the transformation of nesquehonite to hydromagnesite in the system cao mgo h20 co2 an experimental spectroscopic study abstract this study reports the nature of the nesquehonite to hydromagnesite transition at 52 c in an aqueous medium hosting magnesian calcite and nesquehonite the latter mineral occurs with abundant calcite at the floor of the experimental chamber substrate and as a film of needles at the interface between the mother liquor and the atmosphere surface film the experimental vessel was held at 52 c for 336 h and at 60 c for a further 192 h precipitates were analyzed by fourier transform ft raman augmented by ft infrared and x ray diffraction at 52 c hydromagnesite and dypingite occur with abundant quantities of a hitherto unreported transitory magnesium hydrate carbonate tmhc together with huntite magnesian calcite and traces of nesquehonite and monohydrocalcite the ft raman spectra of the first formed hydromagnesite crystals contain the raman forbidden v2 mode interpreted to indicate a relaxation in selection rules caused by rapid precipitation hydromagnesite growth at the expense of t

boron rich groundwater in central eastern italy a hydrogeochemical and statistical approach to define origin and distribution analysis of boron within groundwater was undertaken for an area of central eastern italy although boron is a minor analyte in groundwater concentrations can often be above limits set by legislation a hydrogeochemical study supported by a statistical multifactorial analysis was undertaken to investigate the most likely origin of the boron within the groundwater it was possible to distinguish contamination caused by anthropogenic activities from natural pollution within the study hydrochemical analysis has highlighted that anomalous concentrations of boron are only seen in groundwater from the alluvial valley deposits a strong correlation between high boron concentrations and groundwater with chloride sodium facies was also identified the principal components analysis has confirmed the results from the assessment undertaken with hydrochemical analysis the most important component is characterised by high loading of boron sodium chloride and electrical conductivity the most likely origin of the boron within the hydrogeochemical context of the area appears to be connected to the uprise of chloride sodium connate groundwaters naturally enriched in boron

coupling between geochemical reactions and multicomponent gas and solute transport in unsaturated media a reactive transport modeling study 1 the two way coupling that exists between biogeochemical reactions and vadose zone transport processes in particular gas phase transport determines the composition of soil gas to explore these feedback processes quantitatively multicomponent gas diffusion and advection are implemented into an existing reactive transport model that includes a full suite of geochemical reactions multicomponent gas diffusion is described on the basis of the dusty gas model which accounts for all relevant gas diffusion mechanisms the simulation of gas attenuation in partially saturated landfill soil covers methane production and oxidation in aquifers contaminated by organic compounds e g an oil spill site and pyrite oxidation in mine tailings demonstrate that both diffusive and advective gas transport can be affected by geochemical reactions methane oxidation in landfill covers reduces the existing upward pressure gradient thereby decreasing the contribution of advective methane emissions to the atmosphere and enhancing the net flux of atmospheric oxygen into the soil column at an oil spill site methane oxidation causes a reversal in the direction of gas advection which results in advective transport toward the zone of oxidation both from the ground surface and the deeper zone of methane production both diffusion and advection contribute to supply atmospheric oxygen into the subsurface and methane emissions to the atmosphere are averted during pyrite oxidation in mine tailings pressure reduction in the reaction zone drives advective gas flow into the sediment column enhancing the oxidation process in carbonate rich mine tailings calcite dissolution releases carbon dioxide which partly offsets the pressure reduction caused by o2 consumption

carbon dioxide fixation within mine wastes of ultramafic hosted ore deposits examples from the clinton creek and cassiar chrysotile deposits canada carbon dioxide co2 is sequestered through the weathering and subsequent mineralization of the chrysotile mine tailings at clinton creek yukon territory and cassiar british columbia canada accelerated weathering is attributed to a dramatic increase in surface area which occurs during the milling of ore we provide a detailed account of the natural process of carbon trapping and storage as it occurs at clinton creek and cassiar including mineralogy modes of occurrence methods of formation for carbonate alteration light stable isotope geochemistry and radiocarbon analysis powder x ray diffraction data were used to identify weathering products as the hydrated magnesium carbonate minerals nesquehonite mgco3 3h2o dypingite mg5 co3 4 oh 2 5h2o hydromagnesite mg5 co3 4 oh 2 4h2o and less commonly lansfordite mgco3 5h2o textural relationships suggest that carbonate precipitates formed in situ after milling and deposition of tailings samples of efflorescent nesquehonite are characterized by 13c values between 6 52 and 14 36 per mil 18o values between 20 93 and 26 62 per mil and f14c values fraction of modern carbon between 1 072 and 1 114 values which are consistent with temperature dependent fractionation of modern atmospheric co2 during mineralization samples of dypingite hydromagnesite collected from within 0 2 m of the tailings surface give 13c values between 1 51 and 10 02 per mil 18o values between 17 53 and 28 40 per mil and f14c values between 1 026 and 1 146 which suggests precipitation from modern atmospheric co2 in a soil like environment field observations and isotopic data suggest that hydrated magnesium carbonate minerals formed in two environments nesquehonite formed in an evaporative environment on the surface of tailings piles and dypingite and hydromagnesite formed in the subsurface environment with characteristics similar to soil carbonate in both cases these minerals

assessment of groundwater water quality in central and southern gulf coast aquifer tx using principal component analysis principal component analysis has been applied for source identification and to assess factors affecting concentration variations in particular this study utilizes principal component analysis pca to understand groundwater geochemical characteristics in the central and southern portions of the gulf coast aquifer in texas pca along with exploratory data analysis and correlation analysis is applied to a spatially extensive multivariate dataset in an exploratory mode to conceptualize the geochemical evolution of groundwater a general trend was observed in all formations of the target aquifers with over 75 of the observed variance explained by the first four factors identified by the pca the first factor consisted of older water subjected to weathering reactions and was named the ionic strength index the second factor named the alkalinity index explained greater variance in the younger formations rather than in the older formations the third group represented younger waters entering the aquifers from the land surface and was labeled the recharge index the fourth group which varied between aquifers was either the hardness index or the acidity index depending on whether it represented the influences of carbonate minerals or parameters affecting the dissolution of fluoride minerals respectively the pca approach was also extended to the well scale to determine and identify the geographic influences on geochemical evolution it was found that wells located in outcrop areas and near rivers and streams had a larger influence on the factors suggesting the importance of surface water groundwater interactions

kinetic testing to evaluate the mineral carbonation and metal leaching potential of ultramafic tailings case study of the dumont nickel project amos quebec abstract ultramafic mine wastes are known to react passively with co 2 to form stable hydrated magnesium carbonates this study uses kinetic tests to evaluate the carbonation potential of ultramafic mine tailings from the dumont project rnc minerals quebec canada during their weathering and to determine the impact of carbonation on the long term quality of drainage waters the weathering of awaruite ni 2 5 fe pentlandite fe ni 9 s 8 and heazlewoodite ni 3 s 2 which are the main sources of ni in the studied materials were also investigated due to their potential to generate contamination a column test and small scale weathering cell tests were used to simulate the passive weathering of ultramafic mine wastes as well as concentrates of awaruite and ni sulfides results from the kinetics tests confirmed that the dumont tailings have a significant carbon sequestration potential which ranged from 8 5 to 33 6 kgco 2 t the surface normalized carbonation rates varied from 600 to 2200 g of co 2 m 2 year results demonstrated that brucite mg oh 2 content is the main parameter controlling co 2 uptake by the dumont wastes weathering of brucite and serpentine mg 3 si 2 o 5 oh 4 are driven by co 2 dissolution in pore water and by sulfide oxidation the rapid dissolution of brucite results in leachates with alkaline ph values thus preventing metal mobility metals such as ni zn fe and cu are suggested to precipitate as hydroxide or carbonate species within the wastes immediately upon being released through sulfide oxidation the ni fe alloy awaruite is stable and does not release metals in kinetic tests the dumont tailings are found to be non acid generating and co 2 sequestration is shown to play a significant role in drainage water quality which allow generation of significant alkalinity and the rise of ph

delineation of groundwater provenance in a coastal aquifer using statistical and isotopic methods southeast tanzania rapid population growth and urbanization has placed a high demand on freshwater resources in southeast costal tanzania in this paper we identify the various sources of groundwater and the major factors affecting the groundwater quality by means of multivariate statistical analyses using chemical tracers and stable isotope signatures the results from hierarchical cluster analyses show that the groundwater in the study area may be classified into four groups a factor analysis indicates that groundwater composition is mainly affected by three processes accounting for 80 6 of the total data variance seawater intrusion dilution of groundwater by recharge and sewage infiltration the hydrochemical facies of shallow groundwater was mostly of the na ca cl type although other water types were also observed the deep groundwater samples were slightly to moderately mineralized and they were of the nahco3 type this water type is induced mainly by dissolution of carbonate minerals and modified by ion exchange reactions the signal from the stable isotope composition of the groundwater samples corresponded well with the major chemical characteristics in the shallow groundwater both high nitrate and high chloride concentrations were associated with localized stable isotope enrichments which offset the meteoric isotopic signature this is inferred to be due to the contamination by influx of sewage as well as intrusion by seawater the depleted stable isotope values which coincides with a chemical signature for the deep aquifer indicates that this deep groundwater is derived from infiltration in the recharge zone followed by slow lateral percolation this study shows that a conceptual hydrogeochemical interpretation of the results from multivariate statistical analysis using hca and fa on water chemistry including isotopic data provides a powerful tool for classifying the sources of groundwater and identifying the significant factors governing the groundwater quality the derived knowledge generated by this study constitutes a conceptual framework for investigating groundwater characteristics this is a prerequisite for developing a sound management plan which is a requirement for ensuring a sustainable exploitation of the deep aquifer water resource in the coastal area of tanzania

sequestration of atmospheric co2 in chrysotile mine tailings of the woodsreef asbestos mine australia quantitative mineralogy isotopic fingerprinting and carbonation rates since closure of the woodsreef asbestos mine located in the great serpentinite belt gsb new south wales australia extensive carbonate rich crusts have formed by recessive weathering of fine grained material on the surface of the tailings pile a relationship exists between the mode of carbonate occurrence the mineralogy and the isotopic fingerprint of carbonates from the tailings pile vertical carbonate crusts covering most of the tailings predominantly consist of the hydrated mg carbonate hydromagnesite mg5 co3 4 oh 2 4h2o which has precipitated from evaporating meteoric waters incorporating atmospheric co2 as reflected in high 18o 13c and f14c signatures respectively low and variable concentrations of magnesite dolomite and calcite represent bedrock carbonate which has formed during alteration of the serpentinite bedrock before mining and is characterised by moderately high 18o low 13c and f14c a signature typical for weathering derived magnesite deposits in the gsb the carbonate fraction of deep cement samples collected from 70 to 120 cm below the surface representing the bulk tailings material at depth predominantly consists of pyroaurite mg6fe2 co3 oh 16 4h2o and despite stable isotope signatures similar to bedrock contains significant radiocarbon this indicates that pyroaurite forming under different conditions as hydromagnesite may represent an additional trap for atmospheric co2 in the woodsreef mine tailings the distribution of carbonates and quartz together with the absence of isotopic mixing trends between bedrock carbonate and atmospheric derived carbonate strongly indicates that dissolution and re precipitation of bedrock carbonate is not a dominant process in the woodsreef tailings the cations for carbonate formation are instead derived from the dissolution of serpentine minerals lizardite and chrysotile and brucite the internal standard method and the reference intensity method have been used with x ray diffraction data to estimate the abundance of the two major carbonate minerals hydromagnesite and pyroaurite respectively considering the formation of hydromagnesite on the outer surface of the tailings pile alone or together with formation of pyroaurite within the tailings pile we conclude that between 1400 and 70 000 t of atmospheric co2 have been sequestered in the mine tailings since closure of the mine 29 a ago carbonation rates of 27 g c m 2 y 1 and 1330 g c m 2 y 1 are significantly higher than background rates of co2 uptake by chemical weathering and demonstrate the potential of passive carbonation of mine tailings as a cost and energy effective alternative for storage of co2 in carbonate minerals

dissolution of fluoride in groundwater a water rock interaction study fluoride rich groundwater is well known in granite aquifers in india and the world although its presence is necessary chances of health risk become high if the fluoride concentration is more than the permissible limit of 1 5 mg l world health organization who in drinking water fluoride mainly occurs in groundwater as a natural constituent results of a laboratory study on water rock interaction at normal temperature pressure and different chemical conditions indicate that the specific conductivity ph ca and hco3 are important chemical parameters for the dissolution of fluoride to groundwater from fluoride rich minerals e g fluorite experimental results indicate that an alkaline medium ph 7 6 to 8 6 high hco3 concentration ranging from 350 450 mg l and moderate specific conductivity ranging from 750 1 750 s cm are favourable for fluoride dissolution no significant correlation existed between fluoride and cahco3

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

geochemical characteristics of groundwater in different climatic zones of sri lanka sri lanka is characterized by well demarcated climatic zones based on the rainfall pattern known as wet zone dry zone and intermediate zone groundwaters in these three zones are extracted mainly for drinking and irrigation from metamorphic hard rock aquifers and saprolite developed on metamorphic rocks detailed hydrogeochemical investigations were carried out covering these three climatic zones in order to characterize the groundwater a total of 166 groundwater samples were collected representing three climatic zones and analyzed for their major and trace element geochemistry the results indicate a clear difference in the geochemistry of groundwater between climatic regions whereas semiarid dry zone groundwater is characterized with higher dissolved mineral contents compared that of the wet and intermediate zones low ph levels were noticed in the wet zone areas while high calcium and fluoride contents were observed in the dry and intermediate terrains remarkably high phosphate contents were observed in all three regions indicating the influence of fertilizer application on groundwater particularly in the dry zone regions the groundwater chemistry is mainly controlled by rock water interactions and ion exchange processes in which high mineral contents are added from underlying metamorphic rocks to the drinking and irrigation water the results indicate that groundwater in the dry zone area is under stress compared to other climate areas but in the wet zone groundwater shows remarkable influence of anthropogenic activities

integrated hydrochemical assessment of the quaternary alluvial aquifer of the guadalquivir river southern spain the alluvial aquifer of the guadalquivir river comprises shallow quaternary deposits located in the central eastern part of the province of jaen in southern spain where groundwater resources are used mainly for crop irrigation in an important agricultural area in order to establish the baseline hydrochemical conditions and processes determining the groundwater quality groundwater and river water samples were collected as part of an integrated investigation that coupled multivariate statistical analysis with hydrochemical methods to identify and interpret the groundwater chemistry of the aquifer system three main hydrochemical types mg ca hco3 ca mg so4 hco3 cl and na ca mg cl so4 were identified further interpretation using r mode principal components analysis pca conducted with 13 hydrochemical variables identified two principal components which explain of the variance in the original data in combination with the hydrochemical interpretation mineralogical analyses of the aquifer sediment together with inverse geochemical modelling using netpath showed that dedolomitization calcite precipitation and dolomite dissolution driven by gypsum dissolution is the principal hydrochemical process controlling the regional groundwater chemistry other processes such as silicate weathering ion exchange mixing between river water and groundwater and agricultural practices also affect the groundwater chemistry

the principal components statistical method as a complementary approach to geochemical methods in water quality factor identification application to the coastal plain aquifer of israel abstract in general schoeller and piper diagrams as well as other classical techniques facilitate the description of the various geochemical groups of water and help to explain quality changes in an aquifer we propose the use mainly of principal components analysis for identification of relevant groups of water and the factors that bring about a change in their quality the major advantage of this method is its suitability for simultaneous analysis of a great number of variables and observations it is here being applied for the investigation of the dan metropolitan region of israel s coastal plain the variables involved include major ions as well as the physical factors of depth of the well intake filter below sea level distance from the sea and aquifer recharge the primary purpose of this work is to demonstrate the use and reliability of principal components analysis pca as a method complementary to classical approaches for hydrogeochemical research subsidiary purposes involve determination of the major water groups characterizing the coastal plain aquifer identification of some of the principal variables that influence changes in water quality in the aquifer and description of some of the geochemical phenomena contributing to change in aquifer water quality the following results were achieved for the test area 1 1 two major groups of water were identified a low salinity calcium bicarbonate water occurring in the phreatic portion of the coastal plain aquifer and a more saline sodium chloride water characterizing the neighboring cenomanian aquifer and the confined portions of the coastal plain aquifer 2 2 the major water input sources such as rain injection water waste water irrigation etc may vary in their influence upon resulting water quality this water quality is affected by such physical factors as distance from the sea depth of well intake filters below sea level proximity to streams and the lithology of the saturated and unsaturated zones 3 3 the evolutionary alteration in content of specific ions with time can be clearly visualized on the same graph by means of pca the universal applicability of such a statistical approach to other hydrological settings is noted

hydrogeochemical and isotopic constraints on the origins of dryland salinity murray basin victoria australia abstract combined hydrogeological and hydrogeochemical data allow flow systems and the origins of solutes in the honeysuckle creek area of the southeastern murray basin which is an area affected by dryland salinity to be constrained recharge occurs both on the uplands that are composed of fractured violet town volcanic rocks and the riverine plain that comprises sediments of the shepparton and coonambidgal formations groundwater from the violet town volcanics has low salinity 20 mmol l groundwater has intermediate cl br ratios 600 1000 which indicate that the high salinities do not simply result from halite dissolution rather mixing of groundwater homogenises cl br ratios and evaporation as a consequence of a shallow water table is the dominant process that increases salinity oxygen and h isotopes also indicate that mixing and evaporation have occurred these results indicate that land use over the whole region not just the uplands needs to be considered in any salinity management plans additionally future development of salinity is controlled by depth to the water table on the plains and the efficiency of recharge rather than by salt stores halite or brines in the unsaturated zone

field based accounting of co2 sequestration in ultramafic mine wastes using portable x ray diffraction carbon mineralization the sequestration of carbon within minerals presents one method through which we could control rising levels of anthropogenic carbon dioxide co emissions the mineral wastes produced by some ultramafic hosted mines have the ability to sequester atmospheric co via passive carbonation reactions carbon accounting in mine tailings is typically performed using laboratory based quantitative x ray diffraction xrd or thermogravimetric methods which are used to measure the abundances of carbonate bearing minerals such as hydromagnesite mg co oh 4ho and pyroaurite mg fe23 text fe 3 2 co oh 4ho the recent development of portable xrd instruments now allows for the characterization and quantification of minerals in the field here we assess the feasibility of using a portable xrd instrument for field based carbon accounting in tailings from the woodsreef chrysotile mine new south wales australia modal mineralogy was obtained by rietveld refinements of data collected with an inxitu terra portable xrd the partial or no known crystal structures ponkcs method was used to account for turbostratic stacking disorder in serpentine minerals which are the dominant phases in tailings from woodsreef weighed mixtures of synthetic tailings were made to evaluate the precision and accuracy of quantitative phase analysis using the portable instrument an average absolute deviation bias of 8 2 wt from the actual composition of the synthetic tailings was found using the portable instrument this is comparable to the bias obtained using a laboratory based diffractometer 9 6 wt absolute and to the results from previous quantitative xrd studies involving serpentine minerals the methodology developed using the synthetic tailings was then applied to natural tailings samples from woodsreef surface crusts forming on the tailings pile were found to contain hydromagnesite 5 8 wt and pyroaurite 2 1 wt comparable results were obtained using the laboratory based instrument and these results are expected to have similar biases to the analyses of the synthetic tailings these findings demonstrate that portable xrd instruments may be used for field based measurement of carbon sequestration in minerals in engineered and natural environments

groundwater residence time and movement in the maltese islands a geochemical approach the maltese islands are composed of two limestone aquifers the upper and lower coralline limestone separated by an aquitard the blue clay the lower coralline limestone is overlain in part by the poorly permeable globigerina limestone the upper perched aquifers are discontinuous and have very limited saturated thickness and a short water level response time to rainfall frequent detections of coliforms suggest a rapid route to groundwater however the unsaturated zone has a considerable thickness in places and the primary porosity of the upper coralline limestone is high so there is likely to be older recharge by slow matrix flow as well as rapid recharge from fractures measurement of sf6 from a pumping station in a deep part of one of the perched aquifers indicated a mean saturated zone age of about 15 years the main sea level aquifers msl on both malta and gozo have a large unsaturated thickness as water levels are close to sea level on malta parts of the aquifer are capped by the perched aquifers and more extensively by the globigerina limestone the limited detection of coliform bacteria suggests only some rapid recharge from the surface via fractures or karst features transmissivity is low and tritium and cfc sf6 data indicate that saturated zone travel times are in the range 15 40 years on gozo the aquifer is similar but is more extensively capped by impermeable blue clay cfc data show the saturated zone travel time is from 25 years to possibly more than 60 years groundwater age is clearly related to the extent of low permeability cover the 13c signature of groundwater is related to the geochemical processes which occur along the flowpath and is consistent with residence time ages in the sequence perched aquifers malta msl gozo msl the 18o and 2h enriched isotopic signature of post 1983 desalinated water can be seen in more modern groundwater particularly the urbanised areas of the perched and malta msl aquifers in all aquifers movement of solutes from the surface travelling slowly through the matrix provide a long term source of groundwater contaminants such as nitrate

climatic and lithologic controls on the temporal and spatial variability of co2 consumption via chemical weathering an example from the australian victorian alps abstract a detailed geochemical study on river waters of the australian victorian alps was carried out to determine i the relative significance of silicate carbonate evaporite and sulfide weathering in controlling the major ion composition and ii the factors regulating seasonal and spatial variations of co2 consumption via silicate weathering in the catchments major ion chemistry implies that solutes are largely derived from evaporation of precipitation and chemical weathering of carbonate and silicate lithologies the input of solutes from rock weathering was determined by calculating the contribution of halite dissolution and atmospheric inputs using local rain and snow samples despite the lack of carbonate outcrops in the study area and waters being undersaturated with respect to calcite the dissolution of vein calcite accounts for up to 67 of the total dissolved cations generating up to 90 of dissolved ca and 97 of mg dissolved sulfate has 34s values of 16 to 20 cdt indicating that it is derived predominantly from atmospheric deposition and minor gypsum weathering and not from bacterial reduction of fes2 this militates against sulphuric acid weathering in victorian rivers ratios of si vs the atmospheric corrected na and k concentrations range from 1 1 to 4 3 suggesting incongruent weathering from plagioclase to smectite kaolinite and gibbsite estimated long term average co2 fluxes from silicate weathering range from 0 012 106 to 0 039 106 mol km2 yr with the highest values in rivers draining the basement outcrops rather than sedimentary rocks this is about one order of magnitude below the global average which is due to low relief and the arid climate in that region time series measurements show that exposure to lithology high physical erosion and long water rock contact times dominate co2 consumption fluxes via silicate weathering while variations in water temperature are not overriding parameters controlling chemical weathering because the atmospheric corrected concentrations of na k and mg act non conservative in victorian rivers the parameterizations of weathering processes and net co2 consumption rates in particular based on major ion abundances should be treated with skepticism

in situ sequestration of atmospheric co2 at low temperature and surface cracking of serpentinized peridotite in mine shafts abstract the investigation of carbonate formation at low temperature during weathering of ultramafic rocks has become increasingly important as it represents an analog study for a cost efficient carbon disposal strategy here we present new insight into carbonate formation under subarctic surface conditions obtained from extensively carbonated chromite mine shafts in the feragen ultramafic body e norway carbonation proceeded by formation of mm to cm thick carbonate surface coatings on the serpentinized peridotite host rock the surface coatings consist in most cases of pure lansfordite mgco 3 5h 2 o and sometimes nesquehonite mgco 3 3h 2 o heavy o and c isotopes are strongly enriched in the carbonate coatings relative to drip water samples from the mines and water samples from subaerial ponds the major element composition of the water samples reveal that infiltrating rainwater reacts rapidly with the peridotite mainly due to brucite dissolution within the mines discharging alkaline water forms thin films on walls and ceilings that evaporate upon circulation of cold dry air in mines with only one opening the carbonation is limited to the entrance area in mines with a more efficient air circulation due to multiple entrances carbonation is found throughout the mine evaporation of the mine water results in lansfordite saturation and precipitation and is accompanied by a rayleigh type distillation effect causing enrichment of the heavy c and o isotopes in the liquid from which the carbonates precipitate formation of the carbonate coatings involved fragmentation of the underlying serpentinite substrate fragmentation proceeded by subcritical cracking i e by a combination of substrate weakening due to brucite dissolution and stress build up due to lansfordite precipitation in fractures close to the surface reaction induced fracturing represents a positive feedback mechanism as it creates additional reactive surface area during the carbonation mining operations in the area ceased in the mid 1920s indicating that the described carbonation occurs on a time scale relevant for the disposal of anthropogenic co 2

hydrodynamical changes and their consequences on groundwater hydrochemistry induced by three decades of intense exploitation in a mediterranean karst system the lez karst spring located in the mediterranean basin southern france supplies drinking water to the metropolitan area of montpellier france since the nineteenth century since 1981 an intense pumping is being performed directly in the main conduit with a maximum exploitation flow rate of about 1 700 l s to improve the understanding of groundwater origins and circulation dynamic in this karst system as well as the impact of three decades of intense water exploitation groundwater samples have been collected during various hydrologic conditions since march 2006 a previous hydrochemical study on the lez karst system had been carried out before the installation of the pumping plant this dataset was compared to the present one to identify possible changes on groundwater hydrochemistry the results of this analysis indicate the existence of historical changes in water hydrogeochemistry and evidence a decrease of the deep compartment participation to the lez spring outflow this change in spring water hydrogeochemistry may be attributed to the intense pumping of the karst system and in the absence of noticeable climatic changes expresses the direct consequences of anthropogenic forcing on the overall functioning of the aquifer this study aims to analyze the differences to understand the water chemistry changes and to better foresee the aquifer evolution for the future

quantifying carbon fixation in trace minerals from processed kimberlite a comparative study of quantitative methods using x ray powder diffraction data with applications to the diavik diamond mine northwest territories canada abstract the capacity of mine waste to trap co2 is in some cases much larger than the greenhouse gas production of a mining operation in mine tailings the presence of secondary carbonate minerals that trap co2 can therefore represent substantial fixation of this greenhouse gas the abilities of three methods of quantitative phase analysis to measure trace nesquehonite mgco3 3h2o in samples of processed kimberlite have been assessed the method of reference intensity ratios rir the internal standard method and the rietveld method with x ray powder diffraction data tests on synthetic mixtures made to resemble processed kimberlite indicate that both the rir and rietveld methods can be used accurately to quantify nesquehonite to a lower limit of approximately 0 5 wt for conditions used in the laboratory below this value estimates can be made to a limit of approximately 0 1 wt using a calibration curve according to the internal standard method the rir method becomes increasingly unreliable with decreasing abundance of nesquehonite primarily as a result of an unpredictable decline in preferred orientation of crystallites for rietveld refinements structureless pattern fitting was used to account for planar disorder in lizardite by considering it as an amorphous phase rietveld refinement of data collected from specimens that were serrated to minimize preferred orientation of crystallites gives rise to systematic overestimates of refined abundances for lizardite and underestimates for other phases the resulting pattern of misestimates may be mistaken for the effect of amorphous and or nanocrystalline material in samples this effect is mitigated by collecting data from non serrated specimens which typically give relative errors on refined abundances for major and minor phases in the range of 5 20 however relative error can increase rapidly for abundances less than 5 wt nonetheless absolute errors are sufficiently small that estimates can be made for the amount of co2 stored in secondary nesquehonite using the rir method or the rietveld method for abundances 0 5 wt and a calibration curve for abundances

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

mass balance simulation and principal components analysis applied to groundwater resources essaouira basin morocco the water resources of the essaouira coastal basin west of marrakesh are characteristic of a semi arid climate and are severely impacted by the climate in terms of quantity and quality considering the importance of the essaouira aquifer in the groundwater supply of a vast region nearly 1 200 km2 a research study was conducted in order to better understand groundwater evolution in this aquifer system it is a coastal aquifer located on the atlantic coastline southern morocco and salinization problems have been reported covering the palaeozoic bedrock the sedimentary series range from the triassic to the quaternary besides the possibility of seawater intrusion problems the geological structures delineate a syncline bordered by the tidzi diapir of triassic age outcropping to the east and south this is a recharge area for the aquifer whereas the main groundwater flow direction is from se to nw towards the atlantic ocean in spite of the occurrence of calcareous and dolomitic levels all waters in the essaouira basin are of the na cl type based on a range of experimental methodologies combined with pca and geochemical modelling it was possible to identify the mineralization processes occurring in the groundwater system and the importance of the water rock interaction in the water chemistry scenarios were tested using a simple mass balance model through the phreeqc programme the reaction path was assumed to be such that waters observed at shallow depths evolved to more mineralized waters an important contribution of water rock interaction in groundwater mineralization was found corroborating the influence of preferential recharge from the tidzi diapir in the water s signature anthropogenic contamination was also identified and could lead to serious problems with groundwater degradation in the near future in a country with scarce water resources

accelerating mineral carbonation in ultramafic mine tailings via direct co2 reaction and heap leaching with potential for base metal enrichment and recovery accelerated carbonation of ultramafic mine tailings has the potential to offset co2 emissions produced by mining ores from cu ni platinum group element podiform chromite diamondiferous kimberlite and historical chrysotile deposits treatments such as acid leaching reaction of tailings with elevated concentrations of gaseous co2 and optimization of tailings pore water saturation have been shown to enhance co2 sequestration rates in laboratory settings the next challenge is to deploy treatment technologies on the pilot and field scale while minimizing cost energy input and adverse environmental impacts implementation of accelerated tailings carbonation at field scale will ideally make use of in situ treatments or modified ore processing routes that employ conventional technology and expertise and operate at close to ambient temperatures and pressures here we describe column experiments designed to trial two geochemical treatments that address these criteria 1 direct reaction of partially saturated ultramafic tailings with synthetic flue gas from power generation 10 co2 in n 2 and 2 repeated heap leaching of ultramafic tailings with dilute sulfuric acid in the first experiment we report rapid carbonation of brucite mg oh 2 in the presence of 10 co2 gas within tailings sampled from the woodsreef chrysotile mine new south wales australia within four weeks we observe a doubling of the amount of co2 stored within minerals relative to what is achieved after three decades of passive mineral carbonation via air capture in the field our simulated heap leaching experiments treated daily with 0 08 m h2so4 produce high mg leachates that have the potential to sequester 21 2 kg co2 m 2 which is approximately one to two orders of magnitude higher than the rate of passive carbonation of the wood sreef mine tailings although some nesquehonite mgco3 center dot 3h 2 o forms from these leachates most of the mg is precipitated as mg sulfate minerals instead therefore an acid other than h2so4 could be used otherwise sulfate removal would be required to maximize co2 sequestration potential from acid heap leaching treatments reactive transport modeling min3p is employed to simulate acid leaching experiments and predict the effects of heap leaching for up to five years finally our synchrotron x ray fluorescence microscopy results for leached tailings material reveal that valuable trace metals fe ni mn co cr become highly concentrated within secondary fe hydr oxide minerals at the ph neutralization horizon within our column experiments this discrete horizon migrates downward and our reactive transport models indicate it will become increasingly enriched in first row transition metals in response to continued acid leaching acid leaching treatments for accelerated mineral carbonation could therefore be useful for ore processing and recovery of base metals from tailings waste rock or low grade ores

verifying and quantifying carbon fixation in minerals from serpentine rich mine tailings using the rietveld method with x ray powder diffraction data most carbon on earth is bound within minerals and increasing the uptake of atmospheric carbon dioxide into minerals may reduce the greenhouse gas content of the atmosphere we document carbon disposal through the mineralization of mine tailings at clinton creek yukon territory and cassiar british columbia we confirm crystallographic binding of carbon in these tailings and quantify carbon dioxide uptake using quantitative phase analysis with the rietveld method for x ray powder diffraction data planar disorder in the structures of the kaolinite serpentine group minerals makes rietveld refinements of x ray powder diffraction data for serpentinites problematic using structureless pattern fitting and with the addition of a known quantity of a well crystallized material the problem of structural disorder is overcome by considering the serpentine minerals as amorphous phases we test the accuracy and precision of this refinement method using synthetic serpentine rich mine tailings of known composition estimates of the abundance of hydrated magnesium carbonates in these tailings have a precision of approximately 5 relative for mineral species present in amounts greater than 10 wt precise estimates of carbonate mineral content and crystallographically bound atmospheric co 2 are made for samples of serpentine rich tailings from clinton creek and cassiar results for mine tailings are also compared to mineralogically similar samples from a carbonate playa at atlin british columbia the potential for decomposition of metastable hydrated magnesium carbonate phases to geologically stable magnesite may represent long term stability of the products of mineral sequestration in mine tailings

chrysotile dissolution rates implications for carbon sequestration abstract serpentine minerals e g chrysotile are a potentially important medium for sequestration of co2 via carbonation reactions the goals of this study are to report a steady state far from equilibrium chrysotile dissolution rate law and to better define what role serpentine dissolution kinetics will have in constraining rates of carbon sequestration via serpentine carbonation the steady state dissolution rate of chrysotile in 0 1 m nacl solutions was measured at 22 c and ph ranging from 2 to 8 dissolution experiments were performed in a continuously stirred flow through reactor with the input solutions pre equilibrated with atmospheric co2 both mg and si steady state fluxes from the chrysotile surface and the overall chrysotile flux were regressed and the following empirical relationships were obtained f mg 0 22 ph 10 02 f si 0 19 ph 10 37 f chrysotile 0 21 ph 10 57 where fmg fsi and fchrysotile are the log10 mg si and molar chrysotile fluxes in mol m2 s respectively element fluxes were used in reaction path calculations to constrain the rate of co2 sequestration in two geological environments that have been proposed as potential sinks for anthropogenic co2 carbon sequestration in chrysotile tailings at 10 c is approximately an order of magnitude faster than carbon sequestration in a serpentinite hosted aquifer at 60 c on a per kilogram of water basis a serpentinite hosted aquifer however provides a larger sequestration capacity the chrysotile dissolution rate law determined in this study has important implications for constraining potential rates of sequestration in serpentinite hosted aquifers and under accelerated sequestration scenarios in mine tailings