11 000 yrs of environmental change in the northwest passage a multiproxy core record from central parry channel canadian high arctic article i nfo piston core 97022 004pc 74 48 0 n 97 05 9 w 267 m water depth represents a rare paleoenvironmental archive from the understudied west central canadian arctic archipelago lithological biogeochemical and microfossil dinoflagellate cysts non pollen palynomorphs benthic and planktonic foraminifera character istics in combination with a chronostratigraphy based on seventeen radiocarbon dates show seven promi nent paleoenvironmental episodes since the end of the last regional glaciation the basal diamict zone i records decoupling of previously grounded glacial ice followed by ice proximal conditions zone iia commencing at 10 8 cal ka bp age depth model extrapolation after an interval of pervasive sea ice zone iib ice distal conditions are established zone iic although sparse microfossils are present in glaciomarine sediments zone ii noticeable biological activity with heightened abundances and diversities across all groups begins in the postglacial zone iii 10 3 10 0 cal ka bp when planktonic foraminifera neogloboquadrina pachyderma appear as planktonics are excluded from the study area today due to shal low inter channel sills this likely signals the inflow of relatively warm and saline atlantic derived arctic intermediate water below 250 m presumably facilitated by glacio isostatically enhanced deglacial water depths the subsequent zone iv 10 0 7 0 cal ka bp characterized by heightened biological productivity in both plankton and benthos and reduced seasonal sea ice cover may correspond to a previously proposed holocene thermal maximum this apparent amelioration ends by the mid holocene zone v 7 0 5 7 cal ka bp when arctic intermediate water is excluded from the study area and water depths approach modern values high arctic conditions with seasonal sea ice cover a circulation dominated by arctic ocean surface water and microfossil assemblages similar to modern are found from 5 7 cal ka bp onwards zones vi vii as only minor environmental fluctuations are apparent during the late holocene shorter term climatic episodes e g little ice age are not recognized in this record

geoenvironmental characterization of unstable abandoned mine tailings combining geophysical and geochemical methods cartagena la union district spain abstract this study presents the results of the geoenvironmental characterization of the brunita mine pond in the cartagena la union mining district murcia se spain the main objective was to evaluate the present conditions of the mine tailings in order to identify related environmental hazards since 1956 the brunita mine tailings were being stored in four stepped ponds at the watercourse of a nno sse trending ravine subsequently they were stored in a single large pond after the closure of the pond operations certain work on dike stabilization was performed and debris from the brunita mine started to accumulate the mining works for 50 years have led to the complete burial of the surrounding valleys and hills by mine waste material electrical resistivity tomography ert has allowed the determining of both the general geometry of the pond base and the thickness of the mine tailings surveys along a total of 6 ert profiles 3 longitudinal and 3 transverse profiles to the largest dimension of the pond were carried out the strong resistivity contrast between the infilling and the bedrock is high enough to clearly define the bottom pond boundary low resistivity values 200 m correspond to the paleozoic rocks that constitute the base of the deposit vertical steps have been recognized defining strong variations in the thickness of the deposit this geometry results from the interaction between the paleotopography of the previous valley and the different growth stages of the deposit the depth of the pond s base obtained from two boreholes has confirmed the results obtained from ert profiles significant amounts of pyrite and siderite and an appreciable presence of sphalerite and galena were determined by xrd of representative samples accordingly high contents of toxic metals cd cu pb sn and zn and as were detected in chemical analyses which show the potential of the tailings to release substantial amounts of these pollutants into the surrounding soils and watercourses amd has been identified and percolation through the base of the pond could occur at its northeast sector where a low resistivity area is recognized the manifest instability of the tailings pond makes it necessary to include physical stabilization in remediation and monitoring in order to minimize the environmental impact of the tailings on the areas affected which is located in one of the most popular tourist areas in se spain

constancy of silicate mineral weathering rate ratios between natural and experimental weathering implications for hydrologic control of differences in absolute rates abstract inverse models which apportion watershed effluxes geochemical mass balance over estimated mineral surface area give weathering rates for individual silicate minerals e g feldspar 1 3 orders of magnitude slower than laboratory rates comparisons of rates calculated from several recent watershed geochemical mass balance studies with experimentally determined rates reveal that the ratio of mineral weathering rates for a given silicate mineral pair determined in an internally consistent field study equals the ratio of rates for the same minerals in any internally consistent set of laboratory experimental data thus the coefficient which corrects the weathering rate for any mineral from a laboratory data set to a field setting is identical to the corresponding coefficient for any other mineral in the same data sets the correction factor linking experimental and natural rates must be independent of composition physical e g hydrologic controls rather than compositional or chemical controls cause the difference between weathering rates in nature and the laboratory because flow in natural weathering profiles is spatially heterogeneous not all of the potentially available surface in natural systems actually participates in reactions with pore fluids

global chemical erosion during the last glacial maximum and the present sensitivity to changes in lithology and hydrology geographically based calculations for 18 000 years ago 18 ka and today were made to examine the potential effects on terrestrial chemical erosion of changes in lithology and hydrology on glacial interglacial timescales runoff fields were derived from general circulation model predictions of precipitation minus evaporation then global lithologic maps were prepared so that empirical relationships for runoff versus bicarbonate flux for different rock types could be used to calculate global chemical erosion rates assuming that significant chemical erosion does not occur beneath ice sheets we find that chemical erosion in ice free areas at 18 ka was only slightly greater than today this result arises because the amount of land covered by ice sheets is roughly compensated for by exposed shelf areas and because there is little difference in global runoff the small 20 increase in the global chemical erosion rate during glacial conditions is due to exposure on the shelves of a relatively high proportion of carbonates which weather faster than average data on glacial interglacial movements of the calcite compensation depth ccd are inconclusive but seem to indicate little change whereas even a 20 increase in the riverine bicarbonate flux should cause an observable deepening if the ccd did not indeed change then our predicted increase in the bicarbonate flux from land during glaciations would have to be accommodated by other means such as increased carbonate productivity about half of the observed decrease in atmospheric pco2 at 18 ka could be explained if increased silicate chemical erosion accompanied increased total chemical erosion in ice free areas consideration of the maximum possible effect of meltwater at ice margins leads to an 80 increase in the global chemical erosion rate at 18 ka such an increase would lead to a larger and faster drop in atmospheric pco2 but also to an excessive deepening of the global ccd this scenario seems unrealistic our results are contrary to interpretations of a much higher silicate chemical erosion rate during glaciations based on recently published records of quaternary marine sr isotopic ratios therefore if these records are indeed globally representative and entirely due to increased silicate chemical erosion as opposed to changes in source areas or hydrothermal inputs then other factors such as a shift in the global weathering regime which we do not explicitly consider here may be involved sensitivity tests show that considering spatial heterogeneities in lithology and runoff leads to lower predictions of global chemical erosion rates than what one would obtain by considering only global averages in a non spatially resolved calculation

integrated geophysical and geochemical study on amd generation at the haveri au cu mine tailings sw finland the haveri tailings area contains 1 5 mt of sulfide bearing waste from the au cu mine that operated during 1942 1961 geophysical and geochemical methods were used to evaluate and characterize the generation of acid mine drainage amd correlations were examined among the electrical resistivity tomography ert data the total sulfide content and concentrations of sulfide bound metals cu co fe mn ni pb and zn of tailings samples and the resistivity and geochemistry of surface water the resulting geophysical geochemical model defines an area in the vadose tailings where a low resistivity anomaly 10 ohm m is correlated with the highest sulfide content extensive sulfide oxidation and low ph average 3 1 the physical and geochemical conditions resulting from the oxidation of the sulfide minerals suggest that the low resistivity anomaly is associated with acidic and metal rich porewater i e amd the lower resistivity values in the saturated zone of the central impoundment suggest the formation of a plume of amd the natural subsoil layer silt and clay and the bedrock surface below the tailings area were well mapped from the ert data the detected fracture zones of the bedrock that could work as leakage pathways for amd were consistent with previous geological studies the integrated methodology of the study offers a promising approach to fast and reliable monitoring of areas of potential amd generation and its subsurface movement over large areas ca 9 ha this methodology could be helpful in planning drill core sampling locations for geochemical and mineralogical analysis groundwater sampling and choosing and monitoring remedial programs

immobilization of copper under an acid leach of colloidal pyrite waste rocks by a fixed bed column colloidal pyrite waste rocks cpwr which are mainly composed of colloidal pyrite and siderite widely deposit in sulfide mines in the middle and lower reaches of the yangtze river belt china especially in tongling city anhui province china in this paper a fixed bed column was used to investigate the weathering and oxidation of cpwr and its role in immobilizing low concentration cu 10 mg l 1 under weakly acidic leach ph 5 0 the experimental results indicated that the breakthrough capacity was around 14 0 mg cu g 1 cpwr when cu2 breakthrough concentration was 0 5 mg l 1 sequential extraction of cu and dithionite citrate bicarbonate extraction of free iron in the used cpwr after the column breakthrough indicated that cu removal by cpwr consisted of the following processes oxidation of pyrite and dissolution of siderite in cpwr ferrous oxidation and adsorption of cu on ferric hydr oxides this study shows the potential application of cpwr as an effective sorbent for the removal of low concentration cu from acid mine drainage

comparing results from two continental geochemical surveys to world soil composition and deriving predicted empirical global soil pegs2 reference values analytical data for 10 major oxides al2o3 cao fe2o3 k2o mgo mno na2o p2o5 sio2 and tio2 16 total trace elements as ba ce co cr ga nb ni pb rb sr th v y zn and zr 14 aqua regia extracted elements ag as bi cd ce co cs cu fe la li mn mo and pb loss on ignition loi and ph from 3526 soil samples from two continets australia and europe are presented and compared to 1 the composition of the upper continetal crust 2 published word soil awerage values and 3 data from other continetal scale soil surveys it cab be demonstrated that average upper continetal crust values do not provide reliable estimates for natural concentrations of elements in soil for many elements there exist substantial differences between published world aoil averages and the median concentrations observed on two continets direct comparison with other continetal datasets is hampered by the fact that often mean instead of the statistically more robust median is reported using a database of the worldwide disstribution of lithological units it can be demonstrated that lithology is a poor predictor of soil chemistry climate related processes such as glaciation and weathering are strong modifiers of the geochemical signature inherited from bedrock during pedogenesis to overcome existing shortcomings of predicted global or world soil geochemical reference values we propose preliminary empirical global soil reference values based on analytical results of a representative number of soil samples from two continets pegs2

mineralogical and geochemical investigations of pyrite rich mine waste from a kyanite mine in central virginia with comments on recycling a pyrite rich waste stream is one of three types generated from a kyanite mine in central virginia near the town of dillwyn buckingham county currently ore consists of approximately 3 pyrite waste and an estimated 382 000 tons of this waste stream has been generated over the past 60 years the mineralogy of the waste stream consists of variable amounts of pyrite 70 99 talc 1 20 quartz 1 10 kyanite 0 5 5 with minor or trace amounts of magnetite hematite galena anorthite and rare earth phosphate energy dispersive spectroscopy analysis indicates that talc has minor amounts of al up to 1 57 wt and fe up to 4 29 wt and pyrite grains have no impurities above detection limit of approximately 0 1 wt bulk chemical analysis of selected elements using inductively coupled plasma mass spectrometry analysis indicate that zn 28 82 367 71 ppm as 8 94 18 26 ppm se 44 62 64 50 ppm cd 0 19 1 03 ppm hg 0 87 35 91 ppm and pb 65 10 189 66 ppm occur at levels of some environmental concern au and ag concentrations are negligible currently the waste stream is well managed and sold but for a low price talc is of sufficient quality to be of interest for recycling but the estimated 540 tons generated per year is not a suitable quantity to be economically viable currently the waste stream is not viable for recycling for higher monetary value however the characteristics of the pyrite may enable such recycling in the future for solar energy technologies this and other associated waste streams show long term promise for integrated recycling and may play important economic roles in an economically disadvantaged region

terrestrial and aquatic ecosystem responses to late holocene climate change recorded in the sediments of lochan uaine cairngorms scotland abstract we summarise the results of a range of sediment based studies at lochan uaine a remote corrie lake in the heart of the cairngorm massif in scotland the site lies above the holocene forest limit and has been minimally affected by human activities the results presented are mainly based on magnetic measurements element analysis granulometry organic geochemical analysis and pollen analysis carried out over a period of some 15 years the magnetic properties and element concentrations record a coherent sequence of changes reflecting mainly stages in catchment erosion in terms of the chronology developed for the sedimentary record from the site increases in allochthonous minerogenic sediment delivery to the lake occurred around 1000 bc ad 330 480 and ad 1260 1410 the only notable change in the pollen diagram records a period of deforestation at lower altitude predating the last of the periods of increased erosion the organic geochemistry analyses record a series of higher frequency responses in the aquatic ecosystem already noted in previous papers e g battarbee et al 2001 these include fluctuations in organic carbon content and in the concentrations of biomarkers indicative of changing lake productivity both the terrestrial and aquatic ecosystem responses are superimposed on a longer term trend of declining aquatic productivity progressive catchment weathering and increasing erosion the sediments of lochan uaine thus appear to have recorded complex system responses on three timescales reflecting a the long term decline in northern hemisphere insolation during the holocene b the millennial scale forcing of the kind found in many other mid late holocene records and c much shorter term quasi cyclic but clearly a periodic sub millennial fluctuations

determining weathering rates of soils in china abstract as an important parameter for critical load calculation and soil acidification simulation weathering rates of soils in china were studied using different methods of calculation the approaches used were the mass balance approach the soil mineralogical classification the total analysis correlation the profile model the magic model and a simulated leaching experiment since chemical weathering of secondary minerals usually plays a much more important role in neutralizing the long term acidification of soils in china than that of parent material soil mineralogy rather than parent rock material type which is regarded as the most suitable factor representing weathering rates in europe should be adopted as the basis for soil classification the weathering rate assigned to each soil should also be corrected when the effect of temperature is considered due to the variation in experimental conditions the weathering rates of soils from laboratory experiment may be difficult to compare with field determined rates and should be adjusted by ph and percolation rate the comparison of various methods in this study shows that the weathering rates of soils estimated by the profile model coincide well with those from other independent methods such as the dynamic modeling by magic and the modified leaching experiment the weathering rates were very low usually lower than 1 0 keq ha 1 year 1 for allites including latosol lateritic red earth red earth yellow earth and yellow brown earth in south china and silalsols consisting of dark brown forest soil black soil and podzolic soil in northeast china and very high for alpine soils desert soils and pedocals in west china the content of weatherable minerals in soil is the most important factor in determining the spatial distribution of weathering rate in china while the difference in temperature may be the reason why the weathering rate of soil in northeast china was lower than that in southeast china

characterization of acid mine drainage sources in the iberian pyrite belt base methodology for quantifying affected areas and for environmental management the present work aims to propose a methodology for quantifying the sources of acid mine drainage amd and to characterize the magnitude of the affected areas in the iberian pyrite belt sw spain such an approach allows the creation of a support tool for managing land and natural resources valorization which may be easily applied in similar mining regions the motivation and usefulness of this work can be realized by focusing on two main emerging strategic issues 1 water resources management with the example of alcolea dam that will receive water from affected areas in the iberian pyrite belt and 2 mineral resources valorization especially regarding copper exploration due to increasing market prices the used methodology included the following general steps it started with an inventory of the mines in the iberian pyrite belt followed by field cartography campaigns and finally the quantification of affected areas and contaminant discharges the results of the present work serve to confirm and quantify the magnitude of the amd pollution in the pyrite belt a total affected area of about 4 847 ha was estimated taking into account this figure and combining it with the annual average precipitation 650 l m2 results in an estimation of 31 503 680 m3 year of discharging water affected by the presence of sulphides in this scenario a total annual contribution of 260 056 tonnes year was obtained for sulphates which means more than 712 tonnes a day in the case of arsenic a toxic element the total annual contribution is more than 20 tonnes or close to 55 kg day regarding copper this economically interesting metal translates into total contributions of 10 364 tonnes year in the generating medium this gave more than 28 tonnes day which today sits at 8 200 dollars tonne this result suggests that solutions aimed at recovering this resource should be searched it may represent a financial return at the same time that it would mean overcome environmental liabilities

regional unconformities and the sedimentary architecture of the oak ridges moraine area southern ontario seismic stratigraphy geometry and sediment facies within the oak ridges moraine orm area of ontario record major structural elements and surfaces of the quaternary sedimentary sequence the derived stratigraphic architecture can be used to identify the key elements of a regional erosional surface represented by an unconformity in the subsurface and associated overlying channel sediments the erosional surface unconformity forms a distinct time datum in the quaternary sequence which provides an important aid to lithostratigraphic correlation the architecture also gives improved understanding of the effects of erosion on the late glacial landscape the surfaces of erosional drumlins and intervening troughs and the beds and banks of meltwater channels in the orm area define the regional unconformity highlighted by seismic profiles linked to continuously cored boreholes these features are attributed to regional scale subglacial meltwater flow events the sculpted surfaces which are analogous to water eroded forms the presence of boulder lags and coarse grained deposits on the regional erosional surface and the channels with undulating profiles provide the vital supporting evidence for a meltwater interpretation the inter regional extent of the unconformity is inferred from the coherence of regional paleoflows and the extent of drumlinized uplands tunnel channels and scoured bedrock terrain across 75 of the landscape from the orm area east and south to the finger lakes new york the implied magnitude of erosion suggests a pressing need for directed sedimentological study in those ocean basins that were probable depositional sites for flood deposits

glacial outburst flood sediments within disenchantment bay alaska implications of recognizing marine jokulhlaup deposits in the stratigraphic record abstract glacial outburst floods have been observed or inferred in most glaciated regions of the world outburst flooding events along past ice sheet margins have been discussed as possible causes for changes in ocean circulation while subglacial lake drainage under ice sheets may influence ice sheet stability the recognition of these geologically instantaneous events in the marine sediment or rock record is critical in order to characterize the magnitude and frequency of past outburst events as well as to predict the likelihood of future occurrences in this paper we characterize outburst lithofacies and infer depositional processes from two outburst floods within disenchantment bay alaska and compare these deposits to other recognized outburst deposits within marine depositional settings here we show that the outburst deposits are lithologically similar and are composed of stratified mud sand and diamicton we interpret these facies to have been formed by sediment gravity flows and hypopycnal plume sedimentation these results show that the volume of sediment lithofacies and inferred depositional processes cannot be easily distinguished from normal sediment accumulation within the proximal temperate glacimarine depositional environment the paucity of fluvial subglacial discharge in polar glacimarine environments suggests the potential for recognition of such deposits in the antarctic

the acidic mine pit lakes of the iberian pyrite belt an approach to their physical limnology and hydrogeochemistry abstract this study examines some relevant limnological and hydrogeochemical characteristics of 22 mine pit lakes of the iberian pyrite belt ipb the studied pit lakes include some of the largest and historically most important mines of the ipb including corta atalaya and cerro colorado in riotinto filon norte filon centro and filon sur in tharsis aznalcollar or san telmo and many other of minor size as a whole these lakes constitute at present a large volume of highly acidic and metal polluted water some of these pit lakes are very recent e g corta atalaya 2 5 a los frailes 6 a and present a continuous hydrological and geochemical evolution although many others were abandoned decades ago and show nearly constant water volume depth profiles obtained in several pit lakes e g san telmo confesionarios cueva de la mora concepcion indicate that many of them have developed meromixis and show at present a permanent thermal and chemical stratification with a well defined chemocline separating an anoxic fe ii rich monimolimnion and a well mixed oxygenated and fe iii rich mixolimnion in the upper layer the bacterial oxidation of fe ii competes with photoreductive processes which take place in the surface water thus provoking diel cycles of fe ii concentration the observed water chemistry reflects the oxidation and dissolution of pyrite and other sulphides and gangue aluminosilicates from the country rock the pit lakes of the ipb cover a wide range of water compositions from circumneutral and relatively low metal e g los frailes ph 7 2 0 07 mg l fe 3 8 mg l mn 30 mg l zn to extremely acidic and metal loid rich e g corta atalaya ph 1 2 36 7 g l fe 6 7 g l zn 1 3 g l cu 159 mg l as most pit lakes however are comprised within the ph range of 2 2 3 6 and appear to be strongly buffered by the hydrolysis and precipitation of fe iii in the form of schwertmannite which forms colloids that can sorb trace elements from the aqueous phase

sediment and organic carbon focusing in the shelikof strait alaska abstract profiles of excess 210 pb and 137 cs in sediment cores were used to determine sediment accumulation rates in outer cook inlet and the shelikof strait alaska in outer cook inlet and the northern shelikof strait sediment accumulation rates averaged 0 16 cm yr 1 and ranged from 0 10 to 0 21 cm yr 1 in contrast sediment accumulation rates were 4 times higher in the central and southern shelikof strait where the average was 0 68 cm yr 1 with a range of 0 46 to 0 94 cm yr 1 in addition to higher rates of sedimentation higher activities of excess 210 pb and higher levels of silt clay total organic carbon pb and mn also were found in surface sediments from the central and southern shelikof strait relative to outer cook inlet and the northern shelikof strait these trends are directly related to the progressive sorting and focusing of sediments along the transport pathway from cook inlet to the shelikof strait the flux of excess 210 pb and organic carbon to the sediments increased by 2 and 4 8 fold respectively from outer cook inlet and the northern shelikof strait to the central and southern shelikof strait based on 13 c values for surface sediments the amount of carbon derived from marine sources increased from 30 in outer cook inlet and the northern shelikof strait to 60 in the central and southern shelikof strait the good correlation between the accumulation rate of sediment organic carbon and excess 210 pb fluxes r 0 93 suggests that scavenging of excess 210 pb by organic carbon is an important process in this region modern sediment budgets for outer cook inlet and the shelikof strait indicate that 70 of the total sediment accumulation of 61 10 6 tons yr 1 is deposited in the central and southern shelikof strait these sediment budgets are in good agreement with the calculated value of 70 10 6 tons yr 1 of riverine and erosional sediment transported into outer cook inlet and the shelikof strait collectively the data support focusing of fine grained sediments and organic carbon to the central and southern shelikof strait

continental erosion and large scale relief a worldwide investigation of continental erosion is carried out by the study of large drainage basins on the basis of hydrological data environmental factors and basin relief distribution inside each basin mean geochemical and mechanical denudation rates are defined a multicorrelation analysis shows that the mechanical denudation rates ds are uncorrelated with environmental factors and correlated with mean basin elevation h while chemical denudation rates dd are insensitive to relief but correlated with mean annual precipitation furthermore two linear relationships between h and ds are detected 1 ds m 10 yr 419 10 6 h m 0 245 with v explained variance 95 1 this law concerns basins related to orogenies younger than 250 ma the negative intercept is interpreted as a continental sedimentation rate of 245 m m y an alternative model in which one invokes a critical elevation separating erosion from sedimentation is equally successful and leads to lower sedimentation rates 60 110 m m y for both models one derives from the slope of the adjustments erosion time constants on the order of 2 5 m y 2 ds m 10 yr 61 10 6 h m with v 86 5 this law concerns basins related to older orogenies the null intercept suggests the lack of continental storage because of the more important dispersion of the data the erosion time constant is calculated separately for each basin it ranges from 15 to 360 m y the tectonic implications of these results are discussed in particular the short time constant 2 5 m y agrees with orogenic uplift rates on the order of 1 mm yr observed in active mountain chains

biogeochemistry of glacial landscape systems abstractglaciers affect biogeochemistry of landscapes through their sediments glacial erosion rates are high and the sediments produced are distinctively fine grained hence glaciers can be thought of as producers of mineral surface area although this mineral surface area is highly reactive temperature limits chemical weathering fluxes from glaciers and their surroundings more significant effects may be associated with silt deposited in loess and on continental margins thick deposits in both settings contribute to carbon cycling through both silicate weathering and organic carbon burial the impact of glaciers on biogeochemical cycles will be long lasting as the legacy of glacial erosion processes continues as long as sediment yields are elevated

pedogenesis significantly decreases the stability of water dispersible soil colloids in a humid tropical region abstract the stability of soil colloids influences soil physicochemical properties soil development and transfer of nutrients and contaminants to surface and ground waters a better understanding of soil colloids stability dynamics during soil evolution is important for the evaluation of soil s capacity to retain nutrients and or accommodate toxic contaminants this study was aimed to determine changes in the stability of water dispersible soil colloids that accompany mineral transformation and surface charge evolution during pedogenesis using a well characterized chronosequence derived from basalt in the humid tropical region of hainan island south china the results demonstrated that the ph dependent colloid stability decreased significantly with tropical soil development which we attribute to the substantial changes in clay mineral compositions and colloid surface charge properties clay minerals in the studied chronosequence were characterized by an increase of kaolinite gibbsite and fe oxides and a decrease of quartz and halloysite towards more advanced stages of weathering which resulted in the decline of permanent negative charges in the older soils the point of zero charge phpzc increased while ph decreased across the tropical soil chronosequence being in good agreement with the observed lower colloid stability in aged soils dominated by kaolinitic minerals our study of colloid stability at long term pedogenic time scale suggests young tropical soils

evidence for rapid sedimentation in a tunnel channel oak ridges moraine southern ontario canada abstract in south central ontario a late wisconsinan regional unconformity consisting of tunnel channels and drumlinized till crops out north of lake ontario the tunnel channels are locally infilled and the unconformity buried by sediment of the oak ridges moraine based on seismic reflection profiling and drillcore the tunnel channels are known to continue beneath the moraine detailed sedimentological analysis of 300 m of continuous core from two drillholes located 7 km apart in subparallel tunnel channels identified three facies the gravel facies is 17 m thick and occurs in only one of the cores it directly overlies the unconformity and may include a number of upward fining units seismic reflection data suggests the gravel forms stacked gravel mesoforms or quasi horizontal gravel layers bed load sheets deposited from fluidal flows along the deep channel axis the graded massive sand facies up to 37 m thick is the most common facies and consists of silty medium sand with minor coarse sand strata are reverse graded normal graded or massive with isolated silt intraclasts and evidence locally for dewatering this facies is interpreted to have been deposited from hyperconcentrated dispersions downflow of a hydraulic jump or major channel confluence the third facies consists of medium scale and small scale cross stratified sand medium scale cross stratification occurs predominantly in the lower 37 m of the core and is interbedded with the graded massive sand facies small scale cross stratified sand is progressively more common upward in core medium and small scale cross stratified sands was deposited respectively by subaqueous dunes and ripples formed in dilute fluid flows the complete succession is interpreted to have been deposited very rapidly within a subglacial tunnel channel before discharge ceased along the channel deposition followed closely and in part coincided with rapid expansion of the channel by erosion in a hydraulic jump or at a major channel confluence along the grounding line of a subglacial lake scour into unconsolidated sediment contributed to the sediment flux and quickly overloaded the flow with suspended sediment which in turn resulted in extremely high rates of sedimentation immediately downflow such depositional conditions support the notion that tunnel channels in the study area formed and or served as conduits for subglacial jokulhlaup discharges and that the laurentide ice sheet most probably did not generally drain by steady state processes but instead by short lived catastrophic events

assessment of tailings pond seals using geophysical and hydrochemical techniques abstract tailings impoundments associated with former mining districts are currently sources of pollutants to soils and waters because of this issue many of these tailings ponds have been treated by restoration and sealing processes in recent years in this work the efficacy of geophysical techniques electrical resistivity imaging and ground penetrating radar as tools for assessing the effectiveness of the insulating process of these structures has been analysed for this purpose we selected the abandoned mining district of linares la carolina southern spain where during the mining activity these materials were stockpiled without corrective measures this study demonstrates the usefulness of electrical resistivity imaging eri for characterising the inner structure of abandoned tailings ponds determining the geometry of such deposits and evaluating the potential risks that they pose furthermore eri makes it possible to visualise higher moisture zones associated with the leaking of leachates that circulate through these residues the presence of humid areas could denote defects at the sealing stage the ground penetrating radar gpr technique was very useful for an accurate analysis of the most superficial part where the seal is constructed in particular the technique made it possible to differentiate between various encapsulation levels created during sealing as well as detect imperfections in the insulation layers and zones with higher moisture at a low depth a chemical quality analysis of the surface waters surrounding the dumps studied indicates that with the exception of as the concentrations of most metal loid s analysed al ba co cr cu fe mn ni pb rb se sr and zn have significantly decreased after the restoration works however it appears that leaks continue to appear in some sludge pond sectors that favour the mobilisation and even incorporation of certain toxic elements from the mining waste into the riverbed therefore pb 20 g l and se 1 5 g l dissolved in the surface waters continue to exceed the maximum concentrations allowed by the european union environmental quality standards

erosion of deccan traps determined by river geochemistry impact on the global climate and the 87sr 86sr ratio of seawater abstract the impact of the deccan traps on chemical weathering and atmospheric co2 consumption on earth is evaluated based on the study of major elements strontium and 87sr 86sr isotopic ratios of the main rivers flowing through the traps using a numerical model which describes the coupled evolution of the chemical cycles of carbon alkalinity and strontium and allows one to compute the variations in atmospheric pco2 mean global temperature and the 87sr 86sr isotopic ratio of seawater in response to deccan trap emplacement the results suggest that the rate of chemical weathering of deccan traps 21 63 t km2 yr and associated atmospheric co2 consumption 0 58 2 54 106 mol c km2 yr are relatively high compared to those linked to other basaltic regions our results on the deccan and available data from other basaltic regions show that runoff and temperature are the two main parameters which control the rate of co2 consumption during weathering of basalts according to the relationship f r f c 0 exp ea r 1 t 1 298 where f is the specific co2 consumption rate mol km2 yr rf is runoff mm yr c0 is a constant 1764 mol l ea represents an apparent activation energy for basalt weathering with a value of 42 3 kj mol determined in the present study r is the gas constant and t is the absolute temperature k modelling results show that emplacement and weathering of deccan traps basalts played an important role in the geochemical cycles of carbon and strontium in particular the traps led to a change in weathering rate of both carbonates and silicates in carbonate deposition on seafloor in sr isotopic composition of the riverine flux and hence a change in marine sr isotopic composition as a result deccan traps emplacement was responsible for a strong increase of atmospheric pco2 by 1050 ppmv followed by a new steady state pco2 lower than that in pre deccan times by 57 ppmv implying that pre industrial atmospheric pco2 would have been 20 higher in the absence of deccan basalts pco2 evolution was accompanied by a rapid warming of 4 c followed after 1 myr by a global cooling of 0 55 c during the warming phase continental silicate weathering is increased globally since weathering of continental silicate rocks provides radiogenic sr to the ocean the model predicts a peak in the 87sr 86sr ratio of seawater following the deccan traps emplacement the amplitude and duration of this spike in the sr isotopic signal are comparable to those observed at the cretaceous tertiary boundary the results of this study demonstrate the important control exerted by the emplacement and weathering of large basaltic provinces on the geochemical and climatic changes on earth

frank oldfield and his contributions to environmental change research frank oldfield s immense contribution to palaeoenvironmental science is summarized in relation to pollen analysis vegetation history and peat stratigraphy palaeolimnology and 210pb dating environmental magnetism catchment lake relationships and soil erosional history multiproxy approaches pages and editing the holocene the tribute includes an introduction to the 14 other papers in this special issue which were inspired in diverse ways by this remarkable scientist

enhanced chemical weathering of rocks during the last glacial maximum a sink for atmospheric co2 abstract it has been proposed that increased rates of chemical weathering and the related drawdown of atmospheric co2 on the continents may have at least partly contributed to the low co2 concentrations during the last glacial maximum lgm variations in continental erosion could thus be one of the driving forces for the glacial interglacial climate cycles during quaternary times to test such an hypothesis a global carbon erosion model has been applied to a lgm scenario in order to determine the amount of co2 consumed by chemical rock weathering during that time in this model both the part of atmospheric co2 coming from silicate weathering and the part coming from carbonate weathering are distinguished the climatic conditions during lgm were reconstructed on the basis of the output files from a computer simulation with a general circulation model only the predicted changes in precipitation and temperature have been used whereas the changes in continental runoff were determined with an empirical method it is found that during the lgm the overall atmospheric co2 consumption may have been greater than today by about 20 mainly because of greater carbonate outcrop area related to the lower sea level on the shelves this does not however affect the atmospheric co2 consumption by silicate weathering which alone has the potential to alter atmospheric co2 on the long term silicate weathering and the concomitant atmospheric co2 consumption decreased together with a global decrease of continental runoff compared to present day both by about 10 nevertheless some uncertainty remains because the individual lithologies of the continental shelves as well as their behavior with respect to chemical weathering are probably not well enough known the values we present refer to the ice free continental area only but we tested also whether chemical weathering under the huge ice sheets could have been important for the global budget although glacial runoff was considerably increased during lgm weathering under the ice sheets seems to be of minor importance

marine record of surge induced outburst floods from the bering glacier alaska the bering glacier alaska is the largest temperate glacier in the world it episodically surges with rapid advances of the glacier terminus followed by large outburst floods delivering freshwater and sediment to the adjacent gulf of alaska we describe the marine record of the 1993 1995 surge and document a 100 yr history of surges recorded in marine sedimentary deposits seaward of the bering glacier in 1994 and 1995 we collected box cores that contained high porosity laminated sediments at the seabed surface profiles of 234 th and chlorophyll a indicate that these sediments were deposited very rapidly 0 1 cm day 1 in association with the surge a 250 cm long kasten core extended this record in which 7 laminated beds 10 30 cm thick alternated with bioturbated sediments on the basis of 210 pb chronology 6 of these beds accumulated in the past 100 yr and can be correlated with historical surges

rapid least squares inversion of apparent resistivity pseudosections by a quasi newton method1 a fast inversion technique for the interpretation of data from resistivity tomography surveys has been developed for operation on a microcomputer this technique is based on the smoothness constrained least squares method and it produces a two dimensional subsurface model from the apparent resistivity pseudosection in the first iteration a homogeneous earth model is used as the starting model for which the apparent resistivity partial derivative values can be calculated analytically for subsequent iterations a quasi newton method is used to estimate the partial derivatives which reduces the computer time and memory space required by about eight and twelve times respectively compared to the conventional least squares method tests with a variety of computer models and data from field surveys show that this technique is insensitive to random noise and converges rapidly this technique takes about one minute to invert a single data set on an 80486dx microcomputer

diffusive transport of water in porous fresh to altered mid ocean ridge basalts abstract studying diffusive transport in porous rocks is of fundamental importance in understanding a variety of geochemical processes including element transfer primary mineral dissolution kinetics and precipitation of secondary phases here we report new findings on the relationship between diffusive transport and textural characteristics of the pore systems on the example of mid oceanic ridge basalts having different degree of alteration but very similar bulk pore volume diffusion processes in porous basalts were studied in situ using h 2 o d 2 o exchange experiments the effective diffusion coefficients of water molecules increase systematically from 5 05 10 11 to 1 19 10 10 m 2 s for fresh and moderately altered basalts and from 2 40 10 11 to 6 72 10 11 m 2 s for completely altered basalt as temperature increases from 5 to 50 c the activation energy of the diffusion process increases from 12 29 0 71 kj mol for fresh and moderately altered basalts to 14 3 1 33 kj mol for completely altered basalt the results indicate that neither the bulk porosity nor the degree of alteration can be used as proxies for the efficiency of element transport during morb water interaction the formation of secondary phases that replace primary minerals and fill the pore space in the rock leads to the formation of tiny pores and phases with large specific surface area these factors might have a dominant control on the transport properties of altered basaltic rocks

evaluation of the effectiveness of backfilling and sealing at an open pit mine using ground penetrating radar and geoelectrical surveys kimheden northern sweden at kimheden a small copper mine in northern sweden reclamation of the two open pits was investigated using ground penetrating radar and geoelectrical multiple gradient array measurements the pits had been backfilled with waste rock with a dry cover being applied on top in 1996 in order to reduce the influx of oxygen to the sulphidic mine waste and the subsequent production of acid mine drainage the dry cover consists of a sealing layer of clayey till and a protective layer of unsorted till as geochemical sampling in the drainage from the pits had previously revealed the continued release of contaminating oxidation products the purpose of the geophysical survey undertaken in 2010 was to identify deficiencies in the cover or other pathways for oxygen to reach the waste rock the radar images did not reveal any damage in the sealing layer but risks of deterioration of the cover in the long term were identified with both the radar and geoelectrical data the radar localised regions of thinner protective layer where the sealing layer could be exposed to frost action the geoelectrical measurements indicated the existence of seepage through the dry cover that presented a risk of erosion of the sealing layer 2 d inversion of geoelectrical data also imaged some pathways of groundwater around the main pit the results from the geophysical investigations were used together with other site data in order to show that both deficiencies in the cover and superficial fractures in the pit walls may explain an ongoing influx of oxygen to the mine waste

silicate rock weathering and atmospheric soil co2 uptake in the amazon basin estimated from river water geochemistry seasonal and spatial variations abstract using the data of the camrex project 1982 1984 on the water geochemistry of the amazon river and its main tributaries it was possible to assess the silicate rock weathering processes and the associated consumption of atmospheric soil co2 taking into account seasonal and spatial variations this study confirms the important role of the andes in the fluvial transport of dissolved and particulate material by the amazon and it shows for the first time that the silicate weathering rate and atmospheric soil co2 consumption are higher in the andes than in the rest of the amazon basin the seasonal variations exhibit the significant role of runoff as a major factor controlling silicate weathering processes and show that the chemical erosion rates vary greatly from low discharge to high discharge the average weathering rate estimated for the whole amazon basin 15 m my is comparable to other estimations made for other tropical equatorial environments a comparison between physical and chemical weathering rates of silicate rocks for the amazon basin and for each tributary basin show that in the andes and in the amazon trough the soil thicknesses are decreasing whereas in the shield the soil profiles are deepening

a reactive transport model for marcellus shale weathering abstract shale formations account for 25 of the land surface globally and contribute a large proportion of the natural gas used in the united states one of the most productive shale gas formations is the marcellus a black shale that is rich in organic matter and pyrite as a first step toward understanding how marcellus shale interacts with water in the surface or deep subsurface we developed a reactive transport model to simulate shale weathering under ambient temperature and pressure conditions constrained by soil and water chemistry data the simulation was carried out for 10 000 years since deglaciation assuming bedrock weathering and soil genesis began after the last glacial maximum results indicate weathering was initiated by pyrite dissolution for the first 1000 years leading to low ph and enhanced dissolution of chlorite and precipitation of iron hydroxides after pyrite depletion chlorite dissolved slowly primarily facilitated by the presence of co2 and organic acids forming vermiculite as a secondary mineral a sensitivity analysis indicated that the most important controls on weathering include the presence of reactive gases co2 and o2 specific surface area and flow velocity of infiltrating meteoric water the soil chemistry and mineralogy data could not be reproduced without including the reactive gases for example pyrite remained in the soil even after 10 000 years if o2 was not continuously present in the soil column likewise chlorite remained abundant and porosity remained small if co2 was not present in the soil gas the field observations were only simulated successfully when the modeled specific surface areas of the reactive minerals were 1 3 orders of magnitude smaller than surface area values measured for powdered minerals small surface areas could be consistent with the lack of accessibility of some fluids to mineral surfaces due to surface coatings in addition some mineral surface is likely interacting only with equilibrated pore fluids an increase in the water infiltration rate enhanced weathering by removing dissolution products and maintaining far from equilibrium conditions we conclude from these observations that availability of reactive surface area and transport of h2o and gases are the most important factors affecting rates of marcellus shale weathering of the in the shallow subsurface this weathering study documents the utility of reactive transport modeling for complex subsurface processes such modelling could be extended to understand interactions between injected fluids and marcellus shale gas reservoirs at higher temperature pressure and salinity conditions

long term average mineral weathering rates from watershed geochemical mass balance methods using mineral modal abundances to solve more equations in more unknowns abstract the number of phases for which weathering rates can be determined by watershed geochemical mass balance is limited by the number of equations that can be constructed from elemental flux losses from the watershed and mineral stoichiometries mass balance studies of watershed weathering rates routinely use the flux losses of the six major cations sio 2 al na k mg and ca analyses of these species in water are common but following matrix algebraic methods limits the number of weathering rates that can be calculated to six for the brubaker run watershed located in the northern piedmont physiographic province of pennsylvania usa long term 10 3 10 6 year watershed chemical flux losses have been determined using 10 be derived total denudation rates and zirconium normalized total chemical concentrations from bedrock and soils chemical flux losses calculated from solid phase data have three advantages they 1 permit generation of a relatively large number of equations because both major and trace analyses are included 2 eliminate the need for many years of regular e g weekly sampling and chemical analyses of stream water and atmospheric precipitation and measurement of hydrologic parameters i e precipitation stream discharge etc and 3 long term weathering rate calculations need not address biomass for brubaker run eight minerals are involved in weathering the five primary minerals are ree rich epidote ankerite almandine spessartine garnet muscovite chlorite and the three secondary products are weathered muscovite kaolinite and gibbsite the long term average weathering rates of these minerals were calculated using the six major cations and two trace elements selected from rb sr ba la pr nd sm gd and dy despite having the eight equations needed geochemically reasonable weathering rates e g positive primary mineral rates that reflect destruction could not be achieved regardless of the two trace elements used in the mass balance calculations for brubaker run this is primarily attributable to the natural heterogeneity of the trace element concentrations within the host mineral grains with trace element stoichiometries in some minerals varying by as much as an order of magnitude because the trace elements are hosted by a relatively small number of minerals the computed weathering rates of other minerals become very sensitive to small variations in trace cation stoichiometry ree rich epidote garnet and ankerite within the brubaker run watershed together host nearly all of the ca in the bedrock and completely dissolve at or near the weathering front consequently approximately all of the ca in bedrock is lost from the regolith in bedrock the mole percentages of ca hosted by ree rich epidote garnet and ankerite are 49 mol 4 mol and 43 mol respectively and are determined by the modal abundance of the mineral in the bedrock and its ca stoichiometry the weathering rates of ree rich epidote garnet and ankerite can be determined by distributing to each mineral that fraction of the total watershed ca flux loss for which it is responsible based on its mole percent ca in bedrock by using a base cation that is completely lost from the regolith and knowing the mole percentage of that element in the mineral s undergoing weathering additional equations may be added to the mass balance matrix we term this technique the flux distribution method the flux distribution method eliminates the need for additional equations established using trace elements based on the mineral weathering rates for the brubaker run watershed determined using the flux distribution method the rates at which the weathering front penetrated the bedrock the saprolitization rate are 4 5 m myr 1 and 6 5 m myr 1 for chlorite and muscovite respectively these measured long term average saprolitization rates compare very favorably with published theoretical values for the nearby northern maryland piedmont which range from 2 2 to 5 3 m myr 1

soil development on moraines of mendenhall glacier southeast alaska 1 the moraines and soil morphology abstract soils on a sequence of well drained neoglacial moraines up to 240 years old plus an older soil were sampled to investigate soil development through the initial stages of podzolization pebbles and cobbles in the moraines are about 75 to 80 granitic rock computations based on minerals observed optically and on chemical analyses indicate that plagioclase and quartz are the predominant minerals in the fine earth the climate is perhumid leaching of the moraines may have begun before they were free of glacial ice but little organic matter accumulated under the initial vegetative cover of sparse dwarf fireweed 10 year site as alder thicket developed organic matter accumulated rapidly in oi oe and a horizons 38 year site as spruce trees began to replace alder organic matter was lost from the surface mineral soil to form an e horizon and an incipient bs horizon formed below it an oa horizon formed and the a horizon disappeared 70 and 90 year sites organic acid leaching continued to form a spodic bhs horizon in spruce forest 240 year site and a spodic bh horizon in spruce hemlock forest 240 year site hornblende has been etched slightly within 240 years apatite has been lost from e horizons and free fe presumeably in ferrihydrite has accumulated in b horizons the younger moraine soils both with and without incipient bs horizons are typic cryorthents and the 240 year old and older soils with spodic bhs and bh horizons are typic haplocryods they are expected to accumulate more organic matter and become andic humicryods which is the most common subgroup of soils in the area

monitoring study of the mine pond reclamation of mina concepcion iberian pyrite belt spain mining of massive cu pb and zn sulphide bodies in the iberian pyrite belt sw spain has generated a great number of abandoned waste deposits such as mine ponds these represent large accumulations of reactive minerals and subsequently emission sources of trace elements and formation of acid drainage even if they have been restored monitoring studies are required to evaluate the corrective effects and how they may change over time this work presents the results of a monitoring study carried out at mine concepcion mine pond based on mineralogical xrd geochemical inaa x ray fluorescence icp ms and geophysical electrical resistivity tomography techniques in it a series of relevant parameters have been well delimited such as the infilling thickness and its variation and the position geometry and absence of water leakages through the base of the mine pond additionally the existence of an internal remnant flow of acid waters that tends to come out through the pond dyke has been identified chemistry of these waters indicates that oxidation processes affecting the mina concepcion mine tailings are generating acid drainage waters which could potentially release substantial amounts of trace elements to the river odiel thus giving that not complete sealing is accomplished by the restoration capping and rainfall water infiltrates into the pond materials at least the sealing of the dyke through which leakages occur should be revised

chemical weathering rates of a soil chronosequence on granitic alluvium iii hydrochemical evolution and contemporary solute fluxes and rates although long term changes in solid state compositions of soil chronosequences have been extensively investigated this study presents the first detailed description of the concurrent hydrochemical evolution and contemporary weathering rates in such sequences the most direct linkage between weathering and hydrology over 3 million years of soil development in the merced chronosequence in central california relates decreasing permeability and increasing hydrologic heterogeneity to the development of secondary argillic horizons and silica duripans in a highly permeable younger soil 40 kyr old pore water solutes reflect seasonal to decadal scale variations in rainfall and evapotranspiration et this climate signal is strongly damped in less permeable older soils 250 to 600 kyr old where solutes increasingly reflect weathering inputs modified by heterogeneous flow elemental balances in the soils are described in terms of solid state exchange and pore water reservoirs and input output fluxes from precipitation et biomass solute discharge and weathering solute mineral nutrients are strongly dependent on biomass variations as evidenced by an apparent negative k weathering flux reflecting aggradation by grassland plants the ratios of solute na to other base cations progressively increase with soil age discharge fluxes of na and si when integrated over geologic time are comparable to solid state mass losses in the soils implying similar past weathering conditions similarities in solute and sorbed ca mg ratios reflect short term equilibrium with the exchange reservoir long term consistency in solute ratios when contrasted against progressive decreases in solid state ca mg requires an additional ca source probably from dry deposition amorphous silica precipitates from thermodynamically saturated pore waters during periods of high evapotranspiration and result in the formation of duripans in the oldest soils the degree of feldspar and secondary gibbsite and kaolinite saturation varies both spatially and temporally due to the seasonality of plant respired co2 and a decrease in organically complexed al in deeper pore waters k feldspar is in equilibrium and plagioclase is about an order of magnitude undersaturated hydrologic heterogeneity produces a range of weathering gradients that are constrained by solute distributions and matrix and macropore flow regimes plagioclase weathering rates based on precipitation corrected na gradients vary between 3 and 7 10 16 mol m 2 s 1 these rates are similar to previously determined solid state rates but are several orders of magnitude slower than for experimental plagioclase dissolution indicating strong inhibitions to natural weathering partly due to near equilibrium weathering reactions

a quantitative comparison of soil development in four climatic regimes abstract a new quantitative soil development index based on field data has been applied to chronosequences formed under different climatic regimes the four soil chronosequences developed primarily on sandy deposits have some numeric age control and are located in xeric inland merced calif xeric coastal ventura calif aridic las cruces n mex and udic susquehanna valley pa soil moisture regimes to quantify field properties points are assigned for developmental increases in soil properties in comparison to the parent material currently ten soil field properties are quantified and normalized for each horizon in a given chronosequence including two new properties for carbonate rich soils in addition to the eight properties previously defined when individual properties or the combined indexes are plotted as a function of numeric age rates of soil development can be compared in different climates the results demonstrate that 1 the soil development index can be applied to very different soil types 2 many field properties develop systematically in different climatic regimes 3 certain properties appear to have similar rates of development in different climates and 4 the profile index that combines different field properties increases significantly with age and appears to develop at similar rates in different climates the soil development index can serve as a preliminary guide to soil age where other age control is lacking and can be used to correlate deposits of different geographical and climatic regions

sediment accumulation rates in subpolar fjords impact of post little ice age glaciers retreat billefjorden svalbard abstract the little ice age 1600 1900 ad and 20th century sediment accumulation rates in billefjorden a subpolar fjord on svalbard were reconstructed by applying 210 pb 137 cs and ams 14 c datings the modern sediment accumulation rate decreases from more than 0 39 cm y 1 at the fjord head to 0 08 cm y 1 close to the fjord mouth however during the little ice age the sediments accumulated at a much lower rate of 0 02 cm y 1 in the central fjord basin this difference is most likely related to the rapid retreat of glaciers during the 20th century when most of them withdrew up to 2 km the post little ice age increases in temperature and a negative glacier mass balance resulted in a larger meltwater discharge transferring substantial amounts of sediments released from the glaciers as well as those eroded from previously stored unconsolidated glacial sediments a comparison of data from the subpolar fjords of svalbard suggests that the increase in the sediment accumulation rate is a common trend and further increases might be expected if climate warming continues the properties of the fjord sediments grain size ird coarse fraction composition clay mineralogy from the little ice age and the 20th century showed no distinct differences the change in the accumulation rate may be the most evident sedimentary record of this climatic change

testing competing hypotheses for soil magnetic susceptibility using a new chemical kinetic model a chemical kinetic model is presented for the formation and accumulation of secondary ferrimagnetic minerals sfms in soil constructed using experimentally determined rate constants and validated against field data the primary objective is to critically assess the significance of competing causal mechanisms and disputed environmental controls under temperate conditions four findings are important in relation to current application of soil magnetic susceptibility data first transformation of hydrous ferric oxide to magnetite should dominate sfm formation controlled primarily by parent material ferrous silicate concentration and climate second abiotic reactions should account for most of the sfm production the most significant impact of high fe2 concentrations created by dissimilatory iron reducing bacteria is enhanced export of iron from the soil in runoff third the model predicts a correlation between hematite and magnetite concentrations weakening field support for direct transformation of hydrous ferric oxide to maghemite fourth magnetic susceptibility enhancement should increase strongly with weathering duration

modelling of atmospheric co2 consumption by chemical weathering of rocks application to the garonne congo and amazon basins modelling of atmospheric co consumption by chemical weathering of rocks application to the garonne congo and amazon basins

simulating loss of primary silicate minerals from soil due to long term weathering using allogen comparison with soil chronosequence lake sediment and river solute flux data this paper presents allogen a process model of soil mineral chemical weathering though designed principally to aid interpretation of lake sediment geochemical records by providing mass balance constraints for competing interpretations the model is also applicable to more general questions about long term weathering and soil development the model is constructed around a generalised version of the mineral weathering submodel of profile modified to minimise the need for site specific data and to optimise performance for long term change comparison with observed weathering rate data river flux studies chronosequences and lake sediment chemical stratigraphy suggests that soil mineral depletion can be usefully simulated over timescales applicable to quaternary and holocene studies to illustrate this the plausibility of a weathering interpretation is demonstrated for sediment records at lake hope simpson and moraine lake and the lake chronosequence at glacier bay while long term soil mineral depletion appears predictable reliable simulation of past runoff quality is hampered by lack of a suitable long term model for soil carbon

clay mineralogy chemical weathering and landscape evolution in arctic alpine sweden abstract the purpose of this research was to 1 characterize the clay mineralogy of soils in and adjacent to karkevagge a recently deglaciated valley in arctic sweden 2 document chemical weathering in a periglacial environment and 3 use the mineralogy to help explain landscape evolution soil samples were analyzed from 11 sites that differ in elevation parent material drainage slope and vegetation parent materials include residuum alluvium colluvium and glaciofluvial material derived from garnet mica schist plus in one locality a till of granitic origin x ray diffraction xrd was used to characterize the clay size fraction

using a reactive transport model to elucidate differences between laboratory and field dissolution rates in regolith the reactive transport model flotran was used to forward model weathering profiles developed on granitic outwash alluvium over 40 3000 ka from the merced california usa chronosequence as well as deep granitic regolith developed over 800 ka near davis run virginia usa baseline model predictions that used laboratory rate constants km measured fluid flow velocities v and bet volumetric surface areas for the parent material a o m were not consistent with measured profiles of plagioclase potassium feldspar and quartz reaction fronts predicted by the baseline model are deeper and thinner than the observed consistent with faster rates of reaction in the model reaction front depth in the model depended mostly upon saturated versus unsaturated hydrologic flow conditions rate constants controlling precipitation of secondary minerals and the average fluid flow velocity va unsaturated hydrologic flow conditions relatively open with respect to co2 g resulted in the prediction of deeper reaction fronts and significant differences in the separation between plagioclase and potassium feldspar reaction fronts compared to saturated hydrologic flow relatively closed with respect to co2 g under saturated or unsaturated flow conditions the rate constant that controls precipitation rates of secondary minerals must be reduced relative to laboratory rate constants to match observed reaction front depths and measured pore water chemistry additionally to match the observed reaction front depths va was set lower than the measured value v for three of the four profiles the reaction front gradients in mineralogy and pore fluid chemistry could only be modeled accurately by adjusting values of the product kma o m by assuming km values were constrained by laboratory data field observations were modeled successfully with tst like rate equations by dividing measured values of a o m by factors from 50 to 1700 alternately with sigmoidal or alinhibition rate models this adjustment factor ranges from 5 to 170 best fit models of the wetter hydrologically saturated davis run profile required a smaller adjustment to a o m than the drier hydrologically unsaturated merced profiles we attributed the need for large adjustments in va and a o m necessary for the merced models to more complex hydrologic flow that decreased the reactive surface area in contact with bulk flow water e g dead end pore spaces containing fluids that are near or at chemical equilibrium thus rate models from the laboratory can successfully predict weathering over millions of years but work is needed to understand how to incorporate changes in what controls the relationship between reactive surface area and hydrologic flow

abandoned mine tailings in cultural itineraries don quixote route spain abstract metallic mining wastes are a crucial environmental concern because of the accumulation and emission of toxic elements the abandoned san quintin mine tailings from the exploitation of galena and sphalerite puertollano mining district spain are surrounded by farmland and are crossed by the european cultural itinerary known as the don quixote route geophysical mineralogical and geochemical techniques have been applied to determine the geometry and composition of mine ponds and the possible occurrence of amd that could entail ecosystem and human risks seven electrical resistivity tomography profiles were surveyed and re worked tailing samples of two ponds five soil samples nine water samples and gaseous mercury emissions were analyzed both mine ponds are 8 m deep and overlie quaternary colluvial sediments deposited over precambrian metasediments the pond infilling is mainly composed of quartz and clay minerals and minor amounts of gypsum and sulfides with significant as cd hg pb sb and zn contents this metal emission source affects the underlying colluvial sediments and high hg and pb contents have also been found in nearby agricultural soils amd has been identified but metal contamination in the stream that borders the tailings is below the usepa s recommended limits although gaseous mercury emissions from a cinnabar stockpile increase in summer the measured levels do not reach the who s recommended limit the enrichment factor and igeo indexes for as cd hg pb sb and zn indicate strong to extreme contamination in the mine ponds and moderate contamination in the colluvial sediments metasediments aeolian dispersion is the most important contaminant agent the surrounding soils show strong to extreme levels of hg and moderate to extreme levels of as cd pb and sb restoration of these abandoned wastes is recommended to reduce the health risks for residents and tourists due to this aeolian contaminant dispersion

predicting radioactive accessory mineral dissolution during chemical weathering the radiation dose at the solubility threshold for epidote group detrital grains from the yangtze river delta china abstract the influence of heavy ion irradiation on the solubility of natural epidote group minerals has been investigated the epidote group are calc silicate minerals that if soluble during terrestrial chemical weathering are capable of consuming atmospheric co 2 over geologic time the experimental design was to calculate the particle dose for actinide rich epidote group grains from the deltas of rivers draining large watersheds large watersheds should yield a suite of epidote group grains spanning the range of compositions and radiation damage commonly observed in nature these grains would be resistant to dissolution during chemical weathering and survive into fluvial sediments therefore the highest particle dose calculated for the suite of grains represents a minimum solubility threshold for the epidote group minerals during chemical weathering the particle dose is calculated from the 232 th 238 u and 235 u content of a grain and the grain s date actinide rich epidote group grains were isolated from yangtze river and river nile delta sediments although only the grains from the yangtze delta had 232 th 208 pb ratios sufficiently high to yield meaningful dates a total of 28 th rich epidote group grains were isolated from the yangtze delta sediment with 24 being classified as allanite and four being classified as ree rich epidote isotopic ratio data were measured by laser ablation microprobe inductively coupled plasma mass spectrometry dates and ree patterns revealed at least 17 different sources of grains with tho 2 contents ranging from 0 057 to 4 37 wt and dates ranging from 32 2 to 3788 263 ma the calculated maximum particle dose of the suite of yangtze delta epidote group mineral grains and hence the minimum solubility threshold is 7 1 10 15 decay mg 1 therefore to predict the likelihood of an epidote group mineral dissolving during chemical weathering at a specific study site the particle dose may be calculated from the date of the rock even if estimated and the radioactinide concentrations of the mineral a calculated particle dose below 7 1 10 15 decay mg 1 likely reflects epidote group mineral stability during chemical weathering calculation of the particle dose may be superior to microscopic identification of accessory the particle dose at the solubility threshold of 7 1 10 15 decay mg 1 value is approximately double that reported for zircon therefore relative to zircon epidote group minerals can withstand more radiation prior to becoming soluble this finding is surprising considering the chemical durability of zircon this substantial variance in solubility threshold radiation doses between the two minerals cannot be explained by the bond strengths of non tetrahedral cations and structural oxygen which are lower in allanite than zircon

assessing the role of submarine groundwater discharge as a source of sr to the mediterranean sea abstract submarine groundwater discharge sgd has been identified as an important source of sr to the ocean and the sgd driven sr flux to the global ocean has been recently re evaluated beck et al 2013 however the uncertainty of this value is still high because of the uncertainties related to the determination of sgd flow rates and the paucity of 87 sr 86 sr data in sgd end members as carbonates have high sr concentrations and are subjected to intense heightened weathering they might significantly influence the sgd input of sr to the ocean here we present data on sr concentrations and 87 sr 86 sr ratios in three carbonate dominated sites of the western area of the mediterranean sea a semi enclosed basin characterized by abundant coastal carbonates the 87 sr 86 sr ratios in groundwater were lower compared to modern seawater 0 70916 as expected for areas dominated by carbonate lithologies concentrations of sr and 87 sr 86 sr ratios in groundwater showed conservative mixing in the studied subterranean estuaries by using sgd flow rates reported in the literature for the study areas a flow weighted fresh sgd end member characterized by a sr concentration of 27 30 m and a 87 sr 86 sr ratio of 0 707834 0 708020 was calculated for the eastern coast of the iberian peninsula integrating these sr data with literature data i e values of sr concentration and 87 sr 86 sr ratio from other lithologies as well as sgd flow rates we also calculated the fresh sgd driven sr flux to the entire mediterranean sea obtaining a value of 0 34 0 83 10 9 mol y 1 with a 87 sr 86 sr of 0 7081 0 7086 thus for the entire mediterranean basin sgd is globally a source of sr less radiogenic compared to seawater the sgd sr flux to the mediterranean sea represents 5 6 of the sgd sr flux to the global ocean and the mediterranean sgd end member has higher sr concentration 5 12 m than the global sgd end member 2 9 m this confirms the significant role of carbonate lithologies on sgd driven sr fluxes to seawater the fresh sgd driven sr flux to the mediterranean sea is about 20 50 of the riverine sr input and significantly higher than the input through atmospheric dust deposition therefore sgd should be considered as an important continental source of sr to the basin

loss of apatite caused irreversible early holocene lake acidification lakes created by retreating ice at the end of the last glaciation underwent rapid acidification during the first few thousand years of their existence a phenomenon attributed in part to progressive leaching of soil bases since it was discovered more than 80 yeas ago though a role for leaching is still acknowledged the most recent studies see this as subordinate to the effects of biological and climatic changes initiated by deglaciation chiefly primary vegetation succession and species immigration until now there has been no quantitative test of the relative importance of these different mechanisms here i use geochemical modelling of runoff acidity to show that the extent and timing of early holocene lake acidification in eight published palaeoecological records can be explained by leaching of the calcium phosphate mineral apatite from the granitic till soils of their catchments at a rate controlled by simple dissolution kinetic factors this shows that a single progressive abiotic process is capabl

the role of the cryosphere in source to sink systems abstract glacial erosion and sediment production are of interest to diverse scientific communities concerned with the interaction of climatic tectonic and surface processes that influence the evolution of orogens and with the climatic signals archived in glacigenic strata we review the current state of knowledge on the generation transfer and accumulation of glacigenic sediment from land to sea we draw from geomorphology marine geology geochronology numerical modeling of surface processes and landscape evolution and experimental and field observations of glacier erosion and deposition and the interaction of ice with its bed and the ocean boundary our primary goal is to examine glacial systems using a holistic source to sink approach with a focus on describing a how glacial motion produces sediment b how the sediments sink record the dynamic nature of glacial systems under different climatic thermal regimes c the challenges in using the sedimentary record to interpret these dynamics in space and time and d the approaches still needed to further our understanding of how ice and associated sediment fluxes respond to climatic and other perturbations the dynamic state of ice i e the ice flux and ice extent is defined differently between the source and sink communities reflecting the challenges of establishing a stratigraphic signal that volumetrically constrains glacigenic sediment production as a function of the ice response to climate advances in marine geophysics have greatly assisted our understanding of mass transfer pathways and of former ice extents as a measure of ice dynamics and have identified the primary depocenters and key lithofacies of glacial sinks sediment fluxes associated with the dynamic state of the ice are best constrained where sediment volumes derived from key lithofacies and seismic reflection isopachs can be temporally partitioned of which there are few examples rather than from discrete point measures of sediment flux that are subject to sediment transfer biases forward numerical modeling of sediment fluxes as a function of ice dynamics agree with observational data at the continental margin scale but finer time space scale ice dynamic models do not yet recreate observed ice extent or flowpaths future source to sink work in glaciated systems should focus on refining empirical relationships between ice velocity and sediment production and expand the application of existing methods to develop sediment volumes and fluxes in known depocenters of former and modern ice streams

glacimarine sedimentation in kangerdluk disko fjord west greenland in response to a surging glacier abstract beginning in 1995 a large outlet glacier of the sermersauq ice cap on disko island surged 10 5 km downvalley to within 10 km of the head of the fjord kuannersuit sulluat reaching its maximum extent in summer 1999 before beginning to retreat sediment discharge to the fjord increased from 13 10 3 t day 1 in 1997 to 38 10 3 t day 1 in 1999 ctd results sediment traps and cores from the 2000 melt season document the impact of the surge on the glacimarine environment of the fjord within 4 km of the inflow sedimentation rates increased by 30 times over those before the surge reaching an estimated maximum value of 29 cm a 1 up to 4 2 mm day 1 between 24 july and 9 september 2000 fine grained deposits from suspension in the water column displayed diurnal laminations in response to the interaction of tidal cycles with the sediment plume these are not found in the sediments deposited before surging thin beds of sandy turbidites from turbidity currents originating from slope failures on the delta front occurred at about 20 day intervals during the melt season each of these effects was limited to within several kilometres of the point of inflow but provide a unique signal significantly different from those generated by normal hydroclimatically induced events

worldwide distribution of continental rock lithology implications for the atmospheric soil co2 uptake by continental weathering and alkalinity river transport to the oceans 1 the silicate rock weathering followed by the formation of carbonate rocks in the ocean transfers co2 from the atmosphere to the lithosphere this co2 uptake plays a major role in the regulation of atmospheric co2 concentrations at the geologic timescale and is mainly controlled by the chemical properties of rocks this leads us to develop the first world lithological map with a grid resolution of 1 1 this paper analyzes the spatial distribution of the six main rock types by latitude continents and ocean drainage basins and for 49 large river basins coupling our digital map with the gem co2 model we have also calculated the amount of atmospheric soil co2 consumed by rock weathering and alkalinity river transport to the ocean among all silicate rocks shales and basalts appear to have a significant influence on the amount of co2 uptake by chemical weathering

impact of atmospheric co2 levels on continental silicate weathering 1 anthropogenic sources are widely accepted as the dominant cause for the increase in atmospheric co2 concentrations since the beginning of the industrial revolution here we use the b witch model to quantify the impact of increased co2 concentrations on co2 consumption by weathering of continental surfaces b witch couples a dynamic biogeochemistry model lpj and a process based numerical model of continental weathering witch it allows simultaneous calculations of the different components of continental weathering fluxes terrestrial vegetation dynamics and carbon and water fluxes the co2 consumption rates are estimated at four different atmospheric co2 concentrations from 280 up to 1120 ppmv for 22 sites characterized by silicate lithologies basalt granite or sandstones the sensitivity to atmospheric co2 variations is explored while temperature and rainfall are held constant first we show that under 355 ppmv of atmospheric co2 b witch is able to reproduce the global pattern of weathering rates as a function of annual runoff mean annual temperature or latitude for silicate lithologies when atmospheric co2 increases evapotranspiration generally decreases due to progressive stomatal closure and the soil co2 pressure increases due to enhanced biospheric productivity as a result vertical drainage and soil acidity increase promoting co2 consumption by mineral weathering we calculate an increase of about 3 of the co2 consumption through silicate weathering mol ha 1 yr 1 for 100 ppmv rise in co2 importantly the sensitivity of the weathering system to the co2 rise is not uniform and heavily depends on the climatic lithologic pedologic and biospheric settings