt with SOM quantification methods. I studied SOM accumulation in two model situations - in post-mining sites after open-cast coal and oil shale mining and in landslides in the Western Carpathians. The results of this thesis are summarized in one book chapter accepted for publication and four papers, out of which three have been published and one is prepared for publication in an international journal with impact factor. The key factor affecting the rate of SOM accumulation after a major disturbance is time. The accumulation rates found in the first 40 to 100 years in both post-mining sites...

[Truncated abstract] Industrial processing to refine alumina from bauxite ore produces millions of tonnes of refining residue each year in Australia. Revegetation of bauxite residue sand (BRS) is problematic for a number of reasons. Harsh chemical conditions caused by residual NaOH from ore digestion mean plants must overcome extremely high pH (initially >12), saline and sodic conditions. At such high pH, manganese (Mn) is rapidly oxidised from Mn2+ to Mn4+. Plants can take up only Mn2+. Thus, Mn deficiency is common in plants used for direct BRS revegetation, and broadcast Mn fertilisers have low residual value. Added to this, physical conditions of low water-holding capacity and a highly compactable structure make BRS unfavourable for productive plant growth without constant and large inputs of water as well as Mn. However, environmental regulations stipulate that the residue disposal area at Pinjarra, Western Australia, be revegetated to conform with surrounding land uses. The major land use of the area is pasture for grazing stock. Hence, pasture revegetation with minimum requirement for fertiliser and water application is desirable. This thesis investigates a number of avenues with potential for maintaining a productive pasture system on BRS whilst reducing the current level of Mn fertiliser and irrigation input. Emphasis was placed on elucidation of chemical and physical factors affecting Mn availability to plants in BRS