Modelling natural attenuation of heavy-metal groundwater contamination in the Selebi-Phikwe mining area,Botswana

Seepage from a tailings dam is the major source of groundwater pollution in the Selebi-Phikwe area, where mining of sulphidic nickel–copper–cobalt ore started in 1973 and will continue until 2014. The seepage water has a pH in the range of 1.7–2.8 and is strongly enriched in SO₄ ²⁻ (5,680 g/L) and heavy metals (6,230 μg/L Ni, 1,860 μg/L Cu and 410 μg/L Co). The fracture aquifer affected by pollution from the dam exhibits a remarkable capacity of heavy-metal sorption. Most of the Ni, Cu and Co is scavenged at less than 500 m distance downgradient from the polluting source, whereas SO₄ ²⁻ is not immobilized significantly. The heavy-metal sorption process is assumed to be due to surface complexation, which is supported by a relatively high groundwater pH (in the range of 6.2–7.8 at >200 m distance from the tailings dam). The objective of this study is to demonstrate that the sorption process can be incorporated into a realistic three-dimensional reactive-transport groundwater model that is implicitly charge-balanced. The simulations are performed with the PHAST1.2 program, which is based on the HST3D flow and transport code and the hydrochemical PHREEQC2.12 code.     

Environmental Geochemistry of Mining Activities in Panzhihua Region, Southwestern China

INTRODUCTIONMining activlties have significant envi ronmenta1 inll)ac'l ssuch as visual intrusions, dust, noise, blasting, trafflc and h}'drology (Kwolek, l999; Ripley et al., l996 ). The l)rot'csst'sof mineral extraction, processing, smelting and refinlng;1rt'never approximate to the environmental neutrality, but tht' affected areas can be ameliorated (KwoIek, l999; Klukanov;1;llltlRapant, 1999). The regions, where mining activities are I,r('sent or continuous for a long tlme, are pote…     

阳朔铅锌矿的环境现状与尾矿废水处理模式分析

阳朔铅锌矿的环境污染因素主要是采矿废石、选矿尾矿、废液等，主要有害物质为Pb、Cd等重金属元素和残余的选矿药剂，对环境特别是下游环境存在潜在危害。该矿通过建设规范化的尾矿库和废水处理系统，采用尾矿浆由坝体向内(上游)倒流排放沉淀尾矿砂、废水经二级多池串联自然沉淀澄清的处理模式，增强了坝体稳定安全；不使用或极少使用化学沉淀药剂，降低了治污成本。废水处理后，水质清澈无异味，达到国家工业生产污水处理二级排放标准。     

地下水对栾川炉场沟尾矿坝稳定性影响分析

据计算结果,栾川炉场沟尾矿坝在正常运行情况下是稳定的,地下水位(浸润线水位)是实测水位;在洪水运行情况下和特殊运行情况下是不稳定的,洪水运行情况下,预测地下水位(浸润线水位)距离坝顶 1 m,地下水位(浸润线水位)埋深较浅时尾矿坝不稳定,提出了相应的预防措施.     

Uranium pollution of South African streams – An overview of the situation in gold mining areas of the Witwatersrand

During more than a century of gold mining in South Africa large amounts of tailings were produced, which now cover vast areas in densely populated regions. These dumps contain elevated levels of uranium and other toxic heavy metals associated with gold in the mined ore. Large-scale extraction of uranium from auriferous ore only took place during the cold war, leaving tailings with high uranium concentrations that were deposited before and after this period. Recent studies found elevated levels of the radioactive heavy metal in groundwater and streams, mainly attributed to the discharge of contaminated water from mines. In this paper the contribution of seepage from slimes dams to the uranium pollution of adjacent streams is analysed. Based on geochemical analyses of samples, field observations and long-term in situ measurements of hydraulic and hydrochemical parameters at selected mining sites across the Witwatersrand goldfields, the extent, mechanisms and dynamics of diffuse stream contamination by tailings seepage is characterised. Temporal and spatial variations of the process and the associated hazard potential are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cyanide from gold mining and its effect on groundwater in arid areas,Yanqul mine of Oman

The use of cyanide (CN), which is characterized by volatility, toxicity and high odor, in gold mining is scarcely addressed in the literature and remain controversial. Environmentalists oppose CN usage as it potentially poses serious environmental threats, whereas economic and mining geologists are in favor of its usage for its extracting capacity and economic feasibility. The present study investigates the possible dispersion of CN into groundwater resources caused by a gold mine (ca. 15 years old) located in the arid area of Yanqul, North Oman. The gold is hosted in gossan deposits associated with ophiolitic rocks and sulfide deposits. Sodium cyanide is mixed with 0.5 m³ of water and then added to a tonne of crushed ore rock to extract 6 g of gold mineral. The final residues are dumped in engineered, lined and uncovered tailing dams. Subsequent to rainfall water draining the mine plateau flows along the wadies and percolates into the shallow Quaternary alluvium aquifer. Hence, groundwater samples were collected from 16 piezometers adjacent to and around the mine. The samples were analyzed for CN using the revised phenolphthalin method and they all show CN concentration below the detection limit (5 ppb). The samples were also analyzed for heavy metals to investigate the potential of CN complexation. Most of heavy metals indicated very trace concentration. The absence of CN in groundwater is attributed to volatilization of CN (converted to HCN), lined dam structure, high evapotranspiration rate and deeper water table. This finding is consistent with the historical CN analysis in the groundwater and solid wastes. It can be pointed out that within few years of operation well engineered tailing dams can provide safe structure preventing CN-groundwater pollution in arid areas. Potential threats to the air and soil are not addressed in this article.     

某磷石膏尾矿库堆积坝渗透稳定性分析

随着尾矿库堆积坝高度的增加,库内的地下水渗流场将发生改变,当尾矿堆积坝处的实际水力梯度大于临界水力梯度时,尾矿库堆积坝将产生渗透变形或失稳破坏。为了预测某已建磷石膏尾矿库堆积坝的渗透稳定性,本文运用地下水位计水位恢复试验去确定磷石膏尾矿渗透系数并计算水力梯度,同时采用Geo-studio软件中的SEEP/W模块分析磷石膏堆积坝在不同工况下的渗透稳定性。计算和分析结果表明当堆积坝处于945m堆积高程,在无干滩和100m干滩情况下,实际水力梯度分别为0.784和0.583;当堆积坝处于960m堆积高程,无干滩情况下,实际水力梯度为0.692,在以上两种情况下,堆积坝渗出点高程高于初始坝高程,堆积坝将出现流土变形,坝体处于不稳定状态。当堆积坝处于960m堆积高程100m干滩时,堆积坝上无渗出点,堆积坝处于稳定状态。分析研究结果对该尾矿库的安全运行和维护管理提供技术依据,同时为同类型尾矿库堆积坝渗透稳定性评价提供参考。     

The long term fate and environmental significance of contaminant metals released by the January and March 2000 mining tailings dam failures in Maramureş County,upper Tisa Basin,Romania

In January and March 2000 two tailings dam failures in Maramureş County, northwest Romania, resulted in the release of 200,000 m³ of contaminated water and 40,000 tonnes of tailings into tributaries of the Tisa River, a major tributary of the Danube. The high concentrations of cyanide and contaminant metals released by these dam failures resulted in pollution and fish deaths not only in Romania, but also downstream in the Tisa and Danube rivers within Hungary, Serbia and Bulgaria. Following these accidents, a research programme was initiated in northwest Romania to establish metal levels in rivers affected by the tailings dam failures and to compare these to metal values in river systems contaminated by historic mining and industrial activity. In July 2000, 65 surface water, 65 river sediment and 45 floodplain sediment samples were collected from trunk streams and principal tributaries of the Lapuş/Someş rivers (affected by the January 2000 spill) and the Vişeu/Tisa rivers (affected by the March 2000 Novat spill) down to the Hungarian and Ukrainian borders, respectively. Sample analyses for Pb, Zn Cu and Cd show that metal contamination in surface water and river sediment decreases rapidly downstream away from presently active mines and tailings ponds. Concentrations of heavy metals in water and sediment leaving Romania, and entering Hungary and the Ukraine, generally fall below EC imperative and Dutch intervention values, respectively. However, Zn, Cu and Cd concentrations in river sediments approach or exceed intervention values at the Romanian border. The results of this survey are compared with earlier surveys to ascertain the long-term fate and environmental significance of contaminant metals released by mine tailings dam failures in Maramureş County.     

River system recovery following the Novaţ-Roşu tailings dam failure, Maramureş County, Romania

The River Vişeu catchment in Maramureş County, northwestern Romania, has a long history of base and precious metal mining. Between 1994 and 2003 waste from mining activity at Baia Borşa was stored in the Novaţ-Roşu tailings pond in the upper Vişeu catchment. However, in March 2000, the tailings dam failed releasing approximately 100,000 m³ of contaminated water and 20,000 t of mineral-rich solid waste, which was routed downstream through the Rivers Novaţ, Vaser and Vişeu into the River Tisa. Following the accident metal (Cd, Cu, Pb, Zn) concentrations in river water and river channel sediment were assessed in samples collected annually (July 2000, 2001, 2002 and 2003) from 29 sites in the Vişeu catchment, downstream of the tailings pond. Additionally, the speciation of sediment-associated metals was established using a 4-stage sequential extraction procedure (SEP) and Pb isotope analysis (^206/204Pb and ^207/204Pb) was carried out to establish the provenance of contaminated sediments. Metal concentrations in river water were found to comply with EU directive ‘target’ values within four months of the failure. However, the impact of the spill upon river channel sediments was found to be much longer-lasting, with evidence of the delayed downstream remobilization of tailings stored within the narrow Novaţ valley following the dam failure, as well as continued inputs of contaminated sediment to the River Vişeu from the River Tisla, another mining-affected tributary. Comparison with data from other recent tailings dam failures, indicates that river system recovery rates depend upon local geomorphological conditions, hydrological regimes, and the nature and scale of post-spill clean-up operations.     

Geological impact of some tailings dams in Sardinia,Italy

This article deals with the results of a survey carried out in Sardinia on both active and abandoned tailings dams, and we also discuss the geological impact of tailings dams of two mines: the Masua mine, a large syngenetic Pb-Zn deposit located in Cambrian limestones, and the Montevecchio mine, a Pb-Zn vein deposit near a Hercynian granite intrusion. The characteristics and metal content of material in the dams were analyzed. A high contamination of heavy metals (Pb, Zn, Cd, Cu) was found both in the soils and water of Rio Montevecchio, a stream draining the tailings dams and other mining operations in the area.The study indicates that a control plan to minimize heavy metal pollution must be drawn up for all mines of the area, whether active or abandoned.     

基于流固耦合作用的某尾矿坝渗流稳定性分析

尾矿坝是矿山重要设施之一,其内部含有大量的水和尾矿,一旦失稳造成的损失不可估量。尾矿坝失稳有众多因素影响,但是坝内浸润线是最活跃的影响因素。本文基于流固耦合理论,建立某尾矿坝有限元计算模型,考虑坝内排水井的存在。模拟坝内不同工况下浸润线分布,对其静力稳定性及流固耦合作用下尾矿坝应力应变场进行分析,并将浸润线模拟位置与实际监测结果进行对比。揭示库内不同工况下浸润线变化规律以及与坝体稳定性之间的关系,并分析评价不同工况下尾矿坝的稳定性。最后,将渗流场与应力场进行流固耦合,模拟出365 d坝内应力位移分布,为尾矿坝施工及安全运行提供可靠的依据及技术支持。     

Geochemical constraints on underground disposal of uranium mill tailings

A three phase investigation has been conducted on groundwater quality impacts of the underground disposal of tailings from acid-leach milling of uranium ores. These phases included field collection and analysis of samples obtained during backfilling of mill tailings in empty underground mine stopes, collection of soil samples from mill tailings piles and previously backfilled stopes, and evaluation of thermodynamic constraints on possible geochemical transformations. Contaminants of principal concern include As, Mo, Se, U, V and Ra-226.The investigation has shown that short-term degradation of groundwater due to backfill disposal of the sand fraction of uranium tailings is negligible. Long-term effects, defined as those occurring after mining operations cease and the mine fills with water, are predicted to also be very small. This is attributed to immobilization of pollutants through chemical reduction and precipitation, as well as adsorption onto aquifer materials. This conclusion is substantiated, in part, by observation of high concentrations of most of the contaminants on the silt and clay fraction of the soil samples collected, in contrast to the concentrations found on the sand fraction.     

Application of lead stable isotopes to the Guadiamar Aquifer study after the mine tailings spill in Aznalcóllar (SW Spain)

On 25 April 1998 the tailings dam of the Aznalcóllar mine burst, a great quantity of pyrite waste sludge and acid water was spilled reaching the vicinity of the Doñana National Park. In surface and ground water samples taken a week after dam breaking, metals, trace elements and Pb isotopic ratios (²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁶Pb) were analysed. In September 1998 a second sampling survey was carried out. The surface waters have a similar isotopic composition as the lead contained in the pyrite from the Aznalcóllar mine. The polluted groundwater of the Guadiamar aquifer also shows the influence of the mining origin of the lead. Lead isotope ratios (²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁶Pb) in the groundwater of the Almonte-Marismas are very low and they differ clearly from the rest of groundwater samples. A further group of wells has a lead isotope composition intermediate between the Aznalcóllar mine and the atmospheric aerosols of the Iberian Peninsula.     

黔西南Au-As-Hg-Tl矿化区毒害金属元素的水地球化学

研究了黔西南典型Ａｕ－Ａｓ－Ｈｇ－Ｔｌ矿化区内毒害金属元素在采矿活动和自然状态影响下的水地球化学特征及其环境效应。结果表明,已开采的Ｈｇ－Ｔｌ矿区地下水和地表水中均有很高的毒害金属元素,煤采区地下水中亦表现出类似的特征,而Ｈｇ－Ｔｌ矿区外围地下水中金属元素保持在较低的水平。Ｈｇ－Ｔｌ矿区地素水中Ａｓ和Ｔｌ的分布模式表明,其含量的变化受矿区地下水排泄和尾矿淋滤作用的控制。在尚未开采的金矿区,浅层地下     

Arsenic content and groundwater geochemistry of the San Antonio-El Triunfo, Carrizal and Los Planes aquifers in southernmost Baja California, Mexico

 The San Antonio-El Triunfo mining district, located at a mountainous region 45 km south-east of La Paz, Baja California, has been worked since the late 1700s. Mine waste material produced during 200 years of mineral extraction area poses a risk of local groundwater pollution and eventually, regional pollution to the Carrizal (west basin) and the Los Planes (east basin) aquifers. There are different types of deposits in the mining area. These are dominated by epithermal veins, in which arsenopyrite is an important component. Carrillo and Drever (1998a) concluded that, even though the amount of mine waste is relatively small in comparison to the large scale area, significant As in groundwater derived from the mine waste piles is found locally in the groundwater. This paper shows the results of geochemical analyses of groundwater samples from the San Antonio-El Triunfo area and the Carrizal and Los Planes aquifers during several years of monitoring (1993–1997). The highest values of total dissolved solids (TDS) and As are in the mineralized area where the mining operations occurred (∼1500 ppm TDS and 0.41 ppm As). The lowest concentrations of TDS and As are, in general, away from the mineralized area (∼500 ppm TDS and 0.01 ppm As). Sulfate and bicarbonate (alkalinity) are, in general, high near the mineralized area and low away from it. The arsenic concentrations vary seasonally, especially after the heavy summer thunderstorms. Geochemical modeling (MINTEQA2 and NETPATH) and analysis of the regional geochemical evolution of the groundwater from the mining area towards the aquifer of Los Planes shows that the most likely hydrochemical processes include: dilution, precipitation of calcite, and adsorption of As onto surfaces of iron oxyhydroxides (ferrihydrite). These processes act as natural controls to the extent and amount of As pollution in the Carrizal and Los Planes aquifers. Received: 4 May 1999 · Accepted: 22 February 2000     

宿州矿区浅层地下水污染评价及源解析

宿州矿区由于长期煤炭开采,不仅形成了浅层地下水降落漏斗,而且造成了不同程度的地下水污染,其污染现状及主要形成原因尚不清楚。为此,本文利用研究区水土污染调查获取的21个地下水样品的 {\mathrm{NO}}_3^{-}等13项污染指标开展地下水污染源解析工作。在采用改进内梅罗综合污染指数法对研究区浅层地下水环境质量进行评价的基础上,利用因子分析和反距离权重插值方法对研究区浅层地下水进行污染源及空间分布特征解析。研究结果表明:(1)研究区浅层地下水受到了重度污染,以Ⅳ类水为主,污染较严重的指标为 {\mathrm{NO}}_3^{-}、Mn、Fe和F^-。(2)研究区浅层地下水主要包括4个污染源:原生地质环境(F1),其高值区分布在桃园煤矿及其周边;矿坑排水和矸石山淋溶作用下形成的矿业废水(F2),其在桃园和钱营孜煤矿及其周边地区污染较为严重,其余矿区也存在一定程度的矿业废水污染;由生活垃圾、人畜排泄物造成的农村污水(F3),其污染地区主要为朱仙庄和芦岭煤矿一带; 由化肥施用引起的农业污染(F4), 其高值区集中在朱仙庄煤矿及其周边区域。地下水水质的主要影响因素是浅层地下水原生地质环境和矿业废水,其中约有51.040%的污染来源于原生地质环境及煤矿矿业污染的混合污染,约有11.841%的污染来自煤矿矿业废水,其余污染主要来源于农村生活和生产污水以及农业面源污染。(3)研究区浅层地下水主要污染区域为桃园和钱营孜煤矿一带,祁南和祁东煤矿污染相对较轻,朱仙庄和芦岭煤矿水质较好。(4)建议对矿区地下水主要污染源及污染途径进行综合防治:加强矿坑排水口的污水达标排放监管力度;煤矿企业采用生产建筑材料等方法提高矸石的综合利用率;进一步加强与矿区污水、垃圾填埋处理等相关的基础设施建设。     

Heavy metal and arsenic dispersion in a copper-skarn mining district in a Mexican semi-arid environment: sources, pathways and fate

The Cu–Au rich ores of the Concepción del Oro mining district, located on the semi-arid Mexican Altiplano, have been mined for over 400 years. The residues of these activities were piled on the banks of the main stream that drains the area. The tailings piles are neither treated nor protected, so the waste material has been dispersed over the surroundings by seasonally occurring heavy rains and winds. A small town with 5,000 inhabitants has grown up around the mining operations. Mineralogical observations indicate that sulphates are the first products of alteration of the primary sulphides and that Fe hydroxides are the stable minerals that are formed after longer periods of time. At the present time, an area of about 40 km² along both sides of the stream has being severely contaminated with Cu–As–Zn-rich tailings, indicating that the seasonal heavy rains are indeed the main dispersion factor. Contaminated soils reach Cu-concentrations of up to 100 times, and As-concentrations of up to 20 times the local natural values. Factor analysis and geostatistical methods helped to identify pollutant origins and sources. Extraction tests on polluted agricultural soils using acetic acid mobilized 5–10 % of the total As content, 0.5–2.75 and 1–4.5 % of Cu and Zn, respectively, indicating the potential of the biological activity of the soil to enhance the mobility of the elements mentioned, and, in this way, to get into the food chain and/or groundwater. Stabilization measures of the tailings heaps must be urgently undertaken in order to minimize the risk for the inhabitants of the region and to stop the pollution of a broader area.     

龙井市天宝山矿立山尾矿库地质环境恢复治理方案

龙井市天宝山立山尾矿库,由于企业破产尾矿库对周围环境造成严重危害,需对尾矿库、尾矿坝、排水工程、尾矿碴粉尘污染、水污染进行治理。     

Groundwater regimes and isotopic studies,Ranger mine area,Northern Territory

Three types of groundwater occur in the area of the Ranger mine. Type A groundwater occurs in the loose sands and gravels occupying the present day stream channels, Type B in the weathering profile and Type C occurs in relatively fresh fractured bedrock occupying open fractures and other cavities. The three types of groundwater can be distinguished both chemically and isotopically. Light stable isotope data suggest that most early rains are lost by evapotranspiration and have no imprint on the groundwater. Later in the wet season, the ground is saturated and groundwater recharge occurs on a regional scale. This younger groundwater sits on the older waters. Mixing is probably minimal as before any large scale mixing could occur, most younger waters are lost by evapotranspiration. Stable isotope data suggest that Type B groundwater in certain areas has some connection with evaporated surface water bodies. Stable isotope measurements for the pollution monitoring bores around the tailings dam do not indicate any connection with the polluted pond waters at the time of sample collection.     

采煤排水对区域水资源的影响——以山西阳武河流域上游煤矿区为例

煤炭资源的大量开采,对水资源造成了严重影响。以山西阳武河流域上游煤矿区为例,分析了采煤对水资源污染和水资源量减少的影响。未经处理的矿坑水直接排放不仅污染了过境河流水,同时也对第四系潜水、深层岩溶承压水造成了严重的污染。采煤排水是区域水资源量的减少和可利用水资源量减少的主要原因。对2个不同开采期水资源量变化进行分析对比,提出了采煤排水引起水资源量减少的主要原因是三水转化关系的变化,而可利用水资源量减少的主要原因是地下水流场变化、开采模数远大于径流模数、隔水层连续性破坏、底板突水、水资源污染等。