The Application of Thermal Decomposition for Determination of Carbonate Acid-Neutralising Capacity for Improved Acid Mine Drainage Prediction

This study developed an industry-applicable, thermal decomposition methodology for quantification of carbonate mineral acid neutralisation capacity (ANCtherm-carb) for waste rock, tailings, and other mined materials. Standard titration-based methods for ANC can be compromised due to contributions from silicate minerals, ion exchange, Fe-rich carbonates, and other transition metal carbonates. C emission (CO2 and CO) was measured using IR in a N2 atmosphere. Cneut (wt%) was calculated using the C emission at 800 or 1000 °C minus the C emission at 400, 450 or 500 °C and the weight of sample prior to decomposition (Equation (2) of this manuscript). This value was then input into Equation (3) of this manuscript to calculate ANCtherm-carb. Good correlation of ANCtherm-carb for single-mineral carbonates with ANCcalc, calculated from bulk assay concentrations for Mg, K, Na, Ca, and Mn, was achieved. Thereafter, 18 waste rock samples were examined, resulting in the correlation of ANCtherm-carb versus non-standard ANCtitrate-carb (titration methodology adapted to focus on carbonate neutralisation only) with R2 = 0.96. This correlation is valid for samples containing both non-neutralising carbonates (siderite) and sources of neutralisation arising from non-carbonates (Mg-clay) within this waste rock system. Typically, mining operations use total C measurements for assessment of carbonate neutralisation potential in the block and mining model. This method provides an effective means to cheaply analyse for carbonate neutralisation potential with assignment of potentially acid-forming and non-acid-forming blocks to waste rock cells, etc.

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A Multidisciplinary Approach for the Assessment of Origin, Fate and Ecotoxicity of Metal(loid)s from Legacy Coal Mine Tailings

Toxics ◽

10.3390/toxics9070164 ◽

2021 ◽

Vol 9 (7) ◽

pp. 164

Author(s):

Honorine Gauthier-Manuel ◽

Diane Radola ◽

Flavien Choulet ◽

Martine Buatier ◽

Raphaël Vauthier ◽

...

Keyword(s):

Coal Mine ◽

Mine Tailings ◽

Mine Drainage ◽

Mineral Resources ◽

Subcellular Fractionation ◽

Mining Operations ◽

Biological Responses ◽

Receiving Waters ◽

Coal Tailings ◽

Produce Acid

Over the course of history, the development of human societies implied the exploitation of mineral resources which generated huge amounts of mining wastes leading to substantial environmental contamination by various metal(loid)s. This is especially the case of coal mine tailings which, subjected to weathering reactions, produce acid mine drainage (AMD), a recurring ecological issue related to current and past mining activities. In this study, we aimed to determine the origin, the fate and the ecotoxicity of metal(loid)s leached from a historical coal tailing heap to the Beuveroux river (Franche-Comté, France) using a combination of mineralogical, chemical and biological approaches. In the constitutive materials of the tailings, we identified galena, tetrahedrite and bournonite as metal-rich minerals and their weathering has led to massive contamination of the water and suspended particles of the river bordering the heap. The ecotoxicity of the AMD has been assessed using Chironomus riparius larvae encaged in the field during a one-month biomonitoring campaign. The larvae showed lethal and sub-lethal (growth and emergence inhibition and delay) impairments at the AMD tributary and near downstream stations. Metal bioaccumulation and subcellular fractionation in the larvae tissues revealed a strong bioavailability of, notably, As, Pb and Tl explaining the observed biological responses. Thus, more than 70 years after the end of mining operations, the coal tailings remain a chronic source of contamination and environmental risks in AMD effluent receiving waters.

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A Test of Two Methods for Waste Rock Drainage Quality Prediction: Aqua Regia Extraction and Single-addition Net-acid Generation Test Leachate Analysis

Mine Water and the Environment ◽

10.1007/s10230-021-00784-0 ◽

2021 ◽

Author(s):

Teemu Karlsson ◽

Lena Alakangas ◽

Päivi Kauppila ◽

Marja Liisa Räisänen

Keyword(s):

Mine Drainage ◽

Mine Waste ◽

Extraction Methods ◽

Drainage Water ◽

Waste Rock ◽

Quality Prediction ◽

Aqua Regia ◽

Acid Generation ◽

Leachate Analysis ◽

Single Addition

AbstractThe mobility of contaminants from mine waste can be assessed using different extraction methods. Aqua regia (AR) extraction is the most commonly used method in Finland. Another method is the analysis of leachate from net acid generation (NAG) tests, which is primarily designed for acid production potential assessment. We investigated the performance of single-addition NAG test leachate analysis and AR extraction in drainage quality prediction, using waste rock and drainage water samples from several Finnish waste rock sites. Our objective was to improve interpretation of the AR and single-addition NAG test leachate analysis results in drainage quality prediction. The AR extraction effectively reflected elements that occurred in elevated concentrations in drainage water, though it over-predicted Al, As, Cd, Co, Cu, and Ni in some circumneutral drainages, and Cr in general. The single-addition NAG test leachate analysis also performed well in assessing the mobility of contaminants including Al and Cr at acid mine drainage sites. As the contaminants tend to precipitate in neutral NAG test solution, the usability of the method in neutral mine drainage cases should be further investigated. Furthermore, the conclusions presented in this study are limited to waste rock samples collected from the surface of piles; future work will examine waste rock history, dump cores, drainage quality changes, etc. in more detail.

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In Vivo X-ray Computed Tomography Investigations of Crack Damage Evolution of Cemented Waste Rock Backfills (CWRB) under Uniaxial Deformation

Minerals ◽

10.3390/min8110539 ◽

2018 ◽

Vol 8 (11) ◽

pp. 539 ◽

Cited By ~ 5

Author(s):

Yu Wang ◽

Changhong Li ◽

Zhiqiang Hou ◽

Xuefeng Yi ◽

Xiaoming Wei

Keyword(s):

Computed Tomography ◽

Damage Evolution ◽

Waste Rock ◽

Crack Identification ◽

Mining Operations ◽

Cracking Behavior ◽

Value Analysis ◽

X Ray ◽

Waste Rocks ◽

X Ray Computed

Cemented waste rock backfill (CWRB), which is a mixture of tailings, waste rock, cement, and water, is subjected to combination actions in underground mining operations and has been widely used in deep resource mining. While the strength requirement and macroscopic deformation behaviors of CWRB have been well studied, the mesoscopic damage evolution mechanisms are still not well understood. In this work, a CWRB sample with a waste rock proportion of 30% was studied with a uniaxial compression test under tomographic monitoring, using a 450 kV industrial X-ray computed tomography (CT). Clear CT images, CT value analysis, crack identification, and extraction reveal that CWRB damage evolution is extremely inhomogeneous and affected by the waste rock size, shape, and distribution. Furthermore, the crack initiation, propagation, and coalescence behaviors are limited to the existing waste rocks. When deformation grows to a certain extent, the cracks demonstrate an interlocking phenomenon and their propagation paths are affected by the waste rocks, which may improve the ability to resist compressive deformation. Volumetric dilatancy caused by the damage and cracking behavior has closed a link with the meso-structural changes, which are controlled by the interactions between the waste rocks and the cemented tailing paste.

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Terrestrial Ecosystem Impacts of Sulfide Mining: Scope of Issues for the Boundary Waters Canoe Area Wilderness, Minnesota, USA

Forests ◽

10.3390/f10090747 ◽

2019 ◽

Vol 10 (9) ◽

pp. 747 ◽

Cited By ~ 3

Author(s):

Lee E. Frelich

Keyword(s):

Boreal Forest ◽

Large Scale ◽

Mine Drainage ◽

Terrestrial Ecosystem ◽

Terrestrial Ecosystems ◽

Migration Routes ◽

Metal Mining ◽

Mining Operations ◽

Ecosystem Impacts ◽

Mining Impacts

Large-scale metal mining operations are planned or underway in many locations across the boreal forest biome in North America, Europe, and Asia. Although many published analyses of mining impacts on water quality in boreal landscapes are available, there is little guidance regarding terrestrial impacts. Scoping of potential impacts of Cu-Ni exploration and mining in sulfide ores are presented for the Boundary Waters Canoe Area Wilderness (BWCAW), Minnesota USA, an area of mostly boreal forest on thin soils and granitic bedrock. Although the primary footprint of the proposed mines would be outside the BWCAW, displacement and fragmentation of forest ecosystems would cause spatial propagation of effects into a secondary footprint within the wilderness. Potential negative impacts include disruption of population dynamics for wildlife species with migration routes, or metapopulations of plant species that span the wilderness boundary, and establishment of invasive species outside the wilderness that could invade the wilderness. Due to linkages between aquatic and terrestrial ecosystems, acid mine drainage can impact lowland forests, which are highly dependent on chemistry of water flowing through them. The expected extremes in precipitation and temperature due to warming climate can also interact with mining impacts to reduce the resilience of forests to disturbance caused by mining.

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