the serchio river catchment northern tuscany geochemistry of stream waters and sediments and isotopic composition of dissolved sulfate abstract the serchio river and its tributaries in northern tuscany were investigated for the chemical and isotopic compositions of waters and bed sediments bedrocks are mostly limestone dolomite and siliciclastics thermal spring systems are present in the catchment and the main industrial activity is represented by paper mills main results obtained are 1 major ions in solution appear to be basically controlled by precipitation and lithology as well as subordinately by direct inputs of thermal springs 2 human influence on metals in the waters along the main serchio and lima rivers is indicated at a number of sites by increases in concentration compared to the chemical composition of upstream tributaries 3 s and o isotope compositions delineate two main sources for aqueous so 4 2 that is dissolution of triassic evaporite directly or via thermal springs and oxidation of sulfide dispersed in siliciclastic rocks anthropogenic contributions are probable but they cannot be quantitatively assessed only so 4 2 in the notoriously polluted ozzeri tributary is suspected to be largely anthropogenic and 4 the chemical composition of bed sediments is mainly influenced by lithology apart from a number of technogenic elements in the upper part of the serchio river and in some tributaries contamination possibly occurs at other sites but geochemical indications are weak

back arc strain in subduction zones statistical observations versus numerical modeling 1 recent statistical analysis by lallemand et al 2008 of subduction zone parameters revealed that the back arc deformation mode depends on the combination between the subducting vsub and upper vup plate velocities no significant strain is recorded in the arc area if plate kinematics verifies vup 0 5 vsub 2 3 cm a in the hs3 reference frame arc spreading shortening occurs if vup is greater lower than the preceding relationship we test this statistical law with numerical models of subduction by applying constant plate velocities far away from the subduction zone the subducting lithosphere is free to deform at all depths we quantify the force applied on the two converging plates to sustain constant surface velocities the simulated rheology combined viscous non newtonian and brittle behaviors and depends on water content the influence of subduction rate vs is first studied for a fixed upper plate after 950 km of convergence steady state slab pull the transition from extensional to compressive stresses in the upper plate occurs for vs 1 4 cm a the effect of upper plate velocity is then tested at constant subduction rate upper plate retreat advance with respect to the trench increases extension compression in the arc lithosphere and increases decreases the subducting plate dip our modeling confirms the statistical kinematic relationship between vsub and vup that describes the transition from extensional to compressive stresses in the arc lithosphere even if the modeled law is shifted toward higher rates of upper plate retreat using our set of physical parameters e g 100 km thick subducting oceanic plate and short term simulations our results make valid the choice of the hs3 reference frame for assessing plate velocity influence on arc tectonic regime the subduction model suggests that friction along the interplate contact and the mantle stokes reaction could be the two main forces competing against slab pull for upper mantle subductions besides our simulations show that the arc deformation mode is strongly time dependent

water rock interactions and seawater freshwater mixing effects in the coastal dunes aquifer coos bay oregon abstract groundwater from the seawater freshwater interface in sandy sediments was sampled using a unique profile well designed in which separate pvc tube screens were installed at various depths all major ions except chloride showed non conservative behavior in the mixing zone so4 mg2 and k are depleted and hco3 is enriched relative to cl na is enriched in solutions containing less than 20 seawater and depleted in solutions containing higher percentages of seawater the behavior of ca2 is the mirror image ofthat of na the chemical data on the stratification of groundwater above and within the interface zone were obtained using a unique profile well design in which separate pvc tube screens were installed at various depths thus making it possible to extract water samples at close vertical intervals the chemical changes in the groundwater reflect the following processes 1 a ca2 na and ca2 mg2 base exchange reactions 2 b oxidation of organic matter in the sediment 3 c reduction of sulfate probably due to bacterial processes 4 d reaction of hco3 and s2 with fe2 to produce mineral coatings and cements of pyrite and siderite 5 e k feldspar formation producing lower of k concentrations the authigenic phases were identified using scanning electron microscopy thermodynamic calculations suggest that all solutions are saturated with respect to quartz and chalcedony and many are saturated with respect to calcite dolomite siderite and hematite kaolinite is the stable clay mineral in the top of the freshwater column whereas smectite is the stable clay mineral in the lower part of the freshwater column and in the seawater freshwater mixing zone

groundwater mineralisation processes in mediterranean semi arid systems cap bon north east of tunisia hydrogeological and geochemical approaches the groundwater of the korba plain represents major water resources in tunisia the plio quaternary unconfined aquifer of the cap bon north east tunisia is subject to the intensive agricultural activities and high groundwater pumping rates due to the increasing of the groundwater extraction the degradation of the groundwater quality is characterized by the salinization phenomena groundwater were sampled and analysed for physic chemical parameters ca2 mg2 na k cl so42 hco3 no3 ph electrical conductivity ec and the temperature t the hydrochemical analysis is coupled with the calculation of the saturation indexes si gypsum si halite si calcite and si dolomite ionic derivation and with the ion correlations compared to chloride concentrations na cl ca2 cl and mg2 cl ratios seawater fractions in the groundwater were calculated using the chloride concentration those processes can be used as indicators of seawater intrusion progression ec methods were also conducted to obtain new informations on the spatial scales and dynamics of the fresh water seawater interface of coastal groundwater exchange the mixing zone between freshwater and saltwater was clearly observed from the ec profile in the investigated area where a strong increase in ec with depth was observed corresponding to the freshwater and saltwater interface results of hydrochemical study revealed the presence of direct cation exchange linked to seawater intrusion and dissolution processes associated with cations exchange these results together with ec investigation indicated that the groundwater is affected by seawater intrusion and is still major actor as a source of salinization of the groundwater in korba coastal plain further isotopic and hydrological investigations will be necessary to identify and more understood the underlying mechanisms copyright 2012 john wiley sons ltd

timing of thrust activity in the high zagros fold thrust belt iran from u th he thermochronometry 1 apatite and zircon u th he cooling ages are used to quantify the timing of exhumation associated with thrust faulting in the high zagros fold thrust belt single grain cooling age data were collected from 1 cambrian sandstone in various thrust sheets 2 sandstone and basement clasts derived from structurally controlled salt plugs or fault bounded slices and 3 syntectonic neogene siliciclastics strata in the northwestern kuhrang and central kuh e lajin high zagros apatite u th he ahe ages range from 26 7 to 0 38 ma most cooling and exhumation occurred in the early to middle miocene constrained by ahe ages 19 15 ma from the high zagros thrust sheet localized faults and reset cooling ages from bakhtiyari deposits in the southeastern high zagros kuh e dinar cooling occurred later with ahe ages ranging from 16 5 to 0 79 ma here most cooling and exhumation occurred in the late miocene constrained by ahe ages 12 8 ma from the high zagros fault and exhumed paleozoic clasts in synorogenic strata zircon u th he zhe ages from bedrock samples across the high zagros are reflective of the precollisional thermal history the preservation of precollisional zhe ages limits the pre miocene maximum burial temperature of the exhumed strata to 180 c and indicate 7 9 km of maximum exhumation in the central zagros this study shows that thrust activity in the high zagros and continental suturing along the zagros suture was underway by at least 19 ma and initiated no later than latest oligocene to early miocene time 23 ma

isotopic imaging of surface water groundwater interactions sacramento valley california groundwater isotope data across the sacramento valley california establish two types of groundwater mining 1 overdraft of ancient groundwater with limited recharge by surface waters producing cones of depression 2 ancient groundwater withdrawal followed by rapid recharge of irrigation water reducing groundwater quality the first type occurs in the sacramento metropolitan area where meteoric runoff is unnaturally high and 40 years of pumping have depressed water levels to 25 m below sea level inducing recharge from losing reaches of the sacramento and american rivers lateral migration rates are quantified by the binary mixing between river water 18o 10 8 and natural groundwater 18o 7 0 the second type of mining occurs in agricultural regions to the west where 14c ages indicate that irrigation waters constitute more than 80 of modern recharge this recharge has several characteristics of evaporated irrigation water including 1 high 18o values to 6 0 that define closed contour patterns 2 elevated no3 concentrations to 100 ppm 3 low 14c ages of less than 500 years stable isotope contours augmented by 14c data provide dynamic recharge patterns in this profoundly disturbed giant alluvial aquifer on a large scale 100 km2 the lateral permeabilities of alluvial aquifers are essentially isotropic whereas on a smaller scale 25 km2 anisotropy is evident and isotope values can be geographically complex and seasonally transient groundwater flow patterns implied by the isotope data can differ substantially from steady state models based on head measurements

natural and anthropogenic so4 sources in the arno river catchment northern tuscany italy a chemical and isotopic reconnaissance abstract the 34 s isotope signature of aqueous so 4 2 in the main river arno and principal tributaries was investigated along with major ion chemistry in order to check the pollution effects in the water network of a heavily industrialized and densely urbanized catchment extending in tuscany over an area of 8228 km 2 from the apennine ridge to the tyrrhenian sea major towns include florence and pisa analyses are presented for 29 water samples from the arno river and 36 water samples from the tributaries all collected in 1996 1997 during low flow hydrologic conditions samples from the arno are distributed from source to mouth and those from tributaries upstream from the confluence points the arno river solutes consist mainly of ca 2 and hco 3 but the proportions of na cl and so 4 2 increase downstream in keeping with the basically anthropogenic origin of the latter the 34 s so 4 2 signature also increases downstream with the most depleted values in the source zone the seawater ingression into the river is documented by distinctly higher chemical and isotopic parameters at about 13 km from the mouth in general the tributaries behave similarly to the arno for both their chemical and isotopic compositions with increasing 34 s na cl and so 4 2 downstream the 34 s of so 4 2 in natural inputs is estimated to range approximately between 15 and 4 from oxidation of pyrite disseminated in country rocks and between 15 and 23 from dissolution of evaporites whereas the 34 s of anthropogenic so 4 2 should be variable within the range 1 8

geochemical and isotopic study of paleogroundwater salinization in southeastern tunisia sfax basin salinization is a common environmental problem of groundwater contamination particularly in developed coastal aquifers the sfax basin is located on the mediterranean coast southeastern tunisia and is dominated by industrial activities the problem of groundwater mineralization in the south part of this aquifer has long been attributed to the marine influence in this study a combined hydrogeological and isotopic survey using chemical tracers was conducted in addition to discharge and groundwater level measurements the results preclude seawater intrusion as an origin of groundwater mineralization it seems that the main source of groundwater mineralization is due to the mixture with salty water lodged in the c t cenomanian turonian aquifer this mixture process is carried out by the simultaneous effect of 1 a lateral flow of saline water coming from c t aquifer in the southwest menzel habib and 2 a local vertical leakage from the same c t formation which forms the basement of the studied aquifer the depleted isotope signature of the majority of groundwater is characteristic of old recharge occurring during the late pleistocene holocene with the exception of some local recent refill areas

natural cr vi contamination of groundwater in the cecina coastal area and its inner sectors tuscany italy a detailed hydrogeochemical study of groundwater in the cecina coastal plain livorno province italy and its inner sectors was undertaken in 2008 as chemical analyses carried out on groundwater since 2006 have revealed cr vi concentrations of up to 49 g l well above the permissible limit of 5 g l ophiolite outcrops are present throughout the study area and their fragments likely represent a significant portion of the existing multilayered aquifer skeleton waters delivered by the serpentinite outcrops have a typically mg hco3 composition whereas those of the coastal plain are prevailingly of the ca mg hco3 type with significant mg contents significant no3 contamination characterises the studied coastal plain and an interesting negative correlation exists between cr vi and both no3 and so4 deriving from the widespread use of nh4 2so4 as a farm fertilizer chromium speciation calculations carried out using the eq3nr code reveal that the prevailing cr vi species in solution is cro4 2 however cacro4 and mgcro4 neutral complexes represent significant percentages up to 42 these findings suggest that the mobility and consequently the bioavailability of cr vi can be significantly enhanced by these neutral complexes which are not considered to be affected by adsorption desorption processes the cr vi source investigated by means of the mg sio2 molar ratio seems to be represented mainly by mg bearing minerals of the chlorite group petrographic observations confirm the occurrence of this mineral group the interaction between rainwater and the local serpentinite rock was simulated at different p text co 2 and p text o 2 conditions by reaction path modelling using the eq3 6 software package p text o 2 was varied in accordance with the assumption that redox conditions are determined in part by no3 results are in good agreement with experimental data on spring waters and subordinately with data on some coastal plain groundwater which plot in a rather wide p text co 2 and p text o 2 field although the dissolved cr content is mostly of natural origin fertilization may affect its fate

zagros orogeny a subduction dominated process this paper presents a synthetic view of the geodynamic evolution of the zagros orogen within the frame of the arabia eurasia collision the zagros orogen and the iranian plateau preserve a record of the long standing convergence history between eurasia and arabia across the neo tethys from subduction obduction processes to present day collision from 150 to 0 ma we herein combine the results obtained on several geodynamic issues namely the location of the oceanic suture zone the age of oceanic closure and collision the magmatic and geochemical evolution of the eurasian upper plate during convergence as testified by the successive sanandaj sirjan kermanshah and urumieh dokhtar magmatic arcs the p t t history of the few zagros blueschists the convergence characteristics across the neo tethys kinematic velocities tomographic constraints subduction zones and obduction processes together with a survey of recent results gathered by others we provide lithospheric scale reconstructions of the zagros orogen from 150 to 0 ma across two sw ne transects the evolution of the zagros orogen is also compared to those of the nearby turkish and himalayan orogens in our geotectonic scenario for the zagros convergence we outline three main periods regimes 1 the mid to late cretaceous 115 85 ma corresponds to a distinctive period of perturbation of subduction processes and interplate mechanical coupling marked by blueschist exhumation and upper plate fragmentation 2 the paleocene eocene 60 40 ma witnesses slab break off major shifts in arc magmatism and distributed extension within the upper plate and 3 from the oligocene onwards 30 0 ma collision develops with a progressive sw migration of deformation and topographic build up sanandaj sirjan zone 20 15 ma high zagros 12 8 ma simply folded belt 5 0 ma and with partial slab tear at depths 10 ma to present our reconstructions underline the key role played by subduction throughout the whole convergence history we finally stress that such a long lasting subduction system with changing boundary conditions also makes the zagros orogen an ideal natural laboratory for subduction processes

understanding and modelling spatial drain aquifer interactions in a low lying coastal aquifer the thurne catchment norfolk uk seawater intrusion into fresh groundwater formations generally results inadvertently from human activities such as over abstraction from coastal aquifers this article describes the data analysis to quantify drain aquifer interactions in a low lying pump drained coastal aquifer which is subject to saline intrusion due to widespread land drainage and the resulting development and application of a numerical groundwater model to understand the spatial groundwater system behaviour including groundwater salinity fluxes without measured flow data in this pump drained catchment a novel groundwater head dependent approach to hydrograph separation is described time variant and time invariant modflow analyses are utilised to examine the flow processes a new approach to calculate drain coefficients which represent the extensive network of drainage ditches in the regional model using field information is described the sum of the drainage coefficients are close to the values independently estimated from the head dependent hydrograph separation results show that 1 the groundwater flows into the drainage systems are well reproduced using the new drain coefficients 2 particle tracking of fresh and saline water can explain observed spatial salinity distribution within drainage networks and 3 the modelled flow of seawater across the coast is approximately 25 greater than that discharged by the pumps demonstrating the need for drainage management to be aware of the slow response of groundwater systems to past drainage system changes the article demonstrates that numerical groundwater modelling can produce the improved understanding needed to inform management decisions in such complex environments copyright 2010 john wiley sons ltd

dissolved nitrates in the groundwater of the cecina plain tuscany central western italy clues from the isotopic signature of no3 abstract anthropogenic no 3 is one of the most serious pollutants in the groundwaters from the multi aquifer system of the cecina plain tuscany central western italy according to the ec directive 91 676 cee the local administration of tuscany has declared the cecina plain as vulnerable by nitrates determining the origin and the source s of no 3 contamination is an important step prior to any remediation program in the present work a geochemical survey was carried out on 92 groundwater samples collected in june and october 2006 to highlight the natural and anthropogenic features that concur with the observed chemical composition the geochemical facies of the water samples is dominated by ca mg hco3 and ca mg so4 cl and subordinately by na ca cl so4 likely resulting by water rock interaction processes between meteoric derived groundwaters with the sedimentary formations characterizing the cecina plain at which ingression of seawater in the coastal area is also added a mixing model based on ionic ratios no3 na cl na cl br was applied to distinguish the anthropogenic sources e g sewage agriculture input from natural sources e g seawater intrusion selected samples were analyzed for the isotopic composition of no 3 15n no3 and 18o no3 to formulate hypotheses on its origin and the processes this component may suffer in the water system nitrate concentrations range from 0 01 to 354 mg l about 35 and 19 of the sampled wells in june and october 2006 respectively had levels of no 3 higher that those recommended by the world health organization

geochemical and isotopic evidence for palaeo seawater intrusion into the south coast aquifer of laizhou bay china this research aims to improve the current knowledge of groundwater salinisation processes in coastal aquifers using combined hydrochemical and isotopic parameters and inverse hydrochemical modelling field investigations were conducted in laizhou bay which is the area most seriously affected by seawater intrusion in north china during three sampling campaigns along a vertical transect in the changyiliutuan area 95 ground and surface water samples were collected for major ion and isotope analysis

multivariate statistical analysis and hydrogeochemical modelling of seawater freshwater mixing along selected flow paths case of korba coastal aquifer tunisia abstract groundwater sampling and piezometric measurements were carried out along two flow paths corresponding to two transects in korba coastal plain northeast of tunisia the study aims to identify hydrochemical processes occurring when seawater and freshwater mix those processes can be used as indicators of seawater intrusion progression and freshwater flushing into seawater accompanying submarine groundwater discharge sgd seawater fractions in the groundwater were calculated using the chloride concentration hierarchical cluster analysis hca was applied to isolate wells potentially affected by seawater in addition phreeqc was used to simulate the theoretical mixing between two end members seawater and a fresh brackish groundwater sample geochemical conventional diagrams showed that the groundwater chemistry is explained by a mixing process between two end members results also revealed the presence of other geochemical processes correlated to the hydrodynamic flow paths direct cation exchange was linked to seawater intrusion and reverse cation exchange was associated to the freshwater flushing into seawater the presence of these processes indicated that seawater intrusion was in progress an excess of ca that could not be explained by only cation exchange processes was observed in both transects dedolomitization combined to gypsum leaching is the possible explanation of the groundwater ca enrichment finally redox processes were also found to contribute to the groundwater composition along flow paths

geochemical calculations and observations on salt water intrusions i a combined geochemical minxing cell model abstract a combined geochemical mixing cell flow model has been developed the geochemical model is based on the computer program eq 3 6 wolery 1982 has been modified to include cation exchange reactions and is incorporated in a one dimensional mixing cell model for stationary one dimensional transport dispersion or diffusion is calculated by mixing the cell contents with neighbouring cells relationships between mixing factors and dispersivity and diffusion coefficients are derived the model is used to simulate concentration changes during salt water intrusions fundamental differences are shown to exist between diffusion of salt water from a stagnant water body and dispersive intrusions during marine transgressions or flooding events with dispersive flow characteristic water compositions develop in space and time as a result of cation exchange with diffusion these steep concentration gradients are smoothed out and mixed compositions occur the concept that characteristic concentrations occur during dispersive flow is used to obtain paleohydrological information in a dutch polder the depth of the fresh salt water interface before polder development is deduced from a simulation of observed exchange reactions in the polder groundwater

hydrodynamic analysis of a mediterranean aquifer system with the use of hydrochemical and isotopical analysis as supporting tools the management of groundwater resources in coastal environments within the mediterranean basin has become of paramount importance especially in the light of global changes a typical example of such a hydrosystem is the lavrio basin in greece this research site involves two aquifer types granular and karstic formations that are hydraulically interconnected furthermore the proximity to the sea and the abstractions for irrigation and drinking water supply have led to the phenomenon of seawater intrusion the present study aims at analyzing the hydraulic hydrological and hydrogeological conditions of the area by means of hydrochemical and isotopical data interpretation as supporting tools which will inform and support the development of an integrated conceptual hydrogeological model of the area field investigations were conducted in order to collect piezometric and chemical data and use them to retrieve the quantitative and qualitative status of the local aquifer units new interpretation of an older dataset gave an insight into how the karstic aquifer behaves in terms of hydraulics the results have also demonstrated that there is a hydraulic connection between the different aquifers and the mediterranean sea while natural recharge was quantified for both aquifer types

the utilization of boron and strontium isotopes for the assessment of boron contamination of the cecina river alluvial aquifer central western tuscany italy abstract the groundwater b concentration in the alluvial aquifer of the upper cecina river basin in tuscany italy often exceeds the limit of 1 mg l 1 set by the european union for drinking water on the basis of hydrogeological and geochemical observations the main source of the b contamination of groundwater has been attributed to past releases into streams of exhausted b rich geothermal waters and or mud derived from boric acid manufacturing in larderello the releases were discontinued 25 30 years ago this study confirms that the b dissolved in groundwater is anthropogenic in fact the 11b values of groundwater b match the range 12 2 to 13 3 of the turkish b mineral colemanite processed in boric acid manufacturing in the course of which no significant isotopic effects have been observed this isotopic tracing of the cecina alluvial aquifer occurs just below the confluence of the possera creek which carries the b releases from larderello strontium isotope ratios support this conclusion at about 18 km from the possera creek confluence the groundwater 11b drops to much more negative values 22 to 27 which are believed to be produced by adsorption desorption interactions between dissolved b and the aquifer matrix the 11b of b fixed in well bottom sediments shows a similar variation at present desorption is prevailing over adsorption because the releases of b rich water have ceased a theoretical model is suggested to explain the isotopic trends observed thus b isotopes appear to be a powerful tool for identifying the origin of b contamination in natural waters although isotopic effects associated with adsorption desorption processes may complicate the picture to some extent

nitrogen and sulphur cycling in the saline coastal aquifer of ferrara italy a multi isotope approach abstract the origin of high ammonium and sulphate concentrations characterizing the saline groundwater of the po river floodplain coastal aquifer are documented a detailed understanding of the hydrogeochemical conceptual model is built up using a hydrochemical major ions doc dic and methane and isotopic 15nno3 15nnh4 18ono3 34sso4 18oso4 and 13cdic approach based on previous hydrogeological investigations two boreholes located in contrasting environments urban and agricultural have been sampled at high vertical resolution groundwater is mostly under reducing conditions characterized by high doc and dic concentrations but low to moderate methane content dissolved ammonium as high as 87 8 mgl 1 derives by the mineralization of n organic rich fine sediments as indicated by its n isotopic signatures 1 3 attenuation processes of ammonium are ruled by dilution and by partial nitrification supported by the enrichment in 15nnh4 7 apart from dilution oxidation processes the positive correlation between 15nno3 and 18ono3 agreed with the occurrence of denitrification in the shallow part of the aquifer 34sso4 and 18oso4 data highlight that oxidation of pyrite occurs but is not necessarily linked to nitrate removal the isotope data showed that sulphate 2500 mgl 1 is of marine origin in the deeper part of the aquifer sulphur and oxygen isotopes enrichment patterns demonstrated that sulphate reduction sr occurs in the aquifer and it is also possible that sr occurred in the underlying clay units 13cdic pattern toward depleted 13cdic values even as low as 40 4 documented the occurrence of sr mediated by organic carbon and sr coupled to oxidation of methane aom are involved in the sulphur and carbon cycles the present study shows the advantage of using stable isotopes complemented with geochemical data to characterize the solutes origins both natural and anthropogenic and giving insights on biogeochemical transformations involving nitrogen sulphur and carbon in coastal sediments

factors controlling mechanisms of groundwater salinization and hydrogeochemical processes in the quaternary aquifer of the eastern nile delta egypt in this study combining interpretations of conservative dissolved ions and environmental isotopes in water were used to investigate the main factors and mechanisms controlling groundwater salinization and hydrogeochemical processes in the eastern nile delta egypt hydrogeochemical and isotopic study has been carried out for 61 water samples from the study area total dissolved solid tds contents of groundwater are highly variable rising along flowpath from the south 410 mg l to the north 14 784 mg l implying significant deterioration and salinization of groundwater based on tds and ionic ratios groundwater samples were classified into three groups in low saline groups water chemistry is greatly influenced by cation exchange mineral dissolution precipitation anthropogenic pollutants and mixing with surface water whilst in high saline groups water chemistry is affected by salt water intrusion reverse cation exchange and evaporation the chemical constituents originating from saline water sources reverse ion exchange and mineral dissolution are successfully differentiated using ionic delta and saturation index approaches the 18o 2h relationship plots on a typical evaporation line suggesting potential evaporation of the recharging water prior to infiltration isotope evidence concludes that the groundwater have been considerably formed by mixing between depleted meteoric water recharged under different climatic conditions and recently infiltrating enriched surface water and excess of irrigation water the 18o data in conjunction with chloride concentrations provide firm evidence for impact of dissolution of marine origin evaporite deposits during past geologic periods on groundwater salinity in the northern region moreover the relation between 14c activities and cl concentration confirms this hypothesis

experimental simulation of arsenic desorption from quaternary aquifer sediments following sea water intrusion abstract alluvial sediments from the coastal area in southern tuscany italy characterized by a significant as anomaly as 500 mg kg are subjected to seawater intrusion due to groundwater exploitation sequential extractions and kinetic experiments were carried out on quaternary alluvial sediments to quantify the interaction between as oxianions adsorbed on mineral surfaces and cl in solutions and to establish if this mechanism may contribute to the release of as in groundwater the natural water rock interaction in the aquifer was simulated in two experiments by saturating the samples with four solutions with increasing chlorinity for different time firstly a rapid change in the aquifer salinity e g fast seawater intrusion groundwater over pumping was simulated by an interaction sediment solution of 24 h solutions with cl 2000 mg l extracted up to 76 g kg of as while seawater sol 4 24 cl 18 500 mg l extracted up to 161 g kg of as in a second experiment the ingression of water with increasing salinity in the acquifer followed by the withdrawal of the water after progressively longer interaction times with the aquifer sediments was simulated the timing of the as cl reaction was constrained by saturating the samples with four solutions with increasing salinity sol1 84 cl 0 mg l sol2 84 cl 250 mg l sol3 84 cl 2000 mg l sol4 84 cl 15 886 mg l that interacted with the sediment samples for longer saturation times up to 21 days for each solution after saturation with the previous three solutions up to 62 g kg of as were extracted by seawater following a salinity increase from 2000 mg l cl to a chlorinity close to seawater representing 60 of the exchangable as fraction in the sediments our results constrained the timing of sediment solution interaction of as desorption and showed that after a rapid intrusion of seawater or after a relatively long period of interaction with saline solutions an aquifer with similar geology releases in groundwater concentrations of as exeeding the 10 g l limit for drinking water also this study estimated the potential effects caused by the ingression of seawater in lowland alluvial coastal areas induced by groundwaters exploitation or by extreme weather events such information is crucial for management authorities to mitigate and predict the effects of as hazard in groundwater driven by changes in the environmental aquifer conditions e g seasonal fluctuations of the water table and or changes in salinity of coastal aquifers which are becoming increasingly frequent as consequence of climate change

the potential role of non newtonian rheology in the resurfacing of venus several analyses of the impact cratering record on venus have concluded that 80 of venus was resurfaced sometime in the last 300 m y 700 m y the cratering record further indicates that the resurfacing took place over a 30 m y 100 m y interval since this period there has been little large scale tectonic activity on venus this study proposes that such behavior may result from the interaction of phase change induced avalanches with a non newtonian lithosphere the mechanism proposed here suggests that because of non newtonian rheology the venusian lithosphere becomes highly mobile during brief periods when avalanches occur afterwards due to the reduction in stress levels the lithosphere becomes rigid and large scale tectonics ceases

groundwater resource degradation in coastal plains the example of the cecina area tuscany central italy abstract the paper describes the degradation of the groundwater resources in the cecina area where seawater intrusion b contamination and no 3 pollution are all affecting the heavily exploited pleistocene aquifer over pumping has brought water levels to about 0 m a s l as far as about 7 km from the shore line thereby promoting the seawater intrusion the intrusion which is characterized by cation exchange phenomena and ca cl type waters enters the plain mostly through the shallower horizons the saline front which advanced from 0 5 to 1 km in 4 a has by now reached the foot of the hills to the east of the town where it is also affecting wells of the local aqueduct boron contamination linked to past discharge of industrial waste transported downstream by the river reached concentrations as high as 3 5 mg l in the mid 1980s although a decreasing trend is now under way b content is still close to 1 mg l the presence of high no 3 which together with the seawater intrusion represents a major issue for groundwater management in the area is linked to the widespread utilization of fertilizers nitrate concentration which reaches a maximum of about 300 mg l in the shallow aquifer horizons and then decreases rather regularly with depth is strongly influenced by precipitation however irrigation also contributes significantly to transporting the no 3 contamination to depth as clearly shown by 18 o data the severe decline in the quality of the groundwater resource in the cecina area is further compounded by an overall decrease in water availability in the region of tuscany as evidenced by long term monitoring of precipitation and fluvial discharge

geochemistry and stable isotope composition of surface waters from the ravenna plain italy implications for the management of water resources in agricultural lands this paper examines the issues related to salinization and water quality in the complex drainage system of the historical land reclamation of lamone basin ravenna coastal plain northern italy with the aim of guiding ongoing agricultural related decisions major and trace element concentration and o h b sr isotope ratios were measured on surface water from a network of canals and ditches sampling was carried out during the winter period and in summer to assess the effects of agricultural water management on the aquatic system results show widespread salinization of waters over the entire crop due to both the direct saltwater inland flushing through the canals in proximity of the mouths and sea salt leaching from soils during winter salinization is partly mitigated by rainfalls while in summer dilution processes are due to freshwater input from outside the watershed planned to assist the agricultural water demand in the winter season the concentration of some elements such as fe mn al and cu in waters exceeds the maximum permissible limits imposed by the italian regulations while during summer the concentration of these elements is significantly reduced a seasonal cycling is established where the bottom sediments of canals and ditches act as sinks of harmful elements mostly through adsorption by fe mn al oxy hydroxide solid phases the irrigation practice although improving the water quality increases water turbidity by re mobilization of sediments which act as transport agents of contaminants with detrimental effects that may become significant over the years

hydrogeology and geochemistry of the multilayered confined aquifer of the pisa plain tuscany central italy the pisa plain contains a multilayered confined aquifer made up of pleistocene sands and gravels the groundwater from the wells tapping these horizons are generally of poor quality they exhibit significant tds relatively high cl content and considerable hardness during geothermal prospecting of the pisa plain about 80 wells ranging in depth from 20 to 250 m were sampled and both chemical major ions and isotope analyses were conducted the data collected show that tds is strongly influenced by hco3 and cl and that a 3 component mixing process affects the groundwater s chemical composition the end members of this mixing process have been identified as a diluted hco3 meteoric water which enters the plain mainly from the eastern and northern sides of the study area b cl rich water which largely characterizes the shallow sandy horizons of the multilayered aquifer system and has been attributed to the presence of seawater as also suggested by 18o data and c so4 rich groundwater which is linked to the hot groundwater circulation within mesozoic carbonate formations and at first sight seemed to affect only the gravelly aquifer a so4 rich water also contributes to the sandy aquifer it probably enters the plain both laterally from the margins of the pisan mountains and from depth but promptly undergoes substantial so4 reduction processes by bacteria that such processes are at work is suggested both by the low so4 and high hco3 concentrations found in the well waters and by their c and s isotope compositions the collected data have allowed zones with higher quality waters to be identified which may someday be used for the local water supply

identifying recharge and salinization sources of groundwater in the oussja ghar el melah plain northeast tunisia using geochemical tools and environmental isotopes the recharge sources and groundwater degradation in the coastal plain of oussja ghar el melah were investigated using geochemical and isotopes tools we demonstrate that the water quality of shallow groundwater in the phreatic aquifer is impacted by long term intensive irrigation we show that the factors controlling the salinity and composition of groundwater are the return flow of the irrigation water the water rock interaction in the aquifer and salts formed on the surface by marine sprays in the low plain where no3 content is of up to about 140 mg l groundwater is affected by diffuse pollution caused by intensive agricultural activities in the upstream part of the plain and in the area situated in the sw stable isotopes and tritium values indicate recent recharge by local precipitation