Geochemistry of Mine Stream Sediments and the Control on Potentially Toxic Element Migration: A Case Study from the Baccatoio Basin (Tuscany,Italy)

Mine Water and the Environment - The concentration of 14 potentially toxic elements (PTE), including emerging contaminants, was determined in mine tunnel sludges, streambed sediments, and in the...     

Thallium Contamination in the Raibl Mine Site Stream Drainage System (Eastern Alps,Italy)

The Raibl mine (Cave del Predil village, northern Italy) belongs to the Pb–Zn minerogenetic district in the southeastern Alps, hosted in Middle Triassic carbonates. The drainage water quality reflects the high acid-buffering capacity of the carbonate rocks, which controls the mobility of most metals. In particular, Fe is non-detectable in solution, having formed hydrous-oxides precipitates. Molybdenum, Ni, Zn, Cd, Pb, and Tl are present, and the Pb, Tl, and Zn concentrations sometimes exceed the Italian regulatory thresholds. Thallium concentrations substantially exceed the 2 µg/L limit at some sampling stations, ranging between 12 and 30 µg/L in the mine drainage, and reaching 5 µg/L downstream of the mine site, despite strong dilution. The data indicate that Tl behaves almost conservatively and is not significantly scavenged by the Fe precipitates. The elevated Tl represents a potential risk for the stream ecosystem. Although Tl is not regulated in drinking water in Italy or the European Community, its distribution in natural waters may help to determine if health actions should be taken.     

Comparative Assessment of Leaching Tests According to Lixiviation and Geochemical Behavior of Potentially Toxic Elements from Abandoned Mining Wastes

The release of potentially toxic elements (PTEs) from abandoned mining waste (AMW) is generally assessed with leaching tests. The United States, Mexico, and Spain's geological surveys respectively use leaching tests USGS FLT, NOM-141-SEMARNAT-2003, and EN-12457-2 to assess the potential water pollution from AMW. However, to facilitate preliminary hazard assessment of the potential leaching, especially for daily practice at sites with a large amount of recorded AMW, a comparative assessment of these widely used leaching tests can be helpful. The present research covers this knowledge gap by evaluating the geochemical leaching behavior of As, Ba, Cu, Pb, and Zn, by using these leaching tests in different types of AMW. The results suggest that these methods show slight differences in saturation indices, pH, specific conductance, redox potential, and released PTEs that can be mainly imputed to the contact time. Despite these differences, the findings suggest that the lixiviation patterns from the analyzed methods are comparable, and allow the same conclusions to be reached regarding the potential hazard of the AMW as a function of the solubility of the PTEs.

     

Quantification of Changes in Metal Loading from Storm Runoff,Merse River (Tuscany,Italy)

The Merse River in Tuscany is affected by mine drainage and the weathering of mine wastes along several kilometres of its catchment. The metal loading to the stream was quantified by defining detailed profiles of discharge and concentration, using tracer-dilution and synoptic-sampling techniques. During the course of a field experiment to evaluate metal loading to the Merse, such data were obtained for both storm and pre-storm conditions, providing a unique opportunity for comparison. Iron, Cu, and Mn were chosen to illustrate changes resulting from the storm. The total-recoverable load of Fe increased 21-fold, while loads of Cu and Mn increased by 8- and 7-fold, respectively, during the storm runoff. The increases most likely resulted from flushing particulates from near the stream, resuspension of colloidal material from the streambed, and increased ground-water inflow to the stream. The increases in Cu and Mn loads results from their association with colloids. It is possible that in-stream colloids had relatively more Cu than Mn, while near-stream colloids had relatively more Mn. Each of the metals also increased as a result of increased ground-water discharge during the storm. Despite great increases in load, the filterable concentrations of these metals did not increase substantially, remaining below chronic levels of toxicity.     

Fate of Antimony and Arsenic in Contaminated Waters at the Abandoned Su Suergiu Mine (Sardinia,Italy)

Mine Water and the Environment - We investigated the fate of Sb and As downstream of the abandoned Su Suergiu mine (Sardinia, Italy) and surrounding areas. The mined area is a priority in the...     

Metal Loadings and Alkaline Mine Drainage from Active and Abandoned Mines in the Ivo River Basin Area of Southeastern Nigeria

Discharges from 11 active and abandoned mines were investigated in the Lokpaukwu-Ishiagu mining areas of Nigeria. The discharges had very high concentrations of TDS, hardness, chloride, calcium, conductivity, turbidity, and unacceptable levels of some metals. A conservative estimate is that nearly 33 million L of untreated circumneutral-alkaline drainage and effluents find their way into the Ivo River watershed annually, including about 710,000 kg of dissolved solids and 586 kg of potentially toxic metals. These discharges exceed national (FEPA) and international (EU, WHO, and USEPA) permissible standards for domestic water use and discharge into aquatic sources, and national groundwater protection standards for permitted concentrations of toxic substances in industrial effluents. Our study also revealed that wetlands that serve as sinks for this mine drainage become sources of continuous polluted recharge to both surface and groundwater. We recommend that a task force be established to investigate the environmental operations of mining companies in Nigeria, that mine sites be closely monitored by state agencies, and that host communities receive environmental education.     

Uranium and Potentially Toxic Metals During the Mining,Beneficiation, and Processing of Phosphorite and their Effects on Ground Water in Jordan

Representative samples were collected from various stages of phosphorite mining and beneficiation from the Al-Abiad and Al-Hasa mines in central Jordan and the Eshidiyya mine in southern Jordan. After open pit mining, the rock is crushed and dry-sieved to pass 12 mm in order to concentrate the ore. The sieved material is then agitated, washed with fresh water, and wet sieved to pass 4 mm. Samples were analyzed by ICP-MS for major elements and As, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, Se, U, V, and Zn. We found that throughout the above-mentioned processes, potentially toxic metals are partially removed from the ore. However, most of the contaminants are still retained within the final phosphorite product. The slime and slime water were analyzed; we found no effect of the slime water on the nearby ground water regime. The phosphorite is converted to fertilizer through reactions with sulfuric acid and then ammonia to produce diammonium phosphate (DAP). Gypsum is produced as a reject. The potentially toxic metals follow the behavior of P and are enriched by a factor of more than 1.5 in the DAP compared with the input phosphorite. The trace metal content in the phosphogypsum is very low.     

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.     

Evaluation of Geothermal Potential in the Vicinity of the Flooded Sierra Almagrera Mines (Almeria,SE Spain)

Mine Water and the Environment - We evaluated the hydrogeochemical characteristics of water from the old flooded Sierra Almagrera mines to determine the possible origin of its geothermal fluids, to...     

Cyanides,Arsenic, and Noble Metals in Abandoned Gold Ore Cyanidation Tailings and Surface Waters in a Permafrost Region (Transbaikal Territory,Russia)

Mine Water and the Environment - Geochemical and geophysical investigations were performed in an area of the Darasun ore cyanidation tailings impoundment, which is located in a permafrost region....     

Heavy Metals in Stream Sediments from the Coquimbo region (Chile): Effects of Sustained Mining and Natural Processes in a Semi-arid Andean Basin

Abstract.   Active sediments from the Elqui River in Chile were sampled 4 times at 10 sites during 2000. Concentrations of Ag, Ba, Cd, Co, Cr, Hg, Mn, Mo, Ni, Pb, Sr, Ti, V, Al, Ca, Fe, K, Mg, Na, P, and S were normal. Zinc levels were clearly high, and those of Cu (hundred to thousands ppm) and As (tens to hundreds ppm) were highly anomalous. Dissolved Cu (0.1-12.7 ppm) and Zn (0.2-2.2 ppm) levels were also very high. The anomalies of the upper tributaries are due to the El Indio–Tambo Au-Cu-As district and large hydrothermal alteration zones at altitudes between 3500–4500 m. Lower on the river, old and active tailing waste deposits and on-going mining operations in the Talcuna Cu (Pb) district are responsible. Partially eroded tailing deposits in the alluvial plain of the Elqui River and its tributaries, and especially in the El Indio-Tambo district, after mine closure in 2000, warrant special attention.     

Dust dispersion from haul roads in complex terrain: the case of a mineral reclamation site located in Sardinia (Italy)

In recent years, there has been significant research effort to investigate the use of plume dispersion models to assess the environmental impact of fugitive dust emissions from surface mining operations. In particular, the results of these studies have identified challenges to the use of traditional Gaussian plume dispersion models to satisfactorily reproduce fugitive dust dispersion and deposition experienced from low elevation release heights within complex topography. This paper presents a discussion of the results of a preliminary series of modelling studies that have employed the UK-Atmospheric Dispersion Modelling System (ADMS) model to investigate the dust dispersion and deposition from a former mining site currently undergoing remediation. The remediation site is located within a valley in south-western Sardinia that may be considered an aerodynamically complex terrain. A series of field measurement surveys were conducted along the length of an unpaved surface haul truck roadway to measure the PM2.5 and PM10 dust fractions within the emitted plumes. To investigate the potential effects that the surrounding topography may have on the atmospheric dispersion and deposition experienced a series of UK-ADMS dispersion models were solved for a range of meteorological stability conditions typical of the area under investigation. A preliminary analysis of the results of these simulations concludes that there was a strong influence of the surrounding terrain on the dispersion and deposition phenomena predicted.     

Mineralogical and Geochemical Characterization of Mine Tailings and Pb, Zn, and Cd Mobility in a Carbonate Setting (Northern Tunisia)

Millions of tonnes of Pb–Zn ore flotation tailings and waste rock have been discharged at sites in northern Tunisia without concern for environmental issues. The tailings are dominantly fine grained (<125 μm), with high porosity and permeability. The tailings were characterized to assess base metal (Pb, Zn, and Cd) mobility. The relatively low percentage of iron sulphide and the dominance of carbonates in the matrices of the tailings indicated that only neutral mine drainage is likely. Batch sequential testing showed that the calcium and sulphate, which are the major ionic species in solution, are derived mainly from the dissolution of gypsum and not from neutralization of acidity generated by pyrite oxidation. Yet, despite the carbonate setting, the resultant neutral to slightly alkaline pH, and prolonged weathering, the studied flotation tailings maintain their capacity to release contaminants, notably Zn and Cd, into the environment. The amount of Zn that dissolves (2,400 μg L^?1, on average), though significant, is below the background concentrations in the Mejerda River and the environmental norms established for surface waters. Pb concentrations come close to the standards, but only Cd (18 μg L^?1, on average) sometimes exceeds current river water concentrations and environmental standards.     

Assessment of Trace Elements in Soils and Mine Water Surrounding a Closed Manganese Mine (Anti Atlas,Morocco)

Five mine water samples, 23 topsoil samples, and four mine waste (tailings) samples were collected to assess the effects of a closed Moroccan Mn mine. Based on the pH, electrical conductivity, and concentrations of sulphate, Cu, Zn, As, Cd, Pb, and Mn, mining has not adversely influenced mine water quality. Soil samples were analyzed for 23 chemical elements and the results were interpreted by univariate and multivariate statistical techniques. Based on an enrichment factor (EF) calculation, only Cd, As, V, and Mn were selected for further study. Geochemical background (GB) and geoaccumulation index (I_geo) were determined for these elements to differentiate between geogenic and anthropogenic enrichment. The GB values showed that the Tiwiyyine soils contained a high geogenic content of Cd, As, V, and Mn that reflected the geochemistry of the parental rocks in this mineralized region. The I_geo calculation revealed that these soils were moderately influenced by anthropogenic activity, which had increased the concentrations of those elements. Finally, geochemical maps revealed that mining was likely responsible for the anthropogenic soil pollution.     

Hydrogeochemistry and Contamination of Trace Elements in Cu-Porphyry Mine Tailings: A Case Study from the Sarcheshmeh Mine,SE Iran

Geochemical and hydrochemical investigations were performed to understand the contamination potential of the Sarcheshmeh mine tailings. The geochemical mobility for the tailings is as follows: Cu > Cd > Co > Zn > Ni > Mn > S > Cr > Sn > As > Se > Fe = Bi > Sb = Pb = Mo. Highly mobile and contaminant elements (Cd, Cu, Zn, Mn, Co, Ni, S, and Cr), which significantly correlated with each other, were mainly concentrated in the surface evaporative layer of the old, weathered tailings, due to the high evaporation rate, which causes subsurface water to migrate upward via capillary action. The contamination potential associated with the tailings is controlled by: (1) dissolution of secondary evaporative soluble phases, especially after rainfall on the old weathered tailings, accompanied by low pH and high contamination loads of Al, Cd, Co, Mg, Cr, Cu, Mn, Ni, S, Se, and Zn; (2) processing of the Cu-porphyry ore under alkaline conditions, which is responsible for the high Mo (mean of 2.55 mg/L) and very low values of other contaminants in fresh tailings in the decantation pond; (3) low mobility of As, Fe, Pb, Sb, Mo, and Sn due to natural adsorption and co-precipitation in the tailings oxidizing zone. Speciation modeling showed that sulfate complexes (MSO₄ ⁺, M(SO₄)_(aq), M(SO₄) ₂ ^?2 , and M(SO₄) ₂ ^? ) and free metal species (M⁺² and M⁺³) are the dominant forms of dissolved cations in the acidic waters associated with the weathered tailings. In the alkaline and highly alkaline waters, trace element speciation was controlled by various hydroxide complexes, such as M(OH)⁺, M(OH) ₃ ^? , M₃(OH) ₄ ⁺² , M₂(OH) ₃ ⁺ , M(OH)_2(aq), M(OH) ₄ ^?2 , Me(OH) ₂ ⁺ , Me(OH) ₄ ^? , Me(OH) ₂ ⁺ , Me(OH)_3(aq), and Me(OH) ₄ ^? (where M represents bivalent and Me represents trivalent cations). The speciation pattern of As, Mo, and Se is mainly dominated by oxy-anion forms. The obtained results can be used as a basis for environmental management of the Cu-porphyry mine tailings.     

细菌胞外多聚物（EPS）的特性及在矿物加工工程应用

本文概述了细菌胞外聚合物的特性、提取方法,综述了国内外近年来有关细菌胞外聚合物及其主要成分,在矿物加工工程上应用的现状和研究进展.