u sr isotopic speedometer fluid flow and chemical weathering rates in aquifers abstract both chemical weathering rates and fluid flow are difficult to measure in natural systems however these parameters are critical for understanding the hydrochemical evolution of aquifers predicting the fate and transport of contaminants and for water resources water quality considerations 87 sr 86 sr and 234 u 238 u activity ratios are sensitive indicators of water rock interaction and thus provide a means of quantifying both flow and reactivity the 87 sr 86 sr values in ground waters are controlled by the ratio of the dissolution rate to the flow rate similarly the 234 u 238 u ratio of natural ground waters is a balance between the flow rate and the dissolution of solids and recoil loss of 234 u from the solids by coupling these two isotope systems it is possible to constrain both the long term ca 100 s to 1000 s of years flow rate and bulk dissolution rate along the flow path previous estimates of the ratio of the dissolution rate to the infiltration flux from sr isotopes 87 sr 86 sr are combined with a model for 234 u 238 u to constrain the infiltration flux and dissolution rate for a 70 m deep vadose zone core from hanford washington the coupled model for both 234 u 238 u ratios and the 87 sr 86 sr data suggests an infiltration flux of 5 2 mm yr and bulk silicate dissolution rates between 10 15 7 and 10 16 5 mol m 2 s the process of recoil enrichment while primarily responsible for the observed variation in 234 u 238 u of natural systems is difficult to quantify however the rate of this process in natural systems affects the interpretation of most u series data models for quantifying the recoil loss fraction based on geometric predictions surface area constraints and chemical methods are also presented the agreement between the chemical and theoretical methods such as direct measurement of 234 u 238 u of the small grain size fraction and geometric calculations for that size fraction is quite good

new constraints on the active tectonic deformation of the aegean 1 site velocities from six separate global positioning system gps networks comprising 374 stations have been referred to a single common eurasia fixed reference frame to map the velocity distribution over the entire aegean we use the gps velocity field to identify deforming regions rigid elements and potential microplate boundaries and build upon previous work by others to initially specify rigid elements in central greece the south aegean anatolia and the sea of marmara we apply an iterative approach tentatively defining microplate boundaries determining best fit rigid rotations examining misfit patterns and revising the boundaries to achieve a better match between model and data short term seismic cycle effects are minor contaminants of the data that we remove when necessary to isolate the long term kinematics we find that present day aegean deformation is due to the relative motions of four microplates and straining in several isolated zones internal to them the rms misfit of model to data is about 2 sigma very good when compared to the typical match between coseismic fault models and gps data the simplicity of the microplate description of the deformation and its good fit to the gps data are surprising and were not anticipated by previous work which had suggested either many rigid elements or broad deforming zones that comprise much of the aegean region the isolated deforming zones are also unexpected and cannot be explained by the kinematics of the microplate motions strain rates within internally deforming zones are extensional and range from 30 to 50 nanostrain year nstrain year 10 9 year 1 to 2 orders of magnitude lower than rates observed across the major microplate boundaries lower strain rates may exist elsewhere within the microplates but are only resolved in anatolia where extension of 13 4 nstrain year is required by the data our results suggest that despite the detailed complexity of active continental deformation revealed by seismicity active faulting fault geomorphology and earthquake fault plane solutions continental tectonics at least in the aegean is to first order very similar to global plate tectonics and obeys the same simple kinematic rules although the widespread distribution of aegean seismicity and active faulting might suggest a rather spatially homogeneous seismic hazard the focusing of deformation near microplate boundaries implies the highest hazard is comparably localized

strontium isotopes as tracers to delineate aquifer interactions and the influence of rainfall in the basalt plains of southeastern australia summary to better understand the spatial distribution of groundwater salinisation in western victoria southeast australia the interactions between a surficial basalt aquifer and an underlying extensive palaeodrainage deep lead system were studied using a multi disciplinary approach combining strontium isotope analyses with major ion chemistry and the interpretation of geological and hydrogeological data the strontium isotopes proved particularly useful in delineating flow paths and hydraulic connections between the two aquifers which have contrasting 87sr 86sr ratios the freshest basalt groundwaters lie beneath volcanoes and have 87sr 86sr signatures close to the whole rock strontium isotope ratios of the basalts 0 7045 indicating the strong influence of basalt weathering with increasing distance from the eruption points basalt groundwaters become progressively more saline and the strontium isotope ratios evolve towards the more radiogenic signatures of local rainfall 0 710 0 711 due to the slow addition of infiltration concentrated by evapotranspiration during its passage through the thick clay rich soils developed on the basalt lavas overall the influence of rainwater on the strontium isotope signatures of the basalt groundwater is much greater than that of basaltic weathering indicating that rainwater can play a greater role in determining groundwater strontium composition than is often realised most parts of the palaeodrainage system beneath the basalt are preferentially recharged through the volcanoes as shown by strong downwards hydraulic gradients and groundwater 87sr 86sr ratios similar to the least radiogenic basalt groundwaters however in the northwestern part groundwater 87sr 86sr ratios are closer to those of the source material of the sediments palaeozoic bedrock indicating that here recharge occurs predominantly in the headwaters where the basalts are absent in the southern and western sections of the palaeodrainage system there is an upward flux into the overlying basalts as shown by strong upward hydraulic gradients and elevated strontium isotope signatures in basalt groundwaters this occurs because lateral groundwater flow in the palaeodrainage system is restricted by shallow subsurface basement ridges and ultimately discharges to the surface as salt lakes

observations of thermal diffusivity and a relation to the porosity of tidal flat sediments 1 time series observations of vertical profiles of sediment temperature are presented for several locations at two distinct tidal flats surface sediment temperatures are shown to be strongly dependent on solar insolation during low tide exposure and that signal is communicated to the subsurface sediment temperatures a vertical diffusion balance explains the observations well up to 97 of the observed variance at some locations and 76 on average and an estimate of thermal diffusivity is obtained for each location a theoretical model relating sediment porosity to thermal diffusivity is presented and shown to agree with independent estimates of porosity in addition thermal diffusivity is shown to correlate with direct observations of sediment composition percent sand and surface strength results are suggested for application to remote classification of sediments using infrared time series images

strontium isotope geochemistry of groundwater affected by human activities in nandong underground river system china abstract the nandong underground river system nurs is located in a typical karst area dominated by agriculture in se yunnan province china groundwater plays an important role in the social and economical development in the area the effects of human activities agriculture and sewage effluents on the sr isotope geochemistry were investigated in the nurs seventy two representative groundwater samples which were collected from different aquifers calcite and dolomite under varying land use types both in summer and winter showed significant spatial differences and slight seasonal variations in sr concentrations and 87sr 86sr ratios agricultural fertilizers and sewage effluents significantly modified the natural 87sr 86sr ratios signature of groundwater that was otherwise dominated by water rock interaction three major sources of sr could be distinguished by 87sr 86sr ratios and sr concentrations in karst groundwater two sources of sr are the triassic calcite and dolomite aquifers where waters have low sr concentrations 0 1 0 2 mg l and low 87sr 86sr ratios 0 7075 0 7080 and 0 7080 0 7100 respectively the third source is anthropogenic sr from agricultural fertilizers and sewage effluents with waters affected having radiogenic 87sr 86sr ratios 0 7080 0 8352 for agricultural fertilizers and 0 7080 0 7200 for sewage effluents respectively with higher sr concentrations 0 24 0 51 mg l due to the overlapping 87sr 86sr ratios it is difficult to distinguish the sources of sr in groundwater samples contaminated by agricultural fertilizers or sewage effluents based only on their 87sr 86sr ratios however 87sr 86sr ratios do provide key information for natural and anthropogenic sources in karst groundwater

vadose zone infiltration rate at hanford washington inferred from sr isotope measurements i sr isotope ratios were measured in the pore water acid extracts and sediments of a 70 m vadose zone core to obtain estimates of the long term infiltration flux for a site in the hanford doe complex in eastern washington state the 8 7 sr 8 6 sr values for the pore waters decrease systematically with depth from a high value of 0 721 near the surface toward the bulk sediment average value of 0 711 estimates of the bulk weathering rate combined with sr isotopic data were used to constrain the long term century to millenial scale natural diffuse infiltration flux for the site given both steady state and nonsteady state conditions the models suggest that the infiltration flux for the site is 7 3 mm yr the method shows potential for providing long term in situ estimates of infiltration rates for deep heterogeneous vadose zones

groundwater fast paths in the snake river plain aquifer radiogenic isotope ratios as natural groundwater tracers preferential flow paths are expected in many groundwater systems and must be located because they can greatly affect contaminant transport the fundamental characteristics of radiogenic isotope ratios in chemically evolving waters make them highly effective as preferential flow path indicators these ratios tend to be more easily interpreted than solute concentration data because their response to water rock interaction is less complex we demonstrate this approach with groundwater sup 87 sr sup 86 sr ratios in the snake river plain aquifer within and near the idaho national engineering and environmental laboratory these data reveal slow flow zones as lower sup 87 sr sup 86 sr areas created by prolonged interaction with the host basalts and a relatively fast flowing zone as a high sup 87 sr sup 86 sr area

case for periodic colossal jokulhlaups from pleistocene glacial lake missoula two classes of field evidence firmly establish that late wisconsin glacial lake missoula drained periodically as scores of colossal jokulhlaups glacier outburst floods 1 more than 40 successive flood laid sand to silt graded rhythmites accumulated in back flooded valleys in southern washington hiatuses are indicated between flood laid rhythmites by loess and volcanic ash beds disconformities and nonflood sediment between rhythmites are generally scant because precipitation was modest slopes gentle and time between floods short 2 in several newly analyzed deposits of pleistocene glacial lakes in northern idaho and washington lake beds comprising 20 to 55 varves average 30 40 overlie each successive bed of missoula flood sediment these and many other lines of evidence are hostile to the notion that any two successive major rhythmites were deposited by one flood they dispel the notion that the prodigious floods numbered only a few the only outlet of the 2 500 km 3 glacial lake missoula was through its great ice dam and so the dam became incipiently buoyant before the lake could rise enough to spill over or around it like grimsvotn iceland lake missoula remained sealed as long as any segment of the glacial dam remained grounded when the lake rose to a critical level 600 m in depth the glacier bed at the seal became buoyant initiating underflow from the lake subglacial tunnels then grew exponentially leading to catastrophic discharge calculations of the water budget for the lake basin including input from the cordilleran ice sheet suggest that the lakes filled every three to seven decades the hydrostatic prerequisites for a jokulhlaup were thus re established scores of times during the 2 000 to 2 500 yr episode of last glacial damming j harlen bretz9s spokane flood outraged geologists six decades ago partly because it seemed to flaunt catastrophism the concept that lake missoula discharged regularly as jokulhlaups now accords bretz9s catastrophe with uniformitarian principles

analysis of temperature variability and determination of apparent thermal diffusivity in sandy intertidal sediments at the german north sea coast abstract temperature was measured at depths of 1 10 30 75 and 170 cm in fine sandy intertidal sediments by means of specially designed temperature lances the measurements cover a period from february to october 2007 and have a temporal resolution of 5 min stochastic as well as recurrent processes due to the solar cycle and due to tide induces flooding and drying of the sediment surface lead to a complex composition of the time series curves spectral analyses based on fast fourier transformation fft reveal that temperature variability at the sediment water air interface is widely controlled by recurrent processes with period lengths of 4 93 6 1 8 19 12 24 h and 354 h 14 7 days the importance of the higher frequencies decreases with increasing sediment depth at a depth of 30 cm the 24 h and the 14 7 days cycles mainly determine the temperature development over time while at 75 cm sediment depth contour temperature varies only along the 14 7 days cycle as well as within the seasonal cycle using cross correlation analysis the time necessary for a temperature signal at the surface to trigger a response at a sediment depth of 10 30 and 75 cm was calculated as 1 4 7 0 and 73 1 h respectively utilizing an alternate approach fft derived temperature peak to peak amplitude values and phase angles of up to 9 different cycles were used to calculate apparent thermal diffusivity in different sediment depths the thermal diffusivity decreases from approximately 6 9 10 7 m 2 s 1 from the surface down to a sediment depth of 75 cm the specially designed instrumentation has proven to be robust and precise enough to record high resolution time series of sediment temperature in different depths the time series analysis of the data clearly shows that the temperature variability in the intertidal sediments to a high degree can be explained by recurrent solar and or tidal effects so the methods and results presented in this paper can help to answer questions which are related to sediment temperature in tidal flat environments

colloid mobilization in an undisturbed sediment core under semiarid recharge rates 1 the semiarid us department of energy hanford site has a deep vadose zone with low recharge rates contaminants originating from nuclear waste processing are expected to move slowly through the vadose zone the movement of certain contaminants can be facilitated by colloids we hypothesized that the low recharge rates and low water contents in semiarid regions however tend to inhibit movement of colloidal particles thereby reducing the risk for colloid facilitated contaminant transport the goal of this study was to investigate whether in situ natural colloids can be mobilized and transported in undisturbed deep vadose zone sediments at the hanford site under typical semiarid recharge rates we sampled an undisturbed sediment core i d 50 cm 59 5 cm height from a depth of 17 m below ground at the hanford 200 area the core was set up as a laboratory lysimeter and exposed to an infiltration rate of 18 mm yr by applying simulated pore water onto the surface particle concentrations were quantified in the column outflow and selected samples were examined microscopically and for elemental composition transmission electron microscopy and energy dispersive x ray measured water contents and potentials were used to calibrate a numerical model hydrus 1d which was then applied to simulate colloid mobilization from the sediment core during 5 3 years of monitoring natural colloids like silicates aluminosilicates and fe oxides were observed in the core outflow indicating the continuous mobilization of in situ colloids the total amount of particles mobilized during 5 3 years corresponded to 1 1 of the total dispersible colloids inside the core comparison of the amounts of colloids released with weathering rates suggests that mineral weathering can be a major source of the mobilized colloids the fitted colloid release rate coefficient was 6 to 7 orders of magnitude smaller than coefficients reported from previous studies where disturbed hanford sediments and higher flow rates were used our findings demonstrate that even under low recharge rates and water contents typical for semiarid deep vadose zone sediments particles can continuously be mobilized although the total mass of particles is low

multiple isotope h o n s and sr approach elucidates complex pollution causes in the shallow groundwaters of the taipei urban area summary deterioration of the quality of groundwater under urban areas has become a major environmental concern worldwide this paper presents a pilot case study in the taipei urban area using multiple stable isotopes d h 2 o and 18 o h 2 o 15 n no 3 and 18 o no 3 34 s so 4 and 18 o so 4 and 87sr 86sr with the aim of understanding the subsurface nature and environmental status of such areas a previous study has already characterized taipei shallow groundwaters as sulfate rich in comparison to other southeast asian metropolitan cities our chemical measurements clarified that the arsenic is the important environmental concerns in the aquifers dual isotope approaches for nitrate and sulfate suggested these ions were sourced mainly from municipal sewage leaking from sewer pipes in urbanized area while chemical fertilizers applied in the local agricultural fields partly contribute in the suburb area significant decreases in nitrate and sulfate concentrations due to denitrification and sulfate reduction were observed in some groundwaters which induced increases in isotope ratios up to 24 9 for 15 n no 3 and 27 2 for 34 s so 4 nitrate groundwater pollution in the taipei basin is not a subject of serious concern no 3 for all analyzed samples at the present time due to attenuation by denitrification however arsenic is preferentially released in groundwater 100 g l in anoxic environment under which sulfate reduction occurs the sr isotope data suggested that the arsenic is derived from alluvial deposits of oligocene miocene sedimentary rock origin this study disclosed the complex causes of environmental changes in taipei urban shallow groundwater it is also important as an excellent case study demonstrating the efficient use of multiple isotope diagnosis in the urban groundwater environmental field

geochemical estimates of paleorecharge in the pasco basin evaluation of the chloride mass balance technique the pasco basin in southeastern washington state provides a unique hydrogeologic setting for evaluating the chloride mass balance technique for estimating recharge this basin was affected by late pleistocene catastrophic floods when glacial dams in western montana and northern idaho were breached it is estimated that multiple missoula floods occurred between 13 000 and 15 000 years b p and reached a high water elevation of 350 m these floods removed accumulated chloride from the sediment profile effectively resetting the chloride mass balance clock at the beginning of the holocene the rate of chloride accumulation qcl in the sediments was determined by two methods and compared the first method measured qcl by dividing the calculated natural fallout of 36cl by a measured ratio of 36cl cl in the pore water while the second method used the total mass of chloride in the profile divided by the length of time that atmospheric chloride had accumulated since the last flood although the two methods are based on different approaches they showed close agreement in laboratory studies the sediment to water ratio for chloride extraction was sensitive to the grain size of the sediments low extraction ratios in silt loam sediments led to significant underestimation of pore water chloride concentration br cl ratios were useful for distinguishing nonatmospheric e g rock sources of chloride field studies showed little spatial variability in estimated recharge at a given site within the basin but showed significant topographic control on recharge rates in this semiarid environment an extension of the conventional chloride mass balance model was used to evaluate chloride profiles under transient time varying annual precipitation conditions this model was inverted to determine the paleorecharge history for a given soil chloride profile and the parameters of the root extraction model required to estimate paleoprecipitation

tracing ground water evolution in a limestone aquifer using sr isotopes effects of multiple sources of dissolved ions and mineral solution reactions uplifted pleistocene coral reef terraces on barbados west indies constitute an aquifer that is built on low permeability tertiary pelagic rocks that overlie the barbados accretionary prism the downdip segments of the aquifer are composed of younger reef limestones that contain more aragonite and have higher 87sr 86sr and sr ca ratios than the updip parts of the aquifer ground waters and host limestones display similar stratigraphic trends in 87sr 86sr and sr ca the ground waters have lower 87sr 86sr values however indicating that they acquire a significant fraction of their dissolved sr through interaction with components of tertiary rocks which compose the underlying aquitard and parts of overlying soils geochemical modeling results indicate that ground water evolution is controlled by 1 variations in the age and composition of the aquifer and aquitard rocks and 2 the relative roles of calcite dissolution calcite recrystallization and the transformation of aragonite to calcite sr isotopes can provide unique information for tracing ground water evolution which requires consideration of the multiple components and processes that make up even relatively simple limestone aquifer systems

strontium isotope geochemistry and its geochemical implication from hot spring waters in south korea abstract despite being a non volcanic area the southern korean peninsula has a number of hot water springs with temperatures more than 40 c most of which are commercially used for spa the hot springs are located at the fringes of the granite body rather than the center of the mesozoic granite here we report on the geochemical characteristics of the hot water springs the hot springs in the jurassic granite area are mainly of na ca hco 3 type whereas those in the cretaceous granite area are of na cl so 4 type the stable isotope composition of o and h suggests a meteoric origin of the hot spring water further the chemical components of the hot spring waters indicate that they were all derived from hot spring water rock interaction rather than through anthropogenic input the 87 sr 86 sr ratio of the hot spring waters in the jurassic granite area ranges from 0 711088 to 0 729034 and that in the cretaceous granite area ranges from 0 705652 to 0 707912 such 87 sr 86 sr ratio distribution of hot spring waters corresponds with the distribution of the initial 87 sr 86 sr ratios for the emplacement age of the jurassic and cretaceous granites in the hot spring occurrence area the 87 sr 86 sr ratios in the hot spring waters were also divided into three groups according to their geographical location eastern western and southern groups the constant 87 sr 86 sr ratio of hot spring water from one hot spring area during the last 6 years strongly suggests that the hot spring bearing aquifer system in south korea should be separated from the upper cold shallow groundwater system this indicates that the 87 sr 86 sr ratio of the hot spring waters in the granite area of south korea originates from an equilibrium because of long term water rock interaction rather than short term water rock interaction due to the input of recent meteoric water hence it may be concluded that hot spring water in the granite area may be a limited deep groundwater resource that might deplete with overuse

heat exchanges in muddy intertidal sediments chichester harbour west sussex england abstract temperature observations made from a lightweight tower assembly in chichester harbour west sussex demonstrate that marked changes in temperature at intertidal mud surfaces occur on a flow tide the magnitude and direction of these changes are dependent on the external atmospheric and marine conditions and on the timing of tidal inundation calculated heat exchange values for the 3h prior to high water fall into four distinct timing zones there is a relationship between thermal stress measured as rate of change of temperature with time and time of high water mud surfaces are net receivers of heat energy from inundating water layers

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

the 16 april 2015 m w 6 0 offshore eastern crete earthquake and its aftershock sequence implications for local regional seismotectonics we examine the 16 april 2015 m w 6 0 offshore eastern crete earthquake and its aftershock sequence in southern aegean sea centroid moment tensors for 45 earthquakes with moment magnitudes m w between 3 3 and 6 0 are determined by applying a waveform inversion method the mainshock is shallow focus thrust event with a strike slip component at a depth of 30 km the seismic moment m o of the mainshock is estimated as 1 33 1018 nm and rupture duration of the mainshock is 3 5 s the focal mechanisms of aftershocks are mainly thrust faulting with a strike slip component the geometry of the moment tensors m w 3 3 reveals a thrust faulting regime with ne sw trending direction of t axis in the entire activated region according to high resolution hypocenter relocation of the eastern crete earthquake sequence one main cluster consisting of 352 events is revealed the aftershock activity in the observation period between 5 january 2015 and 7 july 2015 extends from n to s direction seismic cross sections indicate a complex pattern of the hypocenter distribution with the activation of three segments the subduction interface is clearly revealed with high resolution hypocenter relocation and moment tensor solution the best constrained focal depths indicate that the aftershock sequence is mainly confined in the upper plate depth 40 km and are ranging from about 4 5 to 39 km depth a stress tensor inversion of focal mechanism data is performed to obtain a more precise picture of the offshore eastern crete stress field the stress tensor inversion results indicate a predominant thrust stress regime with a nw se oriented maximum horizontal compressive stress s h according to variance of the stress tensor inversion to first order the crete region is characterized by a homogeneous interplate stress field we also investigate the coulomb stress change associated with the mainshock to evaluate any significant enhancement of stresses along crete and surrounding regions positive lobes with stress more than 3 bars are obtained for the mainshock indicating that these values are large enough to increase the coulomb stress failure toward ne sw and nw se directions respectively

a silicate weathering mechanism linking increases in marine 87sr 86sr with global glaciation the 87sr 86sr ratio of sea water is generally regarded as a proxy for the rate of chemical weathering of the continents interpretation of the 87sr 86sr record in marine limestones requires an understanding of how changes in this quantity are linked to climate and tectonic events a connection between the strontium isotope record and the extent of global glaciation has been proposed1 8 but without a well established mechanism glaciation may influence marine 87sr 86sr by changing global riverine sr fluxes that is rock weathering rates and or 87sr 86sr ratios that is relative mineral weathering rates here we investigate how the 87sr 86sr release from silicate weathering is affected by glaciation using the sr isotope systematics of granitoid soils on alpine glacial moraines in the wind river range wyoming we observe a negative correlation between the 87sr 86sr ratio of exchangeable sr in soils and the soil age indicating that the 87sr 86sr ratio of sr released in the early stages of weathering is significantly higher than in later stages we estimate that this mechanism can increase global riverine 87sr 86sr by an average of 0 0002 during periods of glacial interglacial cycling when superimposed on long term trends controlled by tectonic processes2 7 9 10 this shift can account for the correlation between the rate of change of marine 87sr 86sr and the intensity of glaciation over at least the past 10 myr

temperature fluctuation in muddy intertidal sediments forth estuary scotland abstract temperatures in muddy intertidal sediments exhibit rapid changes which occur principally during tidal inundation observations of sub surface temperature were made from an instrument tower in the forth estuary scotland observed rates of temperature change were compared with theoretical rates which would result from molecular diffusion of heat through the mud the discrepancy between observation and theory was likely to be due to rapid non diffusive heat transfers resulting from the movement of water through non capillary pore spaces created by faunal activity

use of vertical temperature gradients for prediction of tidal flat sediment characteristics 1 sediment characteristics largely govern tidal flat morphologic evolution however conventional methods of investigating spatial variability in lithology on tidal flats are difficult to employ in these highly dynamic regions in response a series of laboratory experiments was designed to investigate the use of temperature diffusion toward sediment characterization a vertical thermistor array was used to quantify temperature gradients in simulated tidal flat sediments of varying compositions thermal conductivity estimates derived from these arrays were similar to measurements from a standard heated needle probe which substantiates the thermistor methodology while the thermal diffusivities of dry homogeneous sediments were similar diffusivities for saturated homogeneous sediments ranged approximately one order of magnitude the thermal diffusivity of saturated sand was five times the thermal diffusivity of saturated kaolin and more than eight times the thermal diffusivity of saturated bentonite this suggests that vertical temperature gradients can be used for distinguishing homogeneous saturated sands from homogeneous saturated clays and perhaps even between homogeneous saturated clay types however experiments with more realistic tidal flat mixtures were less discriminating relationships between thermal diffusivity and percent fines for saturated mixtures varied depending upon clay composition indicating that clay hydration and or water content controls thermal gradients furthermore existing models for the bulk conductivity of sediment mixtures were improved only through the use of calibrated estimates of homogeneous end member conductivity and water content values our findings suggest that remotely sensed observations of water content and thermal diffusivity could only be used to qualitatively estimate tidal flat sediment characteristics

kinetic and mineralogic controls on the evolution of groundwater chemistry and 87sr 86sr in a sandy silicate aquifer northern wisconsin usa abstract substantial flowpath related variability of 87sr 86sr is observed in groundwaters collected from the trout lake watershed of northern wisconsin in the extensive shallow aquifer composed of sandy glacial outwash groundwater is recharged either by seepage from lakes or by precipitation that infiltrates the inter lake uplands 87sr 86sr of groundwater derived mainly as seepage from a precipitation dominated lake near the head of the watershed decreases with progressive water chemical evolution along its flowpath due primarily to enhanced dissolution of relatively unradiogenic plagioclase in contrast 87sr 86sr of groundwater derived mainly from precipitation that infiltrates upland areas is substantially greater than that of precipitation collected from the watershed due to suppression of plagioclase dissolution together with preferential leaching of sr from radiogenic phases such as k feldspar and biotite the results of a column experiment that simulated the effects of changing residence time of water in the aquifer sand indicate that mobile waters obtain relatively unradiogenic sr whereas stagnant waters obtain relatively radiogenic sr nearly the entire range of strontium isotope composition observed in groundwaters from the watershed was measured in the experimental product waters the constant mobility of water along groundwater recharge flowpaths emanating from the lakes promotes the dissolution of relatively unradiogenic plagioclase perhaps due to effective dispersal of clay mineral nuclei resulting from dissolution reactions in contrast episodic stagnation in the unsaturated zone along the upland recharge flowpaths suppresses plagioclase dissolution perhaps due to accumulation of clay mineral nuclei on its reactive surfaces differences in redox conditions along these contrasting flowpaths probably enhance the observed differences in strontium isotope behavior this study demonstrates that factors other than the calculated state of mineral saturation must be considered when attempting to simulate chemical evolution along flowpaths and that reaction models must be able to incorporate changing contributions from reacting minerals in the calculations

buried carbonate paleosols developed in pliocene pleistocene deposits of the pasco basin south central washington u s a abstract carbonate rich paleosols represent a small volume of material at the hanford site in south central washington state u s a but their position below highly permeable missoula flood deposits and above the water table makes them an important component of contaminant remediation plans previous work indicated that these buried carbonate paleosols constitute a relatively continuous low permeability paleosurface the distribution of the pliocene pleistocene deposits containing the paleosols depends in part on erosion of the underlying miocene pliocene fluvial lacustrine ringold formation and post depositional erosion by the catastrophic missoula floods the character of the caliche layer s as determined from cores varies across the study area from 0 20 m in thickness at depths of 20 m in the south to 65 m in the northwest bounded above and below by irregular surfaces with as much as 25 m relief and in general co varies in number of carbonate layers with the thickness of the deposits these carbonate layers reflect the geomorphology and hydrology existing during the time they developed i interpret these carbonate layers as paleosols but recognize morphologic features that indicate modification may have occurred after initial development at the surface these include the absence of associated soil horizons no apparent decrease in carbonate content with depth in some of the carbonate layers and unusual bk horizon fabrics including crystalline or popcorn like forms these features and fabric differences influence potential flow pathways of waste fluids

dissolution rates and vadose zone drainage from strontium isotope measurements of groundwater in the pasco basin wa unconfined aquifer abstract strontium isotope ratios 87sr 86sr measured in groundwater samples from 273 wells in the pasco basin unconfined aquifer below the us department of energy hanford site show large and systematic variations that provide constraints on groundwater recharge weathering rates for saturated zone dissolution of the aquifer host rocks communication between unconfined and deeper confined aquifers and vadose zone groundwater interaction the impact of millions of cubic meters of wastewater discharged to the vadose zone 103 105 times higher than ambient drainage shows up strikingly on maps of groundwater 87sr 86sr extensive access through the many groundwater monitoring wells at the site allows for an unprecedented opportunity to evaluate the strontium geochemistry of a major aquifer hosted primarily in unconsolidated sediments and relate it to both long term properties and recent disturbances groundwater 87sr 86sr increases systematically from 0 707 to 0 712 from west to east across the hanford site in the general direction of groundwater flow as a result of addition of sr from the weathering of aquifer sediments and from diffuse drainage through the pasco basin vadose zone the lower 87sr 86sr groundwater reflects recharge waters that have acquired sr from columbia river basalts based on a steady state model of sr reactive transport and drainage there is an average natural drainage flux of 0 1 4 mm yr near the western margin of the hanford site and ambient drainage may be up to 30 mm yr in the center of the site assuming an average bulk rock weathering rate of 10 7 5 g g yr the weathering rates cannot be higher than those assumed by more than a factor of 2 3 in order to match sr isotope data

long history of pre wisconsin ice age cataclysmic floods evidence from southeastern washington state abstract cataclysmic ice age floods in the pacific northwest began as early as 1 5 2 5 ma on the basis of an evaluation of surface exposures and recent borehole studies within southeastern washington field evidence suggests at least two episodes of pre wisconsin i e 130 ka glacial outburst flooding a middle pleistocene flood is identified by normal magnetic polarity calcrete capped deposits that yield maximum th u age dates from 200 to 400 ka the deposits with reversed polarity are correlated to early pleistocene 780 ka floods while exposures of pre wisconsin deposits are limited because of erosion and or burial the record of earlier pleistocene flooding is preserved within giant flood bars these bars show incremental growth representing a composite from cataclysmic floods deposited intermittently through the pleistocene in one giant flood bar up to 100 m thick deposits interpreted as matuyama age indicate that the bar had grown to half its present height by 780 ka furthermore matuy

paleomagnetic and tephra evidence for tens of missoula floods in southern washington paleomagnetic secular variation and a hiatus defined by two tephra layers confirm that tens of floods from glacial lake missoula montana entered washington s yakima and walla walla valleys during the last glaciation in these valleys the field evidence for hiatuses between floods is commonly subtle however paleomagnetic remanence directions from waterlaid silt beds in three sections of rhythmically bedded flood deposits at zillah touchet and burlingame canyon display consistent secular variation that correlates serially both within and between sections the secular variation may further correlate with paleomagnetic data from fish lake oregon and mono lake california for the interval 12 000 17 000 14 c yr b p deposits of two successive floods are separated by two tephras derived from mount st helens washington the tephras differ in age by decades indicating that a period at least this long separated two successive floods the beds produced by these two floods are similar to all of the 40 beds in the slack water sediment sequence suggesting that the sequence is a product of tens of floods spanning a period of perhaps a few thousand years

the transport of u and th series nuclides in sandy confined aquifers a comprehensive evaluation of the transport of u th ra and rn nuclides of the 238 u and 232 th decay series in an unconfined sandy aquifer long island ny was conducted groundwater data are compared with results of a theoretical transport model of weathering of aquifer grains and interaction with surface coatings to establish relationships between the concentrations of the radionuclide activities in the water and flow line distance the data provide estimates for geochemical parameters including weathering rates and chemical reactivities in both the vadose zone and the aquifer a theoretical treatment of the transport is presented that considers the reaction between the water and a reactive surface layer it is found that a model with chemical exchange between the surface layer and the water for all species is not valid and that the effects of saturation and irreversible precipitation of th is required the water table shows a relatively wide range in u activities the only element in the u th series for which vadose zone input is significant in the aquifer high weathering of u and recoil inputs of 234 u to the water occur in the upper 3 m of the vadose zone while lower weathering and removal of u from the water occur below the deeper aquifer has variable 238 u activities that can be accounted for by input from the vadose zone and is not a result of non conservative behavior the isotopic composition of u is shown to be directly related to the recoil rate relative to the weathering rate the wide range of 238 u in the aquifer waters is a reflection of diverse vadose zone inputs showing that dispersive mixing is not a dominant effect the higher values of 234 u in the aquifer reflect the recoil weathering input ratios from within the aquifer where the weathering rate is lower than the vadose zone both high u activities and high 234 u values cannot be obtained in the vadose zone or within reasonable flow distances in the aquifer radium isotopes are found to be in exchange equilibrium with the surface layer 224 ra 228 ra and 226 ra have comparable activities throughout the aquifer in the vadose zone the dominant input of ra to groundwater is weathering and recoil as found elsewhere the 222 rn in the water is a large fraction 5 of the rn produced in the aquifer rock this cannot be due to ra precipitation onto surface coatings in the aquifer as supported by present weathering with th in exchange equilibrium with the surface layer it is found that th is saturated in the waters under oxidizing conditions so that the weathering input is irreversibly precipitating onto surfaces however it is shown that under somewhat reducing conditions th activities are much higher and the th u ratio in the solution is approximately that of the rock we propose that under oxidizing conditions the source of rn is a surface coating enriched in 232 th and 230 th this th was precipitated in an earlier phase during rapid dissolution of readily weathered phases that contain 10 of the u th inventory of the rock with the associated u carried away in solution therefore the previously precipitated 230 th and 232 th produce daughter nuclides in the surface coating which are the dominant contributors of ra and rn to the ground water in particular rn is provided by very efficient losses by diffusion or recoil from the surface coating this then does not require recent large recoil losses from the parent rock or the presence of nanopores in the rock the first data of both long lived 232 th and short lived 234 th and 228 th in ground water is reported the th isotope activities indicate that desorption kinetics are slow and provide the first estimate based on field data of the th desorption rate from an aquifer surface the mean residence time of th in the surface coating is 3000 y while in the water it is 1 h ra is in partition equilibrium with the aquifer surface layer however the strong fixation of th on surface coatings is very susceptible to changes in oxidation state as is shown by a comparison of two adjacent aquifers this makes it difficult to define with certainty the retentive characteristics in natural systems in general it is shown that the distributions of naturally occurring nuclides can be used to calculate values for transport parameters that are applicable to the transport of anthropogenic nuclides

widespread seismicity excitation throughout central japan following the 2011 m 9 0 tohoku earthquake and its interpretation by coulomb stress transfer 1 we report on a broad and unprecedented increase in seismicity rate following the m 9 0 tohoku mainshock for m 2 earthquakes over inland japan parts of the japan sea and izu islands at distances of up to 425 km from the locus of high 15 m seismic slip on the megathrust such an increase was not seen for the 2004 m 9 1 sumatra or 2010 m 8 8 chile earthquakes but they lacked the seismic networks necessary to detect such small events here we explore the possibility that the rate changes are the product of static coulomb stress transfer to small faults we use the nodal planes of m 3 5 earthquakes as proxies for such small active faults and find that of fifteen regions averaging 80 by 80 km in size 11 show a positive association between calculated stress changes and the observed seismicity rate change 3 show a negative correlation and for one the changes are too small to assess this work demonstrates that seismicity can turn on in the nominal stress shadow of a mainshock as long as small geometrically diverse active faults exist there which is likely quite common

using hydrochemical stable isotope and river water recharge data to identify groundwater flow paths in a deeply buried karst system the deeply buried river connected xishan karst aquifer xka in western beijing china has been suffering from diminishing recharge for several decades which in turn leads to the disappearing of spring water outflows and continuously lowering of groundwater level in the area thus it is important to correctly recognize the groundwater recharge and flow paths for the sustainable development of the xka to investigate these issues the hydrochemical and isotopic compositions are analysed for both surface water and groundwater samples collected over an area of about 280 km2 results show that a the river water is characterized by high na contents b the 2h and 18o values in the river water are distinctively higher than those of groundwater samples after experiencing the long time evaporative enrichment in the upstream reservoir c the sr concentrations and 87sr 86sr ratios of groundwater clearly indicated the interaction between water and carbonate minerals but excluded the water silicate interaction and d the groundwater samples in the direct recharge area of the xka have the lowest na concentrations and the 2h and 18o values based on the large differences in the na contents and 18o values of groundwater and surface water a simple two component mixing model is developed for the study area and the fractions of the river water are estimated for groundwater samples we find that the distribution pattern of the river water fractions in the xka clearly shows a change of directions in the preferential flow path of the groundwater from its source zone to the discharge area overall our results suggest that the recharged surface water can be a useful evidence for delineating the groundwater flow path in river connected karst aquifer this study improves our understanding of the heterogeneity in karst groundwater systems