chemical composition of rainfall and groundwater in recharge areas of the bet shean harod multiple aquifer system israel the bet shean and harod valleys are regional recipients and mixing zones for groundwaters draining from a regional multiple aquifer system comprising two different carbonate and two basalt aquifers as well as deep seated reservoirs of confined brines this paper the first of two describes the hydrochemistry of the groundwater bodies related to this multiple aquifer system the paper deals with the chemical composition of rain falling on natural recharge areas the chemical contribution of the aquifer rocks and the chemical evolution of groundwaters in the upper flow courses of all aquifers of this regional system the methodology applied is based on the determination of major dissolved ions and on the examination of their ratios and changes along the upper flow paths rain water falling on natural recharge areas has an average chlorinity of 12mgl 1cl and a calcium bicarbonate composition caused by dust borne terrigenous material this rain water salinity decreases with distance from the sea shore fresh groundwaters flowing through the different aquifers may be identified and differentiated by their characteristic salinity levels and ionic ratios groundwaters flowing through carbonate aquifers are identified by different salinity levels and by distinct rmg rca ratios reflecting dolomite calcite ratios in aquiferr rocks the groundwaters of the two basalt aquifers have typical cation assemblages and high na and mg2 concentrations far in excess of those typical of the recharging rainfall groundwater in the upper flow courses of all aquifers investigated is deficient in so2 4 and k relative to recharging rain water

millennial scale changes in north atlantic circulation since the last glaciation ocean circulation is closely linked to climate change on glacial interglacial and shorter timescales extensive reorganizations in the circulation of deep and intermediate depth waters in the atlantic ocean have been hypothesized for both the last glaciation1 2 3 4 5 6 and the subsequent younger dryas cold interval3 6 7 8 9 10 but there has been little palaeoceanographic study of the subtropical gyres11 12 13 these gyres are the dominant oceanic features of wind driven circulation and as such they reflect changes in climate and are a significant control on nutrient cycling and possibly atmospheric co2 concentrations here we present cd ca ratios in the shells of benthic foraminifera from the bahama banks that confirm previous suggestions11 12 that nutrient concentrations in the north atlantic subtropical gyre were much lower during the last glacial maximum than they are today up to 50 lower according to our data these contrasting nutrient burdens imply much shorter residence times for waters within the thermocline of the last glacial maximum below the glacial thermocline nutrient concentrations were reduced owing to the presence of glacial north atlantic intermediate water a high resolution cd ca record from an intermediate depth indicates decreased nutrient concentrations during the younger dryas interval as well mirroring opposite changes at a nearby deep site3 9 together these observations suggest that the formation of deep and intermediate waters north atlantic deep water and glacial north atlantic intermediate water respectively wax and wane alternately on both orbital and millennial timescales

palynology sedimentology and palaeoecology of the late holocene dead sea abstract palynological and sedimentological studies were performed at two holocene profiles in erosion gullies ze elim and ein feshkha which dissect the retreating western shore of the dead sea the aim of the project was to analyse possible links between climate lithology and vegetation development the section in ze elim shows both lacustrine and fluvial sediments whereas sedimentation at ein feshkha is predominantly lacustrine the ze elim profile previously used for paleo lake reconstruction provides an opportunity to compare climate triggered lake levels as paleo hydrological indicators and vegetation history by use of palynology the vegetation development in ze elim and ein feshkha is influenced by both climate and human impact the pollen record of ze elim begins in the pottery neolithic the section of ein feshkha in the late bronze age both records end in the middle ages the ze elim section is characterized by sedimentary hiati between the beginning of the chalcolithic period until the middle bronze age and within the late bronze age settlement periods during the middle bronze age iron age and hellenistic roman byzantine period are indicated by high values of anthropogenic indicators and or mediterranean trees collapses of agriculture which can be related to climate effects are evident during the late bronze age during the iron age and at the end of the byzantine period when the lake level curve indicates arid conditions a comparison of the two pollen records from different environments illustrates a more prominent influence of mediterranean vegetation and cultivated plants in the pollen diagram of ein feshkha the southern dead sea region at the desert fringe is more vulnerable to regional climate change

temporal transport of major and trace elements in the upper reaches of the xijiang river sw china this study investigated the temporal variations of major and trace element contents and controlling factors in the upper reaches of the xijiang river sw china the results showed the major ions principally derived from the weathering of carbonate and silicate rocks with a seasonal variation impacted by the monsoonal climate the contents of dissolved trace elements also varied seasonally in the two main tributaries the nanpan and beipan rivers most dissolved trace elements such as mn zn and pb being affected by anthropogenic contributions displayed a large seasonal variability from onefold to hundred fold while v rb and u show a relative stable trend uncorrelated with the different seasons suggesting a natural origin by rock weathering suspended particle matter in the nanpan and beipan rivers was depleted in ca mg na k and sr but enriched in al fe and sb compared to the upper crust uc values a binary mixture of silicate rich and carbonate rich sources dominates the behavior of elements such as ca and sr in riverine sediments while a third end member with an anthropogenic signature influenced the content of trace elements like mn sb pb zn cd cr and cu the enrichments of sb relative to the uc would be related to the mining activity in the studied area the study highlights the importance of investigating temporal variations of major and trace element contents of rivers controlled by the monsoon climate and impacted by human activity

water geochemistry controlled by carbonate dissolution a study of the river waters draining karst dominated terrain guizhou province china concentrations of major ions and sr and sr isotopic compositions of two major river systems wujiang river and yuanjiang river in karst dominated regions and during winter were measured the rivers and their tributaries have high total dissolved solid concentrations with tz ranging from 2 1 to 6 3 meq l which are significantly higher than that of the global river average calcium and hco3 followed by mg2 and so42 dominate the chemical composition of major ions in the river waters both na k and cl si account for 5 10 of the cations and anions respectively the waters of the wujiang river have high sr2 concentrations and lower 87sr 86sr ratios 0 7077 0 7110 while those of the qingshuijiang river one of two major tributaries of the yuanjiang river system show higher sr isotopic ratios 0 7090 0 7145 and low sr concentrations the lithology and geography of the river basins largely control the chemical and isotopic compositions of these rivers analyses of the stoichiometry of the river waters show that the water chemistry is controlled by carbonate dissolution by both carbonic and sulfuric acid especially of the wujiang river and suggest an origin of sulfate mainly from atmospheric input because of coal combustion and or oxidation of sulfide minerals in the catchments we identify three main weathering sources limestone dolomite and silicates chemical and sr isotopic composition of wujiang river waters are characterized mainly by limestone weathering while those of the qingshuijiang river waters mainly by dolomite and silicate weathering chemical weathering rates of carbonate and silicate are estimated and the results indicate that the chemical weathering rates of carbonate in the catchments are remarkably high significantly higher than most large rivers it is considered that presence of sulfuric acid in the rock weathering overuse of land and deterioration of vegetation are most likely the key factors responsible for the high weathering rates of carbonate in the catchments

organic and inorganic carbon dynamics in a karst aquifer santa fe river sink rise system north florida usa spatiotemporal variations in dissolved organic carbon doc dissolved inorganic carbon dic major ions concentrations and other geochemical parameters including stable carbon isotopes of dic 13cdic were measured in surface water and deep and shallow well water samples of the santa fe river sink rise eogenetic karst system north florida usa three end member water sources were identified one doc rich dic poor 13cdic depleted one doc poor dic rich 13cdic enriched and one enriched in major ions given their spatiotemporal distributions they were presumed to represent soil water upper aquifer groundwater and deep aquifer water sources respectively using assumed ratios of na cl and so42 for each end member a mixing model calculated the contribution of each water source to each sample then chemical effects of biogeochemical reactions were calculated as the difference between those predicted by the mixing model and measured species concentrations in general carbonate mineral dissolution occurred throughout the sink rise system surface waters were net autotrophic and the subsurface was in metabolic balance i e no net doc or dic production or consumption however there was evidence for chemolithoautotrophy perhaps by hydrogen oxidizing microbes at some deep aquifer sites mineralization of this autochthonous natural dissolved organic matter ndom led to localized carbonate dissolution as did surface water derived ndom supplied to shallow well sites during the highest flow periods this study demonstrates linkages between hydrology abiotic and microbial processes and carbon dynamics and has important implications for groundwater quality karst morphologic evolution and hydrogeologic projects such as aquifer storage and recovery in karst systems

sulfuric acid as an agent of carbonate weathering constrained by δ13cdic examples from southwest china abstract rock weathering by carbonic acid is thought to play an important role in the global carbon cycle because it can geologically sequestrate atmospheric co 2 current model of carbon cycle evolution usually assumes that carbonic acid is the major weathering agent and that other acids are not important here we use carbon isotopic evidence and water chemistry of springs and rivers from the beipanjiang river basin guizhou province southwest china to demonstrate that sulfuric acid is also an important agent of rock weathering the 13 c of dissolved inorganic carbon dic in the water samples ranges from 13 1 to 2 4 and correlates negatively to hco 3 ca 2 mg 2 ratios and positively to so 4 2 ca 2 mg 2 ratios these relationships are interpreted as mixing diagrams between two reactions of carbonate weathering using carbonic acid and sulfuric acid as a proton donor respectively mixing proportions show that around 42 of the divalent cations in the spring water from guizhou are originated from the interaction between carbonate minerals and sulfuric acid it is shown that 40 of this sulfuric acid is derived from the atmosphere and has an anthropogenic origin the remaining 60 are derived from the oxidative weathering of sulfide minerals in sedimentary rocks our results show the positive action of sulfuric acid on the chemical weathering of carbonate particularly we show that sulfuric acid generated by coal combustion has increased by almost 20 the weathering rates of carbonate in southwest china this is a clear evidence that human activities are changing the weathering rates of rocks and demonstrates a negative feedback on the acidification of the ocean by greenhouse gases because of the involvement of sulfuric acid in weathering reactions 63 of the alkalinity exported by rivers is derived from carbonate instead of 50 when atmospheric co 2 is the only acid involved in chemical weathering of carbonate in the guizhou province the weathering of carbonate is thus at least transiently a net source of co 2 to the atmosphere when extrapolated at global scale sulfuric acid induced carbonate weathering could counterbalance a significant part of the co 2 consumed by silicate weathering this paper highlights the competition between silicate weathering by carbonic acid and carbonate weathering by sulfuric acid for the regulation of the atmospheric co 2 level

ca chloride brines at common outlets of the bet shean harod multiple aquifer system israel abstract the bet shean and harod valleys are regional recipients and mixing zones for groundwaters draining into them from a multiple aquifer system which includes carbonate and basalt aquifers and deep seated reservoirs of brine the outlets of the three aquifers are located at the mountain border separating the valleys from the gilboa and ramot issakhar mts the aquifers drain through two types of outlets unique and common the latter type is mainly conditioned by the occurrence of fault blocks acting as connecting media between the aquifers upon reaching the interconnecting zones fresh groundwater flowing from carbonate and basalt aquifers intermix losing their hydrochemical identities ca chloride brines originating from deep seated and confined reservoirs leak along the deep seated faults characterizing the common outlet zones and contaminate the relatively fresh mixing products originating from the three regional aquifers two types of dilute ca chloride brines were identified in the study area the devora type is a hot and hypersaline source brine which was identified at great depth and under very high hydrostatic pressures this brine could be the residual product of seawater that evaporated during the cambrian cretaceous continental interval and subsequent prolonged interaction with surrounding carbonate rocks the neve ur type brine seems to be genetically related to the neogene inland sdom sea that preceeded the contemporary dead sea

enhanced ventilation of the north atlantic subtropical gyre thermocline during the last glaciation the ocean s intermediate1 6 and deep7 8 circulation are both known to have differed during the last glaciation from those of today but little is known about the history of the subtropical gyres variations in gyre processes should be closely linked to variations in global climate as gyre circulation is driven by air sea interactions and reflects the climate at the ocean surface the gyres are also a significant reservoir of carbon and nutrients so that gyre processes affect the distribution of carbon and nutrients in the oceans and thus atmospheric co2 here we use measurements of 13c and 18o in foraminifera from the bahamas to produce a detailed reconstruction of nutrient and temperature profiles in the thermocline during the last glaciation the thermocline of the glacial north atlantic subtropical gyre lacked the oxygen minimum that is characteristic of the modern ocean and was depleted in nutrients indicating greater more uniform thermocline ventilation at that time thus not only intermediate waters1 5 but the entire upper water column within the glacial north atlantic was depleted of nutrients moreover glacial thermocline waters were cooler had a steeper temperature gradient and a shallower base both the ventilation and the thermal structure of the glacial thermocline are consistent with what is known of the glacial climate9 14

structure controlled groundwater flow and salinization paths in the bet she an and harod valleys israel the bet she an and harod valleys are regional recipients and mixing zones for groundwater draining to these valleys from a multiple aquifer system this aquifer system includes two different carbonate aquifers several groundwater bearing basalt flows and deep seated pressurized brine the upflow of which causes salinization of fresh groundwater bodies these aquifers drain through two groups of springs due to lack of information on the subsurface structure of the valley the flow paths of groundwater feeding the springs the initial distribution of salinities along the valley and particularly the inflow paths of the brines have never been understood but were assumed to be fault controlled the interpretation of seismic profiles and analysis of gravity anomalies revealed the subsurface structure of the valley and namely the occurrence of a dense network of faults which branch out from those delineating the jordan dead sea rift the faults formed a series of uplifted and down warped horst and graben structures by joint analysis of structural hydrological and geochemical evidence it occurs that groundwater flow paths leading to the springs emerging in the middle of the bet she an valley are determined by structural elements such as major faults and fault controlled structures the penetration of the pressurized ca chloride rift brines and their inflow into fresh groundwater bodies occurs prevalently along the faults outlining the western margins of the dead sea rift valley and at their intersection with outbranching nw se striking faults

homogenization of potential vorticity in planetary gyres the mean circulation of planetary fluids tends to develop uniform potential vorticity q in regions where closed time mean streamlines or closed isolines of mean potential vorticity exist this state is established in statistically steady flows by geostrophic turbulence or by wave induced potential vorticity flux at the outer edge of the closed contours the expelled gradients of q are concentrated beyond this transition lies motionless fluid or a different flow regime in which the planetary gradient of q may be dominant the homogenized regions occur where direct forcing by external stress or heating within the closed isoline is negligible upon the potential density surface under consideration in the stably stratified ocean such regions are found at depths greater than those of direct wind induced stress or penetrative cooling in channel models of the atmosphere we again find constant q when mesoscale eddies cause the dominant potential vorticity flux in the real atmosphere the results here can apply only where internal heating is negligible the derivations given here build upon the prandtl batchelor theorem which applies to non rotating steady two dimensional flow supporting evidence is found in numerical circulation models and oceanic observations

hydrological and hydrogeochemical methods for the delineation of complex groundwater flow systems as evidenced in the bet shean valley israel abstract the bet shean valley northern israel is the base level of groundwater draining from three regional aquifers in the natural undisturbed state i e at the beginning of the six ties groundwater drained through many springs with widely different chemical composition and with a total discharge of about 135 million m 3 for the efficient utilization of water resources it was decided to recover groundwater from wells at the cost of a considerable reduction of spring discharges since the sequence and the rate of spring decay diverged from the pattern that had been predicted it became necessary to delineate aquifers and their connections to the various springs three groups of methods were employed for this purpose a analysis of discharge characteristics and their relation to source aquifers b methods for the identification of well fields that affect the discharge of a particular spring and c hydrogeochemical methods for the delineation of flow paths the paper presents the relevant data the methods employed and the results that were achieved the utility and the limitations of the various methods were discussed and general guidelines for the delineation of groundwater flow in multi aquifer systems were formulated

runoff generation from successive simulated rainfalls on a rocky semi arid mediterranean hillslope runoff generation in a mediterranean carbonate rock environment the judaean mountains west bank and israel was studied by a 2 day sprinkling experiment on an 18 x 10 m 2 plot during the first day three spells of 24 1 mm h 1 12 3 mm 27 8 mm h 1 12 3 mm and 14 4 mm h 1 12 5 mm were applied almost saturating the runoff plot on the second day 20 h later two spells of 18 7 mm h 1 34 3 mm and 35 2 mm h 1 25 4 mm followed surface runoff was a combination of infiltration excess runoff from rocky portions of the plot and saturation excess runoff from areas covered by soil soil saturation was accelerated by lateral runoff from adjacent rocky areas once the plot was saturated 80 90 of the applied rainfall became surface runoff significantly different concentrations of chloride sulphate and nitrate ions in the sprinkled water on two successive days served as tracers during the second day a two component hydrograph separation pointed to the importance of shallow reservoirs playing active parts in runoff generation about 14 of the flow collected during the second day originated from water applied during the first day during the second day of sprinkling both water sources obviously mixed in saturated soil reservoirs and contributed in variable percentages to surface flow it is hypothesized that at least during high magnitude rainfall the steep rocky slopes investigated might be regarded as flood generating zones rather than areas of pronounced recharge into the underlying yarkon taninim aquifer

geochemical and stable isotope studies on natural water in the taroko gorge karst area taiwan chemical weathering of carbonate rocks by deep source co2 and sulfuric acid the geochemical cycle of co2 and the hydrological cycle in the taroko gorge karst area taiwan are discussed using chemical composition data of the natural water together with stable isotope ratios of carbon and oxygen of the water and soil co2 the soil co2 concentration at a depth of 1 m showed seasonal variations with a maximum of 5 2 v v and the minimum of 0 6 v v at three different altitudes ranging from 50 to 2000 m asl the soil temperature is the most important factor controlling the soil co2 concentration in this area the solubility of carbonates in groundwater can be explained by evolution under closed system conditions depending on the soil co2 concentration measured unexpectedly high 13c values of hco3 in groundwater were observed at some springs there was also an equivalent relationship between the sum of the concentration of mg2 and ca2 ions and that of hco3 and so42 ions in their waters these two facts suggest that some deep source co2 and sulfuric acid derived from weathering of pyrite may take part in the chemical weathering of carbonate rocks mainly calcareous schist as well as the soil co2 after the correction for the contribution of sulfuric acid the 13c values of hco3 of groundwater issuing from some springs were still high suggesting the presence of a deep source co2 flux altitude isotope effects were observed for surface water and rainwater in this area and could be expressed as 18o 0 0024h 3 67 h altitude m asl the estimated altitudes of catchment basins of springs using this equation were over 1000 2000 m higher than those of springs the rain falling high in the mountains is supplied with soil co2 dissolves carbonate rocks under closed system conditions penetrates deep underground and comes out again from springs together with the deep source co2 along fault crushing belts

chemical evolution of saline waters in the jordan dead sea transform and in adjoining areas the ca mg relationship in groundwaters strongly points to the overall dolomitization and local albitization the mg ca ratios reveal two trends by which saline waters develop increase of mg ca ratio by evaporation and decreasing mg ca ratios due to dolomitization and albitization br cl vs na cl ratios demonstrate that albitization does not play a major role which leaves dolomitization to be the main source for decreasing mg ca ratios in saline waters in the eastern and southern region of lake kinneret salinization occurs by mixing with a ca mg molar ratio 1 dominates which developed by the albitization of plagioclase in abundant mafic volcanics and the dolomitization of limestones the most saline groundwater of the tabgha fuliya and tiberias clusters could be regional derivatives of at least two mother brines in diluted form one is represented by ha on water the other is a na rich brine of the zemah type additionally a deep seated ca dominant brine may ascend along the fractures on the western side of lake kinneret which is absent on the eastern side groundwaters of the lower jordan valley are chemically different on both sides of the jordan river indicating that the exchange of water is insignificant all saline waters from the dead sea and its surroundings represent a complex mixture of brines and precipitation and local dissolution of halite and gypsum many wells of the arava araba valley pump groundwater from the upper cretaceous limestone aquifer the origin of the water is actually from the lower cretaceous kurnub group sandstones groundwater drawn from the quaternary alluvial fill either originates from kurnub group sandstones eilat 108 yaalon 117 or from altered limestones of the judea group the origin of these waters is from floods flowing through wadis incised into calcareous formations of the judea group on the other hand as a result of step faulting hydraulic contact is locally established between the kurnub and the judea groups aquifers facilitating the inter aquifer flow of the confined kurnub paleowater into the karstic formations of the judea group two periods of neogene brine formation are considered the post messinan inland lagoon resulting in drying up of the sdom sea and the evaporation of the pleistocene samra lake which went further through the stage of lake lisan to the present dead sea for the first period major element hydrochemistry suggests that the saline waters and brines in the jordan dead sea arava valley transform evolved from the gradual evaporation of an accumulating mixture of sea ground and surface water due to the precipitation of carbonates gypsum and halite such an evaporating primary water body was strongly enriched in mg br and b and shows high molar ratios of br cl b cl and mg ca but low na cl ratios the development of the br cl ratio is chemically modelled showing that indeed brine development is explicable that way along with the evaporation brine evaporites formed which are leached by infiltrating fresh water yielding secondary brines with na cl ratios of 1 when primary brines infiltrated the sub surface they were subjected to mg ca exchange in limestones dolomitization and to chloritization and albitization in basic igneous rocks turning them into ca cl brines these tertiary brines are omnipresent in the rift the brines of the late lisan and dead sea were generated by evaporating drainage waters which leached halite gypsum and carbonates from the soil and from the sub surface all these brines are still being flushed out by meteoric water resulting in saline groundwaters this flushing is regionally enhanced by intensive groundwater exploitation in variable proportions the neogene and late lisan lake and recent dead sea brines have to be considered as the most serious sources of salinization of groundwaters in the rift deep seated pre sdom brines cannot strictly be excluded but if active they play a negligible role only

on the source of water from the thermomineral springs of lake kinneret israel the chemical and isotopical 18o deuterium composition of the thermomineral water emerging around lake kinneret is shown to be similar to that of the saline water found in deep oil exploration wells in the coastal plain of israel and different from the water found near the dead sea it is suggested that an ancient brine which is filling the deep non flushed aquifers is driven from the south towards the rift valley by a piston action and is mixed with paleo and contemporaneous meteoric water before emerging as thermomineral springs

isotopic composition of dissolved inorganic carbon in a large polluted river the vistula poland abstract the vistula is a large lowland temperate river receiving high loads of pollutants from a densely populated catchment on the other hand the river is to a relatively small extent affected by channelisation and damming this study is the first attempt to characterise stable isotope aspects of dissolved inorganic carbon in the vistula which is a major source of pollution to the baltic sea isotopic composition of dic and other chemical properties were measured biweekly at the upper reach and monthly at the mouth of the river two longitudinal samplings were performed in hydrological summer and winter conditions short term and short range observations were carried out in an anthropogenically influenced urban reach at cracow most water samples from the vistula and its tributaries analysed in this study had 13 c dic values around the range 12 to 11 typical for european lowland rivers fed by groundwaters on carbonate areas variablity of 13 c dic in this river system is limited except for the impoundments and the specific hydrological conditions the few impoundments that exist on the vistula intensify the photosynthesis respiration cycle as well as the exchange of co 2 with the atmosphere enhanced contribution of biogenic carbon during floods is reflected by lowering of 13 c dic low flows facilitate photosynthetic assimilation and evasion of co 2 into the atmosphere resulting in positive shifts of 13 c dic principal component analysis confirmed that 13 c dic variability at the fixed cross section in cracow reflected releases and withdrawals of co 2 from the riverine dic pool the apparent 13 c dic variability depends to some extent on the spatio temporal context of observations diurnality can be very pronounced in the impounded anthropogenically influenced reaches in warm periods interpretation of the observed riverine 13 c dic patterns can be difficult as the spatial and temporal variabilities combine resulting in convoluted isotopic signals isotopic investigations into the nature of riverine carbon cycling should be supplemented by discharge records and by observations of the parameters influenced by the photosynthesis respiration cycle dissolved oxygen ph p co 2 and of those conservative with respect to biological processes electrical conductivity stable isotope composition of water

glacial interglacial differences in circulation and carbon cycling within the upper western north atlantic we investigated glacial interglacial changes in the circulation and carbon cycling in the western north atlantic subtropical gyre using hydrographic data and downcore records of the stable isotopic compositions of individual shells of bahamian benthic foraminifera potential temperature salinity depth relations show that modern thermocline 200 1000 m and deep 1000 2000 m waters in the providence channels bahamas originate in the sargasso sea and are typical of the subtropical gyre gradients in the stable isotopic compositions of late holocene planulina and cibicidoides species from the bank margins 400 to 1500 m depth reflect temperature nutrient and isotopic gradients of modern subtropical gyre waters the difference between the 18o of glacial maximum and late holocene foraminifera is 2 1 for the upper 900 m of the water column and 1 6 for deeper waters indicating that these waters were 4 c and 2 c cooler respectively during glacial time the glacial temperature gradient dt dz was similar to today while the base of the thermocline was 100 m shallower these results differ significantly from our earlier results from multiple shell 18o analyses which implied upper thermocline waters were only 1 c cooler and dt dz was greater during the glacial maximum the difference occurs because bioturbation adversely affects multiple shell analyses of glacial aged samples from shallow water depths at all depths above 1500 m foraminiferal 13c are greater during the glacial maximum than the late holocene by at least 0 1 to 0 2 as much as 0 6 in the lower thermocline indicating that nutrient concentrations throughout the thermocline were reduced and there was no oxygen minimum zone during the glacial maximum this suggests greater more uniform ventilation of the thermocline results of single and multiple shell 13c analyses of glacial age foraminifera compare favorably because samples most affected by mixing correspond to water depths where the glacial interglacial change of 13c was small cooler upper ocean waters during the glacial maximum reflect cooler temperatures at the ocean surface where isopycnal surfaces outcrop including large areas of the subtropical ocean a shallower thermocline base is consistent with southward migration of the northern edge of the subtropical gyre or increased mode water production enhanced thermocline ventilation is consistent with more vigorous winds and all isopycnal surfaces outcropping in the area of ekman downwelling

hydrochemistry of groundwater at unique outlets of the bet shean harod multiple aquifer system israel abstract the bet shean and harod valleys are regional recipients and mixing zones for groundwater draining to these valleys from a multiple aquifer system which includes carbonate and basalt aquifers and deep seated reservoirs of brine the outlets of these aquifers are located at the mountain border separating the valleys from the gilboa and ramot issakhar mts the aquifers drain through two types of outlets unique and common the latter type is mainly conditioned by the occurrence of fault blocks acting as connecting media between the aquifers ionic ratios of groundwaters flowing through different carbonate aquifers have not sufficient contrast to facilitate precise identification of source aquifers in the case of basalt aquifers the ratios are unequivocal and sufficient contrast enables such an identification

increased effective moisture in northern vietnam during the little ice age abstract we present a 650 yr record of hydroclimate inferred from 18o values of lacustrine carbonate from ao tien fairy pond in northern vietnam ao tien occupies a collapsed karst basin that formed during the worst drought of the last millennium i e the angkor i drought which marks a dry transitional period between the medieval climate anomaly and the little ice age a multi centennial trend of increasing effective moisture spans the little ice age ending with aridity in the late 18th century that accompanied great societal turmoil across southeast asia after 1850 ce the ao tien record exhibits a drying trend that continues to the present over the last 650 years the 18o inferred hydroclimate is significantly correlated with the reconstructed southern oscillation index of precipitation soipr suggesting that a prolonged la nina like state existed during the little ice age generating overall wetter conditions in vietnam decadal scale droughts and pluvials from the ao tien record agree with a robust tree ring hydroclimate reconstruction from southern vietnam that identified the angkor i and ii droughts of the late 13th early 14th centuries and significant droughts during the early and late 17th century and latter half of the 18th century the decrease in effective moisture during the last 30 years is also evident in the tree rings and is consistent with a documented weakening of the pacific walker circulation major pluvials are indicated for the period between the two angkor droughts and the wettest period of the record is during the early 18th century comparison of the ao tien data with records from indonesia to china indicates regionally coherent climate during the little ice age however the overall wet conditions in easterly sites are difficult to ascribe to shifts in the itcz rather the pattern suggests that pacific walker circulation may have been the overriding control on precipitation

hydrochemical changes due to intensive use of groundwater in the carbonate aquifers of sierra de estepa seville southern spain summary the carbonate aquifers of sierra de estepa situated in southern spain are undergoing intensive groundwater exploitation consequently the volume of pumping surpasses the average recharge for periods of several consecutive years under such conditions nearby springs have either dried up or only function during short time periods after very rainy episodes followed by long droughts during the brief periods when the springs are active their water and the water extracted by pumping are calcium bicarbonates with a spatial temporal variability of their physico chemical characteristics that is mainly conditioned by the degree of functional karstification of each system when the springs are inactive the pumping water gradually increases in salinity and becomes hco 3 clcana clhco 3 naca and clna under the new conditions caused by so much pumping the main factors determining the hydrochemical changes are the mixing of waters and the subsequent reactions of dissolution precipitation between 1 the recharge coming from rainwater 2 the hypersaline inputs from the clay evaporite aquitards situated on the edges and at the base of the aquifer and 3 the water stored in each aquifer the hydrochemical information acquired allowed us to characterize and model the groundwater of these aquifers to study the causes of its great spatial and temporal variability and explain the influence of exploitation this research shows that making sustainable use of water resources associated with carbonate aquifers calls for sound knowledge of the relationship between the aquifer and other bodies of groundwater or surface water the hydrochemical quality of these possible inputs and the vulnerability of the aquifer to exploitation which in turn is conditioned by the ratio between water reserves and recharge

isotopic and geochemical evolution of ground and surface waters in a karst dominated geological setting a case study from belize central america abstract analysis of stable isotopes and major ions in groundwater and surface waters in belize central america was carried out to identify processes that may affect drinking water quality belize has a subtropical rainforest savannah climate with a varied landscape composed predominantly of carbonate rocks and clastic sediments stable oxygen 18 o and hydrogen d isotope ratios for surface and groundwater have a similar range and show high d excess 10 40 8 the high d excess in water samples suggest secondary continental vapor flux mixing with incoming vapor from the caribbean sea model calculations indicate that moisture derived from continental evaporation contributes 13 to overhead vapor load in surface and groundwater concentrations of dissolved inorganic carbon dic ranged from 5 4 to 112 9 mg c l and 13 c dic ranged from 7 4 to 17 4 so 4 2 ca 2 and mg 2 in the water samples ranged from 2 163 2 6593 and 2 90 mg l respectively the dic and 13 c dic indicate both open and closed system carbonate evolution combined 13 c dic and ca 2 mg 2 and so 4 2 suggest additional groundwater evolution by gypsum dissolution and calcite precipitation the high so 4 2 content of some water samples indicates regional geologic control on water quality similarity in the range of 18 o d and 13 c dic for surface waters and groundwater used for drinking water supply is probably due to high hydraulic conductivities of the karstic aquifers the results of this study indicate rapid recharge of groundwater aquifers groundwater influence on surface water chemistry and the potential of surface water to impact groundwater quality and vise versa

seasonal changes in the sources and fluxes of dissolved inorganic carbon through the st lawrence river isotopic and chemical constraint the st lawrence river ranks 16 th in the world rivers for its freshwater discharge into the ocean but its particulate fluxes are relatively low due the upstream presence of the great lakes system using notably 13 c measurements in total dissolved inorganic carbon dic at several stations along stream earlier studies provided information on dissolved inorganic carbon dic fluxes through the st lawrence with some constraints on spatial trends with respect to the in situ dic metabolism here we further document annual dic fluxes and seasonal changes in dic supplies and dic metabolism downstream chemical and isotopic measurements were performed in 1998 on a biweekly basis at four different sites these sites represent respectively the great lakes outflow into the st lawrence system supplies from two tributaries one with a silicate rich precambrian bedrock the other with a carbonate rich paleozoic bedrock and the st lawrence outflow into the maritime estuarine system the 1998 survey yielded a total annual dic flux of 6 10 12 to 7 10 12 g of carbon at the quebec city outlet about 40 higher than estimates from earlier studies this represents about 1 5 of the world river dic supplies to the ocean very strong seasonal variations are observed between the summer low water levels when water supplies from the great lakes into the riverine system may represent up to 80 of the total outflow of the st lawrence river and the spring snowmelt period when tributaries may provide up to 80 of this outflow d 13 c dic values respond to this seasonal cycle with near isotopic equilibrium values with atmospheric co2 during summer and strongly depleted values in other seasons notably during the spring high outflow period this seasonal isotopic cycle is more pronounced at the quebec city outlet where the influence of 13 c depleted dic supplies from tributaries is stronger than upstream the low d 13 c dic values observed from fall to spring may be due to a combination of the following factors i enhanced supplies of 13 c depeleted dic from soils and ground waters from watersheds ii higher oxidation rates of dissolved or particulate 13 c depleted organic carbon and iii a reduced incidence of the in situ photosynthetic activity the outflow and isotopic seasonal cycles result notably in a strong negative correlation between d 13 c dic values and discharge rates estimates of dic supplies from tributaries vs those from the great lakes were calculated using either chemical or isotopic approaches dic supplies from tributaries vary between 5 and 60 of total dic examination of pco2 data indicates a negligible seasonal variability at the great lakes outlet with a mean annual value near equilibrium with atmospheric co2 i n contrast strong seasonal changes are observed downstream at quebec city with minimum pco2 values in summer and a mean

climate controls on soil respired co2 in the united states implications for 21st century chemical weathering rates in temperate and arid ecosystems abstract the most recent ipcc 2007 report predicts that regional scale precipitation patterns will change significantly in the 21st century as a result of increasing atmospheric co 2 the amount of respired co 2 stored in the soil atmosphere is heavily influenced by climate and the concentration of co 2 in soils controls the concentration of dissolved co 2 co 2aq in pore water involved in chemical weathering therefore we can expect changes to chemical weathering rates as a result of climate change which can influence the global carbon cycle through the consumption of co 2 during continental silicate weathering these changes may even be important on human timescales to predict changes to the co 2aq of soil water we have produced an extensive literature review of soil respired co 2 measurements to study the spatial variability of soil respired co 2 we show that respired co 2 concentrations and co 2aq vary with precipitation this study focuses on the western united states where we find a strong relationship between summer average soil respired co 2 and mean annual precipitation for soils forming in or below 900 mm yr 1 precipitation r 2 0 91 the correlation breaks down when higher mean annual precipitation rates are considered restricting the use of this relationship to arid to subhumid precipitation regimes we estimate the response of co 2aq in soil pore water in the western united states to projected anthropogenic co 2 emissions using this new relationship and projected changes in precipitation simulated by the north american regional climate change assessment program for the decade 2051 2060 according to our model co 2aq in soil pore water is expected to decrease by up to 50 in the southwestern united states and to increase by up to 50 in areas of the northern and central great plains these results have important implications for co 2 consumption and changes to terrestrial carbon cycling in the next century

a numerical study on the influence of fractured regions on lake groundwater interaction the lake kinneret sea of galilee case increased lake salinity is a growing problem in arid and semi arid regions operational management which is based on a reliable hydrological understanding has the potential to reduce the lake salinity this is the case of the salinity in lake kinneret sea of galilee where saline water flows into the lake through on shore and off shore springs here we present a time dependent flow and transport numerical model that successfully reproduces the monitored groundwater level discharge and salinity of the lake springs the model utilizes a continuum approach and describes the flow through a confined saline carbonate aquifer which interacts with the discharge lake through fractures and faults in particular the model investigates the hydrology around two groups of springs fuliya and tabgha along the western shore of the lake based on seasonal characteristics of the springs and measured boundary conditions the two springs groups were defined as lake dominated springs lds fuliya and aquifer dominated springs ads tabgha the models of the two groups differ from each other in the distribution of fractured regions that link between the lake and the underlying aquifers the numerical solution shows how the fractured regions affect groundwater head spring discharge and spring salinity the different behavior of the lds and ads was reproduced with an excellent agreement between measured and calculated patterns differences in salinity within a group of springs are shown to be dependent on the depth of the fractured region it was revealed that in addition to the appropriate distribution of fractured regions some adjustment in the up stream boundary conditions is necessary to fully reproduce the system hydrology the model has improved our understanding and provides a prediction tool for future management strategies

uranium isotopes as a natural tracer in the waters of the bet shean harod valleys israel abstract thirty four samples representative of each of the major aquifers and springs in the bet shean harod valleys were analyzed for their uranium isotopes whereas there is relatively small variation in the uranium content large differences are exhibited by the 234 u 238 u activity ratios three distinct water sources are delineated the higher degree of chemical weathering in the basalt aquifer yields low activity ratios it is proposed that the difference in activity ratio within the carbonate waters is due to isotopic changes related to the degree of water maturation which itself is related to the distance the average water travels from the recharge area to the outlets

influence of carbonates on the riverine carbon cycle in an anthropogenically dominated catchment basin evidence from major elements and stable carbon isotopes in the lagan river n ireland abstract investigation of anthropogenic versus natural controls of the carbon cycle in the lagan river revealed a strong influence of carbonates this was evident by increasing ph values along the river as well as isotopic compositions of the riverine dissolved inorganic carbon 13cdic that approached expected values for carbonate dissolution this predominant influence of carbonates existed despite their minor abundance of only 5 in this densely populated catchment basin and outlines their capacity of buffering anthropogenic influences and co2 turnover these effects should be even more pronounced in other rivers where carbonates occupy a larger proportion of the catchment basin geology other controls on the riverine carbon cycle were silicate weathering and respiratory turnover of organic material that originated mainly from anthropogenic inputs and increased the dic pool by up to 26 6 predominant natural controls on the lagan river carbon cycle changed to anthropogenic ones closer to the mouth before discharging into belfast lough a recently installed weir caused stagnant seawater to make up between 53 and 92 of the water mass poor vertical mixing caused o2 decreases and anaerobic sedimentary activity that resulted in methane production recently installed aerators at the sediment surface did not prevent ongoing methanogenesis this was documented by decreased pco2 and more 13c enriched dic values at the sediment water interface when compared to those of surface waters from the same sampling sites installations of such weirs in estuaries of other rivers may cause similar anoxic effects that influence their biogeochemistry

geochemistry of dissolved and suspended loads of the seine river france anthropogenic impact carbonate and silicate weathering this study focuses on the chemistry of the seine river system one of the major rivers in europe and constitutes the first geochemical investigation of both suspended and dissolved loads of this river the seine river drains a typical mesozoic cenozoic sedimentary basin the paris basin constituted of limestones mixed or interbedded with terrigenous sediments derived from the paleoreliefs bordering the mesozoic and cenozoic seas in the context of quantifying the global influence of carbonate and silicate weathering on atmospheric co2 consumption the seine river offers the possibility of examining weathering rates in a flat sedimentary environment under temperate climatic conditions one of the major problems associated with the seine river as with many temperate rivers is pollution we propose in this paper 2 approaches in order to correct the dissolved load of the seine river for anthropogenic inputs and to calculate weathering rates of carbonates and silicates the first uses the dissolved load of rivers and tries to allocate the different solutes to different sources a mixing model based on elemental ratios is established and solved by an inversion technique the second approach consists in using the suspended load geochemistry under steady state conditions we show that the geochemistry of suspended sediments makes it possible to estimate the amount of solutes released during the chemical weathering of silicates and thus to calculate weathering rates of silicates the total dissolved load of the seine river at paris can be decomposed into 2 of solutes derived from natural atmospheric sources 7 derived from anthropogenic atmospheric sources 6 derived from agriculture 3 derived from communal inputs and 82 of solutes derived from rock weathering during high floods the contribution of atmospheric and agriculture inputs predominates the weathering rate of carbonates is estimated to be 48 t km2 yr 25 mm 1000 yr only 10 of carbonates are transported in a solid form the rest being transported in solution co2 consumption by carbonate weathering approaches 400 103 mol km2 yr in the seine river at paris about 2 3 mg l of dissolved cations are found to originate from the chemical weathering of silicates by taking dissolved silica into accounts the total dissolved load derived from silicate weathering is about 6 7 mg l this value is minimal because biological uptake of silica probably occur in the seine river the chemical weathering rate of aluminosilicates is estimated to be 2 t km2 yr the ratio of physical over chemical weathering of silicates range between 1 and 3 and the total chemical and physical erosion rates of sedimentary silicates are about 2 3 mm kyr the co2 consumption by silicate weathering 15 24 103 mol km2 yr and is independent of dissolved silica concentration silicate consumption is thus 20 times less than carbonate consumption in the paris basin compared to the neighboring granitic areas the sedimentary region drained by the seine river has 2 to 3 times lower co2 consumption rates we attribute this difference to the cation depleted nature of the seine basin aluminosilicates which are of sedimentary origin at a world scale the chemical denudation rates found for the seine basin are very low and comparable to those given for tropical lowland rivers draining silicates such as the rivers of the congo and amazon basins in spite of huge climatic differences we attribute this similarity to the low mechanical denudation that characterizes these two types of regions

recharge and salination processes in the carbonate aquifers in israel limestone and dolostone aquifers play a major role in the water supply system of israel in many cases there are brackish to saline springs at their outlets the source of the saline water and the mechanism of salinization differ from place to place in some cases it is due to mixing with seawater mediterranean or dead sea at the fresh saline water interface while in other cases deepseated brines emerge along regional faults the general policy for reclaiming the fresh component of the water before mixing with the saline component is to try to catch the fresh water as far as possible upstream from the outlet in most cases this is the area where the mixing takes place the main case histories in israel are discussed in this paper

hydrologically driven variations in the karst related carbon sink fluxes insights from high resolution monitoring of three karst catchments in southwest china summary rainfall p discharge q water temperature ph and specific electrical conductivity ec of the three karst catchments banzhai huanghou and houzhai with different land uses and carbonate lithologies but similar subtropical monsoonal climate in guizhou province southwest china were monitored with ctdp 300 high resolution multi parameter data loggers during the period of may 2007 october 2013 in addition hco3 and calcium concentrations were titrated in the field and the other major ions determined in the laboratory once every one or two months simple linear regression models were used to link the continuous chemical data to in situ measured data to estimate the concentration of hco3 the co2 partial pressures and the calcite saturation indices on the high resolution logger data continuous karst related carbon sink fluxes csfs were also estimated with the continuous q and hco3 concentrations in each catchment area the primary goal of this study is to understand how discharge and hco3 concentration determine the csfs at the storm scale seasonal scale and annual scale and to estimate the csfs for the three studied catchments results show that the variation in runoff river discharge played a more important role in controlling the csfs than the variation in hco3 for all the karst catchments because of the chemostatic behavior of hco3 in the catchments soil coverage vegetation and bedrock lithology determined the csfs by controlling the proportion of precipitation that recharges groundwater and thus q and controlling the soil co2 productivity and thus hco3 the average csfs in the banzhai huanghou and houzhai karst catchments were 29 3 33 5 and 39 8 t co2 km 2 a 1 respectively which are 15 times higher than those csfs by silicate weathering in the silicate rock catchments with similar hydrology showing the dominant role of carbonate weathering in the rock weathering related carbon sink the interannual change in csfs was large 1 7 2 5 fold for this study depending mainly on the variations of catchment river discharge e g high flow year vs low flow year this suggests that the conventional view that pre and post anthropogenic riverine carbon fluxes are equal is problematic in that large changes in river hydrology caused by global climate and land use and land cover changes have already been documented

weathering processes in the ganges brahmaputra basin and the riverine alkalinity budget abstract we present river chemistry data for a network of rivers draining the western and central nepal himalaya our sampling locations cover the system from the sources of rivers in tibet to the gangetic plain water samples were collected throughout the year including the monsoon season for rivers in nepal and for the ganges and brahmaputra in bangladesh rivers draining the north himalaya are characterized by low discharge under a cold and arid climate main stream waters have 13 c dic near 0 and high so42 so42 hco3 ratios xso4 with values around 40 eq and high cl ca is the dominant cation ca2 cations 55 to 75 eq after correction of sodium by chloride dissolved sulfate is produced in waters from the tethian sedimentary series whereas chlorine is related to thermal waters dissolved sulfate is primarily derived from sulfide oxidation rather than evaporite dissolution 13 c dic values of up to 3 9 show that metamorphic co2 is an important weathering agent rivers of the north himalayan basins have about 50 of their alkalinity derived from carbonate dissolution 20 from biogenic activity and 30 from metamorphic co2 on the south flank of the himalaya rivers are more depleted in 13 c and have on average lower xso4 most rivers have 13 c dic and xso4 values compatible with a simple mixing between soil co2 and sulfate derived from sulfide oxidation during the monsoon discharge increases by a factor 20 but the total dissolved concentration is only slightly reduced xso4 and 13 c decrease while ca cations increases implying enhanced dissolution of pedogenic calcite as a whole the g b riverine flux of alkalinity derived from silicate weathering is around 2 7 1011 mol year modest at the global scale sulphuric acid controls 20 30 of the weathering reaction in the brahmaputra and 6 to 9 in the ganges na and k balance 60 to 65 of the silicate derived alkalinity flux and the long term co2 consumption by ganges and brahmaputra is near 6 4 1010 mol year the flux of metamorphic co2 converted to alkalinity via weathering reactions is ca 1 1010 mol year

interpretation of ancient epikarst features in carbonate successions a note of caution abstract in shallow marine carbonate successions of the phanerozoic evidence for shorter lived subaerial exposure stages of ancient carbonate seafloors is commonly found in the presence of small scale epi karst solution pits in discontinuity surfaces under favorable conditions these solution features are accompanied by soil features including calcretes or root traces alveolar septal structures petrographic evidence such as pendant cements circumgranular cracks or pisoliths bleaching and staining of carbonate rocks or circumstantial geochemical evidence perhaps more often however ancient carbonate successions lack undisputable evidence for meteoric karsting using a well exposed case example from the aptian of oman we here document that the superficial visual field inspection of solution pits in discontinuity surfaces may lead to erroneous interpretations outcrops at jabal madar a diapiric structure allow for an in depth analysis of dissolution features in the regionally extensive top shu aiba discontinuity the solution pits discussed here were investigated for their stratigraphic position their orientation relative to bedding planes diagenetic and petrographic features and their potential relation to extensional fractures related to the updoming of jabal madar the main message brought forward is that under burial conditions spatially localized hypogenic carbonate leaching may form features that are easily mistaken for ancient meteoric epikarst these features preferentially form in interstratal positions where fractured massive carbonate rocks are capped by a major discontinuity surface overlain by non fractured argillaceous sediments thus while dissolution reprecipitation processes in the burial phreatic realm are omni directional in permeable carbonates low permeability argillaceous fines are not or to a much lesser extent prone to chemical corrosion as a consequence carbonate aggressive burial fluids leach out pits at the carbonate shale interface these appear to protrude perpendicular as bowl shaped depressions into the underlying limestones and are in the case examples documented here preferentially aligned along factures these findings have significance for the interpretation of ancient epikarst features in shallow marine carbonate successions

water percolation process studies in a mediterranean karst area to investigate processes of water percolation the drip response of stalactites in a karstic cave below a 143 m2 sprinkling plot was measured the experiment was conducted in mount carmel israel at the end of the dry season and intended to simulate a series of two high intensity storms on dry and wet soils in addition to hydrometric measurements soil moisture surface runoff stalactite dripping rates two types of tracers electrical conductivity and bromide were used to study recharge processes water origin and mixing inside a 28 m vadose zone results suggested that slow continuous percolation through the rock matrix is of minor importance and that percolating water follows a complicated pattern including vertical and horizontal flow directions while bromide tracing allowed identification of quick direct flow paths at all drips with maximum flow velocities of 4 3 m h mixing analysis suggested that major water fractions were mobilized by piston flow pushing out water stored in the unsaturated zone above the cave under dry preconditions 80 mm of artificial rainfall applied in less than 7 h was not enough to initiate significant downward water percolation most water was required to fill uppermost soil and rock storages under wet preconditions during the second day sprinkling higher water contents in soils and karst cavities facilitated piston flow effects and a more intense response of the cave drips results indicate that in mediterranean karst regions filling of the unsaturated zone including soil and rock storages is an important precondition for the onset of significant water percolation and recharge this results in a higher seasonal threshold for water percolation than for the generation of surface runoff copyright 2010 john wiley sons ltd

isotopic effects on inorganic carbon in a tropical river caused by caustic discharges from bauxite processing abstract stable c isotope compositions of dissolved inorganic c dic and carbonate sediment in a jamaican river rio cobre are used as natural tracers of accidental spillage of bauxite processing liquor and waste water bauxite processing produces highly caustic oh and co 2 3 liquor and wash waters these hydroxide rich waters absorb atmospheric co 2 that is isotopically fractionated resulting in very negative carbonate 13 c and 18 o values accidental spillage of these liquors into rivers causes rapid precipitation of caco 3 as a fine grained suspension whiting and subsequent deposition as calcite sediment at the time of dic sampling whiting was not evident however 13 c dic values at sites with a history of contamination were about 2 more negative than ambient values the history of bauxite processing spillages is recorded in the 13 c values of carbonate riverbed sediments at sites known to be impacted particulate carbonate samples have 13 c values between 11 2 and 14 2 values that are between 1 and 4 more negative than the predicted ambient 13 c value similarly 18 o values of carbonate sediments at impacted sites are on average 2 more negative than those from sites above and below them supporting the interpretation that the whiting events form precipitates with isotopically negative values contamination is quite localized because carbonate sediments downstream of impacted sites show no evidence of anomalous isotope values this suggests that the particulate carbonate is either flushed or re dissolves and is diluted downstream the carbonate whitings are thus highly visual but relatively benign although the associated ph and dissolved al 3 and na flushes might have more serious impacts on the river environment

geochemistry of the dissolved load of the changjiang basin rivers anthropogenic impacts and chemical weathering abstract this study focuses on the chemical and sr isotopic compositions of the dissolved load of the rivers of the changjiang basin one of the largest riverine systems in the world water samples were collected in august 2006 from the main tributaries and the main changjiang channel the chemical and isotopic analyses indicated that four major reservoirs carbonates silicates evaporites and agriculture urban effluents contribute to the total dissolved solutes the overall chemical weathering carbonate and silicate rate for the changjiang is approximately 40 ton km2 year or 19 mm kyr similar to that of the ganges brahmaputra system and the basin is characterized by carbonate and silicate weathering rates ranging from 17 to 56 ton km2 year and from 0 7 to 7 1 ton km2 year respectively in the lower reach of the changjiang main channel the weathering rates are estimated to be 36 and 2 2 ton km2 year for carbonates and silicates respectively it appears that sulphuric acid may dominate chemical weathering reactions for some sub basins the budgets of co2 consumption are estimated to be 646 109 and 191 109 mol year by carbonate and silicate weathering respectively the contribution of the anthropogenic inputs to the cationic tds of the changjiang is estimated to be 15 20 for the most downstream stations our study suggested that the changjiang is strongly impacted by human activities and is very sensitive to the change of land use

temperature and co2 dependency of global carbonate weathering fluxes implications for future carbonate weathering research abstract carbonate weathering and transfer of carbon towards the coastal zone is one of the relevant sinks for atmospheric co2 controlled by hydrology ecosystem respiration river water degassing and further factors specifically the connection between the soil rock system to the river systems and instream processes affecting the weathering product fluxes remain under researched based on constraints for soil rock pco2 river pco2 and an identified dependence of river alkalinity on temperature this work tested which controls should be considered at the global scale to accomplish a more holistic carbonate rock weathering model compiled river data suggests that with increasing land temperature above approximately 11 c the amount of instream alkalinity in carbonate catchments decreases due to the temperature effect on the carbonate system while the converse holds true at lower temperatures latter is in accordance with calcite dissolution controlled by soil rock pco2 estimates based on ecosystem respiration in addition the type of the weathering system open semi closed to closed system with respect to co2 was identified to be highly relevant for global weathering estimations open systems seem to be the most dominant boundary condition of calcite weathering in the soil profile tropical areas with thick soil layers however cause the carbonate weathering system to shift from open to semi closed or closed system conditions the findings support that calcite weathering fluxes in the soil profile are higher than the fluxes to the ocean transported by rivers furthermore an increase in mean land temperature does not necessarily translate into an increase of lateral weathering fluxes because it might have an influence on soil development discharge co2 degassing soil respiration and calcite dissolution all these named factors need to be addressed to be able to quantify global carbonate weathering fluxes and to assess the sensitivity of carbonate weathering fluxes on climate variability future works should focus on collecting more temporal river chemistry data mainly in tropical regions to understand the main mechanism causing the observed decrease of alkalinity concentration with temperature

use of 13c to trace origin and cycling of inorganic carbon in the rhone river system dissolved inorganic carbon dic and particulate inorganic carbon pic were sampled at 20 sites on the rhone and its main tributaries from switzerland to the mediterranean in march september and july flood event 1996 flux estimation and dic and pic values are used to trace watershed inputs and fluvial processes affecting the inorganic carbon budget dic concentration and values vary between 1 mm at 5 near the rhone s source and 3 mm at 10 near its mouth with tributaries draining lowland carbonate dominated areas at 3 8 mm and 11 there is an inverse relationship between river dic concentration and dic the headwaters are characterized by high dic values and low dic indicating a minor input of respired co2 dic should be mainly produced through the reaction of carbonate with atmospheric co2 or organic sulfuric acids in lowland carbonate dominated areas values of 11 are consistent with production of dic by weathering of limestone c 1 with co2 derived from the oxidation of organic matter 21 5 the evolution of the rhone s dic concentration and appear to be largely determined by mixing between the rhone and its main tributaries the co2 fluxes and dic mass balance calculated for the different segments of the rhone point to a net but very limited input of fluvial respired co2 from the oxidation of organic c 5 the pic represents a small but quite variable fraction of the inorganic carbon 3 except on alpine catchments and during floods in these cases it can be up to 10 of the dic concentration and export the carbon and oxygen isotopic composition of pic from the rhone during a flood and from alpine tributaries falls within the range of limestones 2 6 relatively light pic isotopic composition indicate mixing of sedimentary rocks and carbonate precipitated in situ data for the rhone system are typical of watersheds presenting high chemical weathering rates for hco3 and alpine lowland conditions

response of dissolved inorganic carbon dic and δ13cdic to changes in climate and land cover in sw china karst catchments abstract monthly hydrochemical data and 13c of dissolved inorganic carbon dic in karst water samples from september 2007 to october 2012 were obtained to reveal the controlling mechanisms on dic geochemistry and 13cdic under different conditions of climate and land cover in three karst catchments banzhai dengzhanhe and chenqi in guizhou province sw china dic of karst water at the banzhai site comes mainly from carbonate dissolution under open system conditions with soil co2 produced by root respiration and organic carbon decomposition with lowest 13c values under its dense virgin forest coverage weaker carbonate bedrock dissolution due to sparse and thin soil cover results in lower 13cdic pco2 dic and ec and lower cation and anion concentrations at the chenqi site larger soil co2 input from a thick layer of soil results in high pco2 and dic and low ph sic and 13cdic in the karst water at the dengzhanhe site a lesser soil co2 input due to stronger karst rock desertification and strong gypsum dissolution contribute to higher 13cdic high ec and high cation and anion concentrations soil co2 inputs controlled by biological activity and available soil moisture carbonate bedrock dissolution dilution and degassing effects vary seasonally following rainfall and temperature changes consequently there are seasonal cycles in hydrochemistry and 13cdic of the karst water with high pco2 and low ph ec sic and 13cdic values in the warm and rainy seasons and vice versa during the cold and dry seasons a strongly positive shift 3 in 13cdic occurred in the drought year 2011 indicating that 13cdic in groundwater systems can be an effective indicator of environmental and or climate changes

the rate of flushing as a major factor in determining the chemistry of water in fossil aquifers in southern israel abstract issar a 1981 the rate of flushing as a major factor in determining the chemistry of water in fossil aquifers in southern israel in w back and r letolle guest editors symposium on geochemistry of groundwater 26th international geological congress j hydrol 54 285ndash 296 a parallel trend has been found to exist between the isosalinity lines and the isopiezo metric lines in the fossil aquifers of the nubian sandstones in southern israel and the central sinai the flow pattern in these aquifers determines the rate of mixing between paleo seawater and paleo meteoric water this flowpattern is determined by the spatial relations between the nubian sandstone outcrops in the central sinai and the major fault lines of the dead sea and suez rift valleys a cumulative chemical composite diagram in which 18o stable isotope data were plotted makes it possible to classify the water and to trace the ratios in the mixture

chemical dynamics of the st lawrence riverine system δdh2o δ18oh2o δ13cdic δ34ssulfate and dissolved 87sr 86sr chemical and stable isotope analyses of the st clair detroit niagara and st lawrence rivers st lawrence system and their tributaries show that the chemical and isotopic compositions of the waters are strongly controlled by the geology of their drainage basins tributaries draining the canadian shield have very low tds hco3 so42 ca2 mg2 no3 sr2 higher si and fetotal and high 87sr 86sr ratios 0 710 0 713 the grand and thames rivers that drain paleozoic limestones dolostones and evaporites are characterized by opposite attributes the st lawrence and the tributaries draining the canadian appalachians fall between these two endmembers the st clair detroit and niagara rivers do not show any pronounced seasonal variations in major component chemistry due to buffering by the great lakes in contrast pronounced seasonal variations characterize the lower st lawrence mainly because of significant tributary inputs into the overall water budget the d and 18o in the st lawrence range from 60 9 to 44 5 and from 8 5 to 6 1 smow respectively much heavier than the comparative values measured for the tributaries 92 8 to 58 3 and 13 1 to 8 5 this is a consequence of evaporative loss that over the residence time of water of 102 years equals about 7 of the water volume in the great lakes the strontium and sulfur isotopic values for the st lawrence system are relatively uniform with measured values from 0 70927 to 0 71112 for 87sr 86sr and from 4 3 to 5 6 for sulfate 34s their seasonal variations are also minor the strontium and sulfur fluxes of the st lawrence river are calculated to be 7 84 108 and 1 09 1011 mol a respectively the relative contributions of the great lakes tributaries and other sources to these fluxes are 73 16 11 for strontium and 64 13 23 for sulfur isotopic composition of dissolved inorganic carbon 13cdic in the st lawrence system ranges from 4 7 to 0 7 considerably heavier than the values for the tributaries 16 5 to 6 7 the light 13cdic values for the tributaries suggest that co2 from bacterial respiration plays an important role in the isotopic composition of riverine dic however in the main stem river s this bacterial signal is masked by isotopic equilibration with atmospheric co2 due to the long residence time of water in the great lakes seasonally the main stem river s have heavier 13c values in the fall than in the spring a consequence of preferential 12c consumption by photosynthetic plants in the epilimnion of the great lakes during the growth season in the down stream portion of the st lawrence river influx of isotopically light tributary waters causes progressive 13c depletion from 1 3 to 2 0 and 1 4 to 3 0 in the fall and spring respectively the total dic carbon flux of the st lawrence river is calculated to be 3 9 1011 mol a mass balance calculations show that the relative contributions of the great lakes tributaries decay of organic matter exchange with the atmosphere and dissolution of carbonates to this total dic flux are 81 13 2 6 10 in the spring and 83 15 2 4 0 in the fall respectively

transport of dissolved carbon and co2 degassing from a river system in a mixed silicate and carbonate catchment summary assessing the origin transformation and transport of terrestrially derived carbon in river systems is critical to regional and global carbon cycles particularly in carbonate terrains which represent the largest carbon reservoir on the earth s surface for this reason we evaluated sources cycling and fluxes of dissolved organic and inorganic carbon doc and dic and riverine co 2 degassing to the atmosphere in the santa fe river in north central florida a sub tropical river that flows across two distinct hydrogeological settings of a region dominated by carbonate karst one setting occurs in the upper river catchment where the carbonate floridan aquifer is confined by the siliciclastic hawthorn group while the other setting occurs in the lower catchment where the river flows across the unconfined floridan aquifer the upper catchment is characterized by doc rich and dic poor water and the dic has more variable and lower 13 c values compared to the lower catchment the river in the upper catchment degasses more co 2 to the atmosphere 1156 g c m 2 yr 1 than in the lower catchment 402 g c m 2 yr 1 because soil respired carbon and organic matter decomposition increase dissolved co 2 concentration much of which is consumed during carbonate dissolution reactions in the lower catchment the co 2 flux from the water surface to the atmosphere during a flood event is three times greater than during base flow suggesting that excess precipitation flushes soil organic carbon to the river through interflow and enhances the loss of terrestrial carbon via river water to the atmosphere our values of co 2 fluxes to the atmosphere lie within the range of fluxes from the world s rivers but fluxes from the carbonate dominated region are at the low end while fluxes from the siliciclastic region are at the high end these results indicate that catchment lithologies particularly whether carbonate or siliciclastic as well as flow are critical to carbon budgets in rivers and thus are linked to the global carbon cycle

carbon fluxes pco2 and substrate weathering in a large northern river basin canada carbon isotope perspectives abstract isotopic composition of dissolved inorganic carbon 13 c dic in the ottawa river basin is about 8 and 16 for lowland carbonate and upland silicate tributaries respectively this suggests that 1 the source of dic to the ottawa river is soil respiration and carbonate weathering 2 exchange with the atmosphere is unidirectional or volumetrically unimportant and 3 in river respiration and photosynthesis are not significant influences on the river carbon budget accepting these constraints chemical and isotopic data are used to reconstitute soil pco2 for tributary catchments averages for upland silicate mixed and lowland carbonate basins are calculated to be roughly 2000 5000 and 30 000 ppm respectively these values are used as input to model the pathway of carbon through the watershed rain water to soil water to river water the flux of carbon from the ottawa river as dic is calculated to be 4 3 1010 mol c a utilizing carbon isotopes 75 and 25 of the ca2 mg2 flux is calculated to originate from carbonate and silicate weathering respectively and 61 of the dic is calculated to originate from organic respiration the latter represents some 6 of respired carbon in the basin assuming an average respiration rate of 0 5 mmol c m 2 h 1 based on a diffusion model co2 evasion to the atmosphere from the ottawa river and its tributaries is estimated to be 1 3 1010 mol c a or 30 of the dic flux

changes in north atlantic deep sea temperature during climatic fluctuations of the last 25 000 years based on ostracode mg ca ratios 1 we reconstructed three time series of last glacial to present deep sea temperature from deep and intermediate water sediment cores from the western north atlantic using mg ca ratios of benthic ostracode shells although the mg ca data show considerable variability scatter that is common to single shell chemical analyses comparisons between cores between core top shells and modern bottom water temperatures bwt and comparison to other paleo bwt proxies among other factors suggest that multiple shell average mg ca ratios provide reliable estimates of bwt history at these sites the bwt records show not only glacial to interglacial variations but also indicate bwt changes during the deglacial and within the holocene interglacial stage at the deeper sites 4500 and 3400 m water depth bwt decreased during the last glacial maximum lgm the late holocene and possibly during the younger dryas maximum deep sea warming occurred during the latest deglacial and early holocene when bwt exceeded modern values by as much as 2 5 c this warming was apparently most intense around 3000 m the depth of the modern day core of north atlantic deep water nadw the bwt variations at the deeper water sites are consistent with changes in thermohaline circulation warmer bwt signifies enhanced nadw influence relative to antarctic bottom water aabw thus maximum nadw production and associated heat flux likely occurred during the early holocene and decreased abruptly around 6500 years b p a finding that is largely consistent with paleonutrient studies in the deep north atlantic bwt changes in intermediate waters 1000 m water depth of the subtropical gyre roughly parallel the deep bwt variations including dramatic mid holocene cooling of around 4 c joint consideration of the mg ca based bwt estimates and benthic oxygen isotopes suggests that the cooling was accompanied by a decrease in salinity at this site subsequently intermediate waters warmed to modern values that match those of the early holocene maximum of 7 c intermediate water bwt changes must also be driven by changes in ocean circulation these results thus provide independent evidence that supports the hypothesis that deep ocean circulation is closely linked to climate change over a range of timescales regardless of the mean climate state more generally the results further demonstrate the potential of benthic mg ca ratios as a tool for reconstructing past ocean and climate conditions

the dynamics of the oceanic subtropical gyres recent theoretical advances in physical oceanography have produced plausible models for the structure of the circulation in the oceans subtropical gyres these theoretical ideas are reviewed and assessed in the light of present observational evidence the dominant role of potential vorticity is emphasized in describing the strong interplay between three dimensional distributions of density and velocity in particular the complementary processes of subduction and recirculation jointly act to shape the circulation pattern of the subtropical gyre

numerical analysis of the groundwater regime in the western dead sea escarpment israel west bank water is scarce in the semi arid to arid regions around the dead sea where water supply mostly relies on restricted groundwater resources due to increasing population in this region the regional aquifer system is exposed to additional stress this results in the continuous decrease in water level of the adjacent dead sea the interaction of an increasing demand for water due to population growth and the decrease of groundwater resources will intensify in the near future thus the water supply situation could worsen significantly unless sustainable water resource management is conducted in this study we develop a regional groundwater flow model of the eastern and southern judea group aquifer to investigate the groundwater regime in the western dead sea drainage basin of israel and the west bank an extensive geological database was developed and consequently a high resolution structural model was derived this structural model was the basis for various groundwater flow scenarios the objective was to capture the spatial heterogeneity of the aquifer system and to apply these results to the southern part of the study area which has not been studied in detail until now as a result we analyzed quantitatively the flow regime the groundwater mass balance and the hydraulic characteristics hydraulic conductivity and hydraulic head of the cretaceous aquifer system and calibrated them with pest the calibrated groundwater flow model can be used for integrated groundwater water management purposes in the dead sea area especially within the framework of the sumar project

karst biogeochemistry in china past present and future the dissolution and deposition processes of carbonate rock called co2 water carbonate rock interaction are controlled by complex interactions among the biosphere pedosphere atmosphere and lithosphere the interactions between biogenic activity and the co2 water carbonate rock system dissolution and precipitation of carbonate rocks element cycles and so forth had been named karst biogeochemistry in order to reveal their internal control mechanism over space and time chinese researchers undertook an in depth exploration of their interrelationships the main results of karst biogeochemistry in china can be summarized as follows i biogenic activity plays an important role in regulating dissolution and precipitation of carbonate rocks ii biogenic metabolic effects are involved in the positive or negative modulation of 13c 15n and the cycling of other elements iii co2 exchange during carbonate rock dissolution and precipitation which is mainly due to photosynthesis results in the accumulation of organic matter and iv primary karst biogeochemistry models have been established to evaluate carbon and nitrogen cycling in addition to these findings future studies should increasingly focus on the following topics i the apparent stability and transformation of dissolved organic carbon caused by microbial activities need to be clarified ii the temporal spatial scales of microbial biomineralization and the accompanying variances of karst biogeochemical cycles should be investigated to comprehensively understand the transformations and transport of substrates from biological activity in the co2 water carbonate rock system iii regional global scale models on karst biogeochemical cycles should be developed for the study of large small scale spatial and temporal variance on karst biogeochemical cycles iv new advanced techniques and methods are required and should be applied for the karst studies involving mathematics hydrochemistry isotope chemistry geology biology and so forth

saline groundwater in israel its bearing on the water crisis in the country abstract one of the major causes for the deterioration of water quality bearing heavily on the water crisis in israel is the ongoing contamination of its water resources by saline water bodies the present paper reviews the geochemical processes forming saline water lists and explains certain chemical and isotopic parameters which enable understanding these processes and describes the saline groundwater bodies and various salinization phenomena occurring in the country s various aquifers deterioration of groundwater in israel is caused by numerous natural processes such as encroachment of sea water migration of connate highly pressurized brines penetrating into fresh groundwater by subsurface dissolution of soluble salts originating in surrounding country rocks and by water rock interaction in addition to sea water two saline water bodies were identified as the main factors causing salinization of fresh groundwater a ca chloride brines encountered in the jordan dead sea rift valley in various parts of the negev and of the coastal plain and b na chloride saline water identified in the subsurface of the negev and in the southern part of the coastal plain intensive exploitation of groundwater in israel has disturbed the natural equilibrium which prevailed between fresh and saline water the newly established groundwater flow regimes have facilitated the migration of saline water bodies their participation in the active hydrological cycle and the progressive contamination of fresh groundwater these processes which were not anticipated by planners and water resources managers emphasize that large scale groundwater exploitation was undertaken without giving sufficient consideration to the occurrence and subsurface migration of saline water and brines

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

the hydrochemical identification of groundwater flowing to the bet she an harod multiaquifer system lower jordan valley by rare earth elements yttrium stable isotopes h o and tritium abstract the bet she an and harod valleys in israel are regional recipients and mixing zones for groundwater draining from a multiple aquifer system which includes carbonate and basalt aquifers and deep seated pressurized brines the aquifers drain through two types of outlets distinct and mixed the latter type is mainly conditioned by the occurrence of fault blocks related to the jordan rift system which act as connecting media between the aquifers and facilitate interaquifer flow conjoint application of rare earth element distribution and water isotopes enables detection of the local areas replenishment by rainfall infiltration and in connection with the position of wells or springs the identification of groundwater flow paths once stationary equilibria are established changes of rey composition between rey in groundwater and their surface adsorption are negligible in areas with little soil coverage and vegetation even recharge over young tertiary and diagenetic cretaceous limestones is distinguishable by their rey distribution patterns groundwater recharged over tertiary limestones show higher rey abundance and more significant ce anomalies than those derived from the cretaceous limestones weathering of alkali olivine basalts leads to rey patterns in groundwater depleted in the middle ree the improved knowledge of the hydrological systems is thought to be useful for regional hydrogeological modeling and for designing rational water management schemes

chemical weathering processes in the yalong river draining the eastern tibetan plateau china abstract to better understand chemical weathering and controlling processes in the yalong river of the eastern tibetan plateau this study presents major ion concentrations and stable isotopes of the dissolved loads the isotopic compositions 13c dic 34s and 18o so4 of the dissolved loads are very useful to quantify solute sources and define the carbon budget related with chemical weathering in riverine systems the isotopic composition of sulphate demonstrates that most of the sulphate is derived from sulphide oxidation particularly in the upper reach of the yalong river the correlations between 13c dic water chemistry and isotopes of sulphate suggest that the carbon dynamics are mainly affected by carbonate weathering by sulphuric acid and equilibration processes approximately 13 of the dissolved inorganic carbon in the yalong river originates from carbonate weathering by strong acid the co2 consumption rates are estimated to be 2 8 105 mol km2 yr and 0 9 105 mol km2 yr via carbonate and silicate weathering in the yalong river respectively in this study the influence of sulphide oxidation and metamorphic co2 on the carbon budget is estimated for the yalong river draining the eastern tibetan plateau

hydrochemical changes induced by overexploitation of groundwater at common outlets of the bet shean harod multiple aquifer system israel abstract the bet shean and harod valleys are regional recipients and mixing zones for groundwaters draining into them from a multiple aquifer system which includes carbonate and basalt aquifers and deep seated reservoirs of brine the aquifers drain through two types of outlets unique and common the latter type is mainly conditioned by the occurrence of fault blocks acting as connecting media between the aquifers ca chloride brines originating from deep seated and confined reservoirs leak along the major faults and contaminate the relatively fresh groundwaters originating from the regional aquifers during the last two decades the salinity of groundwaters at the outlets of aquifers and in springs discharging into the valleys have increased as the result of overexploitation the changes in the chemical composition of these waters indicated inflow of dilute ca chloride brines which replace at an ever increasing rate the fresh water of the area the inflow of brines is limited to fault zones and seems to be controlled by the counterpressure of the overlying fresh water overexploitation diminishes this counterpressure thus facilitating the progressive upflow of brines

chemical weathering in the upper reaches of xijiang river draining the yunnan guizhou plateau southwest china abstract chemical and strontium isotopic compositions of nanpanjiang river and beipanjiang river in the upper reaches of xijiang river draining the yunnan guizhou plateau southwest china were measured with a main purpose to understand the rock weathering and associated co 2 consumption rates in the karstic landform dominated area the chemical ion composition of the river water is characterized by dominance of ca 2 mg 2 and hco 3 and so 4 2 which account for more than 90 of total ion concentration 87 sr 86 sr ratios of nanpanjiang river water range between 0 7080 and 0 7140 while those of most beipanjiang river water vary within a limited range from 0 7075 to 0 7085 weathering of carbonate rocks dominate chemistry of major ions especially in the water of beipanjiang river whereas weathering of silicate minerals in the upper reaches of nanpanjiang river basin is obvious in addition to carbonate weathering mainly according to the sr isotopic composition of the river water analyses of the stoichiometry of the river water show that the water chemistry is controlled by carbonate dissolution not only by carbonic but also by sulfuric acid and indicate that sulfuric acid plays an important role in carbonate weathering the sulfate in river water is mainly from atmospheric input by coal combustion industries and from oxidation of sulfide minerals during weathering of coal containing strata and coal mining in the catchment the chemical weathering rates of silicate and carbonate and associated co 2 consumption rates by both carbonic and sulfuric acid and by only carbonic acid are respectively estimated the results show that chemical weathering rates of carbonate and silicate weathering in beipanjiang river basin are higher than those of nanpanjiang river basin showing linkages of geology and geography in the catchment to crustal weathering the involvement of sulfuric acid in carbonate weathering greatly enhances the carbonate weathering but lowers the co 2 consumption rates indicating that sulfide acid is an important agent to rock weathering and the role of sulfide acid should further be clarified in view of the regional and global budget of co 2

chemical erosion in the eastern himalaya major ion composition of the brahmaputra and δ13c of dissolved inorganic carbon abstract major ion composition of waters 13 c of its dic dissolved inorganic carbon and the clay mineral composition of bank sediments in the brahmaputra river system draining india and bangladesh have been measured to understand chemical weathering and erosion and the factors controlling these processes in the eastern himalaya the time series samples collected biweekly at guwahati from the brahmaputra mainstream were also analyzed for the major ion composition clay mineralogy and chemical index of alteration cia of sediments suggest that weathering intensity is relatively poor in comparison to that in the ganga basin this is attributed to higher runoff and associated physical erosion occurring in the brahmaputra basin the results of this study show for the first time spatial and temporal variations in chemical and silicate erosion rates in the brahmaputra basin the subbasins of the brahmaputra watershed exhibit chemical erosion rates varying by about an order of magnitude the eastern syntaxis basin dominates the erosion with a rate of 300 t km 2 y 1 one of the highest among the world river basins and comparable to those reported for some of the basaltic terrains in contrast the flat cold and relatively more arid tibetan basin undergoes much slower chemical erosion 40 t km 2 y 1 the abundance of total dissolved solids tds 102 203 mg l in the time series samples collected over a period of one year shows variations in accordance with the annual discharge except one of them cause for which is attributable to flash floods na na corrected for cyclic component shows a strong positive correlation with si indicating their common source silicate weathering estimates of silicate cations na sil k sil ca sil mg sil suggest that about half of the dissolved cations in the brahmaputra are derived from silicates a proportion higher than that for the ganga system the co 2 consumption rate due to silicate weathering in the brahmaputra watershed is 6 10 5 moles km 2 y 1 whereas that in the eastern syntaxis subbasin is 19 10 5 moles km 2 y 1 similar to the estimates for some of the basaltic terrains this study suggests that the eastern syntaxis basin of the brahmaputra is one of most intensely chemically eroding regions of the globe and that runoff and physical erosion are the controlling factors of chemical erosion in the eastern himalaya

identification of dissolved sulfate sources and the role of sulfuric acid in carbonate weathering using δ13cdic and δ34s in karst area northern china karst groundwater is one of the most important water resources for agriculture and industry in fenyang city of shanxi province northern china in the last few decades excessive exploitation of groundwater and other human activities have caused serious environmental problems in this area hence it is essential to identify the resources of pollutants that deteriorate the water quality in the area a total of 16 water samples were collected to assess the hydrochemical characteristics from wells and springs in bare karst area northern fenyang and covered karst region south of the city the chemical composition of groundwater was characterized by a dominance of ca2 mg2 hco3 and so42 which accounted for more than 85 of the total ion concentrations indicating that limestone dissolution by weathering controls water chemical composition so42 in the groundwater showed high positive significant correlation with hco3 and 13cdic showing that carbonate dissolution by sulfuric acid has important contribution to groundwater chemical composition and 13cdic value the relationship between 34s and 1 so42 revealed that the sources of so42 are different in various types of groundwater in the bare karst area so42 in springs mainly came from atmospheric precipitation while in the shallow wells it mainly came from human activities in the covered karst region so42 in quaternary pores water was mainly from anthropogenic inputs while in the deep wells it was mainly from gypsum dissolution in gypsum mine water so42 was mainly from gypsum dissolution comparing with the bare karst area human activities have significantly changed the chemical composition of groundwater in the covered karst region therefore more control policies and measures should be formulated and applied to protect the covered karst region in the future

a four component mixing model for water in a karst terrain in south central indiana usa using solute concentration and stable isotopes as tracers the study area lies in a highly karstified carbonate terrain in south central indiana sinkholes conduits and caves form large secondary pathways for the subsurface flow as a result the discharge from a main emergence point for the subsurface flow system the orangeville rise quickly responds to the storm events and shows wide variations in flow rate water chemistry and stable isotopic compositions these responses are attributed to the mixing of water in secondary pathways in the study area recharge occurs through the thick mantled karst plain and the sinkhole plains and the role of soil layer and epikarst in the recharge process is of great importance rain dic 2 hco3 mg l 13cdic 7 soil water dic 544 hco3 mg l 13cdic 14 7 epikarstic water dic 224 hco3 mg l 13cdic 13 6 and phreatic diffuse flow water dic 299 hco3 mg l 13cdic 11 8 generally showed unique and constant dissolved inorganic carbon dic and 13cdic values over time using dic and 13cdic as tracers a four component mixing model was established for the karstic flow system by constructing the discharge hydrograph separation curves the mixing ratio of each component rain 10 6 soil 3 1 epikarstic 52 3 and phreatic 34 0 water was determined for the orangeville rise discharge over the testing period of 104 h after the storm event of 10 4 90 vadose water occupied 55 4 of spring discharge and this demonstrates the importance of the unsaturated zone especially the epikarst in the karstic flow systems

earthquakes and sea level space and terrestrial metrology on a changing planet the complacency with which man inhabits continent ocean margins or plate boundaries is based on the assumption that sea level rise and periodic seismicity are acceptable risks the forecast of future sea level or future seismicity is essential for informed assessment of these risks the historical data from which forecasts may be derived are in each case of limited antiquity and uneven spatial distribution developments in space geodesy and crustal deformation metrology in the past two decades offer the means to acquire a homogeneous global data set for monitoring relative vertical and horizontal motions of the earth s surface to within several millimeters these new tools are reviewed in terms of their application to forecasting trends in sea level rise and forecasting damaging earthquakes

assessment of land subsidence mechanisms triggered by dolomitic marble dissolution from hydrogeochemistry and stable isotopes of spring waters abstract this study presents geochemical results of springs draining a small humid tropical watershed composed of geologically dolomitic marbles in central sri lanka water samples were investigated for their major ion chemistry water stable isotope composition 2 h h2o and 18 o h2o and isotope composition of dissolved inorganic carbon 13 c dic from major ion chemistry ca 2 and mg 2 were the dominant cations and were balanced mostly by hco 3 all collected spring water samples scattered around the local meteoric water line with values from 31 9 to 46 8 for 2 h h2o and from 5 5 to 7 4 for 18 o h2o against vsmow this indicates local groundwater recharge pathways by regional precipitation rather than water from deeper aquifer systems concentrations of dissolved inorganic carbon dic ranged from 0 91 to 9 38 mm l 1 and 13 c dic ranged from 22 to 14 against vpdb with an average of 16 samples of spring water from carbonate rocks had increased dic and 13 c dic together with elevated ph values combined 13 c dic and ca 2 and mg 2 contents suggest that groundwater evolution was dominated by dissolution of dolomitic marble this unexpected weathering process was favored by intense rain and high ambient temperatures and excessive co 2 production in tropical soils the intense weathering resulted in karst structures with high hydraulic conductivities that rendered the terrain tectonically less stable

salinization and dilution history of ground water discharging into the sea of galilee the dead sea transform israel abstract the mechanism governing salinization of ground water discharging into the sea of galilee in israel has been the subject of debate for several decades because the lake provides 25 of the water consumed annually in israel correct identification of the salt sources is essential for the establishment of suitable water management strategies for the lake and the ground water in the surrounding aquifers existing salinization models were evaluated in light of available and newly acquired data including general chemistry and o h c and cl isotopes based on the chemical and isotopic observations the proposed salt source is an ancient intensively evaporated brine 21 to 33 fold seawater which percolated through the valley formations from a lake which had formed in the rift valley following seawater intrusion during the late miocene low na cl and high br cl values support the extensive evaporation whereas high ca cl and low mg cl values indicate the impact of dolomitization of the carbonate host rock on the residual solution based on radiocarbon and other isotope data the dilution of the original brine occurred in two stages the first took place 30 000 a ago by slightly evaporated fresh to brackish lake water to form the sea of galilee brine the second dilution phase is associated with the current hydrological regime as the sea of galilee brine migrates upward along the rift faults and mixes with the actively circulating fresh ground water to form the saline springs the spatially variable chemical and isotopic features of the saline springs suggest not only differential dilution by fresh meteoric water but also differential percolation timing of the original brine into the tectonically disconnected blocks registering different evaporation stages in the original brine consequently various operations to reduce the brine contribution to the lake may be differentially effective in the various areas

geochemistry of dissolved inorganic carbon and carbonate weathering in a small typical karstic catchment of southwest china isotopic and chemical constraints abstract the sources of dissolved inorganic carbon dic and rock weathering processes were studied in the houzhai catchment a typical karstic catchment in the changjiang river basin southwest china the carbon isotopic compositions 13 c dic of dic in the samples collected from the catchment vary from 13 5 to 6 9 with a mean value of 9 8 the dic in the catchment is thereby considered to be mainly derived from soil co 2 and weathering of carbonate rocks the dic concentrations and the 13 c dic values show pronounced seasonal variations with the lowest values being observed during the high flow season from may to october the logpco 2 values in the waters were positively correlated with the dic contents and negatively correlated to the saturation index of calcite sic and 13 c dic values these observations indicate that co 2 derived from organic matter oxidation plays an important role in the dissolution of carbonate for this typical karstic environment based on a chemical mass balance the weathering rate of carbonate rocks in the houzhai catchment was estimated to be approximately 133 t km 2 year or 584 10 3 mol km 2 year in terms of co 2 consumption rate which is higher than the reported values for other rivers in southwest china

impact of nitrogen fertilizers on the natural weathering erosion processes and fluvial transport in the garonne basin knowledge of the impact of n fertilizers on the weathering erosion processes of soils in intensively cultivated regions is of prime importance nitrification of nh4 fertilizers produces hno3 in the basin of the garonne river enhancing soil degradation their influence on the weathering rates was determined by calculating the consumption rate of atmospheric soil co2 by soil weathering and erosion and its contribution to the total dissolved riverine hco3 this contribution was found to be less than 50 which corresponds normally to a complete carbonate dissolution by carbonic acid suggesting that part of the alkalinity in the river waters is due to carbonate dissolution by an acid other than carbonic acid probably hno3

experimental determination of natural carbonate rock dissolution rates with a focus on temperature dependency abstract the denudation of carbonate rocks at landscape scale is controlled by factors like mineral composition temperature precipitation runoff fracture spacing and vegetation cover knowledge on carbonate denudation is important in order to understand landscape development and long term terrestrial marine carbon transport but there are few laboratory studies done on weathering rates of natural carbonate rocks under the low temperatures relevant for glacial interglacial periods to enhance the understanding of carbonate dissolution kinetics we studied low temperature dissolution reactions of various natural triassic carbonate rocks belonging to the lower muschelkalk in germany we conducted batch and flow through experiments investigating the direct correlation of dissolution rates with temperature and to establish whether the fine grained carbonate rocks micrite are more reactive than the coarser grained sparitic limestones by increasing the temperature from 5 to 26 c far from equilibrium dissolution rates of micritic and sparitic limestone samples increased from 2 42 10 07 to 10 88 10 07 and 4 19 10 07 to 7 74 10 07 mol m 2 s 1 respectively specific surface areas ssa of about 0 006 0 01 m 2 g the dissolution rates of dolomite rock samples varied only slightly from 1 06 10 07 to 2 02 10 07 mol m 2 s 1 ssa approximately 0 002 m 2 g in the temperature range 5 25 c at circum neutral ph the obtained apparent activation energies are in the range of earlier experiments done at higher temperatures but there is a distinct difference between the calcite in the micrite 51 kj mol and sparitic 20 22 kj mol lithologies indicating that the dissolution mechanisms are not the same using these activation energies in modelling of natural carbonate denudation we see that there is a clear effect of changing temperature but this is mostly through the increased solubility at lower temperatures and not through the increasing far from equilibrium dissolution rates at higher temperatures formation of fluid pathways by preferential dissolution of framework calcite crystals is suggested to form infiltration pathways and affect denudation rates the difference in crystal size between the micritic and sparitic limestones will affect the formation of such pathways larger crystals may create fewer and larger conduits and this is expected to be more important for the long term denudation than the differences in activation energies

recharge sources and hydrochemical evolution of an urban karst aquifer sete lagoas mg brazil the current water supply for the city of sete lagoas brazil is almost entirely groundwater from the sete lagoas karst aquifer with a small contribution from a fractured basement rock aquifer characterizing the hydrogeologic processes is important for proper water resource management avoiding contamination and other future issues the main goal of this study is to identify active hydrogeological processes such as possible surface ground water interactions sources of recharge and the hydrochemical evolution of groundwater through the use of stable isotopes 18o and 2h and major ion data the groundwater samples were collected from the karst aquifer central urban area and from the fractured aquifer southern part of the city surface water samples were collected from the seven main lakes and rainwater was sampled over a period of one year the stable isotope results indicated the groundwater origin is directly from local precipitation having a limited recharge period and locally receiving surface water contributions groundwater quality in the central urban area may be influenced by surface water infiltration where the karst aquifer is in contact with overlying unconsolidated sediments some samples with nitrate concentration of 10 mg l or higher indicates the natural composition of the groundwater has been altered by urban sewage contamination the highest concentrations of major ions were found in the central region where the most karstified area from the sete lagoas formation is located these data suggest a longer residence time for this water indicating more mineralization in accordance with the geological information

horizontal and vertical zoning of carbonate dissolution in china abstract natural dissolution and denudation are the essential processes of karstification however their intensities depend on geographic and climatic conditions field dissolution tests of carbonate tablets were conducted in hubei province over a three years period to determine the impact of precipitation lithology altitude vegetation and soil on carbonate dissolution results from the study show that carbonate dissolution rates vary from 1 23 to 2 86 mg cm 2 a 1 in addition a comparative analysis of our results with those from 28 other sites reveal two lateral regional boundaries of karstification one trending from south to north china the other from north to northwest china with regional precipitation variations appearing to be the primary control factor comparison of the dissolution rate of carbonate tablets set up on the surface 150 cm above ground surface and on the ground surface with those beneath the surface 20 cm and 50 cm beneath the ground surface at different elevations reveal a vertical karstification boundary in the mountainous areas along the south north karstification transition zone the results also show that surface dissolution rates 1 50 2 18 mg cm 2 a 1 are higher than subsurface dissolution rates 0 53 1 61 mg cm 2 a 1 in high altitude areas conversely in low altitude areas the subsurface dissolution rate 3 94 mg cm 2 a 1 is much higher than surface dissolution rate 1 78 mg cm 2 a 1 therefore the horizontal and vertical karstification boundaries in china highlight the main karstification function based on local elevation as well as varying geographical conditions it was also found that the magnitudes of carbonate dissolution are consistent with recent karstification degree which is critical for modeling karst landform evolution in the near future

δ13c pattern of dissolved inorganic carbon in a small granitic catchment the strengbach case study vosges mountains france abstract the transfers and origins of dissolved inorganic carbon dic were studied for a year in a soil spring stream system in the strengbach catchment vosges mountains france this 80 ha experimental research basin is located on the eastern side of the mountains at an altitude ranging from 883 to 1146 m a s l and is mainly covered by spruce 80 brown acid and podzolic soils developed on a granitic basement and as a result the dic originates solely from co2 generated by oxidation of soil organic matter the 13 c dic in catchment waters is highly variable from about 22 in the springs and piezometers to about 12 in the stream at the outlet of the catchment in the springs pronounced seasonal variations of 13 c dic exist with the dic in isotopic equilibrium with the soil co2 that has estimated 13 c of about 24 in winter and 20 in summer these seasonal variations reflect an isotopic fractionation that seems only induced by molecular diffusion of soil co2 in summer in stream water seasonal variations are small and the relatively heavy dic 12 on average is a result of isotopic equilibration of the aqueous co2 with atmospheric co2