Effect of Water Potential on Growth and Iron Oxidation by Thiobacillus ferrooxidans

The effect of water potential on the growth of two strains of Thiobacillus ferroxidans was determined by adding defined amounts of sodium chloride or glycerol to the culture medium. The two strains differed slightly, and the most tolerant strain had a minimum water potential for growth of -15 to -32 bars when sodium chloride was used and -6 bars when glycerol was used. In another approach, the limiting water potential was determined by equilibrating small amounts of culture medium with atmospheres of relative humidities equivalent to specific water potentials, and the ability of the organism to grow and oxidize ferrous iron was determined. Under these conditions, which are analogous to those which might control water potential in a coal refuse pile or copper leaching dump, the lower limit at which iron oxidation occurred was -23 bars. The water potential of some coal refuse materials in which T. ferrooxidans was present were determined, and it was found that the water potentials at which the organism was active in these habitats were similar to those at which it was able to grow in culture. However, marked variation in water potential of coal refuse materials was found, presumably due to differences in clays and organic materials, and some coal refuse materials would probably never have water potentials at which the organism could grow. Some literature on the water potentials in copper leach dumps is reviewed, and it is concluded that control of water potential is essential to maximize the success of leaching operations. Because adequate drainage is necessary in a leach dump to ensure sufficient aeration, in many cases water availability in leach dumps may restrict the development of the bacterium necessary for the process.     

Diversity of native and alien plant species on rubbish dumps: effects of dump age, environmental factors and toxicity

Abstract. The flora of 96 rubbish dumps consisting of organic, inorganic and industrial wastes was studied in the Czech Republic. Some dumps contained toxic substances (heavy metals, chlorethylenes, phenols, polychlorinated biphenyls, oil hydrocarbons and biogas). Statistically significant factors explaining the number and proportional representation of native plant species, archaeophytes (introduced before 1500) and neophytes (introduced later) were determined. In total, 588 species of vascular plants were recorded, with archaeophytes (133 species) over‐represented and native species (322 species) and neophytes (133 species) under‐represented compared to their proportions in the national flora. Minimum adequate models were used to determine the effects of several factors on species numbers and proportions, independent of other factors. Dump area, human density in the region and altitude (non‐significant only in archaeophytes) were correlated positively with species numbers. Dump age, expressed as time since dump establishment, interacted with the dump toxicity; species numbers increased with dump age on non‐toxic dumps, whereas on toxic dumps no increase in numbers was noted. For neophytes, dump toxicity also interacted with human density; the increase in numbers of neophytes with human density is more pronounced on toxic than on non‐toxic dumps. The variables measured failed to explain observed differences in proportional representation of native species, archaeophytes and neophytes. This suggests that the occurrence of species growing in such extreme habitats is driven overwhelmingly by factors such as anthropogenic disturbance. A possible explanation for the positive effect of altitude on species numbers on dumps is that the effect of heating of the deposited substrate by microbiological processes, documented by previous studies, overrides the effect of altitude which was shown repeatedly to have a negative effect on species richness. Neophyte distribution is driven by an interplay of factors distinct from those influencing the distribution of native species, namely toxicity and human density (the latter we interpret as a surrogate for propagule pressure). Their distribution on studied dumps is more restricted than that of native taxa and archaeophytes, and they are more limited by toxic substrata; more intensive propagule pressure is required for their establishment at dumps with higher toxicity levels.     

The role of bacteria in copper mining operations

The results of our survey of several mining operations have shown in every instance typical T. ferrooxidans bacteria to be present in the leaching solutions. The numbers of bacteria found are in general what, one would expect considering the chemical reactions occurring in these processes. A major difficulty is encountered when one considers the complex and unknown series of events which occur, as the bacteria-bearing, acidic, ferric-ion solution penetrates the massive ore dumps. Laboratory studies show microbial activity to be the major cause of rapid solubilization of copper sulfide ores. Field studies suggest that microbial activity cannot explain all observations in a typical leaching operation.     

Technological assessment of a mining-waste dump at the Dexing copper mine,China, for possible conversion to an in situ bioleaching operation

In order to extract copper metal from the waste dump of Dexing copper mine and resolve the environmental problems caused by acidic water and heavy metals, a dump bioleaching plant was designed based on a series of experimental investigations. The investigation shown that the low-grade of the dump, refractoriness of chalcopyrite, leakage of pad, small Acidithiobacillus population and low dump permeability are the main factors that contribute to the challenges faced by the plant. Stability of the high and steep slope of the dump is the other hidden danger to which much attention is not paid. To evaluate the potential unstability of the dump, the leaching process, ore surface erosion, particle size, chemical elements and mechanical properties of the waste rock in DCM were investigated through experiment in this paper.     

Factors influencing the composition of bacterial communities found at abandoned copper-tailings dumps

AIMS: To study the effect that copper residues exert on bacterial communities and the ability of bacteria to colonize different microhabitats in abandoned tailing dumps. METHODS AND RESULTS: We used the terminal-restriction fragment length polymorphism technique, a culture-independent molecular approach based on PCR amplification of ribosomal genes, to compare the structure of the bacterial communities from samples taken at two nearby located abandoned tailing dumps found in the Mediterranean-climate area of central Chile. Our results show that elevated available copper content in tailings has a strong effect on the bacterial community composition, but that other factors like pH and organic matter content also play an important role in the structure of these communities. We also found that the number of abundant bacteria in these samples was significantly lower than in soils not exposed to metal pollution. CONCLUSIONS: In addition to bioavailable copper, bacterial communities found in copper-tailings dumps are also affected by several other environmental factors. SIGNIFICANCE AND IMPACT OF THE STUDY: This first report on environmental factors influencing microbial communities in copper-tailings dumps will help to devise appropriate restoration procedures in this type of polluted habitat.     

油页岩废渣场的生态恢复

油页岩开采带来一系列的生态与环境问题 ,但对油页岩废渣场进行生态恢复的历史还较短 ,也缺少系统专门的研究报道。国外对油页岩废渣的利用始于 2 0世纪 4 0年代 ,对废渣场生态恢复的研究始于 2 0世纪 6 0年代 ,均早于我国。由于废渣场的基质成分恶劣 ,缺乏一般的土壤结构 ,复垦难度大。一般有 3种常规的复垦方法 :不经处理直接栽种植物 ;常规的物理或化学处理后栽种植物 ;表土覆盖后再进行植被恢复。前 2种方法均难产生显著效果 ,第 3种见效较快 ,但工作量大。近年来 ,一些新技术 ,如生物降解、生物富集和生物强化技术等被发明并用来恢复油页岩废弃地 ,取得了较好的生态恢复与修复效果。我国从 1985年开始 ,在广东茂名进行油页岩废渣场的生态恢复工作 ,先后对面积达 1.4 km2 和 6 .7km2 的 2个大型废渣场 (南排土场和北排土场 )进行了治理 ,主要是采用生物修复技术中的植物修复来进行试验。南排土场经过 19a的复垦演替成了郁郁葱葱的森林 ;北排经过 5 a的实践也取得了很好的恢复效果 ,一些幼林初步形成。然而 ,当前北排土场恢复实践中出现了一些很值得关注的现象 ,如乔木树种矮化、分枝增多等 ,但这些问题还有待进一步研究解决。此外 ,还探讨了油页岩废渣场开展生态恢复的步骤与原则     

油页岩废渣场植物修复的生态效应

对广东茂名页岩油工业固体废物裸露灰渣地植林18a(南排)和3-5a(北排)后的植物生长、凋落物、土壤容重、有机质、pH和植物多样性进行了对比调查和分析。结果表明,南排和北排已形成了森林环境。土壤基质已得到了改善,南排的凋落物现存量增加了1.39倍,土壤有机质增加了52.39%(0-20cm)、50%(20-40cm),土壤pH值提高了0.28个单位。南、北排林地土壤pH值分别比植林前裸地提高了0.99个单位和0.71个单位。这说明植树造林对增加土壤有机质效果明显,对提高土壤pH值则相对较慢。南排自堆放油页岩灰渣后,45a来入侵定居的野生植物有48科118属138种,其中草本植物占总种数的54%,乔木15种;北排堆放28a来,有24科63属66种植物入侵定居,其中草本种类占67%。     

Biotechnology in hydrometallurgical processes

The presence of microorganisms in metal sulfide leaching operations has been found to be beneficial in catalysing the dissolution process. Currently this technology is applied on a commercial scale in the recovery of copper and uranium in heap, dump and in-situ leach techniques. However, the biotechnological principles are not limited to the extraction of these two elements. Cobalt, nickel and zinc could be solubilized from their respective sulfides, and coal, silver and gold resources purified from pyrite and arsenopyrite inclusions.     

Rate controls on the oxidation of heaps of pyritic material imposed by upper temperature limits on the bacterially catalysed process

Abstract: Oxidation of a fraction of the pyrite in gold-bearing pyrite ores before leaching often increases gold recovery rates. There are a number of techniques availablc, one of which is dump oxidation. Commercial viability of such an operation requires a net oxidation of 50% or more in 1 year. This is possible in a dump provided convection is established quickly. Since convection requires temperatures in the dump to be well above ambient, a question arises as to the constraints that might be imposed by the upper temperature limit ( T _kill) of the microorganisms which catalyse the oxidation of the pyrite. Our objective is to investigate, by way of a computer model, the importance of T _kill as a parameter effecting the oxidation rate and the fraction of pyrite oxidised after 1 year in dumps where the goal is to oxidise about 50% of the pyrite in a year or less.     

贵州典型煤矸石堆场微生物群落结构及功能特征

【背景】煤矸石堆场用于堆放煤矿开采过程中产生的一种热值低、含重金属的固体废弃物,会产生大量的酸性废水,对堆场周边的生态环境造成严重影响。【目的】探究煤矸石堆场的微生物群落结构和功能特征。【方法】选择贵州省六枝特区典型煤矸石堆场作为研究对象,采集堆场表层土壤、矸石层土壤、废水浸出口沉积物和堆场下游河道沉积物,通过宏基因组学技术进行分析。【结果】细菌的优势菌门为变形菌门(Proteobacteria)和放线菌门(Actinobacteria),优势菌属为钩端螺菌属(Leptospirillum)和硫化杆菌属(Sulfobacillus);古菌的优势菌门为Candidatus＿Thermoplasmatota和泉古菌门(Crenarchaeota),优势菌属为热原体属(Thermoplasma)和金属球菌属(Metallosphaera)。不同采样点细菌和古菌的优势菌属存在显著差异,矸石层土壤和废水浸出口沉积物中的铁氧化细菌和硫氧化细菌比其他2个样点丰富。煤矸石堆场中微生物的碳、氮、硫代谢基因丰度较高,共检测到6条固碳途径、6条氮代谢途径和3条硫代谢途径。主要的固碳基因为ACAT和E2.2....     

Bioindicators and accumulators in geobotanical and biogeochemical prospecting of metals

Results of geobotanical and biogeochemical studies carried out on the known lead-zinc deposits of Zawar Mines and Khetri Copper Deposits, India, are discussed. A wild variety of Impatiens balsamina was found to be the most characteristic species on lead-zinc metal dumps, which can be regarded as a local 'bioindicator' for these metals. A number of 'accumulators' for lead, zinc, copper with high BAC values, as well as some 'excluders' are also discussed.     

Bioleaching review part B:

This review describes the historical development and current state of metals leaching and sulfide mineral biooxidation by the minerals industries. During the past 20 years commercial processes employing microorganisms for mineral recovery have progressed from rather uncontrolled copper dump leaching to mineral oxidation and leaching in designed bioheaps for oxidation of refractory gold ores and for copper recovery. Also during this period of time, stirred tank bioleaching has been commercialized for cobalt recovery and for biooxidation of refractory gold ores. Chalcopyrite bioleaching in stirred tanks is on the verge of commercialization. Commercial applications of biohydrometallurgy have advanced due to favorable process economics and, in some cases, reduced environmental problems compared to conventional metal recovery processes such as smelting. Process development has included recognition of the importance of aeration of bioheaps, and improvements in stirred tank reactor design and operation. Concurrently, knowledge of the key microorganisms involved in these processes has advanced, aided by advances in molecular biology to characterize microbial populations.     

Copper and boron fixation in wood by pyrolytic resins

A phenol-formaldehyde (PF)-resin designed to penetrate wood and immobilize copper and boron in wood cells for protection against decay was investigated. The phenol portion of the PF-resin was partially substituted with pyrolysis oil derived from softwood bark. The objective was to reduce the environmental impact associated with the production of petroleum-borne phenol, as well as to improve the product economics. Leaching tests were conducted with three different formulas of resins containing 50%, 75% or 85% by weight of pyrolytic oil on a total phenol basis. The leachates were analyzed for the presence of copper by atomic absorption spectroscopy while inductively coupled plasma spectroscopy was used for boron detection. Copper leaching was reduced up to 18 times when comparing the treatments with and without the resin. Preservative leaching varied between wood species as well as between the resins containing different concentrations of pyrolytic oil. The organic leachates were measured using gas chromatography and mass spectroscopy. Trace amounts of organics, mostly acetic acid, were found in the leachates.     

Homogeneity of fossil assemblages extracted from mine dumps: an analysis of Plio-Pleistocene fauna from South African caves

Mine dumps associated with limestone cave deposits are common in dolomitic areas of southern Africa. The dumps often contain blocks of breccia, which are rich in micro-mammalian fossils (especially rodents, shrews and bats). Unfortunately, these fossiliferous breccia blocks are out of geological and stratigraphic context. Nevertheless, they provide a large amount of palaeontological material of great interest. In order to use this kind of material, a first approach is to test for homogeneity of the fossil assemblages extracted from the breccia blocks. Fisher's exact test can be used. Two analyses were undertaken. The first was performed on block samples taken in situ from breccia at the Drimolen hominid site. The results indicated that the samples were homogenous, as expected. The second analysis was carried out on different samples extracted from blocks of breccia collected from a dump at the Gondolin site. The results show that it is possible to group several samples in a single representative assemblage. Some blocks could be grouped together and then used to address taphonomic issues. Once these problems are solved, the data set can be used with greater confidence to address matters concerning palaeoenvironmental reconstructions associated with Plio-Pleistocene hominids.     

The use of genetic probes to detect microorganisms in biomining operations

Summary Microorganisms are currently used for the recovery of copper from mining dumps of low-grade ore. One of the most important microorganisms involved in copper-solubilization isThiobacillus ferrooxidans, although many other microbial genera are also thought to be implicated. A mining dump poses some special problems for the industrial microbiologist because it represents a non-sterile and heterogeneous substrate. Consequently, to enhance our knowledge of the role of microorganisms in metal recovery we must identify the indigenous microorganisms and understand their respective contributions to the process. In addition, when a superior strain of microorganism is developed in the laboratory, by genetic engineering or by other means, we must have a method to evaluate the maintenance of such a strain in the mining dump. In this paper, we describe DNA homology studies, using dot blot and Southern blot analysis of hybridizations of both whole genomic DNA and cloned DNA sequences, to identify and enumerate several bioleaching microorganisms. We demonstrate that it is possible to identify different species of microorganisms and, in one case, to discriminate between different strains of a single species. It is also possible to identify and quantitate certain species in a mixed culture. DNA hybridization analysis has several advantages over the more conventional bacteriological methods of identification, especially in a complex bioleaching situation.     

黄土区露天煤矿排土场土壤与地形因子对植被恢复的影响

在脆弱的生态环境改善和恢复过程中,植被恢复与重建扮演着重要的角色。黄土露天煤矿区生态环境极其脆弱,认识矿区损毁土地植被恢复与地形、土壤因子之间的作用规律对矿区土地复垦与生态恢复改善至关重要。为此,选择山西平朔安太堡露天煤矿南排土场对2条样带27个复垦样地的土壤、地形、植被参数进行了采集与测定,并应用单因素方差分析与CANOCO4.5软件的降趋势对应分析和冗余分析研究了地形与土壤因子对植被恢复的影响。结果表明:植被与土壤变量之间呈显著相关,与地形变量之间相关性不明显;坡度主要影响草本覆盖度,坡向与有机质和速效磷之间具有线性相关性;速效钾对植被的变化起着重要的作用;土壤容重与砾石含量对土壤养分含量具有明显的指示作用;有机质与全氮呈显著正相关,各土壤养分指标之间存在明显的相关关系。为了改善和恢复黄土区露天煤矿排土场脆弱的生态系统,应该考虑植被和土壤的联合演替。在当地的生态环境状况下土地复垦与生态恢复的关键是改善土壤状况和增加人工植被,同时加强对排土场人工和自然植被的保护。     

Occupancy of spoil dumps by the Mountain Pygmy‐possum Burramys parvus in Kosciuszko National Park

Summary The Mountain Pygmy‐possum Burramys parvus has been listed as an endangered species across its range in the alpine and subalpine areas of New South Wales and Victoria. This study reports on the occurrence of the species in an artificial habitat, spoil dumps that were created in the 1950s as a result of the construction of underground tunnels associated with the Snowy Hydro‐electric Scheme. Thirty‐four B. parvus were captured in 1065 trapnights on spoil dumps in Happy Jacks Creek valley, in northern Kosciuszko National Park in October and November 2011. In January 2012, 22 individuals were captured in 360 trapnights on a spoil dump at Guthega Adit Camp in southern Kosciuszko National Park. Seven radio‐collared individuals tracked in Happy Jacks Creek valley resulted in the location of 5 day shelters in spoil dump habitat, including individuals that were originally trapped in nearby natural habitat. This study indicates that there may be opportunity to create further artificial habitat on sites not currently used by this highly restricted species.     

The role of a plant/fungal consortium in the degradation of bituminous hard coal

The sporadic growth of Cynodon dactylon was observed to occur directly on the surface of hard coal in dumps of the Witbank coal mining area of South Africa with the surface coal being broken down into a humic-like particulate material. Microorganism analysis of plants and rhizosphere material from the dumps revealed the presence of arbuscular mycorrhizal fungi and the coal solubilising fungus, Neosartorya fischeri. Studies established to replicate the dump environment revealed increased coal degradation in the form of humic acid production and an increase in small size particles as a result of Cynodon dactylon growth in association with arbuscular mycorrhizal fungi and Neosartorya fischeri. Results suggest that interactions between Cynodon dactylon, arbuscular mycorrhizal fungi, Neosartorya fischeri and other coal-degrading rhizosphere fungi could lead to the degradation of hard coal in situ and that the application of these organisms to discard dumps could be a novel method of coal dump rehabilitation.     

Artificial boulderfield yields a surprise: The Smoky Mouse in Kosciuszko National Park,Australia

Spoil dumps in the subalpine and montane environments of Kosciuszko National Park in far south‐eastern Australia are modified landscapes which in the past were considered to have little faunal value. Recent finds (2010–2011) of the critically endangered Mountain Pygmy‐possum (Burramys parvus) have resulted in a reconsideration of the importance of such landscapes to fauna. Such re‐evaluation has been translated into on‐ground actions, including the construction of an artificial boulderfield on one spoil dump as habitat targeting Mountain Pygmy‐possum in rehabilitation works. Trapping 7 and 19–20 months, respectively, after these works has so far not recorded this Pygmy‐possum. However, it led to the discovery of another critically endangered species, the Smoky Mouse (Pseudomys fumeus). Two males (with three recaptures) and one female were captured in 250 trapnights in November 2015 and an additional male in 600 trapnights in December 2015. The capture of this enigmatic species is highly significant as it is the first live capture of the species in the park and it is only the second locality in which live captures have been made in New South Wales since 2001. The location of the Smoky Mouse in spoil dumps further emphasises how these areas provide existing and potential habitat for native fauna species.     

Cladonia lichens as the most effective and essential pioneers in strongly contaminated slag dumps

The epigeic lichen biota of ten post-smelting slag dumps were studied to identify the ecological importance of Cladonia species in spontaneous succession within artificial areas. Species diversity, abundance, constancy and cover indices were determined at the initial stages of vegetation establishment. Substrates under lichen vegetation were characterised in terms of the pH, organic C and total N content, C/N ratio and Zn, Pb, Cd and As concentration. Species occurrence and abundance indices were related to habitat type, enabling the ability to identify species-specific responses to environmental factors. Despite the unfavourable and artificial habitat conditions at dump sites, some Cladonia appear abundant and form swards, with Cladonia rei as a dominant species. They appear to be well-adapted for slag substrate and their special arrangement illustrative of site contamination. Certain sward-forming Cladonia lichens play a fundamental role as effective pioneers in the initial stage of succession and provide stable plant cover development.