geochemical signature of the cenomanian to eocene rocks in israel a palaeoenvironmental indicator distinctive trace metal concentrations characterize cenomanian to eocene marine carbonates from israel the cenomanian turonian platform carbonates including clayey formations exhibit low average values ranging between 2 and 29 ppm for zn cr v ni cu u and co the santonian campanian and early to middle eocene marine chalks show higher average concentrations of these trace metals ranging between 3 and 56 ppm the highest average concentrations of these metals 5 118 ppm are found in the maastrichtian and in the palaeocene marine chalks and marls the possible relationship between these metal background levels and the lithology the biogenic productivity the organic matter content the iron oxide concentration the rate of sedimentation of the studied time rock units as well as the palaeogeographical changes are discussed the extent of the exposed palaeo landmasses due to tectonics the intensity of weathering conditions and the detritus supply into the basin control primarily the iron and trace metal content in the studied sediments

hydrogeochemical and isotope evidence of groundwater evolution and recharge in minqin basin northwest china a hydrochemical investigation was conducted in the minqin basin to identify the groundwater evolution and recharge in the aquifer the mbr cl ratio is strongly depleted average 0 000451 compared with sea water 0 0035 indicating an evaporite origin the ionic ration plot saturation index si and chloro alkaline indices cai suggest that the dissolution of halite the glauberite gypsum dolomite and calcite determine na cl ca2 mg2 so42 and hco3 chemistry but other processes such as na exchange for ca2 and mg2 and calcite precipitation also contribute to the water composition the 6180 and 62 h in precipitation near the study area are linearly correlated similar to that for the world meteoric water line wmwl with an equation of delta h 2 7 49 delta o 18 5 11 r 2 0 97 according to radiocarbon residence time estimates the deep groundwater is approximatety 40 ka old and was recharged during a period when the climate was wetter and colder the radiocarbon content of shallow groundwater shows a clear evolution along the groundwater flow path from the beginning of the groundwater flow path to similar to 31 km the radiocarbon values are 73 6 pmc whereas beyond this point the values are 42 9 pmc based on radiocarbon content the shallow groundwater is older than 1 ka and represents pataeowaters mixed with a limited quality of modern recharge the rain fed groundwater direct recharge was estimated by chloride mass balance cmb method to range from 1 55 to 1 64 mm yr 1 with a mean value of 1 6 mm yr 1 this value represents about 1 5 of local rainfall the direct recharge volumes is about 0 666 x 10 8 m 3 yr 1 indirect recharge volumes by the surface water is about 0 945 x 10 8 m 3 yr 1 the total natural recharge in the minqin basin is 1 6 x 10 8 m 3 yr 1 whereas the groundwater abstraction has reached 11 6 x 10 8 m 3 yr 1 far exceeding the groundwater natural recharge c 2006 elsevier b v all rights reserved

water salinization in arid regions observations from the negev desert israel abstract the processes affecting salinization of precipitation surface water vadose water and groundwater were studied in the negev desert israel observations spanning 18 years included the collection of rainfall at three rain sampling stations flood water at six flood stations vadose water from four coreholes penetrating chalk formations and groundwater from 16 monitoring wells tapping the chalk aquitard dissolved carbonate dust and evaporation of the falling raindrops result in ca hco 3 2 facies and increased ion concentration of the rainwater with respect to inland more humid regions the exposure of flood water to evaporation during flood events is minimal the observed ca hco 3 2 facies and salt enrichment by a factor of three to five in the flood water with respect to precipitation results primarily from interactions of the flood water with the chalk and limestone bedrock including ion exchange on na and k bearing minerals and the dissolution of calcite gypsum and halite the presence of these salts at and near land surface results from the complete evaporation of rainwater in land surface depression storage areas following most rain events except for a small portion moving through the low permeability chalk matrix most of the vadose water moves through preferential pathways and is typically not exposed to evaporation this dual movement of water accounts for the nacl facies of vadose water and the variable rates of isotopic depletion and salt dilution observed in the underlying heterogeneous groundwater in the saturated zone although the variable mixing with low salinity isotopically depleted water percolating from the fractures accounts for the depleted isotopic composition of the groundwater its relatively low solute content cannot modify the groundwater nacl facies consequently only groundwater salinity in the chalk is reduced by the preferentially flowing water but the ca hco 3 2 facies prevailing in the rainwater and flood water disappears and the nacl imprint from the vadose zone prevails

recharge in karst and dune elements of a semi arid landscape as indicated by natural isotopes and chloride abstract the rates and mechanisms of local recharge in a semi arid environment have been investigated beneath two major landscape settings in the murray basin in south australia these were calcrete flats with sinkholes and sand dunes in adjacent landscape settings five minor settings were investigated and identified as undisturbed calcrete primary older sinkholes secondary younger sinkholes sand dunes with native vegetation and sand dunes with introduced pasture data from a limited series of boreholes were interpreted to suggest that recharge varied from in excess of 100 mm yr 1 for secondary sinkholes to less than 0 1 mm yr 1 beneath sand dunes with native vegetation the data suggest that recharge under sand dunes has increased by more than two orders of magnitude following clearing of the native vegetation 50 yr ago as 90 of an area of 10 000 km2 has been cleared this clearing has ensured that inflow of saline groundwater to the adjacent river murray will increase and in view of the amount of salt stored in both the unsaturated and saturated zones will continue for a very long time at sites where the inferred recharge is lowest profiles of the chloride concentration of soil water are consistent with the hypothesis that there is in excess of 50 000 yr recharge stored in the thick unsaturated zone some evidence for changes in recharge rate over this time scale is seen

carbon 14 and stable isotope data for an area in the murray basin its use in estimating recharge measurements of the carbon 14 concentration of water in 33 boreholes in a saline unconfined aquifer in southern australia have been interpreted to show that local recharge under natural conditions has a mean annual value which falls between 0 1 and 0 2 mm yr 1 the chloride concentration of groundwater is log normally distributed suggesting that its source is rainfall the estimate of mean annual recharge to the aquifer made using chloride is 0 25 mm yr 1

a review of aridity and groundwater surface hydrological studies are seen as inadequate in hyperarid and arid areas to provide reliable estimates of recharge in most such areas surface discharges are not present so that assessments of groundwater resources are dependent upon ground interpretation and denied the flow control found in assessments elsewhere groundwater models show that gradients are sustained by long term dewatering and very small amounts of modern indirect recharge recharge indications are well within the error of a hydrological balance discharges appear equally small the development of groundwater in arid areas frequently faces problems of salination due to recycling of irrigation water and rising groundwater heads abstraction is often inadequately managed so that uncontrolled mining of groundwater occurs the advantage that groundwater has however is that it offers staged development and staged appraisal

deciphering the interaction between quaternary and continental sabkhas aquifers in central tunisia using hydrochemical and isotopic tools climate aridity and intensive exploitation due to uncontrolled pumping for irrigation have caused a drastic decrease in the piezometric level of the shallow aquifer of chougafiya plain central tunisia and have seriously degraded groundwater quality according to the hydrochemical data cl so42 no3 hco3 br na mg2 k ca2 sr2 and the stable isotopes 18o and 2h content groundwater salinization in the investigated aquifer is caused by four main processes 1 evaporite dissolution 2 cation exchange reactions 3 evaporation processes and 4 mixing with sabkhas salt water causing salinity to increase in the central and southern parts of the basin the radiogenic 3h isotope data provided insight into the presence of significant contemporaneous recharge waters in the western part of the shallow aquifer the movement of the tritiated water may have occurred according to the general flow path nw se when tritium was used in conjunction with the stable isotopes and chloride the mixing process could be clearly identified especially in the central part of the study area

influence of small and large scale variables on the chemical and isotopic compositions of urban rainwater as illustrated by a case study in ashdod israel 1 the source of air pollution must be identified to select the appropriate monitoring activities and remedial measures the present case study illustrates how analyses of 1 regional scale synoptics and air mass trajectories 2 local scale atmospheric measurements wind direction and speed air temperature dust load sulfur and nitrogen oxide concentrations in the air rain amount and intensity and 3 chemical and isotopic compositions of rainwater from 46 rain events collected in the coastal city of ashdod israel were used to identify the various sources contributing to rainwater salts and contaminants and their timing rainwater affected by the mediterranean sea was characterized by a large marine fraction of salts high chloride concentrations and low values of 18o and d these rain events were associated with the cyprus low system which typically prevails in midwinter rainwater affected by continental sources had a small contribution of marine salts high bicarbonate and calcium concentrations and high values of 18o and d these rains were related to continental trajectories from the red sea and north african coast prevailing during the fall and spring rainwater affected by anthropogenic sources was characterized by low marine fraction high sulfate concentrations and low values of 34s whereas remote anthropogenic source was associated with the red sea trough system and were characterized by high nitrate concentrations representing desert dust the local anthropogenic source was characterized by high air concentrations of sulfur oxides at the local monitoring stations and high potassium and low nitrate concentrations the identification of local anthropogenic source suggests that measures taken to reduce emissions from local oil refineries and power stations are likely to reduce the overall air pollution in the study area

chemical composition of rainwater and floodwaters in the negev desert israel abstract rain and floodwater were sampled by self sealing samplers scattered over the area of two drainage basins in the negev desert of israel the sampling was carried out during the winters of 1978 1981 water was analyzed for the following ions ca2 mg2 na k hco 3 cl and so2 4 the chemical type of the rain and floodwater as well as the total quantities of salts precipitated and drained out from the basins were investigated the chemical characteristics of the rainwater falling in the negev resemble those of rainwater in northern israel but the absolute quantities of ions are smaller the total quantities of salts introduced into the basin were found to be larger than the quantities of salts drained out by the floods the chemical composition of the floodwater was found to be governed by the lithology of the drainage basin and not by the initial chemical characteristics of the rain from which it was derived

using hydrochemical and isotopic data to determine sources of recharge and groundwater evolution in an arid region a case study in the upper middle reaches of the shule river basin northwestern china understanding sources of recharge and mechanisms for hydrogeochemical evolution of groundwater in the shule river basin an arid inland river basin in northwestern china is essential for successful water resource management sources of water and associated groundwater recharge processes were investigated using hydrogeological hydrogeochemical and isotopic methods the study area was divided into three parts changma the shule valley and the beishan area the hydrogeochemical and isotopic analysis results show that groundwater in changma mainly originated from precipitation in the qilian mountains lateral flow from changma is the primary recharge mechanism while direct recharge by infiltration of precipitation can be neglected in the shule valley minerals within the aquifer material e g halite calcite dolomite and gypsum dissolve into water that recharges the groundwater system therefore strong linear relationships were found between na and cl and between ca2 mg2 and so42 hco3 with stoichiometry ratios of approximately 1 1 in both cases groundwater quality in the region is generally good with low salinity and hardness local precipitation is the only source of recharge for groundwater in the beishan area low groundwater velocity and dry climatic conditions suggest that dissolution of minerals from the aquifer material controls hydrogeochemical evolution water rarely travels from the beishan area to the shule valley therefore almost all the groundwater in the shule valley originates from changma global climate change and loss of glaciers in the qilian mountains may lead to a reduction of recharge therefore the groundwater resources of the shule valley must be managed to sustain water supply

transient stress coupling between the 1992 landers and 1999 hector mine california earthquakes a three dimensional finite element model fem of the mojave block region in southern california is constructed to investigate transient stress coupling between the 1992 landers and 1999 hector mine earthquakes the fem simulates a poroelastic upper crust layer coupled to a viscoelastic lower crust layer which is decoupled from the upper mantle fem predictions of the transient mechanical be havior of the crust are constrained by global positioning system gps data inter ferometric synthetic aperture radar insar images fluid pressure data from water wells and the dislocation source of the 1999 hector mine earthquake two time dependent parameters hydraulic diffusivity of the upper crust and viscosity of the lower crust are calibrated to 10 2 m 2 sec 1 and 5 10 18 pasec respectively the hydraulic diffusivity is relatively insensitive to heterogeneous fault zone permeabil ity specifications and fluid flow boundary conditions along the elastic free surface at the top of the problem domain the calibrated fem is used to predict the evolution of coulomb stress during the interval separating the 1992 landers and 1999 hector mine earthquakes the predicted change in coulomb stress near the hypocenter of the hector mine earthquake increases from 0 02 to 0 05 mpa during the 7 yr interval separating the two events this increase is primarily attributed to the recovery of decreased excess fluid pressure from the 1992 landers coseismic undrained strain field coulomb stress predictions are insensitive to small variations of fault plane dip and hypocentral depth estimations of the hector mine rupture

hydrochemical processes in ground water discharge playas central australia a large groundwater system in the amadeus basin central australia discharges to a chain of playa lakes 500 km long the playas contain highly concentrated brines these are sodium chloride rich waters with appreciable magnesium and sulphate and very low concentrations of calcium and bicarbonate gypsum glauberite and other evaporite minerals are precipitating in the playas the groundwaters evolve to brine by concurrent processes of dissolution evaporative concentration mineral precipitation and mineralogical change chemical evolution is considered with reference to a concentration factor based on chloride ion transfer calculations demonstrate losses of magnesium and bicarbonate throughout as a result of precipitation sodium potassium calcium and sulphate are gained initially as a result of dissolution but lost subsequently as a result of precipitation larger playas in the chain exemplified by lake amadeus have dual shallow and deep groundwater flow paths whereas the smaller playas exemplified by spring lake have only shallow flow paths brines in the larger playas are diluted by deep groundwaters and this is reflected in the degree of saturation attained with respect to particular minerals thus saturation with respect to gypsum and glauberite is attained earlier in spring lake than in lake amadeus saturation with respect to halite is attained in spring lake but not in lake amadeus both playas are undersaturated with respect to hexahydrite and sylvite although these minerals occur in efflorescent crusts in spring lake

geochemical evolution of ground water in smith creek valley a hydrologically closed basin in central nevada u s a abstract smith creek valley is a hydrologically closed basin in which ground water is recharged by subsurface inflow from sorrounding mountains and infiltration of streamflow into alluvial fan deposits near the mountains ground water is discharged by evapotranspiration from shallow ground water areas in the central part of the basin dominant ions in the dilute recharge water are na ca and hco 3 dissolved solids concentration increases during flow through the basin fill sediments with na becoming increasingly dominant in the discharge area a bare soil playa sorrounded by phreatophytic vegetation ground water salinity dominated by na and cl increases markedly the main processe controlling geochemical evolution of ground water in the basin fill aquifer were identified using major ion chemistry mass balance calculations thermodynamic calculations stable isotopes and mineral identification these processes are 1 dissolution of volcanic tuff and tuff derived basin fill deposits 2 cation exchange of ca and mg in the water for na in clay minerals 3 weathering of plagioclase to montmorillonite 4 precipitation of zeolite minerals 2 concentration of dissolved constituents by evapotranspiration 6 dissolution of cl and so 4 evaporative salts 7 precipitation of calcite

prevalence of fluorosis in the fluoride enriched groundwater in semi arid parts of eastern india geochemistry and health implications abstract fluorosis is becoming a global environmental toxicological problem and is most commonly found in water stressed regions in order to evaluate the geochemical mechanism of fluoride enrichment in groundwater and health implications in the padwakodari environs of eastern part of india a total of twenty two samples were collected and analysed for physico chemical parameters spreading across the study area geologically the area mainly comprises of phyllites granite gneiss mica schist and sandstone high fluoride concentrations found mainly in the granite gneisses which are situated central to northwestern parts of the study area the concentration of fluoride in the groundwater samples ranges from 0 3 to 11 mg l with an average of 2 mg l 64 of the groundwater samples containing fluoride concentration that exceed the who drinking water guidelines value of 1 5 mg l chronic ingestion of high doses has been linked to the development of dental fluorosis and in extreme cases skeletal fluorosis the dominant geochemical facies present in water are na ca mg hco 3 11 samples na mg ca hco 3 5 samples ca na mg hco 3 5 samples and ca mg na hco 3 1 sample sodium and bicarbonate ions being major component in majority of the water types located mostly in the granite gneiss formation has a tendency to increase fluoride concentration in groundwater by dissolving the fluoride from fluoride bearing minerals the oversaturation of half of the samples with respect to calcite and majority of samples undersaturation with respect to fluorite makes it feasible for fluoride to get released in to the groundwater decreasing ca activity downgradient recharge to discharge leads to a dominance of fluorite unsaturated conditions and consequently to mobilization of fluoride in groundwater the results indicate that the fluoride concentration in groundwater is mainly governed by high weathering of fluoride bearing minerals i e apatite and biotite in granite gneiss contains abundant fluoride alkaline hydrogeological environment high temperature low rainfall evapotranspiration and ion exchange

rain events in an arid environment their distribution and ionic and isotopic composition patterns makhtesh ramon basin israel abstract forty six individual rain events and successive fractions of these events were studied with a network of instruments in the arid makhtesh ramon basin southern israel during 1981 1983 annual rainfall varied from 47 to 107 mm number of rain events varied from 8 to 20 per year start of the rainy season varied from september to january termination of the rainy season varied from march to may and length of the rainy season varied from 4 to 9 months about 85 of the rain events were recorded at more than one station indicating an aerial distribution exceeding 20 km a cliff amount effect was observed the rain on the cliff 800 m was 73 more than the rain at the bottom of the makhtesh 500 m dust samples revealed the following soluble ions in equivalents ca 2 mg 2 na k and hco 3 cl so 2 4 the dust also contained cacl 2 rain composition of 61 analyzed samples revealed in equivalents ca 2 na mg 2 k and hco 3 cl so 2 4 neutral ph of 7 1 7 6 and presence of cacl 2 a similar pattern was observed in 54 samples collected during the same period at sde boker 30 km north of the ramon thus typifying the negev heights two distinct sources of dissolved ions were inferred dust providing mainly ca hco 3 2 and cloud borne sea spray providing mainly na mg 2 cl and so 2 4 a chemical and isotopic effect was observed the rain of the rainier year contained 34 less dissolved ions and was isotopically lighter in 18 o by 54 than the rain of the less rainy year a chemical and isotopic front effect was observed the first fraction of the individual rain events contained more dissolved ions 32 69 and was enriched by more 18 o 31 than the subsequent rain fractions the observed rain distribution and chemical isotopic effects are discussed in terms of input sources evaporation processes and altitude effects the obtained data define rain and salt inputs into the hydrological systems

water recharge and solute transport through the vadose zone of fractured chalk under desert conditions this study focuses on water flow and solute migration through unsaturated fractured chalk in an arid area the chalk underlies a major industrial complex in the northern negev desert where groundwater contamination has been observed four dry drilling holes were bored through the vadose zone core and auger samples collected at 30 to 50 cm intervals were used for chemical and isotopic analyses enabling the construction of the following profiles 1 a tritium profile to estimate the rate of water flow through the unsaturated zone 2 oxygen 18 and deuterium profiles to assess the evaporation of water at land surface before percolation and in the upper part of the vadose zone after infiltration and 3 chloride and bromide profiles as tracers for inert solutes and pollutants the tritium and bromide profiles showed the rate of infiltration through the unsaturated matrix to be very slow 1 6 11 cm yr the chemical and isotopic data from the core holes suggested that the pore water changes characteristics with depth close to land surface the pore water is strongly evaporated 18o 5 94 and highly concentrated 29 meq cl 100 g rock but changes gradually with depth to amore dilute concentration 4 meq cl 100 g rock and isotopically depleted composition 18o 4 4 closer to the isotopic composition of precipitation and groundwater nearby monitoring wells have shown anthropogenic contribution of heavy metals organic compounds and tritium nativ and nissim 1992 a conceptual model is proposed in which a small portion of the rainwater percolates downward through the matrix while a larger percentage of the percolating water moves through preferential pathways in fractures the water flowing through the fractures penetrates the matrix across the fracture walls where it increases the tritium concentrations depletes the stable isotopic composition and dilutes the salt concentrations the observed rapid downward migration of tritium and heavy metals through the profuse fractures makes the chalk inefficient as a hydrologic barrier

groundwater recharge estimation using chloride deuterium and oxygen 18 profiles in the deep coastal sands of western australia the depth distributions of environmental chloride deuterium and oxygen 18 in the deep sands 20 m were monitored with a view to estimate average recharge to groundwater the investigated area is located on the southwestern coast of western australia and supports a perennial native woodland vegetation by using a steady state model based on the conservation of chloride the average areal recharge was estimated to be approximately 15 of the average precipitation 775 mm yr 1 whilst the cl concentration of groundwater was relatively uniform there was a considerable spatial variability in the depth distribution of cl in the unsaturated zone an approximate method of data analysis is developed application of this to cl data shows that possibly some 50 of the total annual recharge occurs via movement of water through preferred pathways thus bypassing the soil matrix stable isotope deuterium and oxygen 18 data show that there has been some isotopic enrichment due to evaporation of the rainfall but the extent of enrichment appears to be too small to estimate recharge rates reliably it is argued that relatively small isotopic enrichment occurs in the system studied since the direct evaporation from soil is a rather small component of the total evapotranspiration the observations on the depth distribution of isotopes qualitatively support the presence of a bimodal system for water movement through the profile as was suggested by the analysis of chloride data

the evolution of holocene reg gravelly soils in deserts abstract reg soil is an aridisol developed upon a stable alluvial surface composed of sand to coarse gravel the objectives of the present study were 1 to examine the initial evolution of reg soil properties with time 2 to assess and explain the rates of development of different properties 3 to establish the suitability of different soil properties for relative age dating the time dependent soil properties examined were 1 mechanical weathering of surficial rocks and desert pavement evolution 2 chemical and biological weathering of surficial rocks 3 the thickness of soil profiles and soil horizons 4 soil texture in the different horizons 5 salts and gypsum distribution and concentration in different soil horizons 6 degree of mechanical weathering of gravel in c horizons fifteen successive surfaces of the nahal wadi ze elim sequence of alluvial fans were selected for study dead sea region israel under an extremely arid climate the sequence is of holocene age 14 000 years b p to recent the main conclusions are 1 reg soils develop rather fast in several 10 3 years since their initiation however the various soil properties developed at different rates 2 the rates of change of three soil properties decrease with time these are the texture in different horizons change in added airborne and rain washed dust salinity within the soil profile change in added salts and gypsum and the amount of mechanically shattered rocks 3 soil thickness is established rather rapidly young and older holocene soil have practically the same depth surficial weathering rates appear to remain fairly constant with time 4 in coarse gravel the evolution of reg soils is dependent on added fines and salts of airborne origin and the resultant changing hydrologic regime in the soil profile the run off infiltration ratio changes as more fines and salts are added to the soil profile and as desert pavement develops 5 surficial features and fine clay in the soil profile may be used for approximate dating of otherwise undatable holocene alluvial surfaces salts and gypsum content should be cautiously used in a rather general way

origin of the high variability of water mineral content in the bedrock aquifers of southern madagascar this study assesses the causes of the high spatial variability of the mineral content of groundwater in crystalline bedrock of southern madagascar although many kilometres from the coast and at a mean altitude of 400 m a s l wells drilled in this area produce water with electrical conductivities in the range of 300 30 000 mu s cm 1 with a high spatial variability chemical and isotopic data are used to identify the processes involved in the groundwater mineralization it is shown that the chemical composition of the groundwater in this region has its origin in i normal silicate and carbonate weathering reactions and ii input of marine salts probably via rainfall recharge modified by evapo concentrative processes probably including precipitation and re dissolution of secondary evaporites in the unsaturated zone to obtain a better understanding of the spatial salinity distribution well parameters such as yields weathered zone thickness weathered materials and morphological positions upper slope mid slope lower slope or valley bottom are scrutinized a correlation was found between high salinity and low flow shallow groundwater environments flat hill tops valley bottoms weakly developed and clayey weathered zones and between low salinity and high flow environments granular well developed weathered zones and situation on valley slopes

indirect detection of subsurface outflow from a rift valley lake abstract naivasha highest of the kenya gregory rift valley lakes has no surface outlet however unlike other rift lakes it has not become saline despite high potential evaporation rates which indicates that there must be some subsurface drainage the fate of this outflow has been the subject of speculation for many years especially during the general decline in lake water level during the 1980 s particularly to the south of the lake there are few opportunities to obtain information from direct groundwater sampling however the stable isotopic composition of fumarole steam from late quaternary volcanic centres in the area has been used to infer groundwater composition using a simple mixing model between rift flank groundwater and highly evaporated lakewater this has enabled subsurface water flow to be contoured by its lakewater content by this method outflow can still be detected some 30 km to the south of the lake stable isotope data also confirm that much of the steam used by the local olkaria geothermal power station is derived from lakewater though simple balance considerations show that steam use cannot alone be responsible for the fall in lake level observed during the 1980 s

geochemical tracing and hydrogeochemical modelling of water rock interactions during salinization of alluvial groundwater upper rhine valley france in the southern upper rhine valley groundwater has undergone intensive saline pollution caused by the infiltration of mining brines a consequence of potash extraction carried out during the 20th century major and trace elements along with sr and u isotopic ratios show that groundwater geochemical characteristics along the saline plumes cannot reflect conservative mixing between saline waters resulting from the dissolution of waste heaps and one or more unpolluted end members the results imply the occurrence of interactions between host rocks and polluted waters and they suggest that cationic exchange mechanisms are the primary controlling process a coupled hydrogeochemical model has been developed with the numerical code kirmat which demonstrates that cationic exchange between alkalis from polluted waters and alkaline earth elements from montmorillonite present in the host rock of the aquifer is the primary process controlling the geochemical evolution of the groundwater the model requires only a small amount of montmorillonite between 0 75 and 2 25 which is in agreement with the observed mineralogical composition of the aquifer the model also proves that a small contribution of calcite precipitation dissolution takes places whereas other secondary mineral precipitation or host rock mineral dissolution do not play a significant role in the geochemical signature of the studied groundwater samples application of the model demonstrates that it is necessary to consider the pollution history to explain the important cl na and ca concentration modifications in groundwater samples taken over 2 km downstream of waste heaps additionally the model shows that the rapidity of the cationic exchange reactions insures a reversibility of the cation fixation on clays in the aquifer

the relation between the 18o and deuterium contents of rain water in the negev desert and air mass trajectories abstract sampling of rain water was carried out in the negev israel from 1978 till 1981 by means of a self sealing sampler which enables the sampling of each separate rain storm as well as parts of each storm the relation between the isotopic composition and various synoptic parameters is discussed based on deuterium excess values the rain samples can be separated into three groups the majority of the samples have a deuterium excess between 10 and 22 these samples have different histories from the meteorological point of view however there are two extreme groups one has deuterium excess values above 22 and the other has values less than 10 it was found that the rains which are most depleted with regard to deuterium and with the lowest deuterium excess values are associated with air masses that reach the region concerned from the southwest rains with a deuterium excess of more than 22 are associated with air masses which come mainly from northeastern europe and reach the considered region from west to northwest following intense interaction with the central eastern mediterranean sea

chemical weathering of fractured eocene chalks in the negev israel abstract ba ca fe k mg mn sr and insoluble residue i r contents of eocene chalks and of vein filled derivative matter from the northern negev israel were analyzed the eocene chalk country rock weathered physically and chemically and the eroded material has filled the fault planes and some of the joints two types of filling material were found calcite crystals and soft fine carbonate material the latter as the chalk are sometimes associated with fe and mn oxides i r ca mg ca sr ca and k ca values decrease from the country rock chalk to the fine carbonates and are lower in the calcite minerals the ba ca values are low in the soft fine carbonates and high in the calcite minerals barite was found in places in the chalk fe ca and mn ca values are higher in the soft fine carbonate based on k d values the expected ba ca mg ca and sr ca values in the vein carbonates are lower and the expected fe ca and mn ca are higher than the actual values the analysis of the soft fine carbonates from the various joints and faults shows that chemical precipitation was unaffected by these structures this possibly suggests that the soft fine carbonates are younger and not contemporaneous with the structures

geochemistry of the amazon 1 precipitation chemistry and the marine contribution to the dissolved load at the time of peak discharge analyses of precipitation and surface water are used to estimate the fluxes of marine cyclic salts through that part of the amazon river system draining past obidos 80 of the basin at the time of peak discharge in june amazon precipitation chemistry can be devided into two principal components marine and terrestrial the marine component determined from analyses of marine rain consists of na k mg ca and cl in approximately sea salt proportions with s doubly enriched the excess sulfur is probably derived from gas phase inputs the terrestrial component makes an important contribution of k ca s and n much of which can be related to biological emissions the emission of reduced sulfur in the marine and terrestrial environment and nitrogen in the terrestrial environment is responsible for a natural acid rain in the amazon region with a ph from 4 7 to 5 7 this is about one tenth the acidity of polluted urban rain the chloride content of lowland rivers which drain regions lacking significant geologic sources of chloride shows a systematic decrease in chloride with increasing distance from the ocean this trend is used to define the cyclic salt background for amazonian surface waters cyclic salts in general make only a minor contribution relative to terrestrial inputs to the chemistry of amazon basin rivers even those draining intensely weathered terrains an estimated 17 6 cl 6 9 na 1 3 mg 3 6 s 0 4 k and 0 1 ca of the dissolved load at obidos during peak discharge is cyclic

hydrogeochemical processes affecting groundwater in an irrigated land in central tunisia detailed hydrogeochemical investigation has provided new information concerning the major factors and mechanisms controlling the groundwater chemistry of chougafiya basin the hydrogeochemical characteristics of groundwaters comprise three main types cl so4 ca cl so4 na and cl na hydrochemical characteristics based on the bivariate diagrams of major cl so42 no3 hco3 na mg2 k and ca2 and some trace br and sr2 ions mineral saturation indices and hierarchical cluster analysis indicate different origins of groundwater mineralization the water rock interaction dissolution of evaporitic minerals followed by cation exchange reactions with clay minerals constitute the main processes that control groundwater salinization however the chemical composition of brackish groundwater in the central and southern parts of the study area is influenced by a mixing process with sabkhas salt groundwater the mixing proportions inferred from chloride mass balance prove that the contribution of sabkhas groundwater to quaternary aquifer ranges between 2 7 and 9 1 these intrusion rates reflect the progress of the saltwater freshwater interface which is mainly controlled by the piezometric level variation and the distance to the sabkhas

occurrence of secondary gypsum veins in joints in chalks in the negev israel abstract beds fissures and joints filled with coarse sparitic gypsum were found associated with the upper layers of chalks of eocene age in the beer sheva region in southern israel the average34s so4 value of the gypsum is 15 which signifies an evaporitic origin field observations show that the veins are connected with the loess soil cover of upper pleistocene age which overly the chalks the deposition of the gypsum is suggested to be through a process of leaching from the loess during a more humid period its concentration possibly by roots of sulfate tolerant trees and its deposition from groundwater which became over saturated with caso4 the high contents of sulfate in the loess is explained by the special climatic conditions which prevailed during the uppermost pleistocene and which were characterized by sulfate rich dust and rainstorms

the use of na cl ratios to trace solute sources in a semiarid zone rainwater interaction with soils is a major source of dissolved salts in groundwater the transition zone between the humid and the arid area is characterized by a specific combination of reactions which do not exist elsewhere this combination of caco3 dissolution and base exchange reactions affects the na cl ratio which is the quantitatively most important parameter used for tracing salinity sources of groundwater the increase in the na cl ratio in the coastal plain aquifer of israel from north to south is related to local recharge of na rich water after interaction with soils of loessial origin

freshwater recharge into a shallow saline groundwater system cooper creek floodplain queensland australia freshwater lenses have been identified as having penetrated the shallow regional saline groundwater beneath the cooper creek floodplain near ballera south west queensland piezometers were installed to evaluate the major element chemistry along a floodplain transect from a major waterhole goonbabinna to a smaller waterhole chookoo associated with a sand dune complex the floodplain consists of 2 7m of impermeable mud underlain by unconsolidated fluvial sands with a saline watertable waterholes have in places scoured into the floodplain the transect reveals that groundwater recharge takes place through the base of the waterholes at times of flood scour but not through the floodplain mud total dissolved solids rise with distance from the waterhole and independently of the presence of sand dunes stable water isotopes 2h and 18o confirm that recharge is consistent with and dependant on monsoonal flooding events following floods the waterholes self seal and retain water for extended periods with sulfate 34s and 18o isotopes suggesting bacterial reduction processes within the hyporheic zone and limited interaction between the surface water and groundwater during no flow conditions the area occupied by the freshwater lenses tds 5000 mg l is locally asymmetrical with respect to the channel flow direction extending down gradient along distances of 300 m

the role of topography and surface cover upon soil formation along hillslopes in arid climates abstract two north facing soil toposequences were selected from within the northern negev desert israel where average annual rainfall ranges from 70 to 200 mm both slopes are composed of an upper rocky and a lower colluvial section similar trends were found along both slopes a high salt content was characteristic of soils at the top of the slope salinity decreased downslope within the rocky slope section the opposite occurred along the colluvial slopes with salinity increasing sharply downslope at any location along the slopes the northernmost soil toposequence site 160 mm average annual rainfall represents from a pedological point of view an environment which is far more arid than its climatologically drier more southern counterpart the explanation provided for the variation of soil proporties at the scale of single hillslopes and at the regional scale is the same it is contended that water input into the soil and therefore leaching intensity is positively related to the ratio of bedrock soil cover rocky areas have limited infiltration thus yielding high runoff rates into adjoining soil covered areas and contribute to water concentration deeper infiltration and leaching intensity soil or sediment covered areas having relatively high absorption capacities will experience reduced runoff shallow infiltration and decreased water availability for leaching this leads over time to salt accumulation at a shallow depth the decrease in rock soil ratio downslope within the colluvium is therefore held responsible for the corresponding increase in salinity similarly the greater salinity of the soils in the northern site is explained by the fact that its rock soil ratio is lower than in the southern area the theoretical and practical implications regarding the relationship between climatic change and landscape evolution in arid areas are briefly discussed