sea salt aerosol groundwater salinization in the litorale romano natural reserve rome central italy a yearly survey in a piezometric network was realized in the litorale romano natural reserve rome central italy collecting water table and chemo physical data monthly chemo physical surveys highlighted a groundwater salinization variability in a coastal unconfined aquifer the aquifer is mostly composed by aeolian sands of a still preserved dune ridge environment on which a pine forest develops the groundwater salinity variability resulted is connected to the wind pattern and rainfalls in fact wind speed higher than 4 m s is responsible for generating sea salt aerosols ssa from sea surface a statistical analysis was performed for wind with a speed higher than 4 m s to detect wind orientation the dry deposition of ssa on the tree foliage appeared correlated to the westerly winds blowing in the springtime when the rainy season occurs the ssa is washed out from the trees and it is directed to groundwater where an enhancement of the electrical conductivity ec values is noticed whenever rain events occur and winds are not westerly a dilution of groundwater salinity takes place and consequently a reduction of ec chemical analyzes were realized as well they confirmed that groundwater of piezometers located close to the coast line is enriched of ssa elements

strontium and carbon isotope constraints on carbonate solution interactions and inter aquifer mixing in groundwaters of the semi arid murray basin australia abstract strontium and carbon isotopes are used to study the effect of carbonate mineral dissolution and inter aquifer mixing on the chemical evolution of groundwater from the murray group limestone aquifer in semi arid se australia the 87 sr 86 sr ratio of groundwater evolves from 0 7097 at the basin margin to a less radiogenic value of 0 7084 about 250 km down gradient which is similar to the 87 sr 86 sr ratio of the aquifer carbonate matrix the concomitant increase in 13 c dic sr ca and mg ca ratios in the groundwater along a 250 km transect suggests that incongruent dissolution of high mg calcite controls the carbonate geochemistry in this aquifer further down gradient the groundwater is characterized by a relatively more radiogenic 87 sr 86 sr ratio caused by upward leakage and mixing with more radiogenic groundwater from the renmark group sand aquifer a mixing model using 87 sr 86 sr ratio suggests that the fraction of water that contribute to the murray group aquifer through upward leakage from underlying renmark group aquifer ranges from 15 to 85

high latitude aurora during steady northward interplanetary magnetic field and changing imf by 1 high latitude transpolar arcs tpas are often observed during northward interplanetary magnetic field imf of these theta aurora are seen when transpolar arcs move in the dawn or dusk direction across the entire polar region in response to imf by changes periods of study were chosen when by changes sign during steady northward imf in order to determine the influence of imf bx by the strength of the imf the solar wind and earth dipole tilt on the occurrence and motion of high latitude tpas forming theta aurora for a 4 5 year period there are 55 events for which imf bz is northward for at least 2 hours before and at least 3 hours after a by sign change of these 19 occurred when the polar satellite was over the northern hemisphere for the duration of the event we find that for northward imf and a by sign change theta aurora are almost always formed in the northern hemisphere regardless of bx and dipole tilt this implies that theta aurorae form simultaneously in both hemispheres imf by does not appear to influence the intensity and duration of the arc strongest uv emissions occur in the summer hemisphere evolution time has a fairly complex dependence on solar wind parameters

chlorofluorocarbon apparent ages of groundwaters from west hawaii usa summary the volcanic coastal aquifers of west hawaii supply drinking water to the area s residents and nutrient rich groundwater discharge to the nearby oligotrophic coastal waters despite the societal and ecological importance of the water in these aquifers very little is known about the ages and recharge areas of the groundwater we therefore determined aquifer recharge areas and groundwater residence times by sampling 18 locations for the oxygen and hydrogen isotopic composition of groundwater and chlorofluorocarbon cfc apparent groundwater ages we sampled water supply wells coastal wells and coastal ponds we applied a 18 o altitude gradient and well established lapse rates to find that groundwater recharge predominantly occurs in the area s maximum rainfall zone furthermore the isotopic data suggest that fog drip contributes to aquifer recharge a single water source model yielded recharge years ranging from the mid 1960s to mid 1980s for ten samples 56 of samples alternatively a simple binary mixing model with one water source recharging before1940 and the other after 1940 indicated that 14 samples 78 of samples contained young water that recharged the aquifer between the mid 1970s and mid 1980s we also find that cfcs can be used to distinguish between water originating from different aquifers in the area

groundwater dating with 3h and sf6 in relation to mixing patterns transport modelling and hydrochemistry a comprehensive study of a sandy aquifer of deltaic origin in southern poland included water chemistry isotopes dissolved trace gases and transport modelling tritium sulphur hexafluoride sf6 and freons f 11 f 12 and f 113 showed the presence of modern waters in the recharge areas and shallow confined parts of the aquifer the presence of older holocene waters farther from the recharge areas was indicated by lack of 3h sf6 contents 0 02 fmol l 1 and relatively low 14c values the discharge from the system is by upward seepage in the valley of a major river pre holocene waters of a cooler climate identified on the basis of 18o 2h 14c ne and ar data were found in some distant wells concentrations of n2 ne and ar determined by gas chromatography were used for calculating the noble gas temperatures air excess needed for correction of sf6 and nitrogen content released by denitrification process the time series of 3h content available for some wells supplied quantitative information on age distributions and the total mean ages of flow through the unsaturated and saturated zones the derived 3h age distributions turned out to be very wide with mean values in the range of about 30 to 160 years for each well with determined 3h age the sf6 data showed either a lower age range or the possibility of a lower age as expected due to shorter travel times of sf6 through the unsaturated zone which most probably also resulted in different types of age distributions of these tracers freons appeared to be of little use for individual age determinations a quantitative estimation of two component mixing from sf63h relations is not possible unless the travel time of 3h through the unsaturated zone is comparable to that of sf6 the ratio of integrals of the response function over the age range with tracer and the whole response function yields the ratio of water with tracer to total flow of water that ratio is a tracer dependent function of time transport modelling of sf6 tracer done with mt3d code yielded initially large discrepancies between calculated and measured tracer concentrations some discrepancies remained even after calibration of the transport model with sf6 simulation of tritium contents with a calibrated transport model yielded reasonable agreement with measured contents in some wells and indicated a need for further investigations particularly in the eastern part of the aquifer the existence of distinct hydrochemical zones is consistent with the tracer data young waters with measurable 3h and sf6 contents are aerobic and of hco3ca or hco3so4ca types slightly elevated na and cl contents as well as the highest concentrations of so4 and no3 within this zone are due to anthropogenic influences anaerobic conditions prevail in the far field under the confining cover where pre bomb era holocene waters dominate in that zone dissolved oxygen no3 and u contents are reduced and fe mn and nh4 contents increase in the third zone early holocene and glacial waters occur they are of hco3cana or hco3na types with tds values higher than 1 g l 1 and na content higher than 200 mg l 1 due to either small admixtures of ascending or diffusing older water or freshening of marine sediments a process that is probably occurring till the present time copyright 2005 john wiley sons ltd

investigation of young water inflow in karst aquifers using sf6 cfc 3h he 85kr 39ar and stable isotope components abstract karst aquifers are known for their wide distribution of water transfer velocities from this observation a multiple geochemical tracer approach seems to be particularly well suited to provide a significant assessment of groundwater flows but the choice of adapted tracers is essential in this study several common tracers in karst aquifers such as physicochemical parameters major ions stable isotopes and 13c to more specific tracers such as dating tracers 14c 3h 3h 3he cfc 12 sf6 and 85kr and 39ar were used in a fractured karstic carbonated aquifer located in burgundy france the information carried by each tracer and the best sampling strategy are compared on the basis of geochemical monitoring done during several recharge events and over longer time periods months to years this study s results demonstrate that at the seasonal and recharge event time scale the variability of concentrations is low for most tracers due to the broad spectrum of groundwater mixings the tracers used traditionally for the study of karst aquifers i e physicochemical parameters and major ions efficiently describe hydrological processes such as the direct and differed recharge but require being monitored at short time steps during recharge events to be maximized from stable isotopes tritium and cl contents the proportion of the fast direct recharge by the largest porosity was estimated using a binary mixing model the use of tracers such as cfc 12 sf6 and 85kr in karst aquifers provides additional information notably an estimation of apparent age but they require good preliminary knowledge of the karst system to interpret the results suitably the cfc 12 and sf6 methods efficiently determine the apparent age of baseflow but it is preferable to sample the groundwater during the recharge event furthermore these methods are based on different assumptions such as regional enrichment in atmospheric sf6 excess air and flow models among others 85kr and 39ar concentrations can potentially provide a more direct estimation of groundwater residence time conversely the 3h 3he method is inefficient in the karst aquifer for dating due to 3he degassing

residence time mineralization processes and groundwater origin within a carbonate coastal aquifer with a thick unsaturated zone this study aims at establishing groundwater residence times identifying mineralization processes and determining groundwater origins within a carbonate coastal aquifer with thick unsaturated zone and lying on a granitic depression a multi tracer approach major ions sio2 br ba sr2 18o 2h 13c 3h ne ar combined with a groundwater residence time determination using cfcs and sf6 allows defining the global setting of the study site a typical mineralization conditioned by the sea sprays and the carbonate matrix helped to validate the groundwater weighted residence times from using a binary mixing model terrigenic sf6 excesses have been detected and quantified which permits to identify a groundwater flow from the surrounding fractured granites towards the lower aquifer principally the use of cfcs and sf6 as a first hydrogeological investigation tool is possible and very relevant despite the thick unsaturated zone and the hydraulic connexion with a granitic environment

natural cf4 and sf6 on earth the occurrence of cf4 and sf6 in natural fluorites caf2 is reported contents are found to be typically 200 2000 ppt mass for cf4 and 50 100 ppt mass for sf6 cf4 and sf6 were also detected in granites where fluorite is an accessory mineral cf4 and sf6 thus possess a large reservoir in the continental crust that by degassing can sustain natural atmospheric background levels of 40 ppt mole and up to 0 01 ppt mole respectively the article also discusses how natural sf6 may cause interference in hydrological tracer studies

groundwater transit time distribution and mean from streambed sampling in an agricultural coastal plain watershed north carolina usa we measured groundwater apparent age and seepage rate v in a sandy streambed using point scale sampling and seepage blankets a novel seepage meter we found very similar mtt estimates from streambed point sampling in a 58 m reach 29 years and a 2 5 km reach 31 years the ttd for groundwater discharging to the stream was best fit by a gamma distribution model and was very similar for streambed point sampling in both reaches between adjacent point scale and seepage blanket samples water from the seepage blankets was generally younger largely because blanket samples contained a fraction of young stream water correcting blanket data for the stream water fraction brought estimates for most blanket samples closer to those for adjacent point samples the mtt estimates from corrected blanket data were in good agreement with those from sampling streambed points adjacent to the blankets collectively agreement among age dating tracers general accord between tracer data and piston flow model curves and large groundwater age gradients in the streambed suggested that the piston flow apparent ages were reasonable estimates of the groundwater transit times for most samples overall our results from two field campaigns suggest that groundwater collected in the streambed can provide reasonable estimates of apparent age of groundwater discharge and that mtt can be determined from different age dating tracers and by sampling with different groundwater collection devices coupled streambed point measurements of groundwater age and groundwater seepage rate represent a novel reproducible and effective approach to estimating aquifer ttd and mtt

evidence for crustal degassing of cf4 and sf6 in mojave desert groundwaters dissolved tetrafluoromethane cf4 and sulfur hexafluoride sf6 concentrations were measured in groundwater samples from the eastern morongo basin emb and mojave river basin mrb located in the southern mojave desert california both cf4 and sf6 are supersaturated with respect to equilibrium with the preindustrial atmosphere at the recharge temperatures and elevations of the mojave desert these observations provide the first in situ evidence for a flux of cf4 from the lithosphere a gradual basin wide enhancement in dissolved cf4 and sf6 concentrations with groundwater age is consistent with release of these gases during weathering of the surrounding granitic alluvium dissolved cf4 and sf6 concentrations in these groundwaters also contain a deeper crustal component associated with a lithospheric flux entering the emb and mrb through the underlying basement the crustal flux of cf4 but not of sf6 is enhanced in the vicinity of local active fault systems due to release of crustal fluids during episodic fracture events driven by local tectonic activity when fluxes of cf4 and sf6 into mojave desert groundwaters are extrapolated to the global scale they are consistent within large uncertainties with the fluxes required to sustain the preindustrial atmospheric abundances of cf4 and sf6

the influence of marine inflows on the chemical composition of groundwater in small islands the example of the cyclades greece marine contamination of groundwater may be caused by seawater intrusion and by salt spray the role of both processes was studied in the cyclades archipelago on four small islands 45 195 km2 whose aquifers consist essentially of fractured weathered metamorphic rocks annual rainfall ranges from 400 to 650 mm and precipitation has high total dissolved solids contents of 45 223 mg l 1 the chemical characteristics of the groundwater whose salinity is from 0 4 to 22 g l 1 are strongly influenced by seawater intrusion however the effect of atmospheric input is shown in certain water sampling locations on high ground elevation where the dissolved chloride contents may attain 200 mg l 1

groundwater salinization in the azores archipelago portugal groundwater salinization in coastal regions causes severe constraints to water supply and economic losses to society worldwide in the azores archipelago groundwater abstraction in wells drilled in coastal aquifers is very important for water supply and quality problems have been reported therefore a groundwater chemistry dataset from wells was compiled to study groundwater salinization in these aquifers waters are mainly of the na cl type presenting a slightly acidic to slightly alkaline character with a ph between 5 63 and 8 50 median 7 40 electrical conductivity measurements range from 127 to 9 670 s cm median 862 suggesting highly variable mineralization with higher values observed on santa maria sao miguel pico graciosa and sao jorge islands the major ion composition reflects the contribution of seawater to the groundwater compositional evolution which is essentially explained by seawater intrusion into wells in many samples exchange reactions of na k for ca2 mg2 are associated with salinization the seawater fraction in groundwater composition reaches a maximum of 22 5 these results are extremely challenging to water managers in the azores because failure to comply with national water quality regulations and with european union groundwater directive requirements often occurs

a multi tracer approach for assessing the origin apparent age and recharge mechanism of shallow groundwater in the lake nyos catchment northwest cameroon summary the shallow aquifer in the vicinity of lake nyos northwest cameroon is one of the main water supply sources to meet the water needs of the inhabitants to be resettled after 1986s tragedy unfortunately there is a lack of knowledge on the groundwater recharge and flow systems in the area multiple environmental tracers 18 o d cl cfcs and sf 6 and a yearly record of rainfall surface waters and groundwater were employed to characterize the recharge mechanism of the shallow groundwater seeping in the fractured rock of the lake nyos catchment lnc the 18 o d relationship of the rainfall events gave the nyos meteoric water line d 8 28 18 o 11 87 inland moisture vapor may have impacted the isotopic composition of original vapor masses from gulf of guinea prior to precipitation shallow groundwater in the lnc shows a similar trend of enrichment in 18 o and d as surface waters indicating a well mixed aquifer the proportions of surface waters and rainfall in the groundwater reservoir were 87 and 13 respectively the high annual recharge rate 941 mm yr and the seasonal variability in the isotopic signatures of groundwater indicate a renewable aquifer system cfcs apparent ages based piston flow model revealed a young age average of 24 a of the groundwater in the lnc sf 6 based ages were biased young as compared to relatively younger than cfcs based ages implying an additional terrigenic production of sf 6 the conceptual model for groundwater flow suggests that three main flow regimes mainly controlled by the physical properties of the rock heterogeneities govern the movement of water in the aquifer the piston flow model appears however to be the better model to explain the flow regime in the highly faulted and fissured area where recharge occurs 1200 1600 masl the rapid circulation and the low solubility lead to low mineralization in the middle lower area where waters circulate more in the weathered layer exponential mixing model dominates yielding more mineralized water downward to the valley with prevailing gentle slope interaction between surface and recently infiltrated groundwater better explain the observed similarity in the isotopic compositions and the mineralization of water

heterogeneous behaviour of unconfined chalk aquifers infer from combination of groundwater residence time hydrochemistry and hydrodynamic tools chalk groundwater is an important aquifer resource in france and also in much of northwestern europe large areas between the paris basin the london basin denmark and the northwest of germany as it is intensively exploited for human use with a large proportion reserved for drinking water the improvement of the knowledge on chalk aquifer hydrodynamical functioning and groundwater geochemistry is essential for the management of this resource to achieve this aim we developed a methodology based on a combination of hydrodynamic hydrochemistry and groundwater dating tools a study site of about 500 km2 was selected in ne france where chalk outcrops at 15 sampling points including boreholes and rivers mainly from chalk aquifer drainage groundwater geochemistry were monitored monthly for 2 years from june 2017 to june 2019 groundwater level in boreholes were monitored hourly with in situ water loggers in addition two sampling campaigns for the analysis of cfcs and sf6 have been conducted in boreholes in high and low water level periods to define the groundwater residence time the aquifer at the majority of sampling sites has an inertial behavior with respect to recharge as no impact of individual rainfall event was observed rapid piezometric response following rainfalls was observed at one site suggesting the presence of locally highly developed fracture network contrariwise high spatial and temporal heterogeneities of geochemistry was observed on the study area according to the mixing process piston flow exponential or binary mixing defined at each sampling site groundwater dating indicated rather heterogeneous ages ranging from less than 20 years to more than 50 years a combination of hydrogeological setting residence time and land use information was used to explain the hydrochemical heterogeneities highlighting the main factors governing the chalk groundwater geochemistry including water level fluctuation thickness of the unsaturated zone superficial formations distribution of fracture network aquifer river relations and human activities a conceptual model was proposed to clarify the hydrogeosystem functioning of unconfined chalk aquifers the proposed methodology can be used for the study of other worldwide aquifers chalk or not with the aim to provide appropriate recommendations in terms of water management

solar wind dependence of the occurrence and motion of polar auroral arcs a statistical study 1 polar uv images from a 3 month period in winter 1998 1999 are used for a statistical study of polar arcs the study covers all auroral arcs that are located poleward of the northern auroral ova

dissolved gases in groundwater and groundwater dating methods how useful for hydrogeological modeling foreword to the special issue one of the major challenges in hydrogeology is the basic spatial lack of continuous data as this is restricted to available boreholes basic information is provided by the measurements of physical parameters e g porosity and permeability at the well scale information related to a larger part of the aquifer are provided for example by continuous measurement of piezometric levels or spring flow temporal information is extremely powerful in order to characterize aquifer functioning globally groundwater dating has thus been developed in order to provide time constraints in aquifer studies

groundwater residence time downgradient of trench no 22 at the chernobyl pilot site constraints on hydrogeological aquifer functioning following the explosion of reactor 4 at the chernobyl power plant in northern ukraine in 1986 contaminated soil and vegetation were buried in shallow trenches dug directly on site in an aeolian sand deposit these trenches are sources of radionuclide rn pollution the objective of the present study is to provide constraints for the chernobyl flow and rn transport models by characterising groundwater residence time a radiochronometer 3h 3he method t1 2 12 3 a and anthropogenic tracers including cfc and sf6 are investigated along with the water mass natural tracers na cl 18o and 2h the groundwater is stratified as evidenced by na and cl concentrations and stable isotopes 18o 2h in the upper aeolian layer the na cl relationship corresponds to evapotranspiration of precipitation while in the underlying alluvial layer an increase in na and cl with depth suggests both water rock interactions and mixing processes the 3h 3he and cfc apparent groundwater ages increase with depth ranging from recent 1 3 a at a 2 m depth below the groundwater table to much higher apparent ages of 50 60 a at 27 m depth below the groundwater table discrepancies in 3h 3he and cfc apparent ages 20 25 a and 3 10 a respectively were observed during the 2008 campaign at an intermediate depth immediately below the aeolian alluvial sand limit which were attributed to the complex water transfer processes extremely high sf6 concentrations well above equilibrium with the atmosphere and up to 1112 pptv are attributed to significant contamination of the soils following the nuclear reactor explosion in 1986 the sf6 concentration vs the apparent groundwater ages agrees with this interpretation as the high sf6 concentrations are all more recent than 1985 the persistence of the sf6 concentration suggests that sf6 was introduced in the soil atmosphere and slowly integrated in the groundwater moving along the hydraulic gradient the apparent age distribution in the lumped parameter models suggests an exponential or piston flow model in the upper geological section followed by more pronounced mixing processes in the lower section

miocene rotation of sardinia new paleomagnetic and geochronological constraints and geodynamic implications the miocene rotation of sardinia western mediterranean remains poorly constrained despite a wealth of paleomagnetic data primarily due to poor chronostratigraphic control however this rotation is contemporaneous with the opening of the liguro provencal back arc oceanic basin and its history is key to understanding the kinematics of opening of the western mediterranean we address this issue through paleomagnetic and 40ar 39ar geochronological investigations of miocene volcanic sequences in sardinia precise age control allows secular variation of the geomagnetic field to be evaluated these data provide constraints on the rotational history of this continental microplate sardinia rotated 45 counterclockwise with respect to stable europe after 20 5 ma aquitanian which is a marked increase over the estimate of 30 derived from prior paleomagnetic studies rotation was essentially complete by 15 ma about 30 of rotation occurred between 20 5 and 18 ma burdigalian corresponding to the period of maximum volcanic activity in sardinia the observed rotation validates palinspastic models derived from a morphological fit of basin margins and indicates high rates of opening up to 9 cm yr 1 in the southern part of the basin between 20 5 and 18 ma

3h 3he 14c and u th he groundwater ages in the st lawrence lowlands quebec eastern canada abstract this study attempts to place constraints on groundwater residence times using helium isotopes and 14c of a regional groundwater flow system the becancour river watershed located midway between montreal and quebec city quebec canada this densely populated region is one of the main targets for shale gas exploitation in eastern canada for this reason this watershed has been the focus of a detailed aquifer study to gain a better understanding of groundwater resources both in terms of availability and quality in the current study noble gases were sampled and analyzed in twenty eight wells from a quaternary granular aquifer and a regional bedrock aquifer of ordovician age tritium 3h and radiocarbon a14c activities were measured on selected wells helium isotopic ratios 3he 4he r normalized to that of the atmosphere ra 1 386 10 6 range from r ra 0 039 0 003 to 3 109 0 065 the helium isotopic signatures point to the presence of three water bodies 1 modern infiltration water with nearly atmospheric helium isotopic ratio and little post bomb tritium recharging the shallower granular aquifer 2 mid 50s tritium rich water slightly mineralized and 3 an older water component rich in terrigenic helium flowing in from the bedrock fractured aquifer uncorrected 14c ages range from 15 ka to modern 14c is affected by several dead carbon reservoirs related to carbonate dissolution cations exchange oxidation of organic matter and methanogenesis adjusted 14c ages calculated with netpath range from 7 ka to modern older 14c ages correspond to the end of the regional re organization of the hydrological system following deglaciation and isostatic rebound noble gas recharge paleotemperatures are 4 9 c colder than the present temperatures although no clear relation with ages has been found the relationship between the helium isotopic ratios and 14c ages suggests that the regional bedrock aquifer is affected by mixing between these three water sources calculated u th 4he ages can be partially explained by in situ production of 4he in the aquifer rock and the addition of a radiogenic helium source external to the aquifer calculated minimum helium fluxes of 1 0 10 8 to 1 8 10 7 cm3 stp cm 2 yr 1 are tens to hundreds of times lower than the average continental crust flux of 3 3 10 6 cm3 stp cm 2 yr 1 suggesting local sources possibly from production of radiogenic helium in the shale gas formations underlying the studied aquifers the occurrence of old groundwater in this aquifer system clearly limits the renewable resource and increases the risk of overexploitation in the case of increased use or in the case of pollution from different sources

36cl in modern groundwater dated by a multi tracer approach 3h 3he sf6 cfc 12 and 85kr a case study in quaternary sand aquifers in the odense pilot river basin denmark abstract 36 cl produced by thermonuclear bomb testing has been proposed as an additional tool to date or at least to identify recent groundwater components in order to investigate the behaviour of 36 cl in shallow groundwater a multi tracer approach 3 h 3 he sf 6 cfc 12 and 85 kr was used to characterise and date the groundwater of a quaternary sands aquifer which is located on the island of funen near the city of odense denmark recharge to the semi confined shallow aquifer occurs through permeable sand windows and fractured tills at the surface locally however mixing with older pre bomb water from the underlying limestone aquifer may occur the integrated analyses of the available tracer data allowed a well constrained age structure determination of the investigated water system the 36 cl cl ratios measured in groundwater were used to reconstruct the fallout rates for radioactive 36 cl at odense the calculated fallout values exceeded the fallout estimated based on data from the dye 3 ice core in greenland recycling of the bomb peak fallout seems to be the most probable reason of the high values measured the local extent of this process is difficult to quantify which impedes the use of 36 cl for dating

simultaneous optical observations of transpolar arcs in the two polar caps optical observations with de 1 and viking demonstrate conclusively that transpolar arcs can be present simultaneously at polar latitudes in both hemispheres the arcs observed here are aligned parallel to one another on opposite sides of the magnetic pole and relative to the noon midnight meridian are rotated slightly in the counterclockwise direction when viewed from above the north pole

groundwater residence time and movement in the maltese islands a geochemical approach the maltese islands are composed of two limestone aquifers the upper and lower coralline limestone separated by an aquitard the blue clay the lower coralline limestone is overlain in part by the poorly permeable globigerina limestone the upper perched aquifers are discontinuous and have very limited saturated thickness and a short water level response time to rainfall frequent detections of coliforms suggest a rapid route to groundwater however the unsaturated zone has a considerable thickness in places and the primary porosity of the upper coralline limestone is high so there is likely to be older recharge by slow matrix flow as well as rapid recharge from fractures measurement of sf6 from a pumping station in a deep part of one of the perched aquifers indicated a mean saturated zone age of about 15 years the main sea level aquifers msl on both malta and gozo have a large unsaturated thickness as water levels are close to sea level on malta parts of the aquifer are capped by the perched aquifers and more extensively by the globigerina limestone the limited detection of coliform bacteria suggests only some rapid recharge from the surface via fractures or karst features transmissivity is low and tritium and cfc sf6 data indicate that saturated zone travel times are in the range 15 40 years on gozo the aquifer is similar but is more extensively capped by impermeable blue clay cfc data show the saturated zone travel time is from 25 years to possibly more than 60 years groundwater age is clearly related to the extent of low permeability cover the 13c signature of groundwater is related to the geochemical processes which occur along the flowpath and is consistent with residence time ages in the sequence perched aquifers malta msl gozo msl the 18o and 2h enriched isotopic signature of post 1983 desalinated water can be seen in more modern groundwater particularly the urbanised areas of the perched and malta msl aquifers in all aquifers movement of solutes from the surface travelling slowly through the matrix provide a long term source of groundwater contaminants such as nitrate

geochemical evolution and timescale of seawater intrusion into the coastal aquifer of israel this study is an attempt to quantify the geochemical processes and the timescale of seawater intrusion into a coastal aquifer from changes in the major ionic composition of the water and the natural distribution of the cosmogenic isotopes 14c and 3h for that purpose we sampled saline and brackish groundwaters from the israeli coastal aquifer a multilayer sampler mls was used to obtain very high resolution 10 cm profiles across the fresh saline water interface fsi the chemical and stable isotope data revealed three distinct water types end members that are located in different zones on the route to the coastal aquifer 1 slightly modified mediterranean seawater sws 2 slightly diluted with up to 20 fresh groundwater saline groundwater sds and 3 fresh groundwater fgw the sws samples generally show an excess of total alkalinity and total dissolved inorganic carbon dic and a depletion of 13cdic and 14cdic with respect to normal seawater indicating that anaerobic oxidation of organic matter is the first diagenetic reaction that affects seawater during its penetration into the bottom sediments sds waters appear when sws is slightly diluted gain ca2 and sr2 and is depleted in k suggesting that the main processes that transform sws into sds are slight dilution with fresh groundwater and cation exchange at the fresh saline water interface sds generally shows conservative mixing with fgw inspection of chemical data from coastal aquifers around the world indicates that intensive ion exchange in slightly diluted saline groundwater is a globally important phenomenon of seawater intrusion most of our saline groundwater samples contain substantial amounts of 3h suggesting that penetration of mediterranean seawater and its inland travel to a distance of 50 100 m onshore occurred 15 30 yr ago this is supported by the 14cdic mass balance that explains the relatively low 14cdic activities in the sds as influenced by diagenesis and not by simple radioactive decay

natural fluorinated organics in fluorite and rocks results of measurements of fluorinated compounds in gasses extracted from igneous and metamorphic rocks are reported a new extraction method analogous to a pepper mill for geological samples is described it permits extraction at low temperatures and ensures a rapid transfer of extracted gases from active surfaces to cryogenic pre concentration loop values for cf4 cf3cl cf2cl2 cfcl3 chf3 sf6 and nf3 in fluorites granites basalts and other igneous and metamorphic rocks are reported it is proposed that trifluoroacetic acid tfa that was recently discovered in various environmental archives could also origin from similar geogenic sources

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

40ar 39ar dating and paleomagnetism of the miocene volcanic succession of monte furru western sardinia implications for the rotation history of the corsica sardinia microplate although it is widely acknowledged that the corsica sardinia microplate rotated counterclockwise with respect to europe during oligocene miocene time the precise timing of this event has yet to be determined we have measured the age and degree of rotation of a single tie point in the rotation history of the microplate biotite and sanidine 40ar 39ar age determinations of the 200m thick monte furru volcanic succession indicates that most of the volcanic pile accumulated within less than 200 ky the paleomagnetic pole obtained for the 12 volcanic flow units comprising this succession indicates that by 18 2 ma sardinia remained 13 shy of its final rotation angle these results demonstrate that the movement of the corsica sardinia block and the opening of the liguro provencal basin terminated later than previously estimated based on paleomagnetic and geochronologic studies of sardinian volcanic rocks in agreement with paleomagnetic data from sardinian sediments

identification of different groundwater flowpaths within volcanic aquifers using natural tracers for the evaluation of the influence of lava flows morphology argnat basin chaine des puys france hydrochemical and stable isotopic 2h 18o data were used to characterize the groundwater flow and major chemical features within a complex fractured volcanic aquifer system the argnat basin which is located in the chaine des puys french massif central from 10 sampling points the study of the transfer into the saturated zone from upstream to downstream given the geological context and topography allows to estimate the role of supply from high and low altitudes to the recharge processes this work shows the existence of different types of supply between pahoehoe and a a flows therefore the morphology of volcanic flows impacts the chemical and isotopic signatures of groundwater enhancing or reducing the influence of the unsaturated zone on the pathways of infiltrated water pahoehoe flows imply horizontal water flows of low discharge at the top of the lava whereas a a flows seems to be much more heterogeneous and locally able to promote the existence of perched water bodies and further vertical circulations taking into account these two types of behaviour a conceptual scheme of the functioning of this heterogeneous environment is proposed which will help towards a sustainable management of volcanic aquifers in relation with the european union groundwater directive 2006 118 ce 2006

impacts of human activities on recharge in a multilayered semiarid aquifer campo de cartagena se spain the development of intense agriculture in semiarid areas modifies intensity and spatial distribution of groundwater recharge by summing irrigation return flow to limited rainfall infiltration environmental tracers provide key information but their interpretation is complicated by more complex groundwater flow patterns in multilayered aquifers the real origin of the groundwater samples is hard to assess because of local mixing processes occurring inside long screened boreholes we use environmental tracers 14c 13c 2h 18o 3h to investigate the long term evolution of recharge in the five layer campo de cartagena aquifer in south eastern spain in addition to high resolution temperature loggings to identify the depth of origin of groundwater despite the complex background this methodology allowed a reliable interpretation of the geochemistry and provided a better understanding of the groundwater flow patterns the tritium method did not give good quantitative results because of the high variability of the recharge signal but remained an excellent indicator of recent recharge nonetheless both pre anthropization and post anthropization recharge regime could be identified and quantified by radiocarbon before the development of agriculture recharge varied from 17 mm year 1 at the mountain ranges to 6 mm year 1 in the plain whereas the mean annual rainfall is about 300 mm in response to the increase of agricultural activity recharge fluxes to the plain were amplified and nowadays reach up to 210 mm year 1 in irrigated areas these values are strengthened by global water budget and local unsaturated zone studies copyright 2013 john wiley sons ltd

ionic and isotopic ratios for identification of salinity sources and missing data in the gaza aquifer abstract groundwater is the only source of fresh water in the gaza strip however it is severely polluted and requires immediate effort to improve its quality and increase its usable quantity intensive exploitation of groundwater in the gaza strip over the past 40 years has disturbed the natural equilibrium between fresh and saline water and has resulted in increased salinity in most areas salinization in the coastal aquifer may be caused by a single process or a combination of different processes including seawater intrusion upconing of brines from the deeper parts of the aquifer flow of saline water from the adjacent eocene aquifer return flow from irrigation water and leakage of wastewater each of these sources is characterized by a distinguishable chemistry and well known isotopic ratios in this paper na cl so4 cl br cl ca hco3 so4 and mg ca ionic ratios were used to distinguish different salinization sources 11b and 87sr 86sr isotopic composition were also included in the model to study their importance in this monitoring task the task of monitoring and the associated decision making process are characterized by a high degree of uncertainty with respect to input data and accuracy of models for this reason probabilistic expert systems and more specifically bayesian belief networks bbns are used to identify salinization origins the bbn model incorporates the theoretical background of salinity sources area specific monitoring data that are characteristically incomplete in their coverage expert judgment and common sense reasoning to produce a geographic distribution for the most probable sources of salinization the model is also designed to show areas where additional data on chemical and isotopic parameters are needed

groundwater mixing between different aquifer types in a complex structural setting discerned by elemental and stable isotope geochemistry karst aquifers are well known for their intricate stratigraphy and geologic structures which make groundwater characterization challenging because flowpaths and recharge sources are complex and difficult to evaluate geochemical data collected from ten closely spaced production wells constructed in two karst aquifers bangor limestone mb and tuscumbia limestone fort payne chert mftp in trussville north central alabama illustrate two distinctive groundwater end members 1 higher major ion dissolved inorganic carbon conductivity alkalinity concentrations heavier 13c ratios max 10 2 0 2 vienna pee dee belemnite pdb and lower residence times mean 19 5 2 years n 2 of groundwater in the mb aquifer and 2 lower constituent concentrations lighter 13c ratios min 13 4 0 2 pdb and longer residence times of groundwater mean 23 6 2 years n 4 in the mftp aquifer summer and fall data and the binary mixing model show aquifer inter flow mixing along solution fractures and confirms the distinctive groundwater geochemistry of the two aquifers lowering of static water levels over the summer drawdown from 2 to 5 2 m leads to more reducing groundwater conditions lower eh values and slightly enriched 18o and d ratios during the fall 18o 4 8 0 1 to 5 4 0 1 vienna standard mean oceanic water vsmow n 9 d 25 4 1 to 27 4 1 vsmow n 9 when compared with summer season samples 18o 5 1 0 1 to 5 7 0 1 vsmow n 11 d 25 0 1 to 30 6 1 vsmow n 11 gis analyses confirm the localized origin of recharge to the investigated aquifers the combination of gis field parameters and geochemistry analyses can be successfully used to identify recharge sources evaluate groundwater flow and transport pathways and to improve understanding of how groundwater withdrawals impact the sustainability and susceptibility to contamination of karst aquifers copyright 2015 john wiley sons ltd

chemical and isotopic constraints on evolution of groundwater salinization in the coastal plain aquifer of laizhou bay china a hydrochemical isotopic investigation of the laizhou bay quaternary aquifer in north china provides new insights into the hydrodynamic and geochemical relationships between freshwater seawater and brine at different depths in coastal sediments saltwater intrusion mainly occurs due to two cones of depression caused by concentrated exploitation of fresh groundwater in the south and brine water for salt production in the north groundwater is characterized by hydrochemical zonation of water types ranging from ca hco3 to na cl from south to north controlled by migration and mixing of saline water bodies with the regional groundwater the strong adherence of the majority of ion cl ratios to mixing lines between freshwater and saline water end members brine or seawater indicates the importance of mixing under natural and or anthropogenic influences examination of the groundwater stable isotope delta o 18 and delta h 2 values between 9 5 parts per thousand and 3 0 parts per thousand and 75 parts per thousand and 40 parts per thousand respectively and chloride contents similar to 2 to 1000 meq l of the groundwater indicate that the saline end member is brine rather than seawater and most groundwater samples plot on mixing trajectories between fresh groundwater delta o 18 of between 6 0 parts per thousand and 9 0 parts per thousand cl 1000 meq l locally elevated na cl ratios likely result from ion exchange in areas of long term freshening the brines with radiocarbon activities of similar to 30 to 60 pmc likely formed during the holocene as a result of the sequence of transgression regression and evaporation while deep fresh groundwater with depleted stable isotopic values delta o 18 9 7 parts per thousand and delta h 2 71 parts per thousand and low radiocarbon activity 20 pmc was probably recharged during a cooler period in the late pleistocene as is common throughout northern china an increase in the salinity and tritium concentration in some shallow groundwater sampled in the 1990s and re sampled here indicates that intensive brine extraction has locally resulted in rapid mixing of young fresh groundwater and saline brine the 6180 and delta h 2 values of brines similar to 3 0 parts per thousand and 35 parts per thousand are much lower than that of modern seawater which could be explained by 1 mixing of original 5180 enriched brine that was more saline than presently observed with fresh groundwater recharged by precipitation and or 2 dilution of the palaeo seawater with continental runoff prior to and or during brine formation the first mechanism is supported by relatively high br cl molar ratios 1 7 x 10 3 2 5 x 10 3 in brine water compared with similar to 1 5 x 10 3 in seawater which could indicate that the brines originally reached halite saturation and were subsequently diluted with fresher groundwater over the long term decreasing c 14 activities with increasing sampling depth and increasing proximity to the coastline indicate that the south coastal aquifer in laizhou bay is dominated by regional lateral flow on millennial timescales c 2013 elsevier b v all rights reserved

effect of the unsaturated zone thickness on the distribution of water mean transit times in a porous aquifer summary the mean transit time of groundwater is commonly expected to increase gradually with increasing depth below water table the present study provides evidence that the theoretical distribution of transit times may be significantly altered depending on the thickness of the unsaturated zone an unconfined porous groundwater system formed by tertiary sediments test field scheyern close to munich in southern germany is overlain by an unsaturated zone with variable thickness between 4 and 60 m between 1992 and 2007 the groundwater system has been repeatedly sampled for tritium contents at different depths using two high resolved wells modelled tritium concentrations by using a lumped parameter approach yielded depth profiles of mean transit times of tracer in one well the profile was characterized by two local transit time maxima each of approximately 100 years a moving particle approach mpa developed in this study was used on the streamlines between the recharge zones linked to different sampling depths in the well this suggested that the observed transit time in the profile was mainly governed by variable travel distances of the tracer through the unsaturated zone at the points of recharge this finding was confirmed at a second multi level well of the test site the lumped parameter modelling of chlorofluorocarbon data yielded lower transit times as compared to those obtained from tritium data this effect was explained by the different behaviour of tritium and chlorofluorocarbons in the unsaturated zone the study clearly shows that the impact of a variable thickness of the unsaturated zone may overweigh the effect of local heterogeneities such transit time distributions of water in porous aquifers as observed in the present study can only be achieved with the help of environmental tracer data

hydrogeochemical assessment of groundwater quality along the coastal aquifers of southern tamil nadu india hydrogeochemical investigation of groundwater has been carried out in the coastal aquifers of southern tamil nadu india seventy nine dug well samples were collected and analyzed for various physicochemical parameters the result of the geochemical analysis indicates the groundwater in the study area is slightly alkaline with moderate saline water the cation and anion concentrations confirm most of the groundwater samples belong to the order of na mg2 ca2 k and cl so42 hco3 thereby three major hydrochemical facies ca cl mixed ca mg cl and na cl were identified based on the us salinity diagram majority of the samples fall under medium to very high salinity with low to high sodium hazard the cross plot of ca2 mg2 versus chloride shows 61 of the samples fall under saline water category higher ec tds and cl concentrations were observed from tiruchendur to koodankulam coastal zone it indicates that these regions are significantly affected by saltwater contamination due to seawater intrusion saltpan deposits and beach placer mining activities

discrimination between different water bodies from a multilayered aquifer kaluvelly watershed india trace element signature in the multilayered aquifer of kaluvelly india comprising various sedimentary layers overlying a charnockitic basement concentrations of trace elements were measured in aquifer formations and in groundwaters to identify geochemical tracers for water bodies the two main sandstones cuddalore and vanur originate from the charnockites and the cuddalore sandstone has experienced lateritization in the studied area two charnockite end members were identified a dioritic and a granitic one mineralogical composition and whole rock ti concentrations confirmed the charnockite which displayed the granitic composition as the parent rock of the two sandstones titanium distribution indicates that the cuddalore sandstone originates from a more intense weathering of the parent material than the vanur sandstone despite extensive differences in trace element contents recorded in aquifer formations only a few trace elements were suitable to distinguish the water bodies among soluble elements li in the vanur aquifer and ba in the charnockite and carbonaceous aquifers can be used as tracers as the input of these elements in solution is mainly regulated by the available stock for a given mineralogical origin there is a direct link between the aquifer formation composition and water signature with the exception of as concentrations of redox sensitive elements were not preserved during pumping because of oxidation preventing their use as tracers low mobility elements such as la ce th zr nb hf or ta were too insoluble to be detected in waters and or to record the aquifer formation signature their input in solution was not regulated by the available stock but by the dissolution rate of rock forming minerals only ti can be used to distinguish between two out of the three aquifers charnockite and vanur the specific behavior of ti recorded in these waters may be linked to rutile inclusions within plagioclases and to the influence of climate on ti solubility

isotopic composition of precipitation in italy a first overall map abstract composite monthly samples of atmospheric precipitation were collected over different periods of time ranging from one to seven years at 77 different locations throughout italy these samples were measured for their oxygen and hydrogen isotopic composition to obtain basic information for hydrological and meteorological studies in this area on the basis of the results obtained a first map of the isotopic composition of precipitations in italy has been drawn up the main features of this map are the following 1 no isotopic latitudinal gradient has been found along the tyrrhenian coast from sicily to the italian french border despite the considerable range of latitude 2 a minor latitudinal gradient is found in the southeasternmost section of the country apulia partially favored by the local morphology 3 a marked shadow effect of the apennines is apparent along the southern section of the po valley and along the central section of the adriatic coast 4 the contribution of water vapor from the northernmost section of the adriatic sea affects the eastern and central sections of the po plain 5 the shadow effect of the alps is considerably smaller than expected 6 the isotopic vertical gradients calculated in nine different areas and based on groups of two to five different stations vary but are essentially close to about 0 2 100 m 7 when mean monthly temperature values were available their relationship with the isotopic composition of precipitation was found to be on average very poor 8 the relationship between mean 18o and mean d calculated for the collection locations shows shifts of both the slope and the deuterium excess when compared to the global meteoric water line these shifts are different for northern central and southern italy 9 in a few cases anomalously low monthly values suggest the existence of pronounced amount effects

a further study on seismic response of a set of parallel rock fractures filled with viscoelastic materials the purpose of this study is to further investigate the seismic response of a set of parallel rock fractures filled with viscoelastic materials following the work by zhu et al dry quartz sands are used to represent the viscoelastic materials the split hopkinson rock bar shrb technique is modified to simulate 1 d p wave propagation across the sand filled parallel fractures at first the displacement and stress discontinuity model dsdm describes the seismic response of a sand filled single fracture the modified recursive method mrm then predicts the seismic response of the sand filled parallel fractures the shrb tests verify the theoretical predictions by dsdm for the sand filled single fracture and by mrm for the sand filled parallel fractures the filling sands cause stress discontinuity across the fractures and promote displacement discontinuity the wave transmission coefficient for the sand filled parallel fractures depends on wave superposition between the fractures which is similar to the effect of fracture spacing on the wave transmission coefficient for the non filled parallel fractures

using the cl br ratio as a tracer to identify the origin of salinity in aquifers in spain and portugal summary a study on the applicability of the cl br molar ratio for identifying the origin of groundwater salinity is presented according to the experience gained in spain and portugal cl br ratios in atmospheric bulk deposition have helped to distinguish groundwater in which cl derives only from atmospheric sources from groundwater in which cl is contributed by endogenous lithological or anthropogenic sources considering the seawater cl br ratio of 655 4 cl br ratios may be increased up to 1500 in groundwater by the addition of wastewater loaded with nacl or leaching of solid waste and decreased to 300 by the use of br based pesticides or leaching farm animal or septic waste leaching and dissolution of natural and industrial nacl and of gypsum rich formations containing some nacl may yield cl br ratios between one thousand and several thousand although leaching of potassium halides near salt mines produces cl br ratios below the seawater ratio when cl content in groundwater is not affected by extreme evaporation up to halite saturation at 6 2 mol l 1 of nacl and if there are no other cl sources recharge by rainfall can be estimated by relating cl in atmospheric bulk deposition to derived groundwater the cl br ratio appears to be a good tracer for discriminating non atmospheric cl contributions to groundwater provided chemical analyses are accurate since its variability is not wide data have been collected from different areas of spain and portugal and are explained and illustrated by two cases described in detail the donana aquifer in southwest spain and the canary islands both showing the mixing paths