a technique for determining low concentrations of total carbonate in geologic materials abstract even small quantities of carbonate minerals can impart a significant acid neutralizing capacity to soils impacted by acid waters rain leachate from pyritic mine tailings etc a simple analytical technique is presented for determining the carbonate content of geologic materials containing less than 1 carbonate minerals samples are acidified and the evolved co2 measured accurately using a modified headspace gas chromatographic technique less than 0 001 wt calcite can be accurately detected in geologic samples six replicate analyses of a synthetic sample containing 0 075 wt calcite produced a mean calcite content of 0 079 wt with a standard deviation of 4 7 of the mean a major problem in carbonate determinations where waters high in fe2 are encountered is the loss of carbonates resulting from acid production vis fe2 oxidation during sample collection and handling

pore water extraction from the unsaturated and saturated zones a simple inexpensive method for extracting pore water from unsaturated soils which uses a combination of immiscible fluid displacement suction and mechanical compression is described this method uses a squeezing chamber to contain the unsaturated sediments in aluminum core tubing to prevent exposure of the sediments and pore water to atmospheric o2 and subsequent oxidation reactions geochemical artifacts resulting from high compression squeezing are prevented by maintaining the pressure applied during the squeezing at a minimum comparison of squeezed profiles with field measured profiles of ph eh oxidation reduction potential alkalinity and metal speciation indicates good agreement between these parameters using this method depending on the water content of the sediments a range of water volumes several millilitres to excess of 100 ml can be extracted from a single core section 7 6 cm in diameter by 20 cm long pore water was produced immediately from sediments at near saturated condition

mineralogical geochemical and microbial investigation of a sulfide rich tailings deposit characterized by neutral drainage mineralogical geochemical and microbial characterization of tailings solids from the greens creek mine juneau alaska was performed to evaluate mechanisms controlling aqueous geochemistry of near neutral ph pore water and drainage core samples of the tailings were collected from five boreholes ranging from 7 to 26 m in depth the majority of the 51 samples 77 were collected from the vadose zone which can extend 18 m below the tailings surface mineralogical investigation indicates that the occurrence of sulfide minerals follows the general order pyrite fes 2 sphalerite zn fe s galena pbs tetrahedrite fe zn cu ag 12 sb 4 s 13 arsenopyrite feass and chalcopyrite cufes 2 pyrite constitutes 35 wt of the tailings mineral assemblage whereas dolomite camg co 3 2 and calcite caco 3 are present at 30 and 3 wt respectively the solid phase geochemistry generally reflects the mineral assemblage the presence of additional trace elements including cd cr co mo ni se and ti is attributed to substitution into sulfide phases results of acid base accounting aba underestimated both acid generating potential ap and neutralization potential np recalculation of ap and np based on solid phase geochemistry and quantitative mineralogy yielded more representative results neutrophilic s oxidizing bacteria nsob and so 4 reducing bacteria srb are present with populations up to 10 7 and 10 5 cells g 1 respectively acidophilic s oxidizing bacteria asob and iron reducing bacteria irb were generally less abundant primary influences on aqueous geochemistry are sulfide oxidation and carbonate dissolution at the tailings surface gypsum precipitation dissolution reactions as well as fe reduction below the zone of sulfide oxidation pore water ph values generally ranged from 6 5 to 7 5 near the tailings surface and from approximately 7 8 below the oxidation zone elevated concentrations of dissolved so 4 s 2 o 3 fe zn as sb and ti persisted under these conditions

predicting pyrite oxidation and multi component reactive transport processes from an abandoned coal waste pile by comparing 2d numerical modeling and 3d geo electrical inversion abstract in this paper pyrite oxidation process resulted from an abandoned coal waste pile in northeastern iran was evaluated by a combination of three dimensional 3d geo electrical data inversion and two dimensional 2d numerical modeling of long term pyrite oxidation and multi component reactive transportation of the oxidation products to achieve the goal 42 solid samples were obtained from different depths of two trenches excavated over the pile the samples were analyzed for the fraction of pyrite remaining within the waste particles besides the mole fraction of oxygen at various depths of the pile was measured in situ the results reveal that pyrite oxidized considerably at the shallower depths where oxygen diffused simultaneously 2d geo electrical surveys were conducted on four parallel profiles over the waste pile afterward the measured apparent resistivity values were assembled into a 3d data set and further modeled by inverting these data the results show that horizontal slices of the 3d resistivity model almost correspond with the geochemical data besides a computational fluid dynamics cfd software called phoenics was modified to numerically solve the governing equations of oxygen diffusion pyrite oxidation and solute transport applying a finite volume technique and considering all sources and sinks related to the chemical reactions the results show that the oxidation occurred in the upper layers of the pile which almost correspond with the geo electrical data interpretation moreover the predicted results show that further pyrite oxidation would generate more products that reach the pile base in the future eventually a reclamation scenario was suggested by covering an impermeable cap on the pile surface the results reveal that this process would prevent oxygen diffusion to the pile which in turn limit pyrite oxidation process and acid mine drainage generation in the waste particles and it would lead to termination of the transportation of oxidation products within the pile by surface recharge

the generation and quality of streamflow on inactive uranium tailings near elliot lake ontario this study was undertaken to investigate the physical and chemical interactions between groundwater and surface water in an area of inactive uranium mill tailings near elliot lake ontario the study area had a shallow water table and was drained by a single channel streamflow chemistry and discharge and the hydraulic response of the groundwater system were monitored for several runoff events during the period of september 1981 through may 1982 the hydrographs measured for each event were separated into groundwater and surface water components using the mass balance technique with cl and 18o as conservative tracers the mechanisms of streamflow generation and their effect on runoff quality were evaluated on the basis of the hydrograph separations the observed groundwater response and the characteristics of the precipitation events the results indicate that groundwater constitutes a significant amount of the stormflow generated in the study area the magnitude of this contribution was dependent upon the intensity and duration of rainfall and on the initial depth to the water table the capillary fringe played an important role in the processes of streamflow generation both in causing a large water table rise which increased groundwater flow to the stream and in forming an expanding seepage face which enhanced overland flow during runoff events the stream contained high concentrations of several dissolved inorganic species the groundwater contribution was a major source of these constituents the findings of this study indicate that groundwater can be a major component of streamflow during runoff events in inactive tailings areas and as a result can have a major influence on runoff quality the groundwater contribution to streamflow represents an important pathway of contaminant migration to the biosphere which can be anticipated to persist for long periods of time

grass cover density and metal speciation in profiles of a tailings pile from a mining zones in zacatecas north central mexico the 7 year old mine tailings pile p2 from concepcion del oro has been revegetated spontaneously by xerophyte grasses covering about the 30 of its surface to elucidate the effect of the grass cover in the geochemical behavior of the sulfide minerals sm and metals the strata of four selected profiles p2 i p2 ii p2 iii and p2 iv with high middle low and null grass cover respectively were analyzed mineralogically and chemically using scanner electron microscopy x ray diffractometer and performing a six step sequential extraction method an older 50 year old and uncovered without grass cover profile of the tailings pile p3 was also analyzed in all the profiles from p2 the sm oxidation is not yet an extended process however the samples from the uncovered profile p2 iv showed evidences of sm pyrite and chalcocite oxidation as well as the presence of gypsum and fe oxides as the major secondary phases resulted from the sm oxidation additionally the carbonate content and ph values in p2 iv were lower than in the covered profiles from p2 the oldest and uncovered p3 i profile showed an extensive oxidation of sulfurs which resulted in the depletion of carbonates and a ph 2 another distinctive characteristics of the covered profiles was that pb cu and zn were mainly associated with the reducible fractions carbonates and or amorphous oxides meanwhile in the uncovered p2 iv and p3 i such metals were mainly associated with the oxidizable fraction crystalline oxides the results suggest that the mineralogical transformations control metal stability in plant covered impoundments phytostabilization the occurrence of a thick grass cover with an efficient water usage and retention seems to shun both the acidic dissolution of carbonates and the reductive dissociation of the formerly present oxyhydroxides which is desired for remediation tasks this is the first report about the effects of grass cover for a carbonaceous and unsaturated mine tailings from a semiarid region that can help in a better understanding of the scope of phytoremediation in such conditions

modeling the effect of stratification on cemented layer formation in sulfide bearing mine tailings abstract reactive transport simulations have been applied to investigate possible effects of stratification on the potential of sulfide bearing mine tailings to form protective cemented layers the simulations are based on characteristic strata found at a german tailings site including sulfide enriched heavy mineral layers mica enriched silt layers and homogeneously mixed layers the simulated secondary phases jarosite gypsum amorphous ferric arsenate amorphous fe hydroxide alunite amorphous silica and kaolinite are similar to those observed in the field using scanning electron microscope analyses of cemented layers it has been observed that the pore area becomes disconnected if the porosity is decreased to values below 15 which would indicate a strong decrease in permeability stratification was found to play a crucial role in cemented layer formation cemented layers are absent or insignificant in systems with a homogeneous distribution of fe bearing sulfides they are extensively developed in systems with a an arsenopyrite rich layer or b a mica enriched layer situated immediately below an fe sulfide enriched layer the modeling results have clearly demonstrated that the key processes operating in scenario a are very different from the key processes in scenario b in scenario a the oxidation of arsenopyrite is followed by the precipitation of amorphous ferric arsenate which can be solely responsible for significant pore reduction in scenario b the presence of a large amount of reactive aluminosilicates e g biotite and ca bearing plagioclase immediately below the fe sulfide rich layer appears to be crucial key processes are extensive formation of acid rock drainage ard followed by enhanced ph driven weathering of aluminosilicates resulting in the accumulation of secondary phases directly below the fe sulfide rich layer in both scenarios a cemented layer is formed that effectively retards the further downward movement of the oxidation front the presented details on the role of stratification in the formation of cemented layers could be considered in the construction of mining heaps as a possible measure to stimulate natural attenuation

ice formation in ash influenced clouds after the eruption of the eyjafjallajokull volcano in april 2010 1 the influence of volcanic ash on heterogeneous ice nucleation in tropospheric clouds is investigated on the basis of 90 observed cloud cases the clouds were observed with polarization lidars at the two central european earlinet stations leipzig 51 3 n 12 4 e and maisach 48 2 n 11 3 e 25 km northwest of munich germany in volcanic aerosol layers which originated from the strong eruptions of the icelandic eyjafjallajokull volcano in april 2010 case studies of evolving boundary layer cumuli and long lasting free tropospheric cloud events with unusual behavior mixed phase cloud complex cirrus deck are discussed a clear impact of ash is observed the ice nuclei concentration derived from the lidar observations has been estimated to range from 2 20 per liter in the boundary layer and from 100 300 per liter at cirrus level the statistical analysis based on the 90 evaluated cloud cases revealed that all observed cloud layers with cloud top temperatures of below 15 c contained ice typically under non volcanic aerosol conditions such a high fraction of ice containing clouds is not reached before temperatures decrease below 25 c over central europe

mobility and retention of trace elements in hardpan cemented cassiterite tailings north queensland australia this study reports on the mobility and retention of trace elements in cassiterite tailings at the inactive jumna mill tropical north queensland since the 1980s the uncapped tailings have developed laterally discontinuous fe rich hardpans which are located in the higher parts of gently sloping tailings masses and at the top 50 cm of the tailings piles hardpan cemented tailings comprise thin layers typically 0 2 2 mm thick of hfo hydrous ferric oxides and sulfate efflorescences cementing tailings grains in comparison to the tailings the hardpan cemented tailings contain significantly higher median as ca cd co cu fe in mn mo stotal th u y and zn values partial leaching studies of tailings and pond water analyses indicate that wetting and acidification of fe cemented tailings removes significant proportions of trace elements into pore and surface waters tin shows no mobility due to the presence of weathering resistant cassiterite sno2 and as and pb display limited mobility possibly due to their coprecipitation with jarosite type phases and hfo materials at the top of the tailings profile by contrast the trace elements cd ce cu la ni pb u and zn display the greatest mobility possibly due to their incorporation in soluble sulfate efflorescences and sorption onto mineral and hfo surfaces hence the fe rich hardpans do not protect the sulfidic tailings from further oxidation nor do they cause permanent sequestration of trace elements

the diavik waste rock project measurement of the thermal regime of a waste rock test pile in a permafrost environment abstract the interior thermal regime of a field scale experimental waste rock pile in the northwest territories canada was studied test pile construction was completed in the summer 2006 and temperature data was collected continuously since that time to february 2009 the temperature data indicates the test pile cooled over the study period with an average heat energy release of 2 5 104 and 2 6 104 mj in 2007 and 2008 respectively the mean annual air temperature maat at the site was 8 9 c during the period between 2006 and 2009 with a permafrost table at a depth of 4 m in bedrock away from the pile because of this cold environment the upward movement rate of the 0 c isotherm into the test pile at its base was approximately 1 5 m a 1 during 2007 and 2008 thermistor strings installed immediately below the base of the test pile showed the test pile basal temperatures remained near and below 0 c during the study period furthermore due to low rates of sulfide mineral oxidation elevated temperatures in the interior of the test pile were not observed the average air velocity in the pore space in july 2007 and 2008 was about one third of that during january of each year based on temperature distributions therefore due to higher air velocity during the winter it is expected that heat transfer is greater during winter

coupled thermal hydraulic and geochemical evolution of pyritic tailings in unsaturated column experiments the evolution of pore water and the composition of solid phases in the vadose zone of pyritic tailings was studied by means of unsaturated column experiments several columns of water saturated mine tailings were dried during 125 days under controlled laboratory conditions the columns were dismantled at four successive drying stages and the evolution of pore water mineralogy water content and temperature was characterized sulfide and aluminosilicate minerals present in the waste dissolved releasing sulfate and other solutes mainly fe zn cu al mg and ca to the pore water evaporation caused a crust of efflorescent water soluble sulfates to develop over the complete top surface of the columns and into the pores of the underlying waste material this crust which has also been identified in the field changed the hydraulic properties of the tailings and produced a decrease in the evaporation rate of the columns moreover these water soluble precipitates mainly rozenite szomolnokite halotrichite hexahydrite mirabilite and gypsum acted as temporary sinks for cd pb co and ni which could be released to the surface run off or the groundwaters during rainfall events under field conditions pore water evolution was determined not only by geochemical processes dissolution of sulfides and aluminosilicates precipitation of secondary phases but also by thermal and hydraulic processes progressive dilution was observed in the lower part of the columns dilution was caused by the thermally driven vapor flux from the top of the column to its colder bottom and subsequent condensation therein this process which may also occur in tailings under sub arid climate played a key role on the evolution of pore water with increasing drying

contamination of surface waters by mining wastes in the milluni valley cordillera real bolivia mineralogical and hydrological influences this study is one of very few dealing with mining waste contamination in high altitude tropical latitude areas exploited during the last century geochemical mineralogical and hydrological characterizations of potentially harmful elements phes in surface waters and sediments were performed in the milluni valley main reservoir of water supply of la paz bolivia 4000 m a s l throughout different seasons during 2002 2004 to identify contamination sources and sinks and contamination control parameters phe concentrations greatly exceeded the world health organization water guidelines for human consumption the very acidic conditions which resulted from the oxidation of sulfide minerals in mining waste favoured the enrichment of dissolved phes cd zn as cu ni pb sn in surface waters downstream from the mine stream and lake sediments mining waste and bedrock showed the highest phe content in the mining area with the exception of fe the phes were derived from specific minerals fe pyrite zn cd sphalerite as fe arsenopyrite cu fe chalcopyrite pb galena sn cassiterite but the mining was responsible for phes availability most of the phes were extremely mobile as fe pb cd zn cu sn in the mining wastes and the sediments downstream from the mine ph and oxyhydroxides mainly explained the contrasted availability of zn mostly in labile fractions and as associated with fe oxyhydroxides unexpectedly pb zn as and fe were significantly attenuated by organic matter in acidic lake sediments hydrological conditions highly influenced the behaviours of major elements and phes during wet seasons major elements were diluted by meteoric waters whereas phes increased due to the dissolution of sulfides and unstable tertiary minerals that formed during dry seasons this is particularly obvious at the beginning of the wet season and contributes to flushes of element transport downstream the high altitude of the study area compensates for the tropical latitude rendering the geochemical behaviour of contaminants similar to that of temperate and cold regions these results might be representative of geochemical processes in ore deposits located in the high andes plateau and of their influence on phe concentrations within the upper amazon basin although mining activities in this region stopped 10 years ago the impact of mining waste on water quality remains a serious environmental problem

tritium as an indicator of recharge and dispersion in a groundwater system in central ontario the detailed distribution of tritium 3h in the recharge area of a shallow unconfined sand aquifer near sturgeon falls ontario is described at this forested shallow water table site bomb tritium has penetrated uniformly to a depth of 8 12 m indicating recharge of 15 cm year which is 16 of precipitation the zone of bomb tritium contains 3h concentrations of from 16 to 269 tritium unit tu whereas much lower values 1 tu are observed in groundwaters recharged only a few years prior to 1953 the year when significant fallout of bomb tritium began tritium distribution is accurately simulated using one and two dimensional models when the ottawa record is used for the post 1953 tritium input function when dispersion is low and when a prebomb tritium input value of 3 tu is used this prebomb value is slightly lower than that suggested by kaufman and libby 1954 based on precipitation and surface water samples from the early 1950s the simulations indicate and field data corroborate that in 1986 3h levels of more than 100 tu occur only in groundwaters recharged between 1957 and 1971 while levels in excess of 200 tu occur only in groundwaters recharged during 1961 1967 the 1960s tritium peak is observed within a narrow distinct depth zone at all locations along the flow section investigated

formation of sequences of cemented layers and hardpans within sulfide bearing mine tailings mine district freiberg germany abstract the roles of mineral dissolution precipitation transformation and mass transport processes related to formation of characteristic cemented layer hardpan sequences were studied in low sulfide and low carbonate freiberg polymetallic mine tailings using high resolution profiling combined geochemical geomicrobiological and geophysical methods allowed description of the process of weathering of reactive mineral phases and the position of the oxidation front in detail as well as revealing the mechanisms of cementation of tailings predominantly by the formation of gels poorly crystalline phases autochthonous and allochthonous gels reduced the porosity of cemented layers to values 1 whereas secondary crystalline phases were less efficient in filling the pore space electron microprobe analysis of cemented tailings showed that common jarosite group minerals contained up to about 8 wt pbo and 0 2 1 9 wt as 2 o 5 iron as si gels reached contents of up to 44 wt as 2 o 5 in gel rich cemented layers zinc was below the detection limit in the studied secondary phases sequential extraction of cemented and related oxidized brown silt layers confirmed that the bulk of as was bound to amorphous poorly crystalline hydrous oxides of fe whereas pb was often bound to jarosite zinc was found preferentially in the water soluble and the exchangeable fractions in the grey silt and the sand directly underlying the oxidized layers as pb and zn occurred as sulfide minerals the main effects of the cemented layer hardpan sequences at the studied site are 1 a temporary natural attenuation of the toxic compounds 2 a restriction of the downward movement of the oxidation front and 3 a reduction of the extent of the erosion of the surface of the tailings impoundment by wind and water the potential of a heap to form cemented layers and hardpans is greatly increased by a heterogeneous distribution of grain sizes and reactive materials in the topmost zone as well as by the occurrence of sulfide rich tailings on top of layers with low permeability

eruption of the eyjafjallajokull volcano in spring 2010 multiwavelength raman lidar measurements of sulphate particles in the lower troposphere 1 a fraction of the volcanic plume that originated from the eyjafjallajokull volcanic eruption on iceland in 2010 reached the southern iberian peninsula in may 2010 the plume was monitored and characterized in terms of optical and microphysical properties with a combination of raman lidar and star and sun photometers our observations showed that the plume arriving at the iberian peninsula was mainly composed of sulphate and sulphuric acid particles to our knowledge this is the first study of optical properties and inverted microphysical properties of volcanic sulphate particles in the lower troposphere boundary layer based on multiwavelength raman lidar measurements a remarkable increase in the particle number concentration in the accumulation mode was determined from the inversion of the aerosol optical properties the large angstrom exponents and low linear particle depolarization ratios 4 7 indicated the presence of small and spherical particles the particle effective radii ranged between 0 30 and 0 55 m in situ instrumentation confirmed an increase of sulphate particles at ground level during this period

acid neutralization mechanisms and metal release in mine tailings a laboratory column experiment mining and milling of base metal ore deposits can result in the release of metals to the environment when sulfide minerals contained in mine tailings are exposed to oxygen and water they oxidize and dissolve two principal antagonistic geochemical processes affect the migration of dissolved metals in tailings impoundments sulfide oxidation and acid neutralization this study focuses on acid neutralization reactions occurring in the saturated zone of tailings impoundments to simulate conditions prevailing in many tailings impoundments 0 1 mol l sulfuric acid was passed continuously through columns containing fresh unoxidized tailings collected at kidd creek metallurgical site the results of this column experiment represent a detailed temporal observation of ph eh and metal concentrations the results are consistent with previous field observations which suggest that a series of mineral dissolution precipitation reactions control ph and metal mobility typically the series consists of carbonate minerals al and fe iii hydroxides and aluminosilicates in the case of kidd creek tailings the dissolution series consists of ankerite dolomite siderite gibbsite and aluminosilicates in the column experiment three distinct ph plateaus were observed 5 7 4 0 and 1 3 the releases of trace elements such as cd co cr cu li ni pb v and zn were observed to be related to the ph buffering zones high concentrations of zn ni and co were observed at the first ph plateau ph 5 7 whereas cd cr pb as v and al were released as the ph of the pore water decreased to 4 0 or less

metal mobility due to storm events on an impacted hillslope in palmerton pa abstract water samples were collected continuously from perennial springs on a hillslope impacted by historical metal deposition to study the hydrologic and geochemical behavior of a watershed during storm events and assess the natural attenuation of metals in soil water samples were collected throughout storm hydrographs for inorganic chemistry analyses and a sequential extraction was performed on watershed soil samples despite 30 a of natural attenuation at the site zn is mobilized into streamwater during storm events with concentrations ranging from 18 to 452 g l while cd and pb concentrations in water samples remained relatively constant zn concentration increased corresponding with the peak in the hydrograph indicating this metal is being released from adsorption sites located in an unsaturated zone that is temporarily inundated during storm events zinc is held on exchangeable water and acid soluble sites and in the reducible fraction further indicating zn may be released as a result of the downward movement of water through the soil profile equilibrium geochemical modeling predicts zn desorption with a decrease in ph which may occur as a result of site re vegetation the long legacy of metal emissions from a historical smelting operation will continue to limit the attenuating ability of this site

trace metal and as solid phase speciation in sulphide mine tailings indicators of spatial distribution of sulphide oxidation in active tailings impoundments abstract redistribution of potentially harmful metals and as was studied based on selective extractions in two active sulphide mine tailings impoundments in finland the hitura tailings area contains residue from ni ore processing while the luikonlahti site includes tailings from the processing of cu co zn ni and talc ores to characterize the element solid phase speciation with respect to sulphide oxidation intensity and the water saturation level of the tailings drill cores were collected from border zones and mid impoundment locations the mobility and solid phase fractionation of ni cu co zn cr fe ca al as and s were analysed using a 5 step non sequential parallel selective extraction procedure the results indicated that metal redistribution and sulphide oxidation intensity were largely controlled by the disposal history and strategy of the tailings sorting exposure of sulphides due to delayed burial impoundment structure and water table and reactivity of the tailings metal redistribution suggested sulphide weathering in the tailings surface but also in unsaturated proximal areas beside the earthen dams and in water saturated bottom layers where o 2 rich infiltration is possible sulphide oxidation released trace metals from sulphide minerals at both locations in the hitura tailings with sufficient buffering capacity ph remained neutral and the mobilized metals were retained by secondary fe precipitates deeper in the oxidized zone in contrast sulphide oxidation induced acidity and rise in the water table after oxidation apparently remobilized the previously retained metals in luikonlahti in general continuous disposal of tailings decreased the sulphide oxidation intensity in active tailings unless there was a delay in burial and the reactive tailings were unsaturated after deposition

pedogenesis in mine tails affects macroporosity hydrological properties and pollutant flow mining activities take a direct impact on the environment particularly when this activity is focused on metal ore exploitation abandoned metal mine areas contain different types of residues from ore processing operations that are typically characterized by high concentrations of heavy metals one consequence is the generation of acid mine drainage caused by the oxidation and hydrolysis of metal sulphides mine tail soils have been studied under several points of view but not on how crack formation affects their properties and functioning before irreversible hardening the cartagena la union mining district is one of the more ancient spanish mining regions this region is placed at the south eastern part of spain and contains one of the largest lead and zinc ore deposits in south europe which was exploited for au ag pb zn fe and cu from the phoenician and carthaginian times the aim of this research work was to characterize the pedogenesis that occurred in mine tailings of different age and properties to highlight the physical and hydrological changes that occurred as a consequence of pedogenesis and their consequences on the environmental pollution risk soil profile morphology was studied in the field likewise the surficial pattern of cracks shear strength bulk density and erosion laboratory analyses were conducted to characterize physical chemical elemental mineralogical and hydrological differences between the soil mass in the macro aggregates and in the fissures macroporosity was studied through image analysis of thin sections of undisturbed soil samples x ray diffraction xrd was performed on the clay fraction studied soils resulted strongly polluted especially as for zn pb cd cl mn and ni and were classified as different kinds of spolic technosol crack formation significantly affected shear strength bulk density macroporosity saturated hydraulic conductivity and element distribution gully and tunnel erosion was also driven by crack formation the mineralogy of the clay fraction revealed that smectites are present favouring crack opening crack formation deeply affected soil features and behaviour namely hydrological properties and flow of pollutants which in turn condition environmental health and possible soil stabilization and reclamation strategies

a review of the source behaviour and distribution of arsenic in natural waters the range of as concentrations found in natural waters is large ranging from less than 0 5 g l 1 to more than 5000 g l 1 typical concentrations in freshwater are less than 10 g l 1 and frequently less than 1 g l 1 rarely much higher concentrations are found particularly in groundwater in such areas more than 10 of wells may be affected defined as those exceeding 50 g l 1 and in the worst cases this figure may exceed 90 well known high as groundwater areas have been found in argentina chile mexico china and hungary and more recently in west bengal india bangladesh and vietnam the scale of the problem in terms of population exposed to high as concentrations is greatest in the bengal basin with more than 40 million people drinking water containing excessive as these large scale natural as groundwater problem areas tend to be found in two types of environment firstly inland or closed basins in arid or semi arid areas and secondly strongly reducing aquifers often derived from alluvium both environments tend to contain geologically young sediments and to be in flat low lying areas where groundwater flow is sluggish historically these are poorly flushed aquifers and any as released from the sediments following burial has been able to accumulate in the groundwater arsenic rich groundwaters are also found in geothermal areas and on a more localised scale in areas of mining activity and where oxidation of sulphide minerals has occurred the as content of the aquifer materials in major problem aquifers does not appear to be exceptionally high being normally in the range 1 20 mg kg 1 there appear to be two distinct triggers that can lead to the release of as on a large scale the first is the development of high ph 8 5 conditions in semi arid or arid environments usually as a result of the combined effects of mineral weathering and high evaporation rates this ph change leads either to the desorption of adsorbed as especially as v species and a range of other anion forming elements v b f mo se and u from mineral oxides especially fe oxides or it prevents them from being adsorbed the second trigger is the development of strongly reducing conditions at near neutral ph values leading to the desorption of as from mineral oxides and to the reductive dissolution of fe and mn oxides also leading to as release iron ii and as iii are relatively abundant in these groundwaters and so4 concentrations are small typically 1 mg l 1 or less large concentrations of phosphate bicarbonate silicate and possibly organic matter can enhance the desorption of as because of competition for adsorption sites a characteristic feature of high groundwater as areas is the large degree of spatial variability in as concentrations in the groundwaters this means that it may be difficult or impossible to predict reliably the likely concentration of as in a particular well from the results of neighbouring wells and means that there is little alternative but to analyse each well arsenic affected aquifers are restricted to certain environments and appear to be the exception rather than the rule in most aquifers the majority of wells are likely to be unaffected even when for example they contain high concentrations of dissolved fe

release transport and attenuation of metals from an old tailings impoundment abstract the oxidation of sulfide minerals from mine wastes results in the release of oxidation products to groundwater and surface water the abandoned high sulfide camp tailings impoundment at sherridon manitoba wherein the tailings have undergone oxidation for more than 70 a was investigated by hydrogeological geochemical and mineralogical techniques mineralogical analysis indicates that the unoxidized tailings contain nearly equal proportions of pyrite and pyrrhotite which make up to 60 wt of the total tailings and which are accompanied by minor amounts of chalcopyrite and sphalerite and minute amounts of galena and arsenopyrite extensive oxidation in the upper 50 cm of the tailings has resulted in extremely high concentrations of dissolved so4 and metals and as in the tailings pore water ph 1 m thick geochemical modeling and mineralogical analysis indicate that the hardpan layer consists of secondary melanterite rozenite gypsum jarosite and goethite the minerals indicated mainly control the dissolved concentrations of so4 fe ca and k the highest concentrations of dissolved metals are observed directly above and within the massive hardpan layer near the water table at a depth of 4 m most metals and so4 sharply decline in concentration although dissolved concentrations of metals and so4 decrease below the water table these concentrations remain elevated throughout the tailings with up to 60 600 mg l 1 fe and 91 600 mg l 1 so4 observed in the deeper groundwater during precipitation events surface seeps develop along the flanks of the impoundment and discharge pore water with a geochemical composition that is similar to the composition of water directly above the hardpan these results suggest that shallow lateral flow of water from a transient perched water table is resulting in higher contaminant loadings than would be predicted if it were assumed that discharge is derived solely from the deeper primary water table the abundance of residual sulfide minerals the depletion of aluminosilicate minerals in the upper meter of the tailings and the presence of a significant mass of residual sulfide minerals in this zone after 70 a of oxidation suggest that sulfide oxidation will continue to release acid metals and so4 to the environment for decades to centuries

source and distribution of naturally occurring arsenic in groundwater from alberta s southern oil sands regions abstract arsenic as concentrations as high as 179 g l have been observed in shallow groundwater in the alberta s southern oil sand regions the geology of this area of alberta includes a thick cover up to 200 m of unconsolidated glacial deposits with a number of regional interglacial sand and gravel aquifers underlain by marine shale arsenic concentrations observed in 216 unconsolidated sediment samples ranged from 1 and 17 ppm a survey of over 800 water wells sampled for as in the area found that 50 of the wells contained as concentrations exceeding drinking water guidelines of 10 g l higher as concentrations in groundwater were associated with reducing conditions measurements of as speciation from 175 groundwater samples indicate that as iii was the dominant species in 74 of the wells speciation model calculations showed that the majority of groundwater samples were undersaturated with respect to ferrihydrite suggesting that reductive dissolution of fe oxyhydroxides may be the source of some as in groundwater detailed mineralogical characterization of sediment samples collected from two formations revealed the presence of fresh framboidal pyrite in the deeper unoxidized sediments electron microprobe analysis employing wavelength dispersive spectrometry indicated that the framboidal pyrite had variable as content with an average as concentration of 530 ppm reaching up to 1840 ppm in contrast the oxidized sediments did not contain framboidal pyrite but exhibited spheroidal fe oxyhydroxide grains with elevated as concentrations the habit and composition suggest that these fe oxyhydroxide grains in the oxidized sediment were an alteration product of former framboidal pyrite grains x ray absorption near edge spectroscopy xanes indicated that the oxidized sediments are dominated by as v species having spectral features similar to those of goethite or ferrihydrite with adsorbed as suggesting that fe oxyhydroxides are the dominant as carriers xanes spectra collected on unoxidized sediment samples in contrast indicated the presence of a reduced as species as i characteristic of arsenopyrite and arsenian pyrite the results of the mineralogical analyses indicate that the oxidation of framboidal pyrite during weathering may be the source of as released to shallow aquifers in this region

atmospheric sulfur deposition 1950 1985 inferred from sulfate in groundwater groundwater sulfate that occurs at concentrations of 6 27 mg l in a shallow water table sand aquifer at a forested site 100 km east of sudbury ontario is used to deduce the trend in atmospheric sulfur deposition between 1950 and 1985 the simple geologic nature of the aquifer made feasible this trend reconstruction the age of groundwater that entered the aquifer during the past 60 years was determined with unusual accuracy 3 years from tritium analyses and flow modeling sulfur isotopes and mass balances indicate that the sulfate in the groundwater zone is of atmospheric origin and is not derived from solid phase material in the sediments evapotranspiration enriches atmospheric sulfate by a factor of about three as it enters the aquifer adsorption of sulfate is not significant groundwater sulfate indicates a decrease of 37 in sulfur deposition at the site between a maximum in the 1960s and lower values observed in the 1980s we attributed most of the decrease bout 80 to lower so2 emissions from the sudbury smelters these emissions are now about one third of the 1960s levels further major decreases in sulfur deposition at this site can be achieved only if emissions from sources distant from sudbury are lowered as well because sudbury now contributes less than 25 of total sulfur deposition

determining the contribution of volcanic ash and boundary layer aerosol in backscatter lidar returns a three component atmosphere approach 1 a solution of the lidar equation is discussed that permits combining backscatter and depolarization measurements to quantitatively distinguish two different aerosol types with different depolarization properties the method has been successfully applied to simultaneous observations of volcanic ash and boundary layer aerosol obtained in exeter united kingdom on 16 and 18 april 2010 permitting the contribution of the two aerosols to be quantified separately first a subset of the atmospheric profiles is used where the two aerosol types belong to clearly distinguished layers for the purpose of characterizing the ash in terms of lidar ratio and depolarization these quantities are then used in a three component atmosphere solution scheme of the lidar equation applied to the full data set in order to compute the optical properties of both aerosol types separately on 16 april a thin ash layer 100 400 m deep is observed average and maximum estimated ash optical depth 0 11 and 0 2 it descends from 2800 to 1400 m altitude over a 6 hour period on 18 april a double ash layer 400 m deep is observed just above the morning boundary layer average and maximum estimated ash optical depth 0 19 and 0 27 in the afternoon the ash is entrained into the boundary layer and the latter reaches a depth of 1800 m average and maximum estimated ash optical depth 0 1 and 0 15 an additional ash layer with a very small optical depth was observed on 18 april at an altitude of 3500 4000 m by converting the lidar optical measurements using estimates of volcanic ash specific extinction derived from other works the observations seem to suggest approximate peak ash concentrations of 1500 and 1000 g m3 respectively on the two observations dates

influence of freeze thaw dynamics on internal geochemical evolution of low sulfide waste rock abstract continuous monitoring of a 15 m high heavily instrumented experimental waste rock pile 0 053 wt s since 2006 at the diavik diamond mine in northern canada provided a unique opportunity to study the evolution of fresh run of mine waste rock as it evolved over annual freeze thaw cycles samples were collected from soil water solution samplers to measure pore water properties from twelve 4 to 16 m 2 basal collection lysimeters to measure basal leachate properties in the region underlying the crest of the pile the core and from basal drains to measure aggregate total pile leachate properties by 2012 monitoring of pore water geochemistry within the core structure of the test pile revealed an apparent steady state with respect to weathering geochemistry represented by i a flush of pre existing blasting residuals and applied tracers ii declining ph iii a stepwise progression and subsequent equilibrium with acid neutralizing phases depletion of available carbonates equilibrium with respect to aluminum hydroxide phases and subsequent iron iii hydroxide phases and iv concordant release of so 4 major cations ca mg k na si and trace metals al fe ni co cu zn distinct high concentration spring flushes characteristic of drainage in northern environments and primarily explained by a combination of fluid residence time and the build up of oxidation products over the winter were released from core drainage each season following the initial flush the concentration of all dissolved constituents steadily declined with distinct minimums prior to freeze up the opposite trend was observed in the cumulative pile drainage in which early season leachate dominated by snowmelt and batter flow had low concentrations and late season leachate dominated by contributions from the core of the pile indicated by season end merging of core and cumulative drainage geochemistry had higher concentrations northern waste rock pile drainage geochemistry is strongly influenced by freeze thaw cycling and varying core and batter subsystem contributions to total drainage a comprehensive understanding of thermal cycling in waste rock piles is an important component of temporal predictions of drainage water composition based on up scaling or reactive transport modeling

geochemical and mineralogical aspects of sulfide mine tailings abstract tailings generated during processing of sulfide ores represent a substantial risk to water resources the oxidation of sulfide minerals within tailings deposits can generate low quality water containing elevated concentrations of so 4 fe and associated metal loid s acid generated during the oxidation of pyrite fes 2 pyrrhotite fe 1 x s and other sulfide minerals is neutralized to varying degrees by the dissolution of carbonate oxy hydroxide and silicate minerals the extent of acid neutralization and therefore pore water ph is a principal control on the mobility of sulfide oxidation products within tailings deposits metals including fe iii cu zn and ni often occur at high concentrations and exhibit greater mobility at low ph characteristic of acid mine drainage amd in contrast hydr oxyanion forming elements including as sb se and mo commonly exhibit greater mobility at circumneutral ph associated with neutral mine drainage nmd these differences in mobility largely result from the ph dependence of mineral precipitation dissolution and sorption desorption reactions cemented layers of secondary oxy hydroxide and hydroxy sulfate minerals referred to as hardpans may promote attenuation of sulfide mineral oxidation products within and below the oxidation zone hardpans may also limit oxygen ingress and pore water migration within sulfide tailings deposits reduction oxidation redox processes are another important control on metal loid mobility within sulfide tailings deposits reductive dissolution or transformation of secondary oxy hydroxide phases can enhance fe mn and as mobility within sulfide tailings production of h 2 s via microbial sulfate reduction may promote attenuation of sulfide oxidation products including fe zn ni and tl via metal sulfide precipitation understanding the dynamics of these interrelated geochemical and mineralogical processes is critical for anticipating and managing water quality associated with sulfide mine tailings

long term mineralogical and geochemical evolution of sulfide mine tailings under a shallow water cover abstract the long term influence of a shallow water cover limiting sulfide mineral oxidation was examined in tailings deposited near the end of operation in 1951 of the former sherritt gordon zn cu mine sherridon manitoba canada surface water pore water and core samples were collected in 2001 and 2009 from above and within tailings deposited into a natural lake mineralogical and geochemical characterization focused on two contrasting areas of this deposit i sub aerial tailings with the water table positioned at a depth of approximately 50 cm and ii sub aqueous tailings stored under a 100 cm water cover mineralogical analyses of the sub aerial tailings showed a zone of extensive sulfide mineral alteration extending 40 cm below the tailings surface moderate alteration was observed at depths ranging from 40 to 60 cm and was limited to depths 60 cm in contrast sulfide mineral alteration within the submerged tailings was confined to a

arsenic in iron cements developed within tailings of a former metalliferous mine enguiales aveyron france abstract arsenopyrite rich waste from a former metalliferous mine were spread out over the sloping side of a deep valley after processing over the past 30 a they have been subjected to rainfall and acid water originating from the abandoned mine galleries this intensive leaching has led to the formation of thin layers of as fe crusts on the tailings surface acting as a cement x ray diffraction and sem coupled with eds determined that jarosite was present in all mineral samples and could contain a small amount of as 5 7 wt in addition empa and raman microspectroscopy characterised the presence of amorphous as v fe hydrates as well as rare arsenate minerals e g scorodite raman microspectroscopy in particular identified a preponderance of goethite or hematite within the mineral framework of the tailings materials that is likely to sorb recalcitrant as species the characterisation of the components of the tailings enable the identification of their evolution shows the progressive decrease of their as content and emphasises the consequences of the temporary trapping of as in the very acidic and oxidising conditions prevailing in such environments resinous amorphous material was identified as the richest in as with as 17 1 wt this material evolved toward more crystallised phases e g goethite jarosite which contained less as 3 2 wt

the role of secondary minerals in controlling the migration of arsenic and metals from high sulfide wastes berikul gold mine siberia abstract the role of secondary minerals in controlling the migration of as cu zn pb and cd has been investigated in piles of high sulfide waste at the berikul au mine kemerovo region russia these wastes contain 40 45 wt sulfides and have been stored for approximately 50 a near the mokry berikul river sulfide oxidation generates acid pore solutions ph 1 7 with high concentrations of so42 190 g l fe 57 g l as 22 g l zn 2 g l cu 0 4 g l pb 0 04 g l and cd 0 03 g l from these solutions as is precipitated as amorphous non stoichiometric fe sulfoarsenates in the lower horizons of the waste piles during precipitation of the fe sulfoarsenates the concentration of fe in these phases decreases from 34 to 21 wt that of as increases from 11 to 22 wt while the s content remains approximately constant 5 4 5 8 wt arsenic is also accumulated in jarosite beudantite solid solutions up to 8 4 wt as which occur as inclusions in the amorphous fe sulfoarsenates in efflorescent crusts on the surface of the waste pile as co precipitates with the fe iii sulfates copiapite 0 27 wt as and rhomboclase 0 87 wt as zinc and cu are incorporated primarily into fe ii sulfates i e melanterite in the interior of the waste pile and rozenite in the efflorescent crust the zn mineral dietrichite is also formed at the surface of the waste pile as a result of evaporation of pore solutions and is the only fe ii sulfate containing detectable amounts of as 0 64 wt lead is mainly co precipitated with minerals of the jarosite group where the pb content may reach 4 3 wt co precipitation of toxic elements with sulfates and sulfoarsenates of fe is shown to be a significant mechanism in controlling the concentration of heavy metals in pore solutions of high sulfide mine wastes precipitation of secondary phases causes the formation of a hardpan layer with low permeability at a depth of 1 1 5 m below the surface of the waste pile rainwater accumulates above the hardpan horizons and slowly drains along these aquicludes to the bottom of the pile most of the rainwater evaporates during infiltration this leads to formation of the described efflorescent sulfate crusts dissolution of these crusts during the next rain storm produces highly acidic surface waters ph 1 1 rich in so42 30 g l fe 18 g l as 0 24 g l zn 0 12 g l cu 0 04 g l pb and cd 0 002 g l during the warm t 0 c period of the year which lasts about 7 months these surface waters transport a total of a few tens of kilograms of as and zn several kilograms of cu and a few hundred grams of pb and cd from the waste pile into the mokry berikul river as a result the concentrations of these metals in the river water increase by an order of magnitude thus reaching levels close to or exceeding the maximum values permissible for drinking water

hydrochemical assessment of pond and stream water near abandoned barite mine sites in parts of oban massif and mamfe embayment southeastern nigeria hydrochemical studies were carried out in parts of oban massif and mamfe embayment southeastern nigeria to examine the contributions of barite mining activities on water quality pond and stream water samples were collected from six abandoned barite mines and adjoining streams areas during dry and wet seasons these samples were analysed for physicochemical parameters using standard techniques the results showed that the quality of water samples in the vicinity of barite mine sites was characterized by low ph low mineralization high suspended solids and deep colour sodium na and calcium ca2 are the dominant cations and bicarbonate hco3 and sulphate so4 2 the dominant anions the low concentration of dissolved silica relatively high concentrations of na hco3 and so4 2 suggest a combined influence of silicate carbonate and weathering of mine spoils the total dissolved solids total suspended solids electrical conductivity and major ions except na and k are higher for water draining barite mines from cretaceous sediments while na k ba2 are higher in basement rock areas correlation and factor analyses suggest that the main components of the water samples are related to anthropogenic geogenic mineralization and environmental controls while gibbs diagram plots indicate weathering as the main process controlling the chemistry of water computed values of hardness and some irrigational parameters showed that the pond and stream water samples are generally soft and can be used for irrigation generally the water quality satisfied the who 2008 and nis 2007 standards for domestic agriculture and industrial however there is the need to assess the impact of the pollution on the ecosystem and human health while remediation measures are being considered

the diavik waste rock project initial geochemical response from a low sulfide waste rock pile abstract three large scale experimental waste rock piles test piles were constructed and instrumented at the diavik diamond mine in the northwest territories canada as part of an integrated field and laboratory study to measure and compare physical and geochemical characteristics of experimental low sulfide waste rock piles at various scales this paper describes the geochemical response during the first season from a test pile containing 0 053 wt s bulk drainage chemistry was measured at two sampling points for ph eh alkalinity dissolved cations and anions and nutrients the geochemical equilibrium model minteqa2 was used to interpret potential mineral solubility controls on water chemistry the geochemical response characterizes the initial flushing response of blasting residues and oxidation products derived from sulfides in waste rock exposed to the atmosphere for less than 1 year sulfate concentrations reached 2000 mg l 1 when ambient temperatures were 10 c and decreased as ambient temperatures declined to 1 as total caco 3 suggesting all available alkalinity is consumed by acid neutralizing reactions concentrations of al and fe were 1 respectively trends of ph and alkalinity and the calculated saturation indices for al and fe oxy hydroxides suggest that dissolution of al and fe oxy hydroxide phases buffers the ph the effluent water showed increased concentrations of dissolved mn 1 ni 1 co 1 zn 1 cd 1 and cu 1 as ambient temperatures increased manganese is released by aluminosilicate weathering ni and co by pyrrhotite fe 1 x s oxidation zn and cd by sphalerite oxidation and cu by chalcopyrite cufes 2 oxidation no dissolved metals appear to have discrete secondary mineral controls changes in so 4 ph and metal concentrations indicate sulfide oxidation is occurring and effluent concentrations are influenced by ambient temperatures and possibly increasing flow path lengths that transport reaction products from previously unflushed waste rock

storm water hydrograph separation of run off from a mine tailings impoundment formed by thickened tailings discharge at kidd creek timmins ontario the kidd creek cu zn sulphide mine is located near timmins ontario mill tailings are thickened and deposited as a thickened slurry in a circular conical shaped pile with an area of approximately 1200 ha deposition of tailings as a thickened slurry results in a relatively uniform grain size distribution and hydraulic conductivity and a thick tension saturated zone above the water table the tailings are drained by numerous small ephemeral stream channels which have developed in a radial pattern during storms water from these streams collects in catchment ponds where it is held before treatment the contribution of tailings pore water to the run off is of interest because of the potential for discharge of pore water containing high concentrations of fe ii acidity metals and so4 to the stream hydraulic head measurements measurements of water table elevation and groundwater flow modelling were conducted to determine the mechanisms responsible for tailings pore water entering the surface streams chemical hydrograph separation of storm run off in one of these streams during three rainfall events using na and cl as conservative tracers indicates that the integrated tailings pore water fraction makes up between less than 1 and 20 of the total hydrograph this range is less than the maximum fraction of tailings pore water of 22 65 reported for run off from a conventional tailings deposit at this site preferential flow through permeable fractures may be the dominant mechanism causing discharge of tailings pore water to storm run off estimates of the mass of fe ii that discharges to the surface run off from the pore water range up to 2800 mg s 1 during a moderate intensity long duration rainfall event the greatest potential for discharge of significant masses of solutes derived from the pore water exists during long duration rainfall events when the water table rises to the surface over large areas of the tailings impoundment

element partitioning in sediment soil and vegetation in an alluvial terrace chronosequence limagne rift valley france a landscape geochemical study abstract the geochemical behaviour of specific elements in fluvial sediments topsoils soil profiles and plant material on a sequence of quaternary alluvial terraces was reconstructed semi quantitatively using indices of accumulation or depletion with respect to abundance in the lithosphere local soils and sediments topsoils of different ages and soil profiles are most clearly differentiated by the degree of leaching of ca mg and some minor elements with respect to less mobile si and ti clay translocation within soil profiles of older terraces leads to accumulation of al and associated elements in deeper horizons and accumulation of fe and mn in pseudogley horizons in the upper part of the clay accumulation layers p k ca mn and zn are strongly concentrated in plant materials relative to the topsoils ca is accumulated more strongly in oak bark than in grasses and the relative accumulation is greater on the older terraces due to the low ca content in their topsoils mn contents of both grasses and oak bark are greater on the older terraces than the younger for most elements topsoil and plant material contents show little correlation probably because plant requirements exert a greater control on element uptake than does availability the results illustrate that landscape geochemical analysis is useful for rapid appraisal of long term landscape processes such as erosion sedimentation weathering and preferential plant uptake

geochemical evolution of inactive pyritic tailings in the elliot lake uranium district geochemical data obtained between 1979 and 1983 from a network of piezometer nests and cores from three inactive uranium tailings impoundments in the elliot lake district indicate that oxidation of pyrite taking place in the shallow part of the zone above the water table is causing the chemistry of the pore water above and below the water table to change a two layer hydrochemical zonation has developed in which infiltration water from rain and snow has resulted in an upper zone of low ph water with high concentrations of so4 fe and heavy metals this zone is gradually expanding downward at rates generally between 0 2 and 2 m year causing displacement of the original mill process water which has neutral ph and low concentrations of heavy metals high concentrations of fe iii at shallow depth in the zone above the water table indicate that ferric iron is an important oxidizer of pyrite in the presence of free oxygen the pe of the groundwaters is controlled by the ferric ferrous redox couple and trend

biotite dissolution processes and mechanisms in the laboratory and in nature early stage weathering environment and vermiculitization biotite dissolution in the laboratory and in nature was examined and compared to elucidate certain aspects of the weathering processes batch dissolution experiments of fresh biotite k 0 9 1 na 0 0 1 mg 0 4 0 fe 2 0 7 mn 0 0 5 al 0 1 4 ti 0 1 9 si 2 8 2 al 1 1 8 o 1 0 oh 2 in granite were carried out at 150 c for 1 to 56 days examination by scanning electron microscope sem equipped with an energy dispersive x ray spectrometer eds revealed that in the early stage dissolution proceeds from the edges of crystals inward and secondary minerals such as fe oxide are precipitated mostly at the edges with only a few secondary minerals found on the basal surfaces a dissolution experiment using a mixture of biotite and muscovite done at 150 c for 7 days indicated that hematite crystals formed mostly at the edges of biotite but not on muscovite this observation suggests that released fe is precipitated before it diffuses into the bulk solution because a dissolution rate at the edge is larger by two orders of magnitude than at the basal surface turpault and trotignon 1994 precipitation before diffusion of dissolved elements to bulk solution well explains the preferential secondary mineralization at the edges in the laboratory experiments sem eds of fresh to slightly weathered biotites revealed that early stage weathering proceeds in the same way as in the laboratory with the edges being preferentially weathered and secondary minerals being precipitated mostly at the edges because of the similarity between the occurrence of secondary minerals in the laboratory experiments and in nature the laboratory results elucidate the early stage weathering conditions namely that 1 supersaturation with respect to secondary minerals in a solution occurs around biotite i e the solution is poorly connected to a main flow pathway of water and 2 once supersaturation is achieved secondary minerals are precipitated mainly at the edge before some released elements diffuse into the solution the immobility of water immediately adjacent to primary minerals partly explains the large difference in dissolution rate between the laboratory and natural samples a phlogopite dissolution experiment was done at 150 c for 5 5 days to examine the effect of biotite composition on vermiculitization high resolution transmission electron microscopy revealed that vermiculite layers are formed by layer by layer transformation within phlogopite after 5 5 day dissolution but not within biotite after 56 day dissolution or within slightly weathered biotite a comparison of our data with results of other studies indicates that the formation of vermiculite layers between biotite layers occurs even in the early stage when biotite is not fe rich more than 0 8 mg per o 1 0 oh 2 when biotite is fe rich less than 0 4 mg per o 1 0 oh 2 like the present one released fe is precipitated as for example fe hydroxide and vermiculite is rarely formed because of limited availability of mg thus a higher mg content in biotite facilitates the formation of vermiculite at least in the early stage because vermiculite dissolves at a much slower rate than biotite mg rich biotite dissolves at a slower rate than fe rich biotite in the late stage biotite dissolution still continues from the edge and within biotite which results in a fine comb like texture for weathered biotite vermiculite occurs as a domain within chemically and structurally altered biotite as well as at the edge even during weathering of mg poor biotite

rare earth elements as a tool for studying the formation of cemented layers in an area affected by acid mine drainage abstract in a profile with two cemented layers sampled in an area affected by acid mine drainage both have rare earth element ree signatures with positive ce anomalies in the post archean australian shale normalised patterns both cemented layers have higher contents of environmentally relevant metals cd co cu fe mn u and zn than the over and underlying unconsolidated quaternary sediments and are depleted of al ca k and mg the cemented layers are enriched in middle and heavy ree but only the bulk pattern of the lower cemented layer reveals a positive ce anomaly for the upper cemented layer this positive ce anomaly was only determined by spatially resolved laser ablation inductively coupled plasma mass spectrometry la icp ms studies only for segments with a high abundance of mn occurring as mn phases as proven by energy dispersive x ray spectroscopy the mn phases are formed secondarily to the ferric cement and are especially enriched in ce and co the ce anomaly of the lower cemented layer most probably is inherited from groundwater to the ferric cement whereas the ce anomaly of the upper cemented layer is the result of preferential scavenging of ce onto the mn phases compared to other ree

multiphase flow and reactive transport model in vadose tailings weathering processes affecting pyritic wastes may generate huge amounts of acid waters with high concentrations of potentially toxic contaminants acid mine drainage acid mine drainage is mainly produced in the vadose zone in the present study a coupled non isothermal multiphase flow and reactive transport model of the vadose zone of sulfide mine tailings was developed the geochemical model included kinetically controlled reactions for fe ii oxidation and for the dissolution of sulfide and aluminosilicate phases and the pitzer ion interaction model to describe the behavior of the pore water solutions model results were compared with experimental observations in unsaturated column experiments under strongly evaporative conditions similar to arid or semiarid climates evolution trends for temperature water saturation evaporation rates pore water hydrochemistry and mineral phases observed during the drying experiment were adequately reproduced the coupled model reproduced the increase of solute concentrations in the column top and the precipitation of a crust of secondary mineral phases this crust became a barrier for water vapour diffusion to the atmosphere and modified the thermohydraulic behavior of the tailings enhanced downward migration of water vapour and its condensation in this colder end of the column were correctly taken into account by the model which reproduced the dilution observed in the lower part of the column during the experiments

waste rock hydrogeology and geochemistry abstract the oxidation of sulfide minerals in waste rock has the potential to generate low quality drainage that can present a significant challenge to mine owners regulators and other stakeholders challenges involved in managing waste rock include the large volume of waste rock produced and the difficulty in predicting the quality and quantity of leach water due to the chemical and physical heterogeneities in the waste rock and the highly non linear coupling of geochemical and physical processes many important studies have been conducted over the past decade particularly at the field scale that have investigated the geochemical hydrological microbiological and gas and heat transport aspects of waste rock these studies show that although the parameters and processes that influence amd generation and solute release are fundamentally similar between different waste rock piles major differences in the dominant mechanisms of water gas and heat transport result from differences in the physical and mineralogical properties of the rock piles and the climatic conditions including the amount of precipitation and prevailing temperatures accurate prediction of the leach water quality from waste rock requires a detailed characterization of the properties of the rock piles and the coupling of processes specific to the particular conditions this paper provides a review of the physical and mineralogical characteristics of waste rock piles followed by a discussion of the principal processes related to sulfide oxidation and solute loading and concluding with a discussion on acid mine drainage prediction and prevention techniques

the impact of sulfuric acid on element migration and mineralogy of compacted clays ph 1 0 to 3 0 abstract the transport of h2so4 at ph 1 0 1 0 and 3 0 through two mineralogically different compacted clays kc and km was examined using single reservoir diffusion cells with constant source concentrations at the end of the 216 day test period geochemical analyses indicated increased depth of acid diffusion with increased reservoir acidity for both kc and km cells elevated ca al fe and si concentrations were associated with decreased ph values in all cells xrd results showed that these elevated concentrations corresponded to the loss of carbonate and montmorillonite peaks and decreased peak intensities for illite and kaolinite in the kc and km ph 1 0 and 3 0 km cells moreover si x ray absorption near edge structure xanes indicated dissolution of the phyllosilicate phases a relative increase in the amount of quartz and the potential formation of an amorphous silica phase the results of this study showed that despite the extreme ph values considered movement of h2so4 solutions with ph

comparative lidar study of the optical geometrical and dynamical properties of stratospheric post volcanic aerosols following the eruptions of el chichon and mount pinatubo the spatiotemporal evolution of aerosols formed from precursors injected into the stratosphere by major volcanic eruptions such as those of el chichon in 1982 and mount pinatubo in 1991 has been studied using a ground based lidar system located at the observatoire de haute provence ohp in southern france 44 n 5 e from the inversion of the lidar signals the optical geometrical and dynamical properties of the particles have been determined as a function of time after the eruption in immediate post volcanic conditions when the optical thickness of particles in the stratosphere is largely enhanced an estimate of the aerosols backscatter phase function has been evaluated directly from the lidar measurements using a size distribution model adjusted to in situ balloon measurements the precision of this determination lies in the 15 range values of the mean radius of the particles of their integrated content surface areas and sedimentation velocities are then derived from the systematic lidar measurements performed at ohp these values are compared for the two major volcanic eruptions which have occurred over the last decade although the injection of sulphur dioxide was twice as large for the mount pinatubo eruption as compared to the el chichon case the diffusion of the cloud in the two hemispheres due to the interaction of the particular phase of the quasi biennal oscillation with several other dynamical processes at the time of the eruption led to the observation of similar values for the aerosol content over the observatoire de haute provence in the months just following the two events however the residence time of the particles in atmospheric layers below 20 km are 4 months longer after the mount pinatubo eruption caused by the observed difference in the initial vertical distribution of the aerosol cloud

solid phase control on the mobility of potentially toxic elements in an abandoned lead zinc mine tailings impoundment taxco mexico detailed mineralogical and geochemical investigations were conducted within abandoned pb and zn flotation tailings at el fraile impoundments in taxco guerrero central southern mexico these tailings are divided into an active oxidation zone near the surface an underlying transition zone and an unoxidized zone although these tailings have undergone 30 a of sulfide oxidation the active oxidation zone has only penetrated to a depth of 0 2 m in the settling pond and to 0 6 1 2 m in the dam the oxidation of sulfide minerals and the insufficiency of ph buffering minerals have produced low ph conditions ph 1 9 4 4 and high concentrations of dissolved so42 as and heavy metals so42 1534 10086 mg l 1 fe 1 5 2568 mg l 1 zn 36 7 2435 mg l 1 cd 0 4 30 6 mg l 1 pb 0 01 0 6 mg l 1 cu 0 5 38 2 mg l 1 and as 0 01 164 mg l 1 these concentrations of dissolved constituents are attenuated by a series of precipitation and sorption reactions precipitation of secondary phases gypsum goethite hematite and k jarosite has led to the formation of cemented layers within the active oxidation zone in the tailings dam these cemented layers act as a trap for released potentially toxic elements from the overlying oxidized tailings adsorption and coprecipitation on fe precipitates play an important role in the mobilization and attenuation of zn cd cu and as within the el fraile tailings additionally to the well known ability of fe precipitates to strongly trap as and heavy metals this study shows that precipitation of beudantite pbfe3aso4so4 oh 6 appears to be one of the solid phase controls on the natural attenuation of as and pb and other heavy metals in these tailings

the effect of mineralogy on the mobility of heavy metals in mine tailings a case study in the samsanjeil mine korea this study examined the chemical speciation and mobility of as and heavy metals in a tailings impoundment in samsanjeil mine located in gosung korea as well as the factors affecting them xrd sem and 5 step sequential extraction were used to examine the samples at two sampling sites nn and sn sites the ph of the tailings decreased with increasing depth at the nn site from 7 2 to 2 8 whereas no significant differences were observed at the sn site 8 1 8 8 the samples at the sn site showed a larger amount of calcite than those at the nn site indicating that calcite plays an important role buffering the ph in the study sites jarosite was found only at the lower part of the nn site where calcite was not found the mineralogical observation of jarosite and calcite was also confirmed by sem the concentrations of as and heavy metals in the tailings were as follows cu as zn pb co cr ni cd the total concentrations of ni zn co and cd were higher at the sn site than those at the nn site on the other hand the concentrations of as and cr existing as oxyanions were higher at the nn site which can be explained by the mobility changes of those elements affected by ph variations at the nn site the fractions of heavy metals bound to the fe mn oxides except for as and cr decreased and cu zn and co showed an increasing fraction of exchangeable metals with increasing depth this suggests that the ph and resulting surface charge of minerals such as goethite and jarosite are the dominant factors controlling the chemical speciation of metals these results highlight the importance of mineralogy in controlling the mobility and possible bioavailability of heavy metals in tailings

influence of hardpan layers on arsenic mobility in historical gold mine tailings abstract hardpans or cemented layers form by precipitation and cementation of secondary minerals in mine tailings and may act as both physical and chemical barriers precipitation of secondary minerals during weathering of tailings can sequester metal loid s thereby limiting their release to the environment at montague gold mines in nova scotia tailings are partially cemented by the fe arsenate mineral scorodite feaso4 2h2o previous studies have shown that the formation of scorodite can effectively limit aqueous as concentrations due to its relatively low solubility

the formation and potential importance of cemented layers in inactive sulfide mine tailings abstract investigations of inactive sulfide rich tailings impoundments at the heath steele new brunswick and waite amulet quebec minesites have revealed two distinct types of cemented layers or hardpans that at heath steele is 10 15 cm thick occurs 20 30 cm below the depth of active oxidation is continuous throughout the tailings impoundment and is characterized by cementation of tailings by gypsum and fe ii solid phases principally melanterite hardpan at the waite amulet site is only 1 5 cm thick is laterally discontinuous 10 100 cm occurs at the depth of active oxidation and is characterized by cementation of tailings by fe iii minerals principally goethite lepidocrocite ferrihydrite and jarosite at heath steele an accumulation of gas phase co2 of up to 60 of the pore gas occurs below the hardpan the calculated diffusivity of the hardpan layer is only about 1 100 that of the overlying uncemented tailings the pore water chemistry at heath steele has changed little over a 10 year period suggesting that the cemented layer restricts the movement of dissolved metals through the tailings and also acts as a zone of metal accumulation generation of a cemented layer therefore has significant environmental and economic implications it is likely that in sulfide rich tailings impoundments the addition of carbonate rich buffering material during the late stages of tailings deposition would enhance the formation of hardpan layers

post depositional redistribution of trace metals in reservoir sediments of a mining smelting impacted watershed the lot river sw france abstract mining smelting wastes and reservoir sediment cores from the lot river watershed were studied using mineralogical xrd sem eds empa and geochemical redox dynamics selective extractions approaches to characterize the main carrier phases of trace metals these two approaches permitted determining the role of post depositional redistribution processes in sediments and their effects on the fate and mobility of trace metals the mining smelting wastes showed heterogeneous mineral compositions with highly variable contents of trace metals the main trace metal bearing phases include spinels affected by secondary processes silicates and sulfates the results indicate a clear change in the chemical partitioning of trace metals between the reservoir sediments upstream and downstream of the mining smelting activities with the downstream sediments showing a 2 fold to 5 fold greater contribution of the oxidizable fraction this increase was ascribed to stronger post depositional redistribution of trace metals related to intense early diagenetic processes including dissolution of trace metal bearing phases and precipitation of authigenic sulfide phases through organic matter om mineralization this redistribution is due to high inputs derived from mining smelting waste weathering at the water sediment interface of i dissolved so4 promoting more efficient om mineralization and ii highly reactive trace metal bearing particles as a result the main trace metal bearing phases in the downstream sediments are represented by zn and fe sulfides with minor occurrence of detrital zincian spinels sulfates and fe oxyhydroxides sequestration of trace metals in sulfides at depth in reservoir sediments does not represent long term sequestration owing to possible resuspension of anoxic sediments by natural floods and or anthropogenic dredging dam flush events that might promote trace metal mobilization through sulfide oxidation it is estimated that during a major flood event about 870 t of zn 18 t of cd 25 t of pb and 17 t of cu could be mobilized from the downstream reservoir sediments along the lot river by resuspension induced oxidation of sulfide phases these amounts are equivalent to 13 fold cd 6 fold zn 4 fold pb the mean annual inputs of the respective dissolved trace metals into the gironde estuary

surface saline deposits and their substrates in a polluted arid valley murcia spain this study reports the mineralogical and geochemical variations of surface saline deposits and their substrates along an arid valley with an ephemeral river system spanish rambla affected by pollution from the now closed cabezo de san cristobal mine this mine which is close to mazarron spain once produced pb zn ag and fe ores saline efflorescences and crusts were found on piles of tailings and on the mudflats surrounding acidic ponds associated with the mine these were composed of jarosite 10 60 haematite up to 20 and gypsum 5 20 and the kieserite 20 40 and halotrichite 5 40 mineral groups in the rambla deposits downstream of the mine the mineralogy of the saline efflorescences was similar to that recorded upstream gypsum up to 20 thenardite 5 20 halite 20 40 and bloedite 20 40 however the substrate was very different being mainly composed of jarosite 40 60 haematite 5 20 and goethite 5 20 these minerals were never found upstream of the mining area where carbonates predominated downstream of the mine the rambla deposits contained large quantities of fe 158 251 ppm pb 2 720 ppm zn 3 064 ppm sb 240 ppm and as 1 092 ppm along with co 29 ppm ce 323 ppm v 112 ppm th 23 ppm and nb 19 ppm all figures are maxima upstream these contents were insignificant neither were large quantities found in the actual stream water only cu v and zn were detected and then at concentrations of 0 05 ppm leaching and washing out from the tailings and other mine wastes substantially altered the substrates but not the composition of the saline efflorescences along the arid valley

mineralogical and geochemical constraints on environmental impacts from waste rock at taojiang mn ore deposit central hunan china the mineralogy and geochemistry of the waste rocks distributed at taojiang mn ore deposit central hunan province china were studied using x ray powder diffraction xrd electron microprobe analysis empa fitted with energy dispersive spectrometer eds and inductively coupled plasma mass spectrum atomic emission spectra icp ms aes with the aim of predicting the environmental impacts of weathering of the waste rocks the mineralogical results from microscope observation and xrd and empa studies show that the waste rock is composed of black shale and minor mn carbonates the oxidation of sulfide minerals such as galena pyrite and chalcopyrite is accompanied by decomposition of mn carbonates and k feldspar during exposure to atmospheric o2 the geochemical characteristics of major rare earth elements ree and trace elements of the waste rocks also show that the waste rock can be divided into black shale and mn carbonate and both of them are currently under chemical weathering the major alkalies and alkaline elements ca mg na k rb sr and cs and major elements fe s and p and heavy metals sc v cr th u sn co ni cu zn pb mo cd sb an tl are being released during weathering the mobility of alkalis and alkaline elements ca mg na k rb sr and cs is controlled by decomposition of mn carbonates the dispersion of cr sc and th u might be related to weathering of k feldspar and the release of the heavy metals co ni cu zn pb mo cd sb and tl is dominated by the breaking of sulfide minerals the ree of the waste rocks and surrounding soils and the spidery distribution patterns of heavy metals in the waste rocks the surrounding soils and the surface waters show that weathering of the waste rocks and bedrock might be the sources of heavy metal contamination for the surrounding soils and surface water system for the mining area this is predicted by the mass balance calculation by using zr as an immobile element therefore it is urgently necessary take measures to treat the waste rocks distributed throughout the area for the local environmental protection

characterisation of the sarcheshmeh copper mine tailings kerman province southeast of iran mineral processing operation at the sarcheshmeh porphyry copper mine has produced huge quantities of tailings materials containing sulphide minerals in particular pyrite these tailings materials were geochemically and mineralogically characterised to assess pyrite and chalcopyrite oxidation acid mine drainage generation and trace element mobility to lead development of a proper remediation plan five vertical trenches up to 4 2 m deep were excavated from the tailings surface and 70 solid samples were taken in 0 3 m intervals the samples were first mineralogically analysed pyrite was the main sulphide mineral found in the tailings the gangue minerals include quartz muscovite illite chlorite albite orthoclase halite the samples were geochemically analysed for total concentrations of 62 elements paste ph so4 2 co3 2 and hco3 the maximum concentrations of so4 2 1 300 1 170 1 852 1 960 and 837 mg l were observed at a depth of 0 9 m in profiles a b c d and e respectively the tailings have a high acid producing potential and low acid neutralising potential pyrite 4 6 wt calcite 1 wt fe2 so4 3 cuso4 mgso4 and mnso4 were the dominant secondary sulphate minerals in the tailings the lowest ph values 2 9 3 and 3 were measured at a depth of 0 3 m in the profiles a b and c 3 9 at a depth of 0 6 m in the profile d and 3 at a depth of 0 9 m in the profile e the upper portions of the profiles c 1 8 m and d 2 1 m were moderately oxidised while oxidation in the profiles a b and e did not extend more than 1 2 1 2 and 1 5 m beneath the tailings surface zn pb rb u hf nd zr and ga show almost a constant trend with depth cd sr th la and ce increased with increasing depth of the tailings materials while co v ti cr cu as mn ag mo and ni exhibit initially a decreasing trend from tailings surface to the depths that vary between 0 9 and 1 2 they then remained constant with the depth the results show pyrite and chalcopyrite oxidation at surface layers of the tailings and subsequent leaching of the oxidation products and trace elements by infiltrated atmospheric precipitation

mineralogical and geochemical characterization of the old tailings dam australia evaluating the effectiveness of a water cover for long term amd control abstract establishing a shallow water cover over tailings deposited in a designated storage facility is one option to limit oxygen diffusion and retard oxidation of sulfides which have the potential to form acid mine drainage amd the old tailings dam otd located at the savage river mine western tasmania contains 38 million tonnes of pyritic tailings deposited from 1967 to 1982 and is actively generating amd the otd was constructed on a natural gradient resulting in sub aerial exposure of the southern area with the northern area under a natural water cover this physical contrast allowed for the examination of tailings mineralogy and geochemistry as a function of water cover depth across the otd tailings samples n 144 depth 1 5 m were collected and subjected to a range of geochemical and mineralogical evaluations tailings from the southern and northern extents of the otd showed similar amd potential based on geochemical nag ph range 2 1 to 4 2 and bulk mineralogical parameters particularly at depth however sulfide alteration index sai assessments highlighted the microscale contrast in oxidation in the sub aerial zone pyrite grains are moderately oxidized to a depth of 0 3 m maximum sai of 6 10 under both gravel fill and oxidized covers with secondary minerals e g ferrihydrite and goethite developed along rims and fractures beneath this mildly oxidized pyrite is seen in fresh tailings sai 2 9 10 to 5 8 10 in the sub aqueous zone the degree of pyrite oxidation demonstrates a direct relationship with cover depth with unoxidized potentially reactive tailings identified from 2 5 m directly beneath an organic rich sediment layer sai 0 to 1 10 these findings are broadly similar to other tailings storage facilities e g fox lake sherritt gordon zn cu mine canada and stekenjokk mine sweden where water covers up to 2 m have successfully reduced amd whilst geotechnical properties of the otd restrict the extension of the water cover pyrite is enriched in cobalt up to 2 6 wt indicating reprocessing of tailings as an alternative management option through adoption of an integrated mineralogical and geochemical characterization approach for tailings assessment robust management strategies after mine closure can be developed

the diavik waste rock project geochemical and microbiological characterization of low sulfide content large scale waste rock test piles abstract two experimental waste rock piles test piles each 15 m in height 60 m 50 m were constructed at the diavik diamond mine in northern canada to study the behavior of low sulfide content waste rock with a similarly low acid neutralization potential in a continuous permafrost region one test pile with an average of 0 035 wt s 4 2 and dissolved metals with a decrease in ph to 1 ni 2 3 mg l 1 cu 3 7 mg l 1 zn 35 g l 1 cd and 3 8 mg l 1 co corresponded to decreases in flow rate which were observed at the end of each field season when the contribution of the total outflow from the central portion of the test pile was greatest bacteria were present each year in spite of annual freeze thaw cycles the microbial community within the type i test pile included a population of neutrophilic s oxidizing bacteria each year changes in the water quality of the type iii test pile effluent were accompanied by changes in the microbial populations populations of acidophilic s oxidizing bacteria and fe oxidizing bacteria became more abundant as the ph decreased and internal test pile temperatures increased irrespective of the cold climate conditions and low s content of the waste rock the geochemical and microbiological results of this study are consistent with other acid mine drainage studies indicating that a series of mineral dissolution precipitation reactions controls ph and metal mobility and transport is controlled by matrix dominated flow and internal temperatures

the pore water geochemistry and the mineralogy of the vadose zone of sulfide tailings waite amulet quebec canada low ph waters requiring treatment because of high concentrations of dissolved metals are being discharged from a decommissioned tailings impoundment at the former waite amulet zncu mine in northeastern quebec canada a detailed study of the vadose zone of the tailings comparing mineralogical and geochemical analyses of the tailings solids with geochemical analysis of the tailings pore water and pore gas indicates the presence of three zones within the tailings these zones include an upper sulfide depleted zone in which the sulfides have been extensively removed and oxidation is largely complete an intermediate zone where sulfide oxidation and acid neutralization reactions are occurring and an unoxidized zone below the depth of oxygen penetration where sulfides are unoxidized high aqueous concentrations of dissolved solids are being displaced downward from the sulfide depleted zone through the unoxidized zone toward the water table sulfide oxidation and acid neutralization reactions have generated concentrations of dissolved solids high enough to lead to the precipitation of a series of secondary solid phases precipitation dissolution reactions involving these solid phases control the concentrations of the major ions in the tailings pore water concentrations of dissolved metals are controlled by precipitation dissolution crystal structural replacement and adsorption coprecipitation reactions predictions based on the observed data and numerical simulations suggest that in the absence of an effective remedial program sulfide oxidation and h production will continue for several centuries