recent progress in snow and ice research a review of snow and ice research in 1987 1990 is presented focusing on the effects of layers in seasonal snow covers ice mechanics on fresh water and sea ice and remote sensig of polar ice sheets these topics provide useful examples of general needs in snow and ice research applicable to most areas such as better representation in models of detailed processes controlled laboratory experiments to quantify processes and field studies to provide the appropriate context for interpretation of processes from remote sensing

dispersion of sea ice in the bering sea the dispersion of sea ice in the bering sea is analyzed in terms of the changes in separation between pairs of ice floes the statistics of these changes depend on the separation itself and on the time interval over which the changes are measured rather than being constant as in the case of molecular or fickian diffusion the diffusivity increases according to the 1 8 power of the separation for short times the diffusivity is proportional to time for times greater than 3 days the diffusivity appears to approach a constant value for any particular separation comparison with other data shows that the ice floe diffusivity is about an order of magnitude smaller than the diffusivity at the surface of the temperate ocean and about an order greater than the diffusivity of sea ice in the beaufort sea

structural analysis of the baolun gold deposit hainan island south china implications for metallogeny abstract the baolun gold deposit is a mesothermal orogenic gold deposit located in the southwestern part of hainan island south china the deposit comprises a series of nnw trending quartz sulfide lodes situated within a parallel array of fault zones traversing a sequence of variably foliated flysch siliciclastic rocks of the lower silurian detailed field mapping documented at least five phases of deformation in the deposit including nnw trending folding of the lower silurian rocks d1 development of nnw trending steeply dipping ductile shear zones with an oblique dextral sense corresponding to nne ssw shortening d2 wnw ese shortening and extension associated with an early oblique sinistral ductile shearing along the nnw trending fault zones d3 ene wsw shortening d4 and near n s extension d5 the gold bearing quartz lodes cut the strata folded in the d1 show some laminar layering related to ductile shear in the d2 and are overprinted by brittle structures formed in the d3 to d5 40 ar 39 ar dating on muscovite from an auriferous quartz lode yielded an age of 242 2 5 ma which together with the age of 232 2 5 ma for an aplite vein in the deposit suggests that the mineralization may be related to a tectono thermal event in the triassic in the context of the southern south china plate tectonics the formation of the baolun gold deposit is interpreted to be related to the oblique dextral ductile shearing d2 along the nnw trending fault zones during the indosinian orogeny in relation to the convergence between the indochina and south china plates

inversion of field data in fault tectonics to obtain the regional stress i single phase fault populations a new method of computing the stress tensor summary we attempt a general definition of the inverse problem of computing the components of the regional stress tensor from a set of field data including the measurements of the strike and dip of several faults and the directions and senses of relative motion along these faults as indicated by slickenslides in previous treatments of this problem no experimental errors could be taken into account except those in measuring the pitch of slickenslides thus errors in the orientation of the fault strike and dip which have considerable practical importance were neglected in our work all experimental errors in the field measurements are taken into account so that the agreement between the computed stress tensor and the set of field measurements can be rigorously checked

the role of plastic ice interaction in marginal ice zone dynamics under appropriate conditions the nonlinear nature of plastic ice interaction together with a nonlinear coupling between ice thickness characteristics and ice rheology can substantially modify the character of marginal ice zone dynamics this paper examines the steady state ramifications of these nonlinearities by using a one dimensional simplification of hibler s 1979 two level viscous plastic sea ice model a series of idealized small scale simulations 4 km resolution are carried out with the model formulated in a moving lagrangian grid in order to remove diffusion effects analytic solutions for the equilibrium plastic adjustment case are also constructed the results show that if the ice thickness distribution is allowed to equilibrate in response to a constant wind field the thickness strength coupling will yield a sharp ice edge with the compactness dropping rapidly to zero near the ice margin despite this compactness falloff the steady adjusted ice velocity is nearly constant across the marginal ice zone however the adjustment to a steady state constant velocity can be preceded by a period of shearing which will abate as the ice strengthens by ridging with an increase in forcing near the edge the ice velocity scales with the wind velocity but with a speed less than free drift in the absence of water drag and wind stress the model exhibits a very slow outward creep but yields no ice edge jet effects the ramifications of plastic interaction on upwelling and downwelling are also examined with the same drag coefficients over ice and ocean and for a north south ice edge the model yields in the northern hemisphere upwelling for northward winds downwelling for southward winds and no effect for off ice winds

mesoscale sea ice deformation in the east greenland marginal ice zone in this paper mesoscale 10 km ice kinematics data obtained during the drift phase of the 1983 marginal ice zone experiment are analyzed the measurements were made with a microwave transponder system accurate to better than 1 m from the point of view of granular media theory the ice pack was close to ideal over the scale of the array the pack was quite regular with floes of relatively uniform size closely packed together the main external driving force for the ice was the ocean current simultaneous current measurements were made at three of the strain array sites the ice behaved in a relatively rigid manner with more shear than dilatation occurring least squares fits of the strain rate tensor showed the deformation field to be quite homogeneous superimposed on the rigid motion were smaller fluctuations with a spectrum falling off proportional to frequency to the power of 3 2 to 2 close examination of individual strain lines showed rather discontinuous distance changes more representative of plastic slip rather than floe bumping although a substantial signal at the inertial period was present in the absolute drift no clear peaks at this period occurred in the spectra of the strain rate tensor invariants analysis of the spatial variation of the underlying ocean currents revealed quite a different picture from that of the ice kinematics in particular the current field exhibited a much greater spatial variability than the ice motion with considerable variance at the inertial period coherence between the ice and ocean differential velocity was small for all frequencies overall the rigid interactive character of the compact ice cover prevented most of the differential ocean currents from being transferred to the differential ice motion

an inverse problem in microtectonics for the determination of stress tensors from fault striation analysis abstract a method is proposed to compute some characteristics of a possible stress tensor related to striations measured in a given faulted area if several tectonic phases are responsible for the striations the method separates and determines the successive stress tensors the iterative algorithm consists of alternatively a sorting the data attributed to a tectonic phase and b computing the characteristics of the stress tensor of this phase the method is tested using an application to synthetic and actual data

a dynamic and thermodynamic sea ice model for subpolar regions a mesoscale dynamic thermodynamic sea ice model is presented the model differs from the large scale sea ice model hibler 1979 parkinson and washington 1979 in both the dynamic and thermodynamic parts in the dynamic calculation a constitutive relation based on ice floe collision is used for the determination of the internal ice force in the marginal ice zone miz while in the thermodynamic calculation a three level approach for the ice thickness distribution is adopted instead of the common two level approach hibler 1979 the simulation results from the mesoscale sea ice model show that the three level approach is more sensitive to geophysical forcing than the two level approach thus it is demonstrated that the mesoscale sea ice model has the potential of a more accurate description of the dynamics and the thermodynamics than the previous models in the simulation of sea ice processes in subpolar regions giving the exact initial conditions and the atmospheric and oceanic forcings this model can be used as a sea ice forecasting model in subpolar regions

marginal ice zone rheology comparison of results from continuum plastic models and discrete particle simulations computer simulations of ice behaviour in the marginal ice zone miz are described two cases were studied a constant velocity wind blowing at certain angle with respect to the coast in what can be considered a simplified miz problem and a vortex wind force field the viscous plastic approach of hibler has been used to model the ice rheology we study the effects of adopting two different rheologies cavitating fluid and mohr coulomb the introduction of shear strength effects through a mohr coulomb yield criterion plays an important role in determining ice drift velocities in the miz the effects that ice floe collisions can have in determining the ice rheological behavior have been tested by using discrete particle simulations in order to do so simulations for the miz were performed using different mean floe sizes as well as different miz widths and wind conditions the predictions of the discrete particle simulations are in general agreement with the results obtained by using the mohr coulomb rheology in the viscous plastic model the continuum models were solved by using a fully lagrangian method known as smoothed particle hydrodynamics sph the method has the advantage of the lagrangian techniques in avoiding problems of numerical diffusion an additional advantage of sph in comparison with classical lagrangian approaches is that sph does not need grids and this makes it well suited to handle problems of large deformations

study of the characteristics of crustal stress field in east china by inversion of nodal plane data abstract we combine a search procedure with an optimization procedure to invert for the average stress tensor and apply this method to the study of the crustal stress field using the data from nodal plane solutions of p wave first motion from the analysis of data from haicheng tangshan xingtai anyang liyang taiwan fujian and guangdong we have obtained the characteristics of the crustal stress field of east china the directions of the principal pressure stress always possess a small dip angle but the azimuths vary from ene in northern east china to ese in the southern part this pattern is probably related to the effects of convergence of the northwestern pacific plate from the east northeast and the philippine plate from the east southeast

modeling linear kinematic features in sea ice abstract sea ice deformation is localized in narrow zones of high strain rate that extend hundreds of kilometers for example across the arctic basin this paper demonstrates that these failure zones may be modeled with a viscous plastic sea ice model using an isotropic rheology if the ice is assumed to be heterogeneous at the grid scale and allowed to weaken in time intersecting failure zones propagate across the region the direction of failure propagation depends upon the stress applied to the ice wind stress and boundary conditions and the rheological model describing plastic failure of the ice the spacing between failure zones is controlled by the magnitude of the wind stress and the distribution describing spatial variability of ice strength sea ice motion and deformation oscillate at close to a 12 h period throughout the arctic and antarctic pack ice this oscillation is found at all spatial scales from hundreds of kilometers to the lead scale it is shown that with an inertial embedded mo

a proposed new type of arsenian pyrite composition nanostructure and geological significance this report describes a new form of arsenian pyrite called as3 pyrite in which as substitutes for fe fe as s2 in contrast to the more common form of arsenian pyrite as1 pyrite in which as1 substitutes for s fe as s 2 as3 pyrite has been observed as colloformic overgrowths on as free pyrite in a hydrothermal gold deposit at yanacocha peru xps analyses of the as3 pyrite confirm that as is present largely as as3 empa analyses show that as3 pyrite incorporates up to 3 05 at of as and 0 53 at 0 1 at 0 27 at 0 22 at 0 08 at and 0 04 at of pb au cu zn ni and co respectively incorporation of as3 in the pyrite could be written like as3 y au 1 y 2 fe2 where au and vacancy help to maintain the excess charge hrtem observations reveal a sharp boundary between as free pyrite and the first overgrowth of as3 pyrite 20 40 nm thick and co linear lattice fringes indicating epitaxial growth of as3 pyrite on as free pyrite overgrowths of as3 pyrite onto as free pyrite can be divided into three groups on the basis of crystal size 8 20 nm 100 300 nm and 400 900 nm and the smaller the crystal size the higher the concentration of toxic arsenic and trace metals the yanacocha deposit in which as3 pyrite was found formed under relatively oxidizing conditions in which the dominant form of dissolved as in the stability field of pyrite is as3 in contrast reducing conditions are typical of most environments that host as1 pyrite as3 pyrite will likely be found in other oxidizing hydrothermal and diagenetic environments including high sulfidation epithermal deposits and shallow groundwater systems where probably kinetically controlled formation of nanoscale crystals such as observed here would be a major control on incorporation and release of as3 and toxic heavy metals in oxidizing natural systems

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

a reassessment of the stress and natural fracture orientations from analysis of image logs in the chinese continental scientific drilling program borehole at donghai county jiangsu province china abstract the chinese continental scientific drilling ccsd project has drilled a 5100 m deep research borehole in the sulu ultra high pressure uhp metamorphic belt eastern china the uhp metamorphic belt is thought to be a product of continent continent collision and has consequently experienced very intensive structural deformation based on a more complete well log data set of ccsd borehole we can have a more detailed and reliable study on the structure features of borehole wall and other rock physical properties than a previous study published in 2009 abundant data related to borehole breakouts bos drilling induced tensile fractures ditfs and natural fractures were collected from the image logs the bo and ditf data indicate that the average direction of the maximum horizontal principal stress sh of the ccsd borehole site is about 79 2 which is consistent with the convergent direction e w of the pacific sea plate with respect to the eurasian plate analysis of ditfs indicated that in the case of the ccsd borehole axial drilling induced tensile fractures aditfs occur occasionally in the upper section 0 2300 m of the borehole with low dipping angle 0 10 while transverse drilling induced tensile fractures tditfs occur significantly in the lower section 3800 5000 m with high dipping angle 10 30 the natural fracture distribution at depth in the metamorphic rocks of the ccsd borehole indicates that 1 the failure strength of rocks and borehole depth are two factors that affects natural fracture frequency 2 most of the dip azimuth of natural fractures is consistent with the dip azimuth of foliations observed in the core 3 the development of most of the natural fractures probably was dominated by the development of foliations and both the natural fractures and foliations developed in response to the subduction and exhumation of the sulu terrene

the occurrence and geochemistry of arsenic in groundwaters of the newark basin of pennsylvania abstract elevated as concentrations in groundwater in the eastern united states have been recognized predominantly in the accretionary geologic terranes of northern new england a retrospective examination of more than 18 000 existing groundwater samples from the pennsylvania department of environmental protection pa dep drinking water and sampling information system database indicates that elevated groundwater as concentrations occur throughout the northern half of the piedmont province of pennsylvania chemical analyses of 53 samples collected in 2005 from drinking water wells in this area all had detectable as and 23 of these samples contained elevated 133 nmol l or 10 g l concentrations of as elevated concentrations of as in the groundwater samples were most common in the mesozoic sedimentary strata composed of sandstone and red mudstone with interbedded gray shale and gray to black siltstone and shale arsenic was typically not elevated in groundwater of diabase intrusions of the newark basin or in crystalline and calcareous aquifers to the north of the newark basin geochemical parameters such as ph and oxidation reduction potential can indicate mobility mechanisms of as in some regions in this area measured groundwater conditions were predominantly oxidizing eh 50 mv and more than 85 of samples contained arsenate as the dominant as species variations in ph were strongly correlated to the as concentration with highest as concentrations observed at ph values greater than 6 4 the original source of as is most likely the black and gray shales that contain some arsenian pyrite with groundwater concentrations likely to be controlled by adsorption desorption reactions with fe oxides in the red mudstone aquifer materials

arsenic release and attenuation in a multilayer aquifer in the po plain northern italy reactive transport modeling abstract groundwater as concentrations who limit 10 g l are frequently found in the po plain n italy although several hypotheses on as mobilization exist i e reductive dissolution driven by peat degradation the mechanisms of as release and subsequent attenuation acting in the multilayer aquifer in the po plain were poorly understood the present work aims at implementing a reactive transport modeling of the aquifer system in cremona affected by as the model based on a partial equilibrium approach revealed that the observed as fe and mn chemistry could be mostly explained by the simultaneous equilibrium between fe oxide and sulfate reduction and fes precipitation and by the equilibrium of rhodochrosite precipitation dissolution model results together with litholog analysis supported the assumption of peat as the likely source of organic matter driving as release the model fitted to measured data showed that the peak in the organic carbon degradation rate at 20 40 m below surface average of 0 67 mm y corresponding to the shallow peaty aquitard and the upper portion of the underlying semiconfined aquifer is associated with the peak of net release of as average of 0 32 m y that is followed just downstream by a net precipitation in iron sulfides at 40 60 m below surface average of 0 30 m y these results support the assumptions of peaty aquifers as drivers of as release and iron sulfides as as traps the model also outlined the following aspects that could have a broad applicability in other alluvial as affected aquifers worldwide a shallow peaty aquitards may have a greater role in driving the as release since they likely have young and more reactive organic matter b the occurrence of fe oxide reduction and fes precipitation that represent the as source and sink together with sulfate reduction occurring simultaneously close to equilibrium may restrict the as mobility limiting the extent of contamination just downstream the source of organic matter that drives its release

arsenic incorporation into authigenic pyrite bengal basin sediment bangladesh abstract sediment from two deep boreholes 400 m approximately 90 km apart in southern bangladesh was analyzed by x ray absorption spectroscopy xas total chemical analyses chemical extractions and electron probe microanalysis to establish the importance of authigenic pyrite as a sink for arsenic in the bengal basin authigenic framboidal and massive pyrite median values 1500 and 3200 ppm as respectively is the principal arsenic residence in sediment from both boreholes although pyrite is dominant ferric oxyhydroxides and secondary iron phases contain a large fraction of the sediment bound arsenic between approximately 20 and 100 m which is the depth range of wells containing the greatest amount of dissolved arsenic the lack of pyrite in this interval is attributed to rapid sediment deposition and a low sulfur flux from riverine and atmospheric sources the ability of deeper aquifers 150 m to produce ground water with low dissolved arsenic in southern bangladesh reflects adequate sulfur supplies and sufficient time to redistribute the arsenic into pyrite during diagenesis

an improved method for determining the regional stress tensor using earthquake focal mechanism data application to the san fernando earthquake sequence the orientations of fault planes and slip directions indicated by a population of earthquake focal mechanisms can be used to determine best fit regional principal stress directions and r 2 1 3 1 a measure of relative stress magnitudes under the assumption of uniform stress in the source region this analysis allows for the possibility that failure occurs on preexisting zones of weakness of any orientation in the inversion we perform a grid search of stress models to find the one which requires the smallest total rotation of all the fault planes that is needed to match the observed and predicted slip directions the method allows for errors in orientations of both the fault planes and slip directions we have an objective means for identifying the more likely of the two possible fault planes from each focal mechanism relative to a given stress model thus we do not face the problem of ambiguity of nodal planes which plagues other analyses of this kind by using a grid search of stress models rather than a linearization scheme we are able to perform a realistic error analysis and thus establish confidence limits for the preferred regional stresses the method can be used to investigate possible stress inhomogeneities during earthquake sequences by analyzing subsets of the data population the technique has been applied to 76 events from the san fernando earthquake sequence for which we have found best fit stresses plunge and azimuth 1 7 187 2 27 281 3 62 84 and r 0 65 the average misfit between this stress model and all the data is about 8 and all but eight of the aftershocks have misfits of less than 20 these values are considerably less than the uncertainty of the focal mechanism determinations therefore significant stress inhomogeneities are not required by the data our analysis does not support the suggestion of a change in stresses during the aftershock sequence as proposed by others on the basis of an apparent change in focal mechanisms

the role of floe collisions in sea ice rheology a collisional rheology for an idealized two dimensional flow of a fragmented ice field is derived this fragmented ice field is modeled as an assembly of identical smooth disks collisions between neighboring disks are caused by the mean deformation field these collisions transfer momentum which produces the internal stresses in the deforming ice field by equating the collisional energy losses to the deformational energy a relationship between the stress and strain rate is quantified to demonstrate the essential idea an analytical derivation is first given under quite restricted assumptions a monte carlo simulation is then developed to provide a more general approach for the analysis it is found that the collisional stresses are proportional to the square of disk diameter and the square of the deformation rate the magnitude of stresses is also found to increase rapidly as the collisional restitution of disks increases the collisional rheology yields zero tensile strength the associated normal flow rule commonly used in the plastic rheology is not valid in the collisional rheology it is found that the collisional stresses are very small consequently the resulting stress divergence is estimated to be much lower than the air stress typically encountered in the marginal ice zone however these collisional stresses become singular as the maximum compactness is reached indicating that a different mechanism may exist in that extreme

on the role of ice interaction due to floe collisions in marginal ice zone dynamics a constitutive relation based on floe collisions as introduced by shen et al 1986 is used in a sea ice model for calculating the internal ice force the formulation is generalized to collisions of discs of two sizes and of multiple sizes and a comparison with existing constitutive models is presented a coupling of the floe collision model with a viscous plastic model hibler 1977 in the simulation of mesoscale sea ice processes in subpolar regions is suggested in order to account for the marginal ice zone dynamics

speciation and natural attenuation of arsenic and iron in a tidally influenced shallow aquifer abstract the mobility of subsurface arsenic is controlled by sorption precipitation and dissolution processes that are tied directly to coupled redox reactions with more abundant but spatially and temporally variable iron and sulfur species adjacent to the site of a former pesticide manufacturing facility near san francisco bay california usa soil and groundwater arsenic concentrations are elevated in sediments near the prior source but decrease to background levels downgradient where shallow groundwater mixes with infiltrating tidal waters at the plume periphery which has not migrated appreciably in over two decades of monitoring we used synchrotron x ray absorption spectroscopy together with supporting characterizations and sequential chemical extractions to directly determine the oxidation state of arsenic and iron as a function of depth in sediments from cores recovered from the unsaturated and saturated zones of a shallow aquifer to 3 5 m below the surface arsenic oxidation state and local bonding in sediments as as sulfide as iii oxide or as v oxide were related to lithologic redox horizons and depth to groundwater based on arsenic and iron speciation three subsurface zones were identified i a shallow reduced zone in which sulfide phases were found in either the arsenic spectra realgar like or orpiment like local structure the iron spectra presence of pyrite or both with and without as iii or as v coordinated by oxygen ii a middle transitional zone with mixed arsenic oxidation states as iii o and as v o but no evidence for sulfide phases in either the arsenic or iron spectra and iii a lower oxidized zone in the saturated freshwater aquifer in which sediments contained only oxidized as v and fe iii in labile non detrital phases the zone of transition between the presence and absence of sulfide phases corresponded to the approximate seasonal fluctuation in water level associated with shallow groundwater in the sand dominated lower oxic zone total sediment arsenic concentrations showed a minimum in the transition zone and an increase in the oxic zone particularly in core samples nearest the former source equilibrium and reaction progress modeling of aqueous sediment reactions in response to decreasing oxidation potential were used to illustrate the dynamics of arsenic uptake and release in the shallow subsurface arsenic attenuation was controlled by two mechanisms precipitation as sulfide phases under sulfate reducing conditions in the unsaturated zone and adsorption of oxidized arsenic to iron hydroxide phases under oxidizing conditions in saturated groundwaters this study demonstrates that both realgar type and orpiment type phases can form in sulfate reducing sediments at ambient temperatures with realgar predicted as the thermodynamically stable phase in the presence of pyrite and as iii under more reduced conditions than orpiment field and modeling results indicate that the potential for release of arsenite to solution is maximized in the transition between sulfate reduced and iron oxidized conditions when concentrations of labile iron are low relative to arsenic ph controlled arsenic sorption is the primary attenuation mechanism and mixed fe ii iii oxide phases do not form and generate new sorption sites

sediment pore water interactions associated with arsenic and uranium transport from the north cave hills mining region south dakota usa abstract the extent of historical u mining impacts is well documented for the north cave hills region of harding county south dakota usa while previous studies reported watershed sediment and surface water as and u concentrations up to 90 established background concentrations it was unclear whether or how localized changes in sediment redox behavior may influence contaminant remobilization five pore water equilibration samplers peepers were spatially and temporally deployed within the study area to evaluate seasonal solid liquid as and u distributions as a function of sediment depth pore water and solid phase as and u concentrations fe speciation eh and ph were measured to ascertain specific geochemical conditions responsible for as and u remobilization and transport behavior at a mine overburden sedimentation pond adjacent to the mine sites high total aqueous as and u concentrations 4920 and 674 g l respectively were found within surface water during summer sampling however pond dredging prior to autumn sampling resulted in significantly lower aqueous as and u concentrations 579 and 108 g l respectively however both as and u still exceeded regional background concentrations 20 and 18 g l respectively at a wetlands dominated deposition zone approximately 2 km downstream of the sedimentation pond pore water geochemical conditions varied seasonally summer conditions promoted reducing conditions in pore water resulting in active release of as iii to the water column autumn conditions promoted oxidizing conditions decreasing pore water as aspw 5 and increasing upw 10 peak u pore water concentrations 781 g l were 3 5 greater than determined for the surface water 226 g l and approximately 40 background concentrations at the bowman haley reservoir backwaters 45 km downstream from the mine sites as and u pore water concentrations increased significantly between the summer and autumn deployments attributed to increased fe reduction processes geochemical modeling suggests solid phase fe reduction promotes the liberation of pore water as and u via suppressing the formation of thioarsenite intermittent hydrological processes facilitate as and u transport and deposition throughout the watershed while biogeochemical influenced redox changes cycle as and u between pore and surface water within localized environments

under ice noise resulting from thermally induced fracturing of the arctic ice pack theory and a test case application a theory is presented that relates thermally induced fracturing of pack ice to under ice noise level variations it begins with the governing equations for the thermomechanics of pack ice the thermomechanics relates thermally induced strain rates to the stresses within various vertical layers of the floe in addition paradigms are developed which specify the relative quantity of fracturing and stress relief in the floe as the tensile yield strength of the ice is exceeded the thermomechanics is complemented by an acoustic propagation model that relates the number of fracture events at a given time to the acoustic levels at arbitrary frequency and depth below the ice the acoustic theory assumes that each fracture acts as a simple monopole source the fractures are evenly distributed horizontally and the energy of each fracture propagates through the ice and the water column on the basis of the governing equations for elastic waves in a horizontally stratified medium the results indicate that noise episodes resulting from fracturing occurring over the top 40 cm of a 160 cm thick floe will propagate over distances of up to 100 km however noise episodes associated with fracturing occurring in the lower 100 cm of the floe will only propagate over a range of 10 km the thermomechanics and acoustic propagation theories were used to develop a numerical model for predicting under ice noise levels for a given thermal forcing of floes within the arctic ice pack the model was used to simulate stresses in a multiyear floe and under ice noise levels at 500 hz at 305 m below the floe model predicted ice stresses and under ice noise levels compare quite well to observed stresses and noise variations during the fall of 1988 in the eastern arctic ocean the model predicts that most of the thermally induced under ice noise at 500 hz was a result of fracturing occurring between 5 and 30 cm below the ice surface for a 1 6 m thick multiyear floe

dependence of ph in coastal waters on the adsorption of protons onto sediment minerals we measured ph total alkalinity talk dissolved inorganic carbon dic and 13c dic in groundwater of a subterranean estuary in hwasun bay in the volcanic island of jeju korea in the sandy aquifer the ph values 7 4 0 2 of fresh groundwater increased sharply to 10 and then behaved conservatively in the mixing zone between alkalified fresh groundwater and seawater the distributions of 13c dic ca2 and mg2 in coastal groundwater along with the results from lab experiments on sediment columns suggest that the increase of ph in this subterranean estuary is associated with the adsorption of protons protonation onto sandy sediments rather than other geochemical processes our lab experiments showed that the protonation 1 occurs commonly for various sediments of jeju island 2 increases ph effectively for low salinity salinity 10 groundwater and 3 depends on the relative amount of transition metal i e fe ti and mn oxides the chamber experiments at the interface of seawater and groundwater indicate the direct seepage of high ph water into the ocean this increase in ph leads to corresponding uptake of co2 from the atmosphere thus our result suggests that the reaction between groundwater and coastal sediments should be considered as an important driver of ph change that regulates the magnitude of chemical species in coastal groundwater seeping into the ocean at the volcanic island jeju korea