quantitative zn speciation in a contaminated dredged sediment by μ pixe μ sxrf exafs spectroscopy and principal component analysis dredging and disposal of sediments onto agricultural soils is a common practice in industrial and urban areas that can be hazardous to the environment when the sediments contain heavy metals this chemical hazard can be assessed by evaluating the mobility and speciation of metals after sediment deposition in this study the speciation of zn in the coarse 500 to 2000 m and fine 2 m fractions of a contaminated sediment dredged from a ship canal in northern france and deposited on an agricultural soil was determined by physical analytical techniques on raw and chemically treated samples zn partitioning between coexisting mineral phases and its chemical associations were first determined by micro particle induced x ray emission and micro synchrotron based x ray radiation fluorescence zn containing mineral species were then identified by x ray diffraction and powder and polarized extended x ray absorption fine structure spectroscopy exafs the number nature and proportion of zn species were obtained by a coupled principal component analysis pca and least squares fitting lsf procedure applied herein for the first time to qualitatively number and nature of species and quantitatively relative proportion of species speciate a metal in a natural system the coarse fraction consists of slag grains originating from nearby zn smelters in this fraction zn is primarily present as sphalerite zns and to a lesser extent as willemite zn2sio4 zn containing ferric oxyhydr oxides and zincite zno in the fine fraction zns and zn containing fe oxyhydr oxides are the major forms and zn containing phyllosilicate is the minor species weathering of zns zn2sio4 and zno under oxidizing conditions after the sediment disposal accounts for the uptake of zn by fe oxyhydr oxides and phyllosilicates two geochemical processes can explain the retention of zn by secondary minerals uptake on preexisting minerals and precipitation with dissolved fe and si the second process likely occurs because dissolved zn and si are supersaturated with respect to zn phyllosilicate exafs spectroscopy in combination with pca and lsf is shown to be a meaningful approach to quantitatively determining the speciation of trace elements in sediments and soils

neat stratigraphic and dynamic relationships between pyroclastic flow and ash cloud surge deposits in the cabo de gata nijar geopark almeria spain the southern end of genoveses bay cala de genoveses in almeria se spain hosts one of the most spectacular examples in europe of combined from base to the top ignimbrite surge and pumice ash fall deposits forming a world class outcrop of pyroclastic rocks at a regional scale the volcanism that led to the formation of these rocks has to be understood in terms of the late alpine tectonic evolution of the western mediterranean

palaeostress analysis of the northern nijar and southern vera basins constraints for the neogene displacement history of major strike slip faults in the betic cordilleras se spain this paper presents the results of a detailed structural analysis of the northern nijar and southern vera basins with special emphasis on the evolution of the regional stress field and the associated timing of movement of the serrata gafarillos and palomares strike slip fault zones these major fault zones control the neogene deformation of the se internal betic cordilleras in spain detailed stress analysis on neogene sediments of the vera and nijar basins shows a strike slip regime with nw se oriented subhorizontal maximum principal stress 1 during tortonian and earliest messinian times under the influence of this stress field dextral displacement along the n090e trending gafarillos fault zone resulted in deformation of the sediments of the southern sorbas and northeastern nijar basins during the early messinian a clock wise rotation of the stress field occurred stress analysis in rocks with late early messinian up to quaternary ages in the nijar and vera basins indicates a strike slip regime with n s oriented subhorizontal maximum principal stress 1 under the influence of this stress field the main activity along the n010e striking palomares strike slip fault zone took place resulting in deformation of the neogene sediments of the southeastern vera basin and culminating in a maximum sinistral displacement of more than 20 km at the same time the stress field was not suitably oriented to exert a large shear component on the gafarillos fault zone which activity ended after the earliest messinian fault and outcrop patterns of syntectonic neogene sediments in the vera basin show that displacement along the palomares fault zone decreased at the end of the middle miocene although minor displacement phases may still have occurred during the late miocene and possibly even pliocene from the middle miocene onward deformation in the nijar basin was controlled by sinistral displacement along the n040e trending serrata strike slip fault zone

shear fracture pattern and microstructural evolution in transpressional fault zones from field and laboratory studies abstract zones of transpressional shear deformation accommodate strike slip and oblique slip displacements field work in a transpressive shear zone and transpressional analogue clay box modelling show that a p oriented foliation and associated p shears are preferentially developed over the more common r 1 riedel shears the carboneras fault system cfs in se spain is a left lateral transpressional shear zone with an internal geometry characterized by first order y oriented faults and widespread p oriented second order faults the mesoscopic to microscopic gouge fabric reflects the regional architecture of the shear zone being dominated by a pervasive poriented foliation and discrete y and p shears friction experiments carried out to investigate the textural evolution of gouge fabrics showed four textural stages of fabric development from foliation formation to extreme shear localization resulting in cross gouge failure transpression clay box models favoured the formation of secondary p oriented shear fractures and p oriented shear lenses further deformation caused differential shear lens rotation and shear lens orientations closer to the mean displacement direction our field studies and laboratory analogue experiments indicate that shear zones dominated by p shears are diagnostic of a transpressional deformation regime

reactive transport model of the formation of oxide type ni laterite profiles punta gorda moa bay cuba oxide type ni laterite deposits are characterized by a dominant limonite zone with goethite as the economically most important ni ore mineral and a thin zone of hydrous mg silicate rich saprolite beneath the magnesium discontinuity fe less soluble is mainly retained forming goethite while ni is redeposited at greater depth in a fe iii and ni rich serpentine serpentine ii or in goethite where it adsorbs or substitutes for fe in the mineral structure here a 1d reactive transport model using crunchflow of punta gorda oxide type ni laterite deposit moa bay cuba formation is presented the model reproduces the formation of the different laterite horizons in the profile from an initial partially serpentinized peridotite in 106 years validating the conceptual model of the formation of this kind of deposits in which a narrow saprolite horizon rich in ni bearing serpentine is formed above peridotite parent rock and a thick limonite horizon is formed over saprolite results also confirm that sorption of ni onto goethite can explain the weight percent of ni found in the moa goethite

environmental assessment of the arsenic rich rodalquilar gold copper lead zinc mining district se spain data from soils and vegetation the rodalquilar mineral deposits se spain were formed in miocene time in relation to caldera volcanic episodes and dome emplacement phenomena two types of ore deposits are recognized 1 the el cinto epithermal au as high sulphidation vein and breccia type and 2 peripheral low sulphidation epithermal pb zn cu au veins the first metallurgical plants for gold extraction were set up in the 1920s and used amalgamation cyanide leaching began in the 1930s and the operations lasted until the mid 1960s the latter left a huge pile of 900 000 1 250 000 m3 of abandoned as rich tailings adjacent to the town of rodalquilar a frustrated initiative to reactivate the el cinto mines took place in the late 1980s and left a heap leaching pile of 120 000 m3 adverse mineralogical and structural conditions favoured metal and metalloid dispersion from the ore bodies into soils and sediments whereas mining and metallurgical operations considerably aggravated contamination we present geochemical data for soils tailings and wild plant species compared to world and local baselines both the tailings and soils of rodalquilar are highly enriched in as mean concentrations of 950 and 180 g g 1 respectively regarding plants only the concentrations of as bi and sb in asparagus horridus launaea arborescens salsola genistoides and stipa tenacissima are above the local baselines bioaccumulation factors in these species are generally lower in the tailings which may be related to an exclusion strategy for metal tolerance the statistical analysis of geochemical data from soils and plants allows recognition of two well differentiated clusters of elements as bi sb se sn te and cd cu hg pb zn which ultimately reflect the strong chemical influence of both el cinto and peripheral deposits mineral assemblages

analysis and simulation of reactive transport of metal contaminants in ground water in pinal creek basin arizona abstract large scale mining activities have generated a plume of acidic ground water more than 15 km long in the regional aquifer of the pinal creek basin a one dimensional reactive transport model was developed using phreeqc to aid in the analysis of transport and chemical processes in the plume and to determine the uses and limitations of this type of modeling approach in 1984 the acidic part of the plume had a ph as low as 3 4 and contained milligram per liter concentrations of iron copper aluminum and other metals from 1984 to 1994 concentrations of contaminants in the alluvial aquifer in pinal creek basin arizona decreased as a result of mixing recharge remedial pumping and chemical reactions for reactions involving gypsum and rhodochrosite the equilibrium modeling assumption of a local geochemical equilibrium was generally valid from 1984 to 1990 water along the simulated flow path was at equilibrium or slightly supersaturated with gypsum and gypsum equilibria controlled dissolved concentrations of calcium and sulfate beginning in 1991 water in the acidic part of the plume became increasingly undersaturated with respect to gypsum indicating that the gypsum available for dissolution in the aquifer may have been completely consumed by about 1991 rhodochrosite precipitation was thought responsible for the measured attenuation in dissolved manganese in the neutralized zone for reactions involving calcite the assumption of a local geochemical equilibrium was generally not valid dissolution of calcite in the transition zone was not sufficient to establish equilibrium although following neutralization the calcite saturation index decreased to 1 2 in 1986 calcite undersaturation decreased along the flow path in the neutralized zone and equilibrium was attained about 7 km downgradient of the transition zone the assumption of a local geochemical equilibrium was not valid for oxidation reduction reactions that involved iron oxides and manganese oxides kinetically controlled oxidation reduction reactions continued in the acidic part of the flow path for years following the passage of the transition zone although the equilibrium approach helped to provide an increased understanding of contaminant transport at pinal creek future work will require a kinetic modeling approach to more accurately simulate selected reactions between the plume and aquifer materials

effect of secondary minerals on electrokinetic phenomena during water rock interaction 1 the main geophysical application of spontaneous potentials sp anomalies i e electrical signal generated by hydroelectric coupling is the mapping of hydrothermal zones laboratory studies of hydroelectric coupling as a function of temperature are scarce because of experimental difficulties up today experiments carried out by ishido and mizutani 1981 with quartz al k no3 system for temperatures ranging from 20 c to 80 c are not well understood in this work we show that ishido and mizutani 1981 s solutions are oversaturated with aluminium and that the precipitation of al oh 3s is expected triple layer model tlm calculations for a gibbsite kno3 system can account for ishido and mizutani 1981 s measurements these results highlight that 1 the precipitation of a secondary mineral can hide the electrical properties of the primary rock 2 the geochemical fluid surveys should be taken into account to grasp the interfacial processes precipitation dissolution and to interpret the sp measurements in the field

building conceptual models of field scale uranium reactive transport in a dynamic vadose zone aquifer river system 1 subsurface simulation is used to build test and couple conceptual process models to better understand the persistence of uranium concentrations above federal drinking water standards in a 0 4 km by 1 0 km groundwater plume beneath the 300 area of the u s department of energy s hanford site in eastern washington state at this location the unconfined aquifer and the variably saturated lower vadose zone sediments are subject to significant variations in water levels driven by diurnal weekly and seasonal fluctuations in the columbia river stage in the near river aquifer uranium contaminated sediments in the highly transmissive hanford formation are subject to high groundwater velocities daily flow reversals and exposure to river water one and two dimensional simulations of variably saturated flow and reactive transport based on laboratory derived models of uranium sorption are used to assess the representation of uranium transport processes in the vadose zone aquifer river system the simulations show that the various frequencies of river stage fluctuation are capable of driving significant inland transport above the average water table which is in contrast to the net groundwater flow to the river inclusion of a rate limited uranium mass transfer process model is notably more important to the timescales of the river stage driven groundwater flow than for vadose zone flow driven by natural recharge spatially and temporally variable solution chemistry from the dynamic exchange of river water and groundwater in the unconfined aquifer is shown to significantly alter uranium mobility as represented by a multicomponent uranium surface complexation model

precipitation of fe iii oxyhydroxide deposits from shallow water hydrothermal fluids in tutum bay ambitle island papua new guinea abstract previous research on sea floor fe iii oxyhydroxide deposits has focused primarily on deep sea hydrothermal systems found along volcanically active portions of the mid ocean ridges and on hydrogenetic deposits formed in deep basins and along continental shelves there is however not much known about their formation in shallow water settings associated with volcanic islands the hydrothermal system at ambitle island papua new guinea provides an excellent opportunity to study the formation of fe iii oxyhydroxides in a shallow water setting precipitation from the hydrothermal solution is caused by mixing with seawater based on a 87 sr 86 sr mixing model the calculated minimum and maximum seawater fractions are approximately 11 and 57 respectively thus precipitation of tutum bay fe iii oxyhydroxides takes place at a temperature range between approximately 60 and 93 c the chemical composition shows low mn contents fe mn 600 and elements that are usually enriched in fe iii oxyhydroxides such as co and v are below crustal abundance and well below their concentrations in island arc volcanics arsenic concentrations on the other hand are by two orders of magnitude higher than those in other marine deposits rare earth element ree concentrations reflect their concentration in the hydrothermal fluids rather than seawater the crystallinity of the deposits increases with age as protoferrihydrite is apparently altered to fe smectite and hematite and as bearing minerals are formed contact with seawater and therefore oxidizing conditions seems to be the factor increasing the crystallinity

ionospheric local model and climatology from long term databases of multiple incoherent scatter radars empirical ionospheric local models have been developed from long term data sets of seven incoherent scatter radars spanning invariant latitudes from 25 to 75 in american european and asian longitudes at svalbard tromso sondrestrom millstone hill st santin arecibo and shigaraki these models as important complements to global models represent electron density ion and electron temperatures and ion drifts in the e and f regions giving a comprehensive quantitative description of ionospheric properties a case study of annual ionospheric variations in electron density and ion temperature is presented based on some of these models clear latitudinal longitudinal and altitude dependency of annual and semiannual components are found

an analysis of the scale heights in the lower topside ionosphere based on the arecibo incoherent scatter radar measurements 1 we statistically analyze the ionospheric scale heights in the lower topside ionosphere based on the electron density ne and temperature profiles observed from the incoherent scatter radar isr at arecibo 293 2e 18 3n puerto rico in this study a database containing the arecibo isr observations from 1966 to 2002 has been used in order to investigate the diurnal and seasonal variations and solar activity dependences of the vertical scale height vsh which is deduced from the electron concentration profiles

precipitation in pores a geochemical frontier the purpose of this article is to review some of the recent research in which geochemists have examined precipitation of solid phases in porous media particularly in pores a few nanometers in diameter nanopores while this is a review it is actually more forward looking in that the list of things about this phenomenon that we do not know or cannot control at this time is likely longer than what we do know and can control for example there are three directly contradictory theories on how to predict how precipitation proceeds in a medium of varying pore size as will be discussed below the confusion on this subject likely stems from the complexity of the phenomenon itself one can easily clog a porous medium by inducing a rapid homogeneous precipitation directly from solution or have limited precipitation occur that does not affect permeability or even porosity substantially it is more difficult to engineer mineral precipitation in order to obtain a specific outcome such as filling all available pore space over a targeted area for the purposes of contaminant sequestration however breakthrough discoveries could occur in the next five to ten years that enhance our ability to predict robustly and finely control precipitation in porous media by understanding how porosity and permeability evolve in response to system perturbations these discoveries will likely stem at least in part from advances in our ability to 1 perform and interpret x ray neutron scattering experiments that reveal the extent of precipitation and its locales within porous media anovitz and cole 2015 this volume and 2 utilize increasingly powerful simulations to test concepts and models about the evolution of porosity and permeability as precipitation occurs steefel et al 2015 this volume a further important technique to isolate specific phenomena and understand reactivity is also microfluidics cell

midlatitude ionospheric plasma temperature climatology and empirical model based on saint santin incoherent scatter radar data from 1966 to 1987 ionospheric plasma temperature variations have recently been studied based on incoherent scatter radar isr observations at a lower midlatitude site shigaraki in east asia otsuka et al 1998 and millstone hill a typical subauroral midlatitude site in north america zhang and holt 2004 the french saint santin isr with a geographic latitude slightly higher but an apex latitude 14 lower than millstone collected bistatic and quadristatic measurements for over two solar cycles beginning in september 1965 a database of these data containing observations between 1966 and 1987 has been used in this study in order to establish the midlatitude ionospheric climatology in particular that of the upper atmosphere thermal status as well as empirical models for space weather applications this paper presents in comparison with the millstone hill results variations of ion and electron temperatures ti and te with solar activity season time of the day and altitude the f2 region te at st santin is found to be lower than at millstone between march and july when the st santin electron density ne is relatively higher the midday te below 300 km increases with f10 7 as at millstone hill above 300 km it tends to decrease with f10 7 at st santin while it increases in summer at millstone hill ti between 250 and 350 km peaks midway between spring and summer we have also created st santin ionospheric models for ne te and ti using a bin fit technique similar to that used for the millstone hill models comparisons with corresponding iri predications indicate good agreement in ti at high solar activity and above the f2 peak te from the iri tends to be higher than both the st santin and millstone hill models

neogene extensional collapse in the western mediterranean betic rif alpine orogenic belt implications for the genesis of the gilbraltar arc and magmatic activity the betic rif orogenic belt crops out in the western mediterranean and constitutes the westernmost part of the alpine edifice the building up of this belt by compressional nappe tectonics occured during a series of alpine deformational episodes subsequent neogene extension resulted from the collapse of the previous compressional edifice through major extensional detachment systems this episode was accompanied by cafe alkaline to shoshonitic and lamproitic volcanism tectonic denudation of metamorphic core complexes and emplacement of peridotite bodies as a final consequence of the evolution of detachment systems furthermore we relate the generation of the gibraltar arc and the opening of the alboran sea to this major extensional event finally two main stages of tectonic denudation of these detachment systems are defined 1 nevado filabride stage with ex humation of metamorphic core complexes and 2 ronda beni boussera stage with a more advanced degree of denudation leading to the exhumation of upper mantle peridotites which may be tentatively termed mantle core complexes

in situ adsorption of mercury methylmercury and other elements by iron oxyhydroxides and organic matter in lake sediments abstract samples of authigenic material sediment overlying water and oxic surface sediment 0 0 5 cm depth from a perennially oxygenated lacustrine basin were analysed to investigate which solid phases are important for binding a suite of trace elements ag as ca cd cu hg in methylmercury mehg mg mo pb sb and zn the authigenic material which was collected with inert teflon sheets deployed for several years across the sediment water interface contained mainly poorly crystallized fe oxyhydroxides and natural organic matter presumably humic substances derived from the watershed manganese oxyhydroxides were not present in the collected authigenic material due to the slightly acidic condition ph 5 6 of the lake that prevents the formation and recycling of these compounds conditional equilibrium constants for the adsorption of cationic kfe m and anionic kfe a trace elements onto the authigenic fe oxyhydroxides were estimated from their concentrations in the authigenic material and in bottom water samples these field derived values of kfe m and kfe a were compared with those predicted by the surface complexation model using laboratory derived intrinsic adsorption constants and the water composition at the study site equilibrium constants kpom m were also calculated for the adsorption of the cationic trace elements onto the humic substances contained in the diagenetic material the field derived values of kpom m were compared to those predicted by the speciation code wham 6 for the complexation of the trace elements by dissolved humic substances in the lake combining the results of the present study with those on the distributions of trace elements in the porewater and solid phase sediments reported in previous studies at the same site it was determined whether the trace elements bind preferentially to fe oxyhydroxides or natural organic matter in oxic sediments the main inferences are that the anionic trace elements as mo and sb as well as the cationic metal pb are preferentially bound to the authigenic fe oxyhydroxides whereas the other trace elements and especially hg and mehg are preferentially bound to the humic substances

a statistical study of the subauroral polarization stream over north american sector using the millstone hill incoherent scatter radar 1979 2019 measurements this work conducts a statistical study of the subauroral polarization stream saps feature in the north american sector using millstone hill incoherent scatter radar measurements from 1979 to 2019

ionospheric data assimilation comparison of extracted parameters using full density profiles and key parameters 1 this paper explores the relative accuracy of deriving solar euv flux exospheric temperature tex and meridional winds using complete altitude profiles of ionosphere electron density as compared to just using key parameters such as nmax hmax and ionospheric electron content incoherent scatter radar observations at millstone hill and shigaraki and an ionospheric model are used in this study we can make the following points 1 with either the profile or key parameter data the euv flux can be inferred with little ambiguity given that background variables such as the meridional wind are known 2 the southward wind and tex can be simultaneously derived from either type of data the results in particular the o n2 results are similar for the two types of data the accuracy of the wind result relies much on the accuracy of hmax as well as the geomagnetic dip angle 3 a few key ionospheric parameters are not always sufficient to give a unique definition of ionospheric conditions additional parameters or even a full profile data are sometimes needed in general however the key parameter pair hmax nmax seems to be a suitable assimilation data source at least for retrieving the local features of the tex and meridional wind variation

applications of mineral surface chemistry to environmental problems environmental surface chemistry involves processes that occur at the interface between the regolith hydrosphere and atmosphere the more limited scope of the present review addresses natural and anthropogenically induced inorganic geochemical reactions between solutes in surface and ground waters and soil and aquifer substrates important surficial reactions include sorption ion exchange dissolution precipitation and heterogeneous oxidation reduction processes occurring at the solid aqueous interface recent research advances in this field have addressed both directly and indirectly societal issues related to water quality pollution biogeochemical cycling nutrient budgets and chemical weathering related to long term global climate change this review will include recent advances in the fundamental and theoretical understanding of these surficial processes breakthroughs in experimental and instrumental surface characterization and development of methodologies for field applications

carbonate compositions in cm and ci chondrites and implications for aqueous alteration abstract carbonate minerals in fourteen cm chondrites and two ci chondrites have been analyzed by electron microprobe to provide a better understanding of the aqueous processes that affected carbonaceous chondrite parent bodies calcites in cm chondrites and dolomites and magnesites in ci chondrites display the compositions expected of stable phases formed at low temperatures dolomites in cm chondrites identified here for the first time in five members of the group have small amounts of excess ca which may reflect metastable growth the distribution of fe between dolomite and coexisting serpentine differs in the two chondrite groups if the distributions reflect an approach to chemical equilibrium then the difference implies higher alteration temperatures for the ci group than the cm group in agreement with the results of previously published oxygen isotope thermometry and mineral solubility modeling of the alteration process dolomite fe contents are relatively uniform in the two chondrite groups dolomite mn contents by contrast vary widely the variations may reflect transport controlled coprecipitation of mn resulting from a heterogeneous distribution of the element in the anhydrous precursor material if this interpretation is correct then the altering fluids were essentially immobile while hydration reactions proceeded on the meteorite parent bodies the near closed system character of the alteration process long known from bulk chemical analyses of the meteorites is a direct consequence of the limited mobility of dissolved species

pb2 and zn2 adsorption by a natural aluminum and iron bearing surface coating on an aquifer sand pb2 and zn2 adsorption was studied in batch experiments with material collected from a shallow unconfined aquifer of glacial outwash sand and gravel in falmouth massachusetts usa the aquifer solids contain primarily quartz 95 w w with minor amounts of alkali feldspars and ferromagnetic minerals pb2 and zn2 adsorption experiments with various grain size and mineral fractions of the aquifer solids showed that 1 zn2 adsorption was independent of grain size but pb2 was preferentially adsorbed by the 64 m size fraction and 2 pb2 adsorption decreased after removal of the paramagnetic fe bearing mineral fraction but zn2 adsorption was unaffected pb2 and zn2 adsorption on mineral separates from the aquifer material compared with metal adsorption on a purified quartz powder indicated that adsorption of both metal ions was dominated by coatings on the quartz fraction of the sediment characterization of the coatings by aes sem eds and tof sims demonstrated that the natural quartz grains were extensively coated with al and fe bearing minerals of variable composition thin sections of quartz grains examined by tem showed that the coatings contained both polycrystalline regions and single mineral crystals the coating thickness varied from 10 nm up to 30 m the coatings were mostly resistant to dissolution by an extraction protocol designed to dissolve noncrystalline phases the effect on metal adsorption of dissolving surface coatings from the sediment by chemical extraction was also measured a hydroxylamine hc extraction designed to dissolve crystalline fe oxide phases decreased pb2 and zn2 adsorption relative to untreated sediment extracted fe al 1 but pb2 and zn2 adsorption were not appreciably changed after sediment was extracted with dithionite citrate extracted fe al 5 overall the results suggest that pb2 preferred to form complexes with iron hydroxyl sites while aluminol sites were more important for zn2 adsorption however a definitive understanding of adsorption reactions in groundwaters will require detailed studies of the extensive coatings formed at mineral water interfaces by chemical weathering processes

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

combination of statistical methods with modelling mineral water interaction a study of groundwater in the great hungarian plain abstract the chemical composition of groundwater samples from the southern part of the great hungarian plain was determined cluster analysis was used to separate aquifer systems on the basis of water chemistry processes controlling the chemical features of the different aquifers were established by simulation modelling combined with statistical calculations has proved to be an efficient tool to establish reactions between groundwater and minerals concentrations of ca and mg were controlled by dissolution of calcite and dolomite or magnesian calcite and by ion exchange on clay minerals sodium concentration is governed by irreversible albite weathering the influence of dissolution and ion exchange reactions was distinguished for both bivalent and monovalent cations decomposition of organic matter probably yields the co2 its pressure exceeds the atmospheric co2 pressure even in the deepest sediments studied

chemical weathering of a soil chronosequence on granitoid alluvium ii mineralogic and isotopic constraints on the behavior of strontium the use of strontium isotopes to evaluate mineral weathering and identify sources of base cations in catchment waters requires an understanding of the behavior of sr in the soil environment as a function of time our approach is to model the temporal evolution of 87sr 86sr of the cation exchange pool in a soil chronosequence developed on alluvium derived from central sierra nevada granitoids during the past 3 ma with increasing soil age 87sr 86sr of ammonium acetate extractable sr initially decreases from values typical of k feldspar to those of plagioclase and hornblende and then remains constant even though plagioclase and hornblende are absent from the soils after approximately 1 ma of weathering the temporal variation of 87sr 86sr of exchangeable sr is modeled by progressively equilibrating sr derived from mineral weathering and atmospheric deposition with sr on exchange sites as waters infiltrate a soil column observed decreases in quartz normalized modal abundances of plagioclase hornblende and k feldspar with time and the distinct87sr 86sr values of these minerals can be used to calculate sr flux from weathering reactions hydrobiotites in the soils have nearly constant modal abundances chemistry and 87sr 86sr over the chronosequence and provide negligible sr input to weathering solutions the model requires time and soil horizon dependent changes in the amount of exchangeable sr and the efficiency of sr exchange as well as a biologic cycling term the model predicts that exchangeable sr initially has 87sr 86sr identical to that of k feldspar and thus could be dominated by sr leached from k feldspar following deposition of the alluvium the maximum value of 87sr 86sr observed in dilute stream waters associated with granitoids of the yosemite region is likewise similar to that of the k feldspars suggesting that k feldspar and not biotite may be the dominant source of radiogenic sr in the streams this study reveals that when attempting to use strontium isotopes to identify sources of base cations in catchment waters and biomass both preferential leaching of sr from minerals during incipient soil development and changing sr exchange efficiency must be considered along with chemical contributions due to mineral dissolution

acidic volatiles and the mars soil large portions of mars surface are covered with deposits of fine homogeneous weathered dusty soil material nanophase iron oxides silicate mineraloids and salts prevail in the soil the mode of formation of this somewhat peculiar type of soil is still far from being clear one scenario suggests that weathering took place during early epochs when mars may have been warm and wet the properties of the soil are not easily reconciled with this scenario we propose another possible scenario that attributes in part the peculiar nature of the martian dust and soil to a relatively young weathering product formed during the last few hundreds of millions of years in a process that involves acidic volatiles we tested this hypothesis in an experimental study of the first step of acidolytic weathering of a partly palagonitized volcanic tephra of hawaiitic lava origin using sulfuric hydrochloric and nitric acids and their mixtures the tephra effectively neutralize the added acidity the protonic acidity added to the tephra attacks the primary minerals releasing fe al and mg which control the ph acting as lewis acid species of varying acid strengths the full amount of acidity added to the tephra is stored in it but only a very small fraction is preserved as the original protonic acidity the majority of the added sulfate and chloride were present as salts and easily solubilized minerals well crystallized sulfate salt minerals of aluminum and calcium were detected by powder x ray diffractometry whereas secondary magnesium and iron minerals were not detected due probably to lack of crystallinity the presence of gypsum caso4 2 h2o and alunogen al2 so4 3 17 h2o is probably responsible for the observed increased hygroscopicity of the acidified tephra and their tendency to form hardened crusts we suggest that if this mechanism is of importance on mars then the chemically weathered component of the martian soil consists of a salt rich mineral mixture containing the salts of the anionicligands so4 and cl resulting from volatiles emitted from volcanoes during more recent eruptions up to 109 years b p the lack of liquid water on mars surface during that time slowed or halted mineralogical evolution into highly crystallized minerals having large mineral grains the chemically weathered components are mixed with the products of physical weathering the recently formed soil may cover and coat more evolved hydrothermally modified mineral deposits formed in earlier epochs of mars

the natural attenuation of two acidic effluents in tharsis and la zarza perrunal mines iberian pyrite belt huelva spain the geochemical evolution of two acid mine effluents in tharsis and la zarza perrunal mines iberian pyrite belt huelva spain has been investigated in origin these waters present a low ph 2 2 and 3 1 and high concentrations of dissolved sulphate and metals fe al mn cu zn as cd co cr ni however the natural evolution of these acidic waters which includes the bacterial oxidation of fe ii and the subsequent precipitation of fe iii minerals represents an efficient mechanism of attenuation this self mitigating process is evidenced by the formation of schwertmannite which retains most of the iron load and by sorption toxic trace elements like as the later mixing with pristine waters rises the ph and favours the total precipitation of fe iii at ph 3 5 and subsequently al compounds at ph 4 5 along with the sorption of trace metals mn zn cu cd co ni until chemical equilibrium at circumneutral conditions is achieved

adsorption of rare earth elements onto carrizo sand experimental investigations and modeling with surface complexation rare earth element ree adsorption onto sand from a well characterized aquifer the carrizo sand aquifer of texas has been investigated in the laboratory using a batch method the aim was to improve our understanding of ree adsorption behavior across the ree series and to develop a surface complexation model for the rees which can be applied to real aquifer groundwater systems our batch experiments show that ree adsorption onto carrizo sand increases with increasing atomic number across the ree series for each ree adsorption increases with increasing ph such that when ph 6 0 98 of each ree is adsorbed onto carrizo sand for all experimental solutions including when actual groundwaters from the carrizo sand aquifer are used in the experiments rare earth element adsorption was not sensitive to ionic strength and total initial ree concentrations in our batch experiments it is possible that the differences in experimental ionic strength conditions i e 0 002 0 01 m nacl chosen were insufficient to affect ree adsorption behavior however cation competition e g ca mg and zn did affect ree adsorption onto carrizo sand especially for light rare earth elements lrees at low ph rare earth element adsorption onto carrizo sand can be successfully modeled using a generalized two layer surface complexation model our model calculations suggest that ree complexation with strong surface sites of carrizo sand exceeds the stability of the aqueous complexes lnoh 2 lnso4 and lnco3 but not that of ln co3 2 or lnpo4 in carrizo groundwaters thus at low ph 7 3 where major inorganic ligands did not effectively compete with surface sites for dissolved rees free metal ion ln 3 adsorption was sufficient to describe ree adsorption behavior however at higher ph 7 3 where solution complexation of the dissolved rees was strong rees were adsorbed not only as free metal ion ln 3 but also as aqueous complexes e g as ln co3 2 in carrizo groundwaters because heavy rare earth elements hrees were preferentially adsorbed onto carrizo sand compared to lrees original hree enriched fractionation patterns in carrizo groundwaters from the recharge area flattened along the groundwater flow path in the carrizo sand aquifer due to adsorption of free and solution complexed rees copyright 2005 elsevier ltd

machine learning predictive models for mineral prospectivity an evaluation of neural networks random forest regression trees and support vector machines abstract machine learning algorithms mlas such us artificial neural networks anns regression trees rts random forest rf and support vector machines svms are powerful data driven methods that are relatively less widely used in the mapping of mineral prospectivity and thus have not been comparatively evaluated together thoroughly in this field the performances of a series of mlas namely artificial neural networks anns regression trees rts random forest rf and support vector machines svms in mineral prospectivity modelling are compared based on the following criteria i the accuracy in the delineation of prospective areas ii the sensitivity to the estimation of hyper parameters iii the sensitivity to the size of training data and iv the interpretability of model parameters the results of applying the above algorithms to epithermal au prospectivity mapping of the rodalquilar district spain indicate that the rf outperformed the other mla algorithms anns rts and svms the rf algorithm showed higher stability and robustness with varying training parameters and better success rates and roc analysis results on the other hand all mla algorithms can be used when ore deposit evidences are scarce moreover the model parameters of rf and rt can be interpreted to gain insights into the geological controls of mineralization

tem observations of particles in groundwater and their prospecting significance in the bofang copper deposit hunan china abstract groundwater is an important medium in geochemical research due to its mobility and low elemental background values currently major ion and isotopic analyses are the methods that are most commonly used to examine elemental contents this paper aims to explore nanoparticles related to deep concealed ore bodies in the bofang deposit through discussions on their classification and origins and ultimately to provide recommendations for prospecting this research takes groundwater as the main medium for tem transmission electron microscope observations all particles in deep and shallow groundwater samples contain cu zn pb as fe and other metal elements that are related to the ore body cu bearing particles which are the focus of this study comprise the following main components cu bearing particles with carriers and those without carriers these two types of particles are discussed and classified then individual particles are selected among these particles the cu bearing particles that originated from concealed ore bodies comprise the following three types 1 cu occurring with and migrated by geochemical carriers 2 cu nanoparticles physically adsorbed and migrated by fe oh 3 3 cu migrating as single cu or cu o nanoparticles these individual particles and the geological information they provide about the bofang copper deposit suggest that metals that are captured by geochemical carriers in groundwater should be analyzed analysis of these particles combined with analyses of other important prospecting geological data could reduce the cost of drilling and narrow areas of interest

behaviors of trace elements in neoarchean and paleoproterozoic paleosols implications for atmospheric oxygen evolution and continental oxidative weathering abstract the behaviors of redox sensitive and or bio essential trace elements in neoarchean and paleoproterozoic paleosols ancient weathering profiles were investigated to better understand atmospheric oxygen evolution the loss or retention of individual trace elements in the paleosols can show how continental oxidative weathering and thus atmospheric oxygen evolution took place against age mainly due to their various redox potentials the v cr ni cu zn and mo concentrations of two paleoproterozoic paleosols were measured by inductively coupled plasma optical emission spectrometry and mass spectrometry and those as well as co w and u concentrations of nine neoarchean and paleoproterozoic paleosols were obtained from the literature the trace element behaviors were constrained by their degrees of loss or retention in the paleosols we applied two methods to the estimation i retention fraction of element m a mass ratio of element m of paleosol to parent rock using immobile elements such as ti and ii element element in particular si element correlations at different profile depths of a paleosol there are two distinct groups in trace element behavior in the neoarchean and paleoproterozoic paleosols co ni zn and w were lost from weathering profiles until the early paleoproterozoic but retained in the middle and late paleoproterozoic while v cr cu mo and u were retained in the profiles until the early paleoproterozoic or slightly later but lost from the profiles in the middle and late paleoproterozoic more precisely the timings of such loss and retention were different between trace elements during the paleoproterozoic the characteristics of these changes from retention to loss or from loss to retention indicate that the changes occurred and lasted throughout the paleoproterozoic the trace element behaviors accordingly suggest that continental weathering became oxidative progressively with age during almost the whole paleoproterozoic and thus atmospheric oxygen increased similarly with age in the same time period but not suddenly in a relatively short term the loss and retention of the trace elements may infer how they were released from the continent to the ocean against age in the neoarchean and paleoproterozoic

discussion of secondary compression of peat with or without surcharging by g mesri t d stark m a ajlouni and c s chen

characterization of geosynthetic clay liner bentonite using micro analytical methods in barrier design familiarity of the structure and composition of the soil material at the micron scale is necessary for delineating the retention mechanisms of introduced metals such as the formation of new mineral phases in this study the mineralogical and chemical makeup of the bentonite from a geosynthetic clay liner gcl was extensively characterized using a combination of conventional benchtop x ray diffraction xrd and micro x ray diffraction mu xrd with synchrotron generated micro x ray fluorescence mu xrf elemental mapping and mu xrd s mu xrd these methods allow for the non destructive in situ investigation of a sample with micro m spatial resolution synchrotron based hard x ray microprobes are specifically advantageous to the study of trace metals due to higher spatial resolution 10 micro m and higher analytical sensitivity femtogram detection than is possible using normal laboratory based instruments minerals comprising less than 5 of the total bentonite sample such as gypsum goethite and pyrite were identified that were not accessible by other conventional methods for the same gcl bentonite two dimensional general area diffraction detector system gadds images proved to be particularly advantageous in differentiating between the microcrystalline clay which appeared as homogeneous debye rings and the spotty or grainy appearance of primary more coarsely crystalline accessory minerals for s mu xrd themore tunability of the synchrotron x rays allowed for efficient distinction of both clay minerals at low scattering angles and in identifying varying fe oxide minerals at higher angles gcl samples permeated with metal bearing mining solutions were also examined in order to consider how mechanisms of metal attenuation may be identified using the same techniques in addition to the cation exchange capacity from the montmorillonite clay tests showed how minerals comprising only 1 2 of the bentonite such as goethite could potentially play a significant role in sequestering a range of metals specifically ni zn and cu less

ca sr and 87sr 86sr ratios as tracers of ca and sr cycling in the rio icacos watershed luquillo mountains puerto rico abstract we investigated ca and sr cycling in a humid tropical forest by analyzing ca sr ratios and 87sr 86sr ratios in soil minerals soil exchangeable cations soil porewater and plant roots wood and leaves and calculating the relative contributions of sr from atmospheric inputs and weathering of local bedrock an unexpectedly large contribution of bedrock derived sr and presumably ca is cycled through the vegetation reflecting the important role of geological processes in controlling the cycling of base cation nutrients even in a system with intensely weathered soil this is surprising because over 99 of the ca and sr that was originally in the bedrock is leached out of the soil and saprolite during early stages of weathering at this site and because there are large atmospheric inputs to the site of both sea salt and saharan dust substantial differences in ca and sr cycling are seen on small spatial scales between a ridgetop and an adjacent steep hillslope site measured ca sr ratios reflect fractionation between these elements during biogeochemical cycling fractionation was particularly evident between wood and foliar tissue but fractionation during soil exchange processes is also likely in comparing the ca sr ratios of plants exchangeable cations and bulk soils we found that foliar ca sr ratios were greater than exchangeable cation ca sr ratios which in turn were greater than soil ca sr ratios similar to patterns observed at other highly weathered tropical sites

ipy observations of ionospheric yearly variations from high to middle latitude incoherent scatter radars 1 upper atmospheric research during the 2007 international polar year features unprecedented yearlong observations by incoherent scatter radars this valuable data set collected under very low solar and magnetic activity conditions from a set of four radars spanning middle millstone hill auroral poker flat and higher latitudes sondrestrom and svalbard enables us to address a fundamental question of background climatology on ionospheric yearly variations the main focus of this paper is on the noon time baseline annual and semiannual variations with an emphasis on the less known height dependency for those geophysically important areas the radar measurements of ion drifts allow us to examine dynamic effects which have not been well addressed previously high latitude ionospheric climatology shows some interesting features in particular the two semiannual peaks of electron density ne the two peaks neither of which is near summer solstice are essentially of equinoctial symmetry at very high latitude sites where downward ion drifts are strong in summer thus causing ne reduction the symmetry vanishes at the midlatitude site clear phase progression is seen from the topside to the f2 peak at the midlatitude site comparisons of millstone hill data from this period and prior solar minima indicate decreases in the ion temperature throughout the f2 peak and the topside ionosphere these decreases do not seem to be associated with solar flux and magnetic activity effects

mineralized and unmineralized calderas in spain part ii evolution of the rodalquilar caldera complex and associated gold alunite deposits the rodalquilar caldera complex is located in the western part of the cabo de gata volcanic field in southeastern spain and is the first documented example of epithermal gold alunite mineralization within a caldera in europe the rodalquilar caldera is an oval collapse structure having a maximum diameter of 8 km and formed at 11 ma from eruption of the cinto ash flow tuff the oval lomilla caldera with a diameter of 2 km is nested within the central resurgent dome of the older rodalquilar caldera the lomilla caldera resulted from the eruption of the lazaras ash flow tuff which was ponded within the moat of the rodalquilar caldera the last phase of volcanic activity in the caldera complex was the emplacement of hornblende andesite flows and intru sions this magmatic event resulted in structural doming of the caldera opening of fractures and faults and pro vided the heat source for the large hydrothermal systems which deposited quartz alunite type gold deposits and base metal vein systems the gold alunite deposits are enclosed in areas of intense acid sulfate alteration and localized in ring and radial faults and fractures present in the east wall of the lomilla caldera like other acid sul fate type deposits the rodalquilar gold alunite deposits are closely related in time and space to porphyritic inter mediate composition magma emplaced along caldera structures but unrelated to the caldera forming magmatic system

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

october 2002 30 day incoherent scatter radar experiments at millstone hill and svalbard and simultaneous guvi timed observations 1 a long duration incoherent scatter radar isr experiment was conducted at millstone hill and svalbard from october 4 november 4 2002 along with the simultaneous guvi timed neutral composition measurements this 30 day run enabled us to study a number of thermosphere ionosphere magnetosphere phenomena this paper focuses on the day to day variability and quasiperiodic oscillation of the ionosphere the day to day variability under quiet magnetic conditions in electron density ne ion temperature ti and electron temperature te respectively changed with local time and height with the largest variability in ne and the smallest in ti midnight through dawn was the period of largest variability quasiperiodic ne oscillations were present with periods 1 day some of these oscillations were correlated with changes in the neutral composition originating from geomagnetic activity which altered the global atmospheric circulation as a result of high latitude heating processes as indicated in svalbard ion temperature enhancements however the wave type oscillation of ne exhibits a downward phase progression which persists up to 600 km and prevails until a large storm appears to impose an upward phase progression

topside ionospheric scale heights retrieved from constellation observing system for meteorology ionosphere and climate radio occultation measurements 1 the vertical scale height vsh in the topside ionosphere can be derived from electron density profiles in this study the electron density profiles retrieved from the cosmic formosat 3 a constellation observing system for meteorology ionosphere and climate mission c f3 for short ionospheric radio occultation iro observations have been collected to investigate the local time seasonal latitudinal and longitudinal variations of the vsh with the postprocessed c f3 iro electron density profiles during the interval from day of year doy 194 in 2006 to doy 60 in 2008 we conduct an analysis on the behaviors of vsh at an altitude of 400 km there are appreciable latitudinal variations in vsh a new finding is a significant peak around dip equator during daytime in four seasons away from the equatorial peak it is obvious that the vsh generally increases at higher latitudes the equatorial vsh undergoes a significant diurnal variation with a local noon maximum the peak shifts to sunrise time with increasing dip latitude and the values of daytime vsh become comparable with those at nighttime at low latitude in both hemispheres which is somewhat different from the feature revealed from arecibo incoherent scatter radar observations one of the crucial findings in our results is the most outstanding feature of vsh that is the presence of a substantial longitudinal structure in equatorial regions a wave like longitudinal feature is found in equatorial vsh during the daytime in four seasons while it becomes weaker or absent at other local time intervals and at higher latitudes this investigation also confirms that the behaviors of vsh are not strongly consistent with those of the neutral or plasma scale heights

simulated equinoctial asymmetry of the ionospheric vertical plasma drifts 1 this paper studies the influence of the lower thermospheric tidal winds below 105 km on the equinoctial asymmetry of the equatorial vertical e b plasma drifts v using theoretical ionospheric dynamo model ii of the institute of geology and geophysics chinese academy of sciences tidm iggcas ii and tidal winds below 105 km from thermosphere ionosphere mesosphere energetics dynamics satellite doppler interferometer tidi observations although a series of other nonmigrating tides also affect the v asymmetry the simulated equinoctial asymmetry in v are mainly driven by the migrating diurnal tide dw1 migrating semidiurnal tide sw2 de3 and dw2 nonmigrating tides the asymmetry in daytime v varies with local time and longitude and mainly shows three features first the simulated daytime v during the march equinox is larger than that during the september equinox in most of longitudinal sectors this asymmetry is mainly driven by the semiannual oscillation sao of the migrating diurnal tide in the tropical mesosphere lower thermosphere mlt region and the equinoctial asymmetry of the migrating semidiurnal tide also plays an important role in the generation of this asymmetry second the daytime v asymmetry in the eastern hemisphere is more significant than that in the western hemisphere our simulation suggests that the longitudinal variations of the geomagnetic fields and dw2 tides play important roles in the generation of this hemisphere difference third there is an obvious wave number 4 longitudinal structure in the v asymmetry our simulation suggests that this wave number 4 structure is mainly driven by the equinoctial asymmetry of the de3 tide

ionospheric climatology and variability from long term and multiple incoherent scatter radar observations climatology in eastern american sector 1 ionospheric climatology and variability studies are conducted using long term incoherent scatter radar isr observations from seven sites around the world these studies result in an empirical model system the isr ionospheric model isrim which represents local and regional ionospheric climatology and variability of the ionosphere this paper addresses some new climatological features revealed by the model for latitudes spanning 18 70 n over the eastern american sector the latitudinal change of the f2 layer electron density exhibits a clear depletion near millstone hill latitudes when solar activity is median or low accompanied by a te enhancement and electron density peaks at 10 both to the north and south of millstone hill possible explanations are discussed we also characterize several types of variation in plasma temperatures in this region including ion temperature elevation for quiet conditions in the auroral zone and electron temperature increases toward higher latitudes

mineralogical and chemical evolution of ochreous precipitates from the libiola fe cu sulfide mine eastern liguria italy abstract the mineralogical and chemical evolution of ochreous precipitates forming from acid mine drainage amd from the abandoned libiola fe cu sulfide mine eastern liguria italy was followed through a multianalytical approach xrd tem xrf icp applied to surface precipitates and associated waters collected from several mine adits the mineralogy of the precipitates changed significantly as a consequence of the variations of the chemical parameters of the circulating solutions mainly ph eh and sulfate concentrations which in turn were mainly controlled by mixing with unpolluted stream and rill waters of the mining area a progressive transition from jarosite to schwertmannite to goethite to ferrihydrite to amorphous dominated precipitates was observed mainly as a consequence of an increase in the ph of the associated solutions this mineralogical evolution agrees well with the aqueous speciation and eh ph stability calculations performed on the waters associated with the different precipitate types furthermore tem analysis indicated that metastable pristine phases schwertmannite tend to transform progressively to well crystallized more stable species here represented by goethite the comparison of the water chemistry and the crystal chemistry of the different precipitates showed a significant decrease in the zn cu ni co contents in waters where the coexisting precipitates were almost exclusively composed of goethite the distribution of v sr as concentrations within the different precipitates showed that the most efficient scavenging phase for these elements was jarosite whereas ferrihydrite efficiently took up pb ions and schwermannite acted as a natural sink for cr the comparative analysis of the precipitates and waters of the libiola mining area indicated that the authigenic fe oxyhydroxides play an important role in controlling the composition of the highly polluted amd waters but this role as cleaning agents was mostly ephemeral minor ph eh oscillations facilitated quick mineralogical transformations via dissolution reprecipitation or solid state transformation which in turn controlled the trace elements that were mobilized or permanently stored within the solid phases

exploring sustainability of aquifers based on predictive modeling of sorption characteristics of arsenic enriched holocene sediments in bangladesh abstract the importance of accessing safe aquifers in areas with high as is being increasingly recognized the present study aims to investigate the sorption and mobility of as at the sediment groundwater interface to identify a likely safe aquifer in the holocene deposit in southwestern bangladesh the upper shallow aquifer at around 18 m depth which is composed mainly of very fine grey reduced sand and contains 24 3 g g as was found to produce highly enriched groundwater 190 g l as in contrast deeper sediments are composed of partly oxidized brownish medium sand with natural adsorbents like fe and al oxides they contain 0 76 g g as and impart low as concentrations to the water 4 g l these observations were supported by spectroscopic studies with sem tem xrd and xrf and by adsorption leaching column tests and sequential extraction a relatively high in situ dissolution rate rr of 1 42 10 16 mol m2 s was derived for the shallower aquifer from the inverse mass balance model the high rr may enhance as release processes in the upper sediment the field based reaction rate kr was extrapolated to be roughly 1 23 10 13 s 1 and 6 24 10 14 s 1 for the shallower and deeper aquifer respectively from the laboratory obtained adsorption desorption data this implies that as is more reactive in the shallower aquifer the partition coefficient for the distribution of as at the sediment water interface kd as was found to range from 5 to 235 l kg based on in situ batch adsorption and flow through column techniques additionally a parametric equation for kd as r2 0 67 was obtained from the groundwater ph and the logarithm of the leachable fe and al concentrations in sediment a one dimensional finite difference numerical model incorporating kd and kr showed that the shallow leached as can be immobilized and prevented from reaching the deeper aquifer 150 m after 100 year by a natural filter of oxidizing sand and adsorbent minerals like fe and al oxides in this scenario 99 of the as in groundwater is reduced the deeper aquifer appears to be an adequate source of sustainable safe water

regional and local ionospheric models based on millstone hill incoherent scatter radar data 1 local and regional statistical models to describe millstone hill incoherent scatter radar observations of electron density electron temperature and ion temperature since 1976 are developed using a bin fit technique the local models generate ionospheric variations with local time day number and altitude from 150 1000 km the prior day s f107 and the ap index from the previous 3 hour period are keyed inputs to specify solar and geomagnetic activity the regional models have a latitude coverage of 32 55 geodetic and an altitude coverage of 200 600 km these climatology models are capable of reproducing primary ionospheric variation features seen in previous studies as well as several newly revealed features such as the semiannual variation of electron density they are accessible through the world wide web at the url http www openmadrigal org

specific surface area of a crushed welded tuff before and after aqueous dissolution specific surface areas were measured for several reference minerals anorthoclase labradorite and augite welded tuff and stream sediments from snowshoe mountain near creede colorado crushed and sieved tuff had an unexpectedly small variation in specific surface area over a range of size fractions replicate surface area measurements of the largest and smallest tuff particle size fractions examined 1 0 3mm and 0 212mm were 2 3 0 2m2 g for each size fraction reference minerals prepared in the same way as the tuff had smaller specific surface areas than that of the tuff of the same size fraction higher than expected tuff specific surface areas appear to be due to porous matrix tuff reacted in solutions with ph values from 2 to 6 had little change in specific surface area in comparison with unreacted tuff tuff reacted with solutions having high acid concentrations 0 1 m hydrochloric acid or sulfuric hydrofluoric acid exhibited a marked increase in specific surface area compared to unreacted tuff

mineral deposits and cu zn as dispersion contamination in stream sediments from the semiarid coquimbo region chile this paper presents cu zn as geochemical data from stream sediment surveys carried out in the three main watersheds of the coquimbo region of chile this mountainous semiarid realm occupies an area of 40 656 km2 between 29 and 32 s given that the area has a long historical record of mining activities important environmental disturbances were expected however despite the detection of three major geochemical anomalies for cu zn or as only one can be unmistakably linked to the development of mining metal recovery procedures andacollo panulcillo an investigation of the other two anomalies elqui and hurtado reveals three major causes that fully or partially account for them 1 the type of ore deposit and associated hydrothermal alteration 2 the regional structural setting intensity of fracturing and 3 climate landscape cu au as epithermal deposits prospects along the so called el indio belt are here regarded as the sources of both the elqui and hurtado anomalies the strong advanced argillic alteration present in some of the epithermal deposits prospects of the el indio belt may have induced the loss of the buffering capacity of rocks and therefore favoured metal dispersion during later oxidation leaching of sulphides this applies to the elqui and hurtado anomalies conversely given that the potassic propylitic and phyllic alterations do not affect the buffering capacity of rocks only minor metal dispersion is observed in relation to the los pelambres porphyry copper deposit besides the epithermal belt is located within a highly fractured andean domain 3 000 4 000 m of altitude which may have conditioned the fast unroofing of ore deposits contributed to enhanced circulation of meteoric waters and eventually to strong oxidation and leaching of metals metal dispersion is aggravated during rainy years in response to strong el nino episodes

iron oxide coatings on sand grains from the atlantic coastal plain high resolution transmission electron microscopy characterization nanoscale characterization of so called iron oxide coatings on aquifer sands is vital for understanding the fate and transport of naturally occurring and anthropogenic chemical species these coatings which typically have a strong reddish color are commonly assumed to consist primarily of iron oxides and oxyhydroxides this work shows that the yellowish red to strong brown coatings on sediments from an atlantic coastal plain aquifer in virginia are predominantly a mixture of si and al rich nanophases of variable crystallinity with interspersed smectite and agglomerates of goethite nanoparticles clusters of bacterial cells diatom fossils sponge spicules and other trace minerals are also observed

the origin of high sulfate concentrations in a coastal plain aquifer long island new york ion exchange batch experiments were run on cretaceous magothy aquifer clay cores from a nearshore borehole and an inland borehole on long island ny to determine the origin of high so4 concentrations in ground water desorption batch tests indicate that the amounts of so4 released from the core samples are much greater 980 4700 mg g of sediment than the concentrations in ground water samples the locally high so4 concentrations in pore water extracted from cores are consistent with the overall increase in so4 concentrations in ground water along magothy flow paths results of the sorption batch tests indicate that so4 sorption onto clay is small but significant 40 120 mg g of sediment in the low ph 5 pore water of clays and a significant part of the so4 in magothy pore water may result from the oxidation of fes2 by dissolved fe iii the acidic conditions that result from fes2 oxidation in acidic pore water should result in greater sorption of so4 and other anions onto protonated surfaces than in neu

the impact of ionic strength on the proton reactivity of clay minerals abstract the reactivity of clay mineral surfaces exerts a fundamental control on elemental cycling in environmental systems however the effect of solution ionic strength is on their reactivity is poorly understood here we quantified the effect of changes in is on clay mineral reactivity through the application of surface complexation modeling scm based on acid base titration data for three different clay minerals kaolinite illite and montmorillonite the results demonstrate that the acidity constants ka values for proton interactions on the clay surface vary linearly as a logarithmic function of solution is and that proton binding ability is inversely related to solution is two possible explanations for the observed relationship are proposed 1 solution electrolytes e g na competitively bind to clay surface sites relative to protons and 2 that the surface electrostatic field is attenuated by solution electrolytes we conclude that the impact of increasing solution is on clay surface reactivity is the result of a weakening negative surface electric field that impacts the surface potential this mechanism ultimately leads to different adsorption behavior for cations and anions under changing is conditions the empirical relationship between k values and is provided here can be applied to predict clay surface reactivity under varied environmental is conditions and has specific implications for trace metal behavior in environments such as estuaries where changes in is can be significant

lithium isotope fractionation during continental weathering processes a comprehensive understanding of lithium isotope fractionation during terrestrial weathering is necessary in order to use lithium isotopes to trace chemical cycles climatic changes and igneous processes this study investigates lithium isotope fractionation in two laboratory experiments and by analyses of natural basalt weathering products partial dissolution of basalts in the laboratory does not result in fractionation of lithium isotopes but similar dissolution of a granite sample causes significant fractionation this may reflect dissolution of secondary minerals from the granite or differences in the li isotope composition of primary minerals in this more evolved igneous rock significant li isotope fractionation was also observed during sorption onto mineral surfaces in the laboratory although this was highly dependent on sample mineralogy no fractionation accompanies the outer sphere physisorption of li to smectite surfaces some fractionation accompanies sorption onto ferrihydrite and significant fractionation with 0 986 is seen during inner sphere chemisorption to gibbsite surfaces repeat experiments with varying amounts of sorption demonstrate that li remains in an exchangeable site on the gibbsite surface the extent of fractionation onto gibbsite observed in this study 13 is about half that required in order for clay surface removal to balance the ocean li isotope budget isotopic fractionation of li was found to occur on a 300 yr timescale in both cold and warm natural environments a minimally altered rock surface from iceland was found to be two lighter in 7li than the sample interior probably due to the preferential incorporation of 6li in clay or oxide rich alteration products on the sample surface soil samples from hawaii also demonstrate li fractionation during weathering in this environment rainwater 7li 10 contributes a significant flux of isotopically heavy li to the developing soil despite this soils have similar li isotope compositions to the primary basalt 7li 4 indicating that 6li is preferentially retained during weathering this conclusion is supported by isotopically heavy river water on hawaii 7li 22 and by the correlation between li concentration and 7li in the soil the lab and field based measurements of this study clearly demonstrate that lithium fractionates during weathering potentially providing information about the weathering environment now and in the past