铜矿采矿废石重金属环境污染的淋溶实验研究——以安徽铜陵凤凰山矿田药园山铜矿床为例

本文基于凤凰山铜矿田药园山矿床采矿废石的淋溶实验研究,着重探索表生环境下影响重金属淋滤迁移的因素,分析重金属在采矿废石中迁移转化的机制。动态淋滤实验考查了重金属从两种采矿废石中淋出的浓度与淋溶液的pH值、淋滤时间以及淋出液酸度的关系。结果表明,采矿废石中重金属淋滤强度随酸度的增加而逐渐增强,而淋滤出的重金属浓度并不总是随时间的延长而递减,同时实验研究也表明,淋溶采矿废石的排放水不一定都是酸性的。因此,在评价矿山环境污染以及治理过程中要对当地雨水的平均pH值、所排放采矿废石的岩性以及废石的堆放时间进行综合考虑。     

桂北及邻区碳酸盐型尾矿的酸中和能力及酸化潜力

对广西北部及其相邻地区金属硫化物矿山的碳酸盐型尾矿(即富含碳酸盐金属硫化物矿尾矿),采用X衍射分析、Sobek-ANC实验测试和Carb-ANC矿物计算法、NAG测试法,以及Sobek-ABA估算法等进行实验分析方法。研究结果表明:(1)的4种类型研究区碳酸盐型尾矿在(方解石型、白云石型、铁白云石型,以及方解石-白云石混合型)中,方解石型尾矿的酸中和能力ANC相对较小,一般400kgH2SO4/t;白云石型尾矿的ANC较大,一般400kgH2SO4/t[最高可达1000kg(H2SO4)/t],铁白云石型尾矿和方解石-白云石混合型尾矿的ANC则较小,接近于方解石型尾矿的ANC。(2)研究区碳酸盐型尾矿酸化的预测评价参数与阈值为:ANC400kgH2SO4/t,Sulfide-S(其值为总硫含量与硫酸盐硫含量的差值)3.0%,APR1.4,NAPP-50kgH2SO4/t。与欧美常用的硫化矿固废酸化阈值相比较,研究区酸化碳酸盐型尾矿(方解石型尾矿)的ANC值及Sul-fide-S含量分别显著高约40倍及10倍;尾矿的酸化势率APR略高(常用阈值APR1),而净酸生成势NAPP则明显偏低(常用阈值NAPP+20kgH2SO4/t)。该尾矿为富含碱性碳酸盐的硫化物矿尾矿,特别是富含方解石的高硫(Sulfide-S3%)尾矿,具有发生酸化污染的潜在危险。     

由采矿活动产生的金属的环境影响过程、预测及防治

虽然采矿活动影响的面积相对较小，但它能对环境产生巨大的局部影响。从采场释放的金属最初是通过矿山排放酸水和废石，尾矿的侵蚀产生的。本文简述了对矿山酸水排放所释放的金属进行预测的现有方法。一项应用地球化学模型预测矿山排放酸水和尾矿带入影响河系中铜浓度研究表明，实测的结果与预测的吻合良好。对于大规模的工业矿山开采，现已有方法对其进行预测并使其免遭污染。但是，大量小规模的采矿活动很难控制。巴西采金矿活动中     

铜陵矿山酸性排水及固体废弃物中的重金属元素

在调查中国铜陵凤凰山铜矿和新桥硫铁矿两种不同类型矿山固体废弃物特征的基础上,研究了矿山尾矿和废石产生酸性排水的可能性及其差异以及矿山固体废弃物中重金属元素的赋存形式。结果表明,凤凰山铜矿的尾矿基本不产生矿山酸性排水,而新桥硫铁矿采矿废石产生矿山酸性排水,并且凤凰山铜矿的尾矿和新桥硫铁矿采矿废石中重金属元素的赋存形式也有差异,前者重金属Cu、Pb、Zn、Cd、As、Hg主要赋存于硅酸盐态中,而后者在还原态中有较高的含量,这反映了在地表条件下尾矿中大量重金属元素已经发生了迁移,而采矿废石已经开始氧化,且酸性排水的存在更有利于废石中重金属元素的迁移和扩散,进而导致矿区周围环境的污染。     

采矿废渣颗粒粒径对矿渣型泥石流起动的控制作用——以小秦岭金矿区为例

泥石流物源的颗粒级配大小对于泥石流的起动具有重要的控制作用,亦是泥石流防治工程设计的重要参数。采矿废石渣构成的矿渣型泥石流,物源特性不同于一般的泥石流。通过对小秦岭金矿区采矿废石渣、尾矿沙、残坡积土的颗粒级配、孔隙度、透水性能的研究,与其他地区泥石流物源级配进行了差异对比,探讨了采矿废渣颗粒级配对泥石流起动的制约影响。研究表明,采矿废石渣松散无联结,粒径变化于0.075~470mm之间,其中大于2mm的砾级含量占总渣量的93.33%,平均粒径为61.2mm,以卵石级为主,粘粒物质几乎没有。粒径小于5mm的废石渣的渗透系数是选矿尾矿渣的103.5陪、残坡积土的2倍、蒋家沟泥石流物源的4.9倍,实际上采矿废石渣堆的渗透系数比试验测试的数据更大。废石渣的松散无联接、高孔隙率及极高渗透性的特点,决定了常遇降水难以导致废石渣堆起动。结合研究区历史上发生的泥石流,构建了堵溃型矿渣型泥石流起动模式,据此提出了清理占据行洪通道的废渣、疏浚行洪通道、修建拦渣挡墙的泥石流防治理念,避免拦沟修筑重力坝。     

重金属元素的淋滤模拟实验

<正>伴随矿产资源的开发与利用所引发的环境问题日益受到了广大学者的关注。目前,矿山环境研究从污染源如废石、尾矿、酸性排水至元素迁移介质如土壤、地表水、大气等均有涉及。此外,相关污染模拟实验及评价模型的建立也为矿山环境的修复及治理提供了切实可靠的方法。矿区内的尾矿坝及露天堆放的废石堆、矿石堆是矿区周围及其下游环境中重金属元素的主要来源,天然雨水淋溶浸泡作用对重金属元素的释放迁移具有一定的促进作用,因此许多国内外学者致力于尾矿、废石、矿石的模拟淋滤实验研究,包括     

铀采矿和选矿场的环境影响证评价：：巴西Pocos de Caldas铀采矿？…

本文描述了Ｐｏｃｏｓ ｄｅ Ｃａｌｄａｓ铀采矿和选矿场释放的放射性核素和金属排入地表水所产生的环境响应的关键分析。由于尾矿坝渗漏水的迁移，也进行了地下水污染的评价。该研究立足于监测数据。结果表明，尾矿废是锰和硫酸盐进入水环境的最主要来源；而酸性矿液和废石排水是＾２２６Ｒａ，＾２３８Ｕ，Ａｌ和Ｆｅ的主要来源。尾矿坝下地下水的研究结果表明仅存在硫酸盐的污染。     

汉源铅锌矿淋滤液中As元素随pH和矿石粒径变化特征

<正>近年来,矿山开采带来的环境污染问题日益严重,矿区内的尾矿坝及露天堆放的废石堆、矿石堆是矿区周围及其下游环境中重金属元素的主要来源,天然雨水淋溶浸泡作用对重金属元素的释放迁移具有一定的促进作用[1],因此,对尾矿、废石、矿石的模拟淋滤实验能够揭示污染源中矿物的分解转化规律、水-岩氧化还原反应机理、重金属元素在水-岩中的迁移转化规律以及影响因素等,从而能够为矿山环境污染     

采矿环境地球化学研究

阐述了采矿对环境造成的负面影响 ,包括 :尾矿或废石堆中的杂质元素会进入表生地球化学循环 ,在不同气候条件下 ,呈现不同的特征模式 ,尾矿氧化带的酸性水的排放 ;矿山污染源对周围土壤和植物的影响使重金属元素等进入食物链 ,对人类和动物健康造成威胁。根据国内外的最新研究动向 ,指出建立环境地球化学模式 ,对采矿环境污染作出客观的监测和评价 ,能为防止污染和治理环境提供可靠的地球化学依据。     

贵州丹寨汞金矿矿山固体废弃物"二次资源"评价 ——兼论该区废弃矿硐的残留金资源

矿山固体废弃物包括废石和尾矿(渣),是重要的二次资源,特别是金矿山尾矿作为一种非常重要的二次矿产资源,更应受到重视。笔者以贵州省丹寨汞金矿的矿山固体废弃物为主要研究对象,对丹寨汞金矿区矿产资源开采及选冶过程中产生的尾矿资源潜力进行了现场调查,并对相关样品进行分析测试,初步掌握了尾矿(渣)资源基本情况及远景资源量,有两个尾矿(渣)堆金潜在资源量达800 kg;并根据丹寨汞和金多共(伴)生的特征,对丹寨排庭汞金矿老采空区矿硐壁围岩研究,发现其1～1. 5 m范围内,普遍含金或具有金矿化,具有找金的潜力,且初步分析了金资源潜力。简要地进行了尾矿(渣)"二次资源"、废弃矿硐的残留金资源综合利用可行性分析。     

Arsenic mobility in weathered gold mine tailings under a low-organic soil cover

Historical gold mining operations in Nova Scotia, Canada, resulted in numerous deposits of publicly accessible, arsenic (As)-rich mine waste that has weathered in situ for 75–150 years, resulting in a wide range of As-bearing secondary minerals. The geochemical heterogeneity of this mine waste creates a challenge for identifying a single remediation approach that will limit As mobility. A 30-cm-thick, low-organic content soil cover was evaluated in a laboratory leaching experiment where, to simulate natural conditions, the equivalent of 2 years of synthetic rainwater was leached through each column and two dry seasons were incorporated into the leaching protocol. Each column was a stratigraphic representation of the four major tailings types found at the historical Montague and Goldenville gold mine districts: hardpan tailings, oxic tailings, wetland tailings, and high Ca tailings. Hardpan tailings released acidic, As-rich waters (max 12 mg/L) under the soil cover but this acidity was buffered by surrounding oxic tailings. Leachate from the oxic tailings was circumneutral, with average As concentrations between 4.4 and 9.7 mg/L throughout the experiment. The presence of carbonates in the high Ca tailings resulted in near-neutral to weakly alkaline leachate pH values and average As concentrations between 2.1 and 6.1 mg/L. Oxidation of sulfides in the wetland tailings led to acidic leachate over time and a decrease in As concentrations to values that were generally less than 1 mg/L. This study shows that the use of a low-organic content soil cover does not create reducing conditions that would destabilize oxidized, As-bearing secondary phases in these tailings. However, oxygen penetration through the cover during dry seasons would continue to release As to tailings pore waters via sulfide oxidation reactions.     

Characterization of Kolar gold field mine tailings for cyanide and acid drainage

The gold mining process at Kolar gold field (KGF) mines has generated about 32 million tons of tailings. Gold was extracted from the mined ores using cyanidation technique that involved dissolution of gold in the ore by water soluble alkali metal cyanides (example, sodium cyanide or potassium cyanide). Of the several dumps that received the mine tailings only the Kennedy’s Line dump was active prior to closure of the KGF mines in the year 2000. The Kennedy’s Line dump received sulfide bearing tailings in slurry form that comprised of spent ore and process water bearing soluble alkali metal cyanide. Depending on the pH of the tailing slurry, the free cyanides may exist as aqueous hydrogen cyanide that can escape to the atmosphere as hydrogen cyanide gas or occur as soluble cyanide (CN⁻) ions that can be leached by infiltrating water to the sub-surface environment. Additionally, the presence of pyrite minerals in the Kennedy’s Line dump makes them susceptible to acid drainage. This study examines the potential of gold tailings of Kennedy’s Line dump to release cyanide ions (CN⁻) and acid drainage to the sub-surface environment by performing physico-chemical and leaching tests with tailing samples collected from various depths of the dump, sub-surface soil samples beneath the dump and groundwater samples from vicinity of Kennedy’s Line dump. The chemical mechanisms responsible for the ambient cyanide and pH levels of the tailing dump, sub-surface soil samples and groundwater are also inferred from the laboratory results.     

Pyrite Oxidation in Leaching Process of Radionuclides and Heavy Metals from Uranium Mill Tailings

Pyrite is a sensitive mineral in the geological environment,and its oxidation produces an important geochemical and environmental effect on the control of the redox and pH conditions.Column experiment results were used for modeling the geochemical processes in uranium mill tailings under leac-hing conditions.Oxidation of pyrite dominates the control of the tailings leaching process.The experi-mental and modeling results show that the leachate chemistry changes substantially with the decrease in pyrite consumption.In the initial stage of the leaching experiment,the pyrite is consumed several hun-dred times grater than that in the later stages,for much more oxygen is present in the tailings in the ini-tial stage.As the experiment continues,the tailings is gradually saturated with water and the oxygen concentration greatly decreases and so does pyrite consumption.The experimental and modeling results are useful for the design of mill tailing decommissioning:oxidation process and transport of radioactive nuclides and heavy metals can be constrained by controlling the oxygen concentration of tailings and the infiltration of meteoric water.     

Assessment of the acid drainage neutralization capacity and the toxic metals lixiviation of tailing from Guanajuato mining district,Mexico

In Mexico, many environmental problems are generated by large mining activities taking place in several mining districts. These mining activities produce great quantities of residues; large majorities of these have high sulfur content, which could generate acid drainage due to their interaction with the oxygen in the environment. The study area was located in the Mining District of Guanajuato, Mexico with abandoned tailings generated mainly by the gold and silver production. Two areas, called as Monte de San Nicolás (SN) and Peregrina (P) were selected for this study. The results study shows that there was no risk of production of acid drainage, since these tailings contained high amount of carbonates, which neutralized the generation of acidity and consequently decreased the possibility of leaching of some elements. However, not all elements leach in acid pH, as arsenic bound to oxyhydroxides, which is in a basic environment and its increased release by increasing the pH.     

A laboratory study of covers made of low-sulphide tailings to prevent acid mine drainage

Covers with capillary barrier effects (CCBE) are considered to be one of the most effective ways to control acid mine drainage (AMD) production from mine wastes. The use of low-sulphide tailings in CCBE has been proposed recently for cases where other types of material may be unavailable near the mining site. This paper presents leaching column test results showing that CCBEs with a moisture-retaining layer made of slightly reactive tailings, with three different sulphide contents, can effectively limit the production of AMD from the acid-generating tailings placed underneath. With these layered covers, the leachate pH was maintained near neutrality throughout the testing period. When compared to uncovered tailings, the efficiency of the cover systems for reducing the amount of contaminants in the percolated water was determined to be greater than 99% for zinc, copper and iron. This study shows that the use of low-sulphide tailings can improve the ability of a CCBE to limit gas diffusion by consuming a fraction of the migrating oxygen.     

Chemical characteristics and acid drainage assessment of mine tailings from Akara Gold mine in Thailand

Acid Mine Drainage (AMD) is a great concern in many abandoned mines because of its adverse effect on the environment. In mining processes, many kinds of wastes are produced. These wastes may become eventually sources of environmental degradation. The focus of this study is the geochemical characterization of the end-processed tailings generated by Akara Gold Mine, the biggest gold mine in Thailand. Tailing samples were systematically collected for analyses of chemical and mineralogical compositions. As a result, their quantitative chemical analyses are slightly different from place to place, but mineral components cannot be clearly differentiated. For instance, it may be assumed that the end-processed tailings, which were a mixture between high and low grade concentrates, would have similar mineral components. However, the little variation of chemical composition may be caused by the ore refining processes that are somehow varied in proportion to chemical additives, alkali cyanide and quick lime in particular. In addition, clay composition in ore-bearing layers may also influence alumina content of tailings, accordingly. Distribution of the tailings is not related to depth and distance of the tailing storage pond because the disposal has sped them over the pond during operation. Total heavy metals of the tailing samples were analyzed on the basis of the EPA 3052 method. Consequently, the most toxic elements (e.g., Co, Cu, Cd, Cr, Pb, Ni and Zn) were found falling within the standard of Thailand Soil Quality Standards for Habitat and Agriculture. Only Mn appears to have higher content than the standard. In addition, leaching tests proved that these tailings contain low metal concentrations. As a result, at pH 2, Mn can leach out exceeding the Thailand Surface Water Quality Standard for Agricultural (Mn <1 ppm) and the Thailand Industrial Effluent Standard (<5 ppm). Although leachate at pH 4 and neutral conditions contains lower Mn than the Industrial Effluent Standard it still exceeds the surface water quality standard. Interestingly, Pb can be leached out exceeding both standards (0.2 ppm for the industrial effluent standard and 0.05 ppm for the surface water quality standard). For Ni leaching, its concentration is lower than the Industrial Effluent Standard at all pH conditions but still exceeds the Surface Water Standard at pH 2 and 4. This information should be taken into consideration for further environmental monitoring. Acid generating potential of the tailings was estimated using acid–base accounting (ABA) and net acid generation (NAG) tests. The results of ABA and NAG tests show that the tailing samples contain a high amount of sulfur. However, they also contain high acid neutralization capacity. Consequently, these tailings may not have potential to generate acid drainage; in the other words, they can be classified as a non-acid forming (NAF) material. However, since these tailings contain some heavy metals (e.g., Ni, Mn and Pb) that are observed in leachates exceeding the standards at low pH, the AMD conditions may lead to heavy metal release. Therefore, prevention of oxidizing process and dissolution should be considered with great care. In addition, Mn and Pb can also be leached at neutral conditions. Barrier of air and water, clay layer for example, should be placed over the tailings pound before covering by topsoil for re-vegetation. Growing native grass is recommended for stabilization of the surface and reducing erosion rate. Monitoring of water quality should also be carried out annually.     

矿山尾砂表生地球化学过程实验研究

在对石菉铜锡矿和河台金矿层砂矿物物相及化学组成研究基础上，利用自行设计的大口径淋滤柱开展了淋滤实验和静置浸泡(溶解)实验。研究结果表明，矿山层矿排放水不一定是酸性，它取决于矿床脉石矿物、赋矿的岩石及其次生蚀变矿物的酸缓冲能力。矿山排放水的组成是地表或地下水与矿山层砂中矿物和氢氧化物及非品态物质相互作用的结果，元素的赋存状态对其被淋滤的程度有很大影响。优先流能使重金属大量带出，因此要尽量防止优先流的形成。研究结果可为矿山综合整治和修复提供重要依据。     

An integrated approach to environmental risk assessment of cumulatively impacted drainage basin from mining activities in southwestern Ghana

Acid rock/mine drainage and metal leaching constitute major environmental management risks in the mining industry. This paper assesses the environmental risks due to acid rock/mine drainage, and the metal leaching potential of multiple mines of gold and manganese on the Ankobra River Drainage Basin in Southwestern Ghana. The basin is a hub of mining activity in Ghana, hosting several mines. A combination of mineralogical, and static geochemical acid drainage predictive investigation of overburden of varied geological units, complimented with hydrochemical drainage quality analysis was used to assess potential environmental risks posed by acid-generating lithologies and mine spoil. Mineralogical investigations revealed sulphide-bearing lithological units with profound compositional variations due to the incorporation of potentially toxic heavy metals and metalloids, in association with carbonates and silicates. Accounting Base Accounting (ABA) and Net acid generation potential pH (NAGpH) tests delimited two tailing sites as potentially acid generating with NAGpH of 3.5 and 4.8, respectively. Five other samples, representing specific lithological units in the stratigraphic sequence, with net acid neutralization potential ratio (NNPR) less than 5.0, were classified as being potentially acid generating according to the categorization requirement of the US Forestry Service. The rest of the samples exhibited moderate to very strong buffering capabilities. The assessment also evaluated drainage quality of the network of streams and rivers constituting the basin and identified sources of drainage contaminants. Acidic waters emanate from identified acid generating sources, while high metal load regimes were identified with both low pH waters and high pH regimes, coincident with high sulphide and carbonate alteration sites, respectively. The study results show that Zn, Cu, Ni, As, Co, Sb, SO₄ ²⁻, pH, alkalinity and conductivity are essential and adequate parameters in routine environmental risk monitoring programmes of mines in the area. Sites characterized by low pH (<5.5) with high sulphate and metal ions are suggestive of acid mine drainage, while sites with high pH (>7.5), metal ions and sulphate are suggestive of net acid neutralizing.     

Release of toxic elements from rocks and mine wastes at the Furtei gold mine (Sardinia, Italy)

The Furtei gold mine in Sardinia (Italy) exploits a volcanic-hosted high-sulphidation epithermal deposit. Large amounts of materials derived from exploitation are present in open pits, waste rock dumps and cyanidation tailings impoundment. Mineralized rocks in outcrops and waste dumps contain significant amounts of sulphides (mainly pyrite and enargite). These materials have a high potential for acid drainage generation and release of toxic elements (notably Cu and As, but also Al, Ni, Co and Cd) as pointed out by laboratory leaching tests and in agreement with chemical composition of waters draining the mining area, that show pH as low as 2, up to 180 mg/L Cu, up to 5 mg/L As, and up to 788 mg/L Al. On the other hand, leaching solutions and waters interacting with mineral assemblages of the propylitic alteration zone (mainly composed of chlorite, quartz, and calcite, with relic magmatic plagioclase) show higher pH, and lower metal loads. Leachates from cyanidation tailings show variable pH (between 6.2 and 9.7, depending on sulphide content in tailings); cyanide concentration varies between 110 µg/L and about 3 mg/L, whereas contents of toxic elements in leachates are, with the exception of Hg, within the limits of Italian regulations for non-dangerous industrial wastes. Reclamation plans provide for confinement of tailings within specific repositories. This measure should effectively reduce the environmental impact of these materials. Reclamation plans should also include an adequate management of other high-sulphide wastes.     

Assessing the acidic potential of waste rock in the Akara gold mine,Thailand

Acid mine drainage (AMD) is the environmental issue that generates the greatest public concern regarding the mining industry. Thus, characterization of mine waste rock according to acid generation potential is necessary for mining operations to ensure proper waste rock storage and to avoid future adverse environmental effects. Therefore, this study was conducted to estimate the potential of AMD generation in the largest operating gold mine in Thailand by using acid base accounting and net acid generation tests. Representative samples of six types of waste rock classified by mining geologists for mineral processing and waste dumping were collected for this study: volcanic clastic, porphyritic andesite, andesite, silicified tuff, silicified lapilli tuff, and sheared tuff. Under various conditions, experimental results indicate that only silicified lapilli tuff and shear tuff are potentially acid-forming materials. The results indicate that AMD generation may possibly occur a long time after mine closure due to the lag time of the dissolution of acid-neutralizing sources. Acidic generation from some waste rocks may occur in the future based on environmental conditions, particularly the oxidation of sulphide minerals by the combination of oxygen and water. Therefore, a proper design for waste rock dumping and storage is necessary to reduce the risk of AMD generation in future. It is advisable to install a surface management system to control the overland flow direction away from the waste dump area and tailing storage facility and to install a second water storage pond next to the main storage pond to store the spilled water during storms and the rainy season. A water quality monitoring plan that focuses on disturbed areas such as water storage ponds and mine pits should be put in place.