Occurrence Of Acid Mine Drainage Research Articles

Geochemical Characterization of Pit Wall Rocks: A Preliminary Step in Predicting the Water Quality of Pit Lake

The quality of pit lake water during development and final condition is affected by various factors, including geochemical characterization of materials of a pit wall, which may consist of in-situ and backfilling materials. This research aims to obtain a geochemical characterization of pit wall materials using 3 main laboratory tests and analysis, namely static test, mineralogical and elemental composition analysis, and kinetic test using free draining column leach test. Static test results show that 5 of 6 samples exhibit low paste pH and NAG pH. Pyrite is found in four samples and is responsible for acid mine drainage production. Some samples contain acid-consuming carbonates and oxides such as calcite and periclase. Four samples exhibit leachates’ pH values lower than 3,00, mostly during all cycles. Alongside the lithostratigraphic distribution of pit wall rocks, these results imply a potential occurrence of acid mine drainage that will become a critical issue for water quality development and final condition in pit lake formation. Therefore, these results become essential feedback for the stakeholders to plan and implement acid mine drainage management to minimize the adverse impact of acid mine drainage in pit lakes. Immediate understanding of the geochemical characteristics of leachates from pit wall rock, which control the overall mine water quality.

Acid mine drainage and heavy metals contamination of abandoned and active mine site at Old Repas Dam in Bentong, Pahang, Malaysia

Acid Mine Drainage (AMD) occurs as a result of mining activities during mineral exploration. Interaction of the minerals in the presence of atmospheric oxygen and water produces AMD as an end product. AMD can also be produced by weathering of sulphide minerals through series of process, which includes oxidation and hydrolysis. The main aim of the study is to determine the presence of Acid Mine Drainage (AMD) and contamination of the active and abandoned mining sites with heavy metals in Bentong Pahang. This study deals with the identification of heavy metal toxins traces in water bodies that result in discoloration of the water catchment, downstream of the Old Repas dam. Any discoloration of the water present proves the occurrence of AMD. In order to have better comprehension of the scenario, site reconnaissance and survey is carried. This is to examine the areas affected and thus recognising two different sampling points that have traces of AMD contamination. Water sampling and testing are carried out in the chosen sampling point using four in-situ parameters and five selected heavy metals. The chosen parameters are water pH, dissolved oxygen content, total dissolved solids and ammoniacal nitrogen. The selected heavy metals are Zinc, Lead, Tin, Mercury and Arsenic. Four samples were collected each from two sampling point on two different sampling days. In addition to that, the surface water with sediments was also collected and analysed for the presence of heavy metals. From the results, it was found that the pH of the sampling point was ranging from 5 to 7 indicating the presence of AMD, which is the major finding in this study. Based on the heavy metal analysis, it was found that the concentration of Pb, Sn, Hg, As & Zn was present in greater than the allowable standard limits for treated water by the Malaysian Ministry of Health. This concludes an urgent intervention required to treat the site to prevent any further environmental deterioration.

Assessment of acid mine drainage formation using geochemical and static tests in Mutki (Bitlis, SE Turkey) mineralization area

In this study, geochemical analyses, as well as short-term contact leaching and acid-base accounting tests, were carried out to determine the occurrence of acid mine drainage (AMD) by static tests in the ore stockpile areas at the Mutki Cu-Fe-Cr deposit (Bitlis, SE Turkey). According to the short-term contact leaching tests, the high enrichment in trace element concentrations in ore-bearing samples, especially in potentially toxic metals such as Cr, Cu, Mn, and Zn, were directly related to sulphide and oxide mineralizations. The pH (3.27–4.05) values of water samples, together with the classification of the intracontinental water resources, indicated that the water quality is the fourth class. Leaching tests, paste pH (3.42–4.46) and sulphide-sulphur (3.9–13.4 wt%) values also suggested that there was AMD production potential in the mineralization area. The AMD production potential was supported by the high mobility of several elements, such as Fe, Mg, Cr, As, Cu, S, and Zn. In ore samples, net neutralization potential (NNP) and net potential ratio (NPR) values were less than –20 kg CaCO3/t and 1, respectively. The basalts forming the basement rock of the stockpile area were characterized by permeable to slightly permeable properties that potentially increase the contamination risk of the groundwater due to seepage in the stockpile area. In order to prevent seepage in the stock area, geomembrane (synthetic waterproofing covers) should be laid at the base to ensure impermeability. The improvements planned in the stock area were modeled by the finite element method and seepage discharges at a depth of 5 m were determined as 1.34 × 10–17m3/s. Thanks to these planned applications, surface and groundwater pollution can be efficiently prevented.

Occurrence of Acid Mine Drainage and its Treatment by Successive Alkalinity Producing System (SAPS): An Overview

Occurrence of Acid Mine Drainage and its Treatment by Successive Alkalinity Producing System (SAPS): An Overview

Interaction between physical and chemical weathering of argillaceous rocks and the effects on the occurrence of acid mine drainage (AMD)

The disintegration of rocks by weathering plays an important role in the occurrence of Acid Mine Drainage (AMD), which is the environmental problem caused by the exposure of sulfide minerals to water and oxygen. The weathering of rocks is, generally, classified into physical or chemical weathering. However, there are few studies that focus on the complex interaction between physical and chemical weathering of rocks and on the effects of the interaction on the occurrence of AMD. This paper elucidates the complex interrelation between physical and chemical weathering of rocks as well as the progress of AMD through leaching test and weathering test with argillaceous rocks taken in open-cast coal mine in Indonesia in addition to sample analysis before and after the wetting and drying cycle: the rock samples were exposed to oxygen and water during the cycle. The results indicated that the argillaceous rocks which consist of sulfide and/or sulfate caused chemical weathering with micro-cracks on the surface of rocks through the dissolution of soluble iron and sulfur during the occurrence of AMD. Additionally, physical weathering of rocks due to clay minerals was accelerated by chemical weathering with the development of cracks with the occurrence of AMD in the argillaceous rocks containing kaolinite and pyrite. Although weathering of rocks also accelerated AMD, it was concluded that the sulfur content, the form of sulfur and iron in rocks, and the supply of oxygen significantly contributed to the occurrence of AMD.

Bioremediation of acidic mine effluents and the role of sulfidogenic biosystems: a mini-review

Acid mine drainage (AMD) is recognised as a serious and global environmental problem. The major producer of these toxic effluents is the mining industry. Owing to the severe effects of these effluents, their prevention and treatment have been a primary focus of research over several decades. The problems have invited the attention of a large group of researchers, governmental bodies, educational and research establishments, mining industries, general public and environmental specialists. A preferable option is to prevent the formation and movement of AMD from its source of origin; however, it is not possible in many locations. It, therefore, becomes essential to collect and treat AMD to which a number of treatment techniques are available. Despite the extreme environmental conditions, several communities of autotrophic and heterotrophic bacteria and archaea are seen to flourish that mainly drive the rate of release of sulfur and toxic metals into the environment. The present review briefly discusses the cause and occurrence of AMD and the microbial diversity observed in such ecosystems. In addition, the bioremediation options are briefly presented with a discussion on the role of sulfidogenic biosystems in the bioremediation of the AMD.

Prediction of acid mine drainage generation potential of various lithologies using static tests: Etili coal mine (NW Turkey) as a case study.

The Etili neighborhood in Can County (northwestern Turkey) has large reserves of coal and has been the site of many small- to medium-scale mining operations since the 1980s. Some of these have ceased working while others continue to operate. Once activities cease, the mining facilities and fields are usually abandoned without rehabilitation. The most significant environmental problem is acid mine drainage (AMD). This study was carried out to determine the acid generation potential of various lithological units in the Etili coal mine using static test methods. Seventeen samples were selected from areas with high acidic water concentrations: from different alteration zones belonging to volcanic rocks, from sedimentary rocks, and from coals and mine wastes. Static tests (paste pH, standard acid-base accounting, and net acid generation tests) were performed on these samples. The consistency of the static test results showed that oxidation of sulfide minerals, especially pyrite-which is widely found not only in the alteration zones of volcanic rocks but also in the coals and mine wastes-is the main factor controlling the generation of AMD in this mine. Lack of carbonate minerals in the region also increases the occurrence of AMD.

Chemical and mineralogical changes of waste and tailings from the Murgul Cu deposit (Artvin, NE Turkey): implications for occurrence of acid mine drainage.

Being one of the largest copper-producing resources in Turkey, the Murgul deposit has been a source of environmental pollution for very long time. Operated through four open pits with an annual production of about 3 million tons of ore at an average grade of about 0.5% Cu, the deposit to date has produced an enormous pile of waste (exceeding 100 million tons) with tailings composed of 36 % SiO2, 39% Fe2O3 and 32% S, mainly in the form of pyrite and quartz. Waters in the vicinity of the deposit vary from high acid-acid (2.71-3.85) and high-extremely metal rich (34.48-348.12 mg/l in total) in the open pits to near neutral (6.51-7.83) and low metal (14.39-973.52 μg/l in total) in downstream environments. Despite low metal contents and near neutral pH levels of the latter, their suspended particle loads are extremely high and composed mainly of quartz and clay minerals with highly elevated levels of Fe (3.5 to 24.5% Fe2O3; 11% on average) and S (0.5 to 20.6% S; 7% on average), showing that Fe is mainly in the form of pyrite and lesser hematite. They also contain high concentrations of As, Au, Ba, Cu, Pb, and Zn. Waters collected along the course of polluted drainages are supersaturated with respect to Fe phases such as goethite, hematite, maghemite, magnetite, schwertmannite and ferrihydrite. Secondary phases such as Fe-sulphates are only found near the pits, but not along the streams due to neutral pH conditions, where pebbles are covered and cemented by Fe-oxides and hydroxides indicating that oxidation of pyrite has taken place especially at times of low water load. It follows, then, that the pyrite-rich sediment load of streams fed by the waste of the Murgul deposit is currently a big threat to the aquatic life and environment and will continue to be so even after the closure of the deposit. In fact, the oxidation will be enhanced and acidity increased due to natural conditions, which necessitates strong remedial actions to be taken.

Data-Based Mechanistic Modeling of Flow-Concentration Dynamics of Non-Point Source Pollution: A Case of Upper Vaal Water Management Area

This study aimed at applying the Data Based Mechanistic (DBM) modelling approach to develop a simple, parsimonious and discernable Flow-Concentration (F-C) model that can be partitioned into the various identifiable pathways associated with the pollutant at the catchment scale. An attempt was made to model the occurrence of acid mine drainage (AMD) in the Vaal River by using an indicator water quality parameter (sulphate concentration). The optimal Instrumental Variable (IV) methods of identifying and estimating discrete and continuous-time transfer function models as implemented in the CAPTAIN MATLAB® Toolbox were applied to the time series data in order to identify the appropriate model. A discernable F-C model was developed of three parallel pathways: the “quick-route” depletion pathway with a residence time months; a “slow-route” build-up pathway with a residence time months and a direct term component pathway regressed in 9 months. The resulting model showed that it is possible to use the DBM modelling approach to address the problem of representing the potential lag between polluting activity and its effect as well as provide more salient information about the system dynamics. This kind of information (i.e. the residence times and the advective time delays in the system) could prove useful for the catchment managers in making informed decisions including laying out remediation measures. Keywords: Flow-Concentration Modelling, Non-Point Source Pollution, Data Based Mechanistic Modelling, Transfer Function models, Water Quality, Flow Pathways

Acid mine drainage and heavy metals contamination at abandoned and active mine sites in Pahang

Active and abandoned mine sites in Pahang have been investigated recently to find out the occurrence of acid mine drainage and heavy metals contamination. Acid mine drainage (or also popularly known as AMD), which is a product of weathering (oxidation and hydrolysis) on sulphide minerals has been a major concern in mining industry. Seven mine and quarry sites in Pahang were visited, namely Bukit Botol, Bukit Ibam, Panching quarry, Sg Lembing, Kota Gelanggi, Padang Piol and Kg Awah. In-situ water quality parameters such as pH, dissolved oxygen and electrical conductivity were measured. Some surface water samples were also collected and analysed for heavy metals. After the first screening test on these sites, the abandoned tin mine of Sg. Lembing (underground mining) was chosen for further examination. Detailed study at Sg. Lembing involved sampling of surface water and mine tailings. The study has revealed that arsenic (As) concentrations in surface water ranges from 0.003-16.20 mg/L and in mine tailings 755-74475 mg/kg. The arsenic level measured in surface water and mine tailings at Sg Lembing Mine are higher than the environmental standard for effluents (Standard A) in Environmental Quality Act (1974) and contaminated soil standard by ICRCL (1987). The concentrations of other heavy metals such as Cu, Fe, Mn, Pb, and Zn are also exceeding the limit allowed by EQA (1974) and ICRCL (1987). The study concludes that there is an urgency to regulate the better closure of abandoned mine sites. Pulverised mine tailings which is very rich in sulphide minerals must be kept away from contact with water and oxygen to avoid reactions that will produce acidic water and harmful chemicals.

Phosphorus Removal by Sediment in Streams Contaminated with Acid Mine Drainage

Acid mine drainage (AMD) affects thousands of stream miles in the Appalachian region of the USA and results in elevated concentrations of iron and aluminum in the stream water and sediments and wide ranging pH values. It was hypothesized that these conditions would lead to increased P buffering capacity of the sediments which in turn would cause a decrease in dissolved reactive phosphorus (DRP) in the water column. In the lab fresh Fe, Al, and Mn oxide precipitates all adsorbed DRP strongly but over different pH ranges. Sulfate and calcium ions inhibited adsorption of DRP with Fe oxides but the effect was less apparent with Al oxides. In the field DRP concentration was reduced 54–90% just downstream of an AMD input compared to upstream of the input. In addition the sediment buffering capacity increased and equilibrium phosphate concentration decreased dramatically downstream of the AMD inputs. The strength of the effect and the widespread occurrence of AMD suggest that AMD could be altering the P dynamics of streams and rivers throughout the Appalachian region.

Galvanic sulphide oxidation as a metal-leaching mechanism and its environmental implications

Following a brief review of the theoretical aspects of galvanic sulphide oxidation, the significance of galvanic interaction in the oxidation of natural mixed sulphide assemblages is demonstrated using test materials prepared from sulphide-containing rocks in a series of chemical and microbial weathering experiments. The test results indicate that: (1) metal leaching can effectively proceed even in a near-neutral environment; and (2) the occurrence of acid mine drainage can be delayed due to cathodic protection of an acid-generating sulphide such as pyrite from oxidative dissolution. While microbial mediation may enhance the weathering of sulphides with a high electrode potential, the competing galvanic processes diminish the dominating role of the microbes in effecting the oxidation of sulphides with a low electrode potential when the sulphides occur in a mixed assemblage. In-situ potential measurements on sulphide surfaces with micro-electrodes demonstrated the occurrence of a significant potential difference between a contacting sulphide pair sufficient to sustain galvanic interaction for the duration of the experiments. It is also shown that galvanic sulphide oxidation and hence metal leaching can occur even under an oxygenated water cover. Therefore, subaqueous disposal may not be the best management option for all reactive mine wastes, especially those containing metals or trace elements that remain mobile under near-neutral pH conditions.

Design and Performance of rRNA Targeted Oligonucleotide Probes for in Situ Detection and Phylogenetic Identification of Microorganisms Inhabiting Acid Mine Drainage Environments.

At Iron Mountain, CA, there is an extreme occurrence of acid mine drainage (AMD). This is a result of past mining activity that has exposed a sulfide ore body to weathering and microbial activity. This study presents seven new oligonucleotide probes for the detection of microorganisms at this AMD site by fluorescent in situ hybridization. In the design of these probes we have accounted for a large body of 16S rRNA sequence data recently compiled by us. This was obtained by PCR and cloning directly from environmental DNA and was mostly represented by novel sequences. The probes were developed to include detection of novel and uncultivated organisms. This includes detection for the Thermoplasmales group, a new group of Leptospirillum, the genus Sulfobacillus, the Acidiphilium genus, Acidimicrobium and relatives, and for organisms within the delta Proteobacteria. These probes have been used to examine the abundance and distribution of organisms, including novel and uncultivated taxa, and to clarify their potential contributions to AMD production at the site. We anticipate that these probes will be useful tools for exploration of the microbiology of other natural acidic environments and bioleaching systems.

Mineralogical constraints on the determination of neutralization potential and prediction of acid mine drainage

Acid-base accounting tests, commonly used as a screening tool in acid mine drainage (AMD) predictions, have limitations in (1) measuring with confidence the amount of neutralizers present in samples and (2) affording an interpretation of what the test results mean in terms of predicting the occurrence of acid mine drainage. Aside from the analytical difficulties inherent to the conventional methods, a potential source of error in neutralization potential (NP) measurements is the contribution from the dissolution of non-carbonate minerals. Non-carbonate alkalinity measured during static tests may or may not be available to neutralize acidity produced in the field. In order to assess the value-added of extending the NP with the knowledge of mineralogical composition and evaluate potential sources of errors in NP measurements, a suite of samples were examined and characterized in terms of their mineralogical and chemical compositions. The results indicate that although the acid-base accounting tests work well for simple compositions, the tests may result in overestimation or underestimation of NP values for field samples. Mineralogical constraint diagrams relating NP determinations to Ca, Mg and CO2 concentrations were developed with the purpose to serve as supplementary guides to conventional static tests in identifying possible NP contributions from non-carbonate minerals and checking the quality of the chemical testing results. Mineralogical NP makes it possible to interpret the meaning of NP results and to assess the behaviour of samples over time by predicting the onset of AMD and calculating NP values for individual size fractions.

Mining, the environment and the treatment of mine effluents

The environmental impact of mining on the ecosystem, including land, water and air, has become an unavoidable reality. Guidelines and regulations have been promulgated to protect the environment throughout mining activities from start-up to site decommissioning, in particular, the occurrence of acid mine drainage (AMD), due to oxidation of sulfide mineral wastes, has become the major area of concern to many mining industries during operations and after site decommissioning. AMD is characterised by high acidity and a high concentration of sulfates and dissolved metals. If it cannot be prevented or controlled, it must be treated to eliminate acidity, and reduce heavy metals and suspended solids before release to the environment. This paper discusses conventional and new methods used for the treatment of mine effluents, in particular the treatment of AMD.

The non-participation of organic sulphur in acid mine drainage generation

Acid mine drainage is commonly associated with land disturbances that encounter and expose iron sulphides to oxidising atmospheric conditions. The attendant acidic conditions solubilise a host of trace metals. Within this flow regime the potential exists to contaminate surface drinking water supplies with a variety of trace materials. Accordingly, in evaluating the applications for mines located in the headwaters of water sheds, the pre-mining prediction of the occurrence of acid mine drainage is of paramount importance.There is general agreement among investigators that coal organic sulphur is a nonparticipant in acid mine drainage generation; however, there is no scientific documentation to support this concensus. Using simulated weathering, kinetic, mass balance, petrographic analysis and a peroxide oxidation procedure, coal organic sulphur is shown to be a nonparticipant in acid mine drainage generation. Calculations for assessing the acid-generating potential of a sedimentary rock should not include organic sulphur content.