Characteristics and Seasonal Variation of Sediments in Lake Junttiselkä, Pyhäsalmi,Finland

Lake Junttiselkä, located in central Finland, has been loaded by effluents from Pyhäsalmi Zn–Cu mine since 1962 and also receives Pyhäsalmi municipal effluent. A total of 32 top sediment samples (0–2, 2–4, and 4–6 cm) were collected in October 2005 and March 2006 to examine the seasonal variation in sediment composition. Furthermore, two sediment cores of 1 m were taken from the northern and southern parts of the lake (Junttiselkä_N, Junttiselkä_S) to investigate the sedimentation history. Electrical conductivity (EC) was measured from the sediment in situ, and sediment pH, redox values, and EC were measured in the winter from the top samples. The sediment samples were freeze-dried and multi-element determinations were performed using ICP-MS on nitric acid extracts (EPA 3051, acid soluble fraction, AF) and on ammonium acetate extracts (bioavailable fraction, BF). The composition of crystalline and semi-crystalline fractions (CF) was calculated by the formula C_CF = C_AF – C_BF. Due to the high clay content of till in the catchment area, the Al, K, and Mg concentrations in the natural lake sediments (>49 cm) are greater than the average level in lake sediments of Finland (AF). Soil cultivation has increased the sedimentation of fines, which has further increased Al, K, and Mg concentrations in the lake sediments (49–19 cm). Mine effluents have had the greatest impact on sediment concentrations of Cu and Zn, with the recorded levels of 166 mg/kg and 434 mg/kg (<19 cm), respectively, being nine- and threefold greater than the natural concentration level. Also, Ca and S concentrations are elevated. The electric conductivity of pore water was elevated at a depth of 1 m. Seasonal variation in the composition of Junttiselkä top sediments is linked to the oxic/anoxic conditions in the water column during the autumn to winter period. The greatest variation was recorded in the 0–2 cm layer in Junttiselkä_S, where Ca_BF and S_BF concentrations were three and sixfold higher in the winter than in the autumn. Mg_BF, Pb_BF, Sr_BF, Cr_BF, P_BF, U_AF, and Se_AF concentrations also increased in the winter, but Mn_BF, Cu_BF, Cd_BF, Co_BF, Zn_BF, Ba_BF, Ni_BF, Fe_BF, and Al_BF decreased. The seasonal variation in composition was less for CF than for BF, and was also partially different. The most significant difference was an increase in Ca_CF and S_CF concentrations in the winter in Junttiselkä_S, with the reverse situation being observed in Junttiselkä_N. Furthermore, the Fe_CF concentration increased in Junttiselkä_N. Equimolar variations in Ca and S suggest that the precipitation and dissolution of gypsum is the most notable seasonal process in the top sediment layer. The seasonally precipitated S corresponds to only 1.4% of the total load of S from the mine effluents.     

Distribution of Organic Carbon in the Berkeley Pit Lake, Butte, Montana

Abstract.  The concentration of dissolved organic carbon (DOC) in the Berkeley pit lake water ranges from 2 to 4 mg/L, and is comparable to that of its inflow waters. On the dates sampled, the DOC concentrations decreased towards the surface of the lake, in a manner similar to the concentration of dissolved Fe. This may reflect adsorption of DOC onto newly formed ferric precipitates in the epilimnion of the lake. The total organic carbon (TOC) content of the lake sediment is 0.20 to 0.33%, and is on the low end of TOC in natural aquatic sediments. In contrast, the DOC concentrations of sediment pore waters are unusually high, ranging from 50 to 380 mg/L, and are much higher than DOC values of pore waters from typical marine or lacustrine sediments. The high DOC concentrations are explained by release of adsorbed organic carbon from ferric precipitates as they age and recrystallize, coupled with the relative scarcity of heterotrophic bacteria in the acidic and heavy metal-rich waters that would otherwise consume DOC through reduction of sulfate.     

Implications of Predicted Hydrologic Changes on Lake Senftenberg as Calculated Using Water and Reactive Mass Budgets

Lake Senftenberg, Germany, is a post-mining lake that was flooded 30 years ago. It is anticipated that the levels of the surrounding post-mining lakes will rise, and that this will lead to a reversal of groundwater flow and consequently to an increase of acidifying groundwater flux into the lake. A tool to predict the future water quality of Lake Senftenberg has been developed. Present and future groundwater fluxes were calculated using a 3D hydraulic model of the surrounding aquifers. Oscillating hydraulic fluxes within the saturated and the unsaturated zones of the island within the lake, caused by continuous lake level changes, were calculated using a 2D sub-model. Mass fluxes into the lake from the aquifers, from the island, and from the River Schwarze Elster were determined by sampling or by laboratory experiments and were coupled with the hydraulic fluxes. The fluxes of acidifying components from the island sediments and sulfide oxidation products from drained zones were determined in laboratory experiments. Sediment erosion due to rill and gully formation after significant lake level change were calculated. The amount of acidifying compounds released from the eroded sediments was determined by laboratory experiments. The input of alkalinity due to the sedimentation of biomass was estimated. Gaseous partial pressures and mineral phases were used to describe the geochemical boundary conditions of the resulting lake water.     

Evaluation of artificial neural networks and kriging for the prediction of arsenic in Alaskan bedrock-derived stream sediments using gold concentration data

The detection of arsenic in sediments of placer gold mining areas is critical for planning future controls on migration and mitigation, or tapping uncontaminated groundwater resources for public water use. Arsenic (As) is often found to be collocated and correlated with gold in sediments. However, due to biogeochemical processes, arsenic can partition between the solid and the dissolved fractions in sediments and their interstitial waters. Such partitioning can mobilize arsenic into areas away from the co-located gold distribution in the sediments. In such cases, it is critical to detect the dispersed arsenic concentration. In this paper, neural network (NN) and kriging techniques were used to predict the presence of arsenic in the sediments of Circle City, Alaska using the gold concentration distribution within the sediments. The results obtained using kriging were more promising than those using NNs, albeit a statistically low correlation existed between the observed and the predicted arsenic concentrations. However, irrespective of the method used, the prediction of arsenic value without using gold concentration data was extremely poor.     

湖泊底泥燃烧特性及其热动力学分析

湖泊底泥为沉积于湖泊水体底部的黏土、泥沙、有机质及各种矿物的混合物,因其含有较高的SiO_2、Al_2O_3等成陶成分和一定的CaO、MgO、K_2O、Na_2O等助熔成分以及部分有机物,可作为焙烧陶粒或其他烧结制品原料进行资源化利用。本文选用湖北黄石某湖泊底泥,测定其烧失量和有机质含量,采用XRF、ICP-OES和XRD研究其物化特性,并用同步热分析-质谱联用仪(TG-DSC-MS)进行热分析,对结果进行热动力学计算。结果表明:湖泊底泥的主要成分为石英、方解石、镁方解石、云母等矿物质;其中,SiO_2含量为52.3%,Al_2O_3含量为14.41%,Fe_2O_3含量为6.89%,S含量为0.39%,P含量为0.13%,以及极少量的重金属,烧失量为14.19%,有机物含量为10.86%。湖泊底泥燃烧过程中气体释放主要发生在120～750℃阶段,主要气体有CO_2、H_2O、NO、NO_2等,不同升温速率对湖泊底泥燃烧过程无明显影响;湖泊底泥的燃烧失重过程可以分为两个阶段,利用Coats-Redfern法的一级反应模型能够很好地描述湖泊底泥的燃烧过程,在第一阶段湖泊底泥活化能约为22.00kJ/mol,可为湖泊底泥烧结制品控制反应历程和研究固化机理提供参考。     

The Limnology of Summer Camp Pit Lake: A Case Study

Abstract.  Surface water bodies are expected to form in several pits at the Getchell Open Pit Mine after mining has ceased due to inflowing surface and ground water. Predicting the long-term geochemical behavior of the pit water is important in assessing potential environmental effects. One of the pits, the Summer Camp Pit, began to develop a pit lake in 1991 when dewatering ceased and the pit was used to store water pumped from underground operations. This provided a field-scale opportunity to identify the controls on lake water chemistry and determine the effects of seasonal mixing events on long-term chemical behavior. During a five-year period (1996-2001), a number of physical, chemical and mineralogical characteristics of the lake were monitored with the intent of using this information as a basis for predicting long-term geochemical behavior of future lakes in the other pits. Seasonal and multiyear cycles were identified within the water column. These cycles were influenced by climatic changes and element and sediment loadings of inflow to the lake. Stratification occurred, with the metalimnion or active layer of the lake evolving from a low total dissolved solids (TDS), alkaline water to a high TDS, neutral to mildly acidic water, until turnover occurred due to density variations between the metalimnion and epilimnion, completely mixing the layers. A hypolimnion that formed has the potential to stabilize metals in the basal sediments as sulfide minerals below a chemolimnion in the lake. Longer-term events also appear to involve the hypolimnion.The monitoring program demonstrated the dynamic nature of a pit lake and how the complex limnology can affect seasonal water quality. Such considerations are important in interpreting water quality from pit lakes and in selecting monitoring data to use when constructing mathematical models for predicting changes in water quality.     

Secondary Sulphate Minerals in a Cyprus-Type Ore Deposit,Apliki, Cyprus: Mineralogy and Its Implications Regarding the Chemistry of Pit Lake Waters

The Apliki mine, a Cyprus-type massive sulphide deposit in Cyprus, was exploited for copper until the mid-1970s. Abandonment of the mine left a deep pit that now hosts a lake fed by surface runoff from the surrounding mineralized zone and hydrothermally altered basalt. Oxidation of the sulphide minerals and factors such as climate and terrain relief control the water–rock interactions that generate acid mine drainage (AMD), which ultimately affects and defines the quality of the lake waters. Pyrite and chalcopyrite constitute an almost inexhaustible sulphide source that leads to the formation of a variety of secondary iron and copper mineral phases. The secondary mineral assemblages in the ore zone are mainly iron, copper, and magnesium sulphates, whereas the lakeshore assemblage is dominated by magnesium-, calcium-, sodium-, and aluminum-bearing sulphate minerals. Near the lakeshore, the highly soluble iron sulphate salts dissolve in the lake water, increasing its iron content. Other less soluble salts are more stable and persist in the lakeshore environment. The precipitation and dissolution of efflorescent salts, and, to a lesser extent, the oxidative weathering of the remaining ore minerals, produce additional AMD. Due to the perpetual cycle of mineral dissolution and precipitation, the lake has a low pH (≈3) and contains high concentrations of some contaminants. The processes that contribute to the formation of the efflorescent mineral assemblages and their environmental impact on pit lake waters, and indeed the complete geochemical system, is a typical example of secondary mineral formation in Cyprus-type Cu-pyrite massive sulphide ore deposits.     

Summary of Deepwater Sediment/Pore Water Characterization for the Metal-laden Berkeley Pit Lake in Butte, Montana

Abstract.  Unconsolidated sediment at the bottom of the Berkeley pit lake is a mixture of detrital silicate minerals derived from sloughing of the pit walls and secondary minerals precipitated out of the water column. The latter include gypsum and K-rich jarosite. The pore waters have a similar pH to the overlying lake waters (pH 3.1 to 3.4), and have similarly high concentrations of dissolved heavy metals, including Al, Cd, Cu, Mn, Ni, and Zn. Sediment cores show that the top meter of the sediment column is moderately oxidized (jarosite-stable). Petrography, chemical analysis and geochemical modelling all suggest a transformation of poorly crystalline ferric compounds such as schwertmannite and/or ferrihydrite near the sediment surface to jarosite with depth in the core. No evidence of bacterial sulfate reduction was found in this study, despite the presence of 0.3 to 0.4 wt% organic carbon in the pit lake sediment.     

Pollution of Water and Stream Sediments Associated with the Vale De Abrutiga Uranium Mine,Central Portugal

Abstract.   The Vale de Abrutiga uranium deposit, located in Central Portugal near the Aguieira dam reservoir, was surface mined. Low-grade ore and waste rock were deposited on permeable ground, close to the mine, and were not revegetated. A lake has formed in the open pit. Surface waters draining the mine site are acidic, have high conductivity, and high concentrations of U, SO42-, Zn, Fe, Mn, Ra, Cu, Th, and Pb. The groundwater and the water from the reservoir cannot be used for human consumption or irrigation. The sampled waters show higher contaminant concentrations in winter than in summer. Stream sediments have high geoaccumulation indices for U, Fe, Ag, Zn, Cr, Co, and Pb. In general, sediments bordering the dam reservoir have higher metal contents in winter than in summer.     

鞍钢脱硫扒渣组成特性研究

以鞍钢集团一炼钢厂的脱硫扒渣为代表,采用粒度组成分析、化学多元素分析、X射线衍射（XRD）分析、扫描电镜（SEM）分析、铁物相分析等检测方法研究了鞍钢脱硫扒渣的组成特性。研究结果表明：鞍钢脱硫扒渣中的主要有用元素为铁,品位达54.18%;主要有害元素为硫,品位达1.01%。脱硫扒渣中所含的主要物相有金属铁、磁铁矿、铁酸盐类、硅酸盐类以及铝酸盐类等,其中金属铁和磁铁矿中的铁占总铁的61.88%。硫主要赋存在硫化钙和硫酸盐矿物中。铁主要分布在粗粒级中,硫主要分布在粗粒级和细粒级中。     

关于太湖污染底泥生态疏浚工程的探讨

目前太湖面临着严峻的富营养化问题，太湖污染底泥生态疏浚工程已经开始启动，但是关于太湖清淤的问题，专家们仍存在不同的见解。针对目前存在的几种观点，认为首先要对太湖疏浚进行前期研究，然后开展太湖示范工程，对污染底泥的空间分布规律、水质影响程度和机制、疏浚和处置技术、环境和生态效应等关系的科学问题进行系统深入的研究，从而为污染底泥的疏浚和处置技术提供理论和实践依据。     

Tracing the Origin and Evolution of Geochemical Characteristics of Waters from the Candiota Coal Mine Area (Southern Brazil): Part I

This work correlates surface and ground water composition to the substrata, and traces how water chemistry evolves at Brazil’s largest coal mine, the Candiota Mine. The water is dominated by SO₄, Fe, Ca, and Mg. A pH range of 2.7–3 in the pit lakes is attributed through chemical models to concomitant pyrite oxidation and carbonate dissolution along with slow hydrolysis of aluminosilicate minerals and buffering provided by several iron oxy-hydroxide species. The Fe deficit of the surface water relative to the expected values is mainly due to precipitation of Fe sulfate salts, hydroxysulfates, and oxyhydroxides in the waste piles and their runoff. A progressive decrease in oxygen partial pressure with increased lake depth leads to destabilization of the iron oxyhydroxides/hydroxysulfates formed near the surface, which explains their absence from the lake sediment. Although interacting with similar rock types, the groundwater has a significantly different composition than the surface water, with less salinity and a pH of 5–6.5, due to limited oxygen and its evolution in a nearly closed system that stabilizes at higher pH values, which is controlled by carbonate/bicarbonate buffering.     

Evidence for surface cleaning of sulphide minerals by attritioning in stirred mills

Recent developments in large scale stirred milling technology using ceramic media have allowed its application to relatively coarse particle streams. Apart from benefits in grinding finer more efficiently, benefits may also be derived from the surface cleaning action of stirred mills. This paper discusses evidence for the cleaning action of a stirred mill on the surfaces of chalcocite and effects on its subsequent flotation. Single mineral samples of chalcocite were ground with either stainless or mild steel grinding media. The effects of surface contamination by iron hydroxide on chalcocite floatability were studied using ethylene diamine-tetra acetic acid (EDTA) extraction, X-ray photoelectron spectroscopy (XPS) surface analysis and contact angle measurements. Depression of both coarse (+75 μm) and fine (?10 μm) size fractions was attributed to the surface precipitation of iron hydroxide species. Transfer of iron hydroxides from coarse particles to fine particles was observed with XPS analysis. Recovery of coarse particles (+75 μm) was improved by attritioning, while additional collector was needed to fully restore chalcocite recovery in both fine and coarse size fractions.     

Lake George as a Sink for Contaminants Derived from the Kilembe Copper Mining Area, Western Uganda

Abstract  The copper mine at Kilembe in the Ruwenzori Mountains in western Uganda ceased to operate in 1978 but a steady flow of contaminants, including Cu, Co, Ni, Zn, Cd, and sulphate, continues to enter the Nyamwamba-Rukoki River, which passes through Queen Elizabeth National Park, and finally flows into Lake George. Lake George is quite shallow, alkaline, and highly eutrophic. Measuring mass-flow of contaminants, water, and suspended solids in the Rukoki River near Kasese allowed us to estimate their input into Lake George. Grid sampling of lake sediments indicated that the contaminants settle near the two mouths of the river; low concentrations in a drill core in the centre of Lake George indicate that further dispersion within the lake is small. Sequential extraction experiments on lake sediments and lake water analyses suggest low bioavailability of the heavy metals. We conclude that Lake George is a highly resilient system that efficiently immobilises contaminants. Though there is no health risk for the population under present environmental conditions, a reduction of the contaminant load is desirable.     

An Investigation of Environmental Contamination at the Silvermines Abandoned Mines Site in Ireland Based on the Preliminary Delimitation of Pollution Hot Spots

This paper describes a holistic methodology for the investigation of environmental contamination from abandoned mine sites (AMSs), and is based on a case study of the Silvermines AMS. Groundwater modelling, surface water temperature monitoring, and a geographical information system (GIS) were used to undertake a preliminary delimitation of areas where soil, fluvial sediments, and surface and groundwater were contaminated. Subsequent soil and water sampling and analysis confirmed the accuracy of these predictions. Significant contamination of environmental media in the vicinity of the AMS was largely the product of water-borne pollutants. The concentration of Pb was high in streams receiving direct discharge from the AMS, but decreased rapidly downstream. Concentrations in stream sediments showed the same pattern. Extremely high Pb concentrations were also observed in sediments downslope from the AMS where groundwater discharges into surface drainage. Soil Pb concentrations were highest on floodplains and in areas affected by surface runoff and seasonal groundwater seepage. The methodology described here allows effective and cost-efficient investigation of the environmental impact of AMSs, which in turn provides the basis for site rehabilitation.     

微生物对巢湖沉积物生物可利用磷的稳定性影响

以巢湖沉积物为研究对象,利用化学提取方法对四个采样点表层沉积物进行生物可利用磷(BAP)的测定。并通过沉积物—湖水体系的好氧厌氧模拟实验,研究添加菌剂对磷的释放或积聚的影响。结果表明:BAP含量与水体中的Chl-a、TP及TDP浓度显著相关,说明表层沉积物的生物可利用磷含量能够反映水体富营养化的强度;好氧环境下,微生物作用有助于磷的积聚;而在厌氧环境下,微生物作用强化了磷的释放;在有菌、无菌厌氧释放实验结束后,BAP含量显著减少。表明微生物在磷的循环中起了重要作用,可以直接或间接影响生物可利用磷中各形态磷的迁移转化。     

Trace Metal Occurrence and Mobility Assessment in Stream Sediments near the Sungun Porphyry Copper Deposit in Northwest Iran

The Sungun porphyry copper deposit is located 100?km northeast of Tabriz in the Azarbaijan province of Iran. The total concentration and chemical fractionation of metals and metalloids (As, Se, Cd, Cr, Ni, Co, and Zn) in sediment downstream of the Sungun mine was investigated. The degree of contamination was evaluated using the sediment pollution index (SPI) and enrichment factor. The concentrations of As, Cd, Se, and Zn in the contaminated sediments were elevated due to anthropogenic activities. According to the SPI, surface sediments in the ephemeral rivers flowing in the vicinity of the Sungun porphyry copper deposit are classified as natural sediment with no ecological risk, while sediments that received contaminated effluents are classified as slightly polluted. Sequential extraction indicated that Co was principally associated with the iron and manganese oxide fraction, while other elements (As, Zn, Cr, Se, and Ni) were mainly distributed in residual phases. Cadmium is the only element that has a high potential for mobility and bioavailability in the sediments and, of the investigated elements, it poses the greatest potential risk to the local aquatic ecosystems. The chemical fractionation pattern of elements appears to be influenced by industrial effluents. Although the bioavailable fraction of most contaminant metals is low due to the freshness of the sediments, over time, the oxidation of sulfide minerals in these sediments could contribute contaminant elements in soluble form.     

Physico-chemical gradients and meromictic stratification in Cueva de la Mora and other acidic pit lakes of the Iberian Pyrite Belt

A marked vertical trend of increasing temperature and dissolved metal concentrations is observed in the monimolimnia of some meromictic pit lakes of the Iberian Pyrite Belt (IPB) in SW Spain. Temperature differences between the chemocline and the pit lake bottom can be as high as 15°C (e.g. Herrerías), and the respective concentration of some metals (e.g. Fe) and metalloids (e.g. As) can increase by several orders of magnitude (e.g. Cueva de la Mora). The redox conditions also change drastically from the upper and oxygenated mixolimnion (strongly oxidizing) to the lower and anoxic monimolimnion (moderately reducing). Processes such as the inflow of metal–sulphate laden ground water from flooded shafts and galleries, and other factors such as the pit geometry or the relative depth of the lakes, must be considered to account for the observed stratification pattern. The vertical profiles of physico-chemical parameters and water chemistry obtained in Cueva de la Mora and other meromictic pit lakes of the IPB are also compatible with a reactive bottom in which several geochemical and microbial reactions (including reductive dissolution of Fe³⁺ minerals, bacterial reduction of Fe³⁺ and SO₄ ²⁻ in pore waters within the sediments, and decomposition of organic matter) could be taking place.     

Chemical Fractionation and Contamination Intensity of Trace Elements in Stream Sediments at the Sarcheshmeh Porphyry Copper Mine, SE Iran

This paper presents chemical fractionation and contamination intensities of trace elements in stream sediments at the Sarcheshmeh mine, southeastern Iran, which is one of the world’s largest Oligo-Miocene porphyry copper deposits. Evaluation of environmental pollution indices and maximum probable background concentrations revealed that As, Cu, Cd, Mo, Pb, Sb, Se, S, and Zn are highly concentrated in the contaminated sediments, while Cr, Co, Ni, Fe, and Mn show lower enrichment values. Discharges of industrial effluents (especially those contaminated by tailings), reject waste from the semi-autogenous mill, and rock waste drainages are the main anthropogenic contaminant sources. High values of As, Cu, Fe, Mo, Pb, and Zn were associated with the oxidizable, primary sulfide, and residual sediment fractions. Relatively high percentages of Co (>92?%), Cr (>58?%), Cu (>79?%), Fe (>40?%), Mn (>97?%), Ni (>87?%), and Zn (>83?%) in the sediments associated with the rock waste drainages were readily released during the extraction of water-soluble, exchangeable, and carbonate fractions. Sediments that received reject waste drainages were also polluted by As (>351.7?mg?kg^?1), Cu (>1.58?%), Mo (>91.8?mg?kg^?1), Pb (>291.8?mg?kg^?1), and Zn (>762.4?mg?kg^?1). A large percentage of these contaminants were found to be adsorbed and co-precipitated with amorphous Fe-oxides and carbonate phases. The chemical fractionation pattern of the potentially hazardous trace elements corresponded well with the mineralogical composition of the contaminated sediments.     

基于锥体排除法的露天矿最终境界优化

我国经济进入新常态,钢铁冶金业大力淘汰过剩产能,加之世界铁矿市场疲软,铁矿价格持续低迷,矿山企业面临降低成本的巨大压力。对于露天矿山,提高帮坡角是充分回收资源、降低生产成本、增加矿山效益的重要手段。鉴于此,通过Opmetalminer软件建立矿床数值模型,按0.5°步长优化得到不同上盘帮坡角所对应的境界内矿岩量、总盈利、开采范围和开采深度的变化情况,通过对比分析给南芬露天矿降低生产成本提供决策。研究表明:随着帮坡角度数的提高,与基准境界相比,采出矿石量有所增加,剥离岩石量有增加有减少,总盈利增加,开采范围和开采深度在不同区域变化趋势相反。