mineralogy and geochemistry of ammonian illite in intra seam partings in permo carboniferous coal of the qinshui coalfield north china abstract ammonian illite is observed to be presented in the intra seam coal partings of the permo carboniferous coal seams from the qinshui coalfield north china this paper provides new insights into its geochemical and mineralogical characteristics as well as the factors influencing its formation and its nitrogen isotope ratios the interlayer cations of ammonian illite in the samples presented in this study were dominated by nh 4 with a certain amount of k and distributed homogeneously in each illite layer ammonian illite has an nh 4 nh 4 k ratio of 0 87 on average with a basal spacing d 001 10 267 a on average greater than those of potassian illite and muscovite but lower than that of tobelite the average stoichiometric formula of the ammonian illite was inferred as nh 40 67 k 0 11 al 1 90 fe 0 06 mg 0 04 al 0 68 si 3 32 o 10 oh 2 and the average si al iv ratio 4 88 was found to be higher than that of tobelite this indicates that the conversion of ammonian illite to tobelite includes the expulsion of si from the tetrahedral sheets and the incorporation of al into the octahedral and tetrahedral sheets the d 005 is influenced not only by the nh 4 nh 4 k ratio but also to some extent by the entrance of al iv into tetrahedral sites it is inferred that the ammonian illite was formed by the incorporation of si into pre existing kaolinite during diagenesis and that its formation was influenced not only by the diagenetic temperature but also by the depositional environment brackish water favors the formation of ammonian illite during deposition the nh 4 of the ammonian illite was mainly derived from pyrrolic n 5 and pyridinic n 6 nitrogen groups at the margins of the coal s carbon matrix during diagenesis on average it has a 15 n value of 8 0 much higher than that of total coal nitrogen 3 9 on average this is related mainly to the higher 15 n values of n 5 and n 6 than the quaternary nitrogen group n q within the carbon matrix

the effect of macropores on bi directional hydrologic exchange between a stream channel and riparian groundwater summary macropores and soil pipes in stream banks are common geomorphic features macropores and soil pipes that are open to the channel i e bank face connected macropores are inundated when channel stage is elevated e g from precipitation snowmelt dam release however previous studies have not investigated macropore impact on bi directional water exchange between the channel and bank riparian groundwater under variable hydrologic conditions we monitored two transects of riparian groundwater wells perpendicular to the bank of a 2nd order stream for a year one with bank face connected macropores m transect and one without bank face connected macropores nm transect fluctuations in water level and temperature during storms in those wells closest to the channel were on average 139 and 29 higher respectively in the presence of macropores rising head tests in the same wells indicated that hydraulic conductivity was 61 140 times higher in the presence of macropores bank storage indicated by gradient reversals between channel and riparian zone occurred on two temporal scales bank storage during storms was more frequent in the m transect occurred all year than in the nm transect occurred just in winter and spring smaller magnitude gradient reversals at the m transect are consistent with faster head equilibration and greater exchange volume bank storage also occurred on an annual basis with channel water entering storage during summer and fall and returning to the channel during winter and spring taken together these results suggest that macropores act as preferential flow paths that enhance the connectivity between channels and riparian groundwater that influences bank storage where bank macropores are present conceptual models of hyporheic and groundwater flow should account for their effects

estimating groundwater exchange with lakes 1 the stable isotope mass balance method groundwater inflow and outflow contributions to the hydrologic budget of lakes can be determined using a stable isotope 18o 16o mass balance method the stable isotope method provides a way of integrating the spatial and temporal complexities of the flow field around a lake thereby offering an appealing alternative to the traditional time and labor intensive methods using seepage meters and an extensive piezometer network in this paper the method is applied to a lake in northern wisconsin demonstrating that it can be successfully applied to lakes in the upper midwest where thousands of similar lakes exist inflow and outflow rates calculated for the wisconsin lake using the isotope mass balance method are 29 and 54 cm yr respectively which compare well to estimates derived independently using a three dimensional groundwater flow and solute transport model of 20 and 50 cm yr such a favorable comparison lends confidence to the use of the stable isotope method to estimate groundwater exchange with lakes in addition utilization of stable isotopes in studies of groundwater lake systems lends insight into mixing processes occurring in the unsaturated zone and in the aquifer surrounding the lake and verifies assumed flow paths based on head measurements in piezometers

nitrogen isotopic composition of ammoniated phyllosilicates case studies from precambrian metamorphosed sedimentary rocks ammonium concentrations in phyllosilicates from archean and proterozoic schists and carbonates were evaluated by fourier transform infrared microspectrometry aftir the y 15 nair values of structural nitrogen in these phases were subsequently measured by laser mass spectrometry a rapid estimate of the concentration of nh4 in biotite by aftir allows the preselection of the samples to be analyzed for their isotopic composition micas from 1 90 2 09 ga metasediments from finland and from 1 025 1 500 ga biotite schists from the moine succession in scotland have high concentrations of structural ammonium between 176 and 1549 ppm suggestive of a biological origin for the nitrogen the heavy nitrogen isotopic signatures y 15 n 4 9x to 19 7x of structural nh4 in these micas are considered consistent with biological denitrification in operation at the time of sedimentation evidence for denitrification in the mesoproterozoic is in agreement with geological and geochemical data for abundant free oxygen in the atmosphere facilitating the stability of marine no3 sequences of early archean ca 3 8 ga garnet mica schists from the isua supracrustal belt isb in southern west greenland contain biotite rich in nh4 between 233 and 512 ppm and nitrogen isotopic signatures y 15 n 1 9x to 5 9x which possibly point to an early evolution of ammonium assimilation and or nitrogen fixation this result appears to be consistent with molecular phylogenetic studies in the bacterial and archaeal domains which suggest that nitrogen fixation and ammonium assimilation were metabolic features of the last common ancestor lca of all organisms d 2004 elsevier b v all rights reserved

a comparison of modeling approaches for steady state unconfined flow abstract the dupuit forchheimer the fully saturated flow and the variably saturated flow models are compared for problems involving steady state unconfined flow through porous media the variably saturated flow model is the most comprehensive of the three and requires more parameters the performances of the three models are compared for different soil properties problem dimensions and flow geometries there are certain types of problems where the simpler models may yield satisfactory results for soils with large pores and or broad pore size density functions the variably saturated flow model solutions to steady state problems approach those of the fully flow model owing to the manner in which the soil water retention curve and relative permeability function respectively affect the variably saturated flow model solutions for problems of significant size the fully saturated flow model may be sufficient as the effects of the vadose zone are relatively diminished for problems with radial symmetry e g steady flow to a well the fully saturated flow model performs well because the variably saturated flow model is relatively insensitive to the parameters describing the soil properties as the amount of vadose zone flow compared with the total flow is relatively insignificant in such problems

modeling hydrocarbon accumulation based on gas origin and source rock distribution in paleozoic strata of the ordos basin china abstract paleozoic gases in the ordos basin china are produced from upper paleozoic tight sandstones ordovician weathered crust and pre salt beneath gypsum deposits dolomite reservoirs their origins have been debated particularly as to whether carboniferous permian c p or ordovician source rocks contributed more gas to the lower paleozoic gas reservoirs the expanded exploration of lower paleozoic gas to the eastern western northern and southern regions of the basin has re initiated the debates in this study geochemical characteristics of gas samples from newly drilled wells in different regions of ordos basin in combination with the source rock evaluation were used to determine the gas origin the carbon and hydrogen isotope of alkane indicate that gas mixing occurred in both upper paleozoic and ordovician weathered crust gases and that tsr occurred in pre salt gases a modified 13c 1 cn plot was suggested to be useful to determine the carbon isotopic patterns of gases generated from the different source rocks the light hydrocarbon characteristic shows that oil type gas mainly distributes in the eastern basin a study of source rock distributions also indicates that the most favorable ordovician source rock is located in the eastern basin based on the distribution of c p coal measures limestones and lower paleozoic carbonate source rock a gas accumulation history was established the results of this study provide applicable method for identifying gas origin in ordos basin moreover the accumulation history proposed in this study is useful for further exploration of the lower paleozoic gas in ordos basin

quantifying hyporheic exchange in a tidal river using temperature time series 1 an investigation into groundwater surface water interaction gswi beneath a large tidally influenced river was conducted to determine the effect of tides on the development of a hyporheic zone hz and to quantify mixing of river water and groundwater temperature measurements coupled with independent hydraulic head measurements were used to detect groundwater flow within the riverbed gwsi under tidal forcing produced a 1 m deep hz time averaged riverbed temperature profiles displayed a distinct compressed convex pattern clear evidence of net groundwater discharge however the instantaneous time series data indicate that riverbed temperatures were affected by tidal forcing to a depth of 1 m heat transport modeling revealed that instantaneous velocities within the shallow sediments of the riverbed are rather high creating a zone of vigorous exchange during either a flooding or ebbing tide furthermore the magnitude of the tidal pressure gradient was found to be significantly greater than the pressure gradient expected across 0 8 m high dunes evidence that bed form driven exchange under these conditions and this scale of observation did not contribute to the development of the hz conditions for exchange induced by shear and current bed form are favorable during ebbing tidal conditions only flow paths are therefore limited in depth exchange flow paths in an estuary setting are complex they are limited in duration and space and dominated by tidal pumping

demarcating saline water intrusion pathways using remote sensing gis and geophysical techniques in structurally controlled coastal aquifers in southern india application of remote sensing and geographical information system gis with the help of ground truth studies like vertical electrical soundings ves and water quality measurements gave a comprehensive picture on saline water intrusion pathways in the structural controlled aquifers of uppanar and cauvery river systems located in sirkazhi and mannanpandal coastal areas of southern india the detailed geomorphic units and lineaments were mapped using irs liss iii 1 50 000 scale and srtm elevation digital data under gis environment the area is mainly alluvial deposits of holocene age and classified into three major geomorphic units i e fluvial fluviomarine and marine geomorphic units the identified lineaments are mostly trending north northeast nne south southwest ssw northeast ne southwest sw northwest nw southeast se east west ew and east northeast ene west southwest wsw directions some of them are potential for fresh groundwater occurrence and movement the lineaments trending ne sw nne ssw and ene wsw act as pathways for saline water intrusion to the inland the lineament l1 nne ssw trending conformed as a sinisterly shifted fault played a significant role in saline water intrusion the area within the parallel lineaments l2 and l3 oriented ene wsw direction indicates low topography beach ridges paleo channel sinuosity large aerial extent of tidal flats and backwater inundation all the above geomorphic units gave indirect evidence of land subsidence which was confirmed with the help of sub surface geo electrical signals obtained through ves and in situ groundwater quality measurements integrating all the above results the saline water spread and fresh water pockets were identified

defining the hyporheic zone in a large tidally influenced river summary an investigation was conducted to characterize the spatial and temporal distribution of the hyporheic zone of a large tidally influenced river the field site is located on the fraser river in british columbia canada approximately 30 km from its outlet to the ocean the physical attributes of the riverbed were mapped using geophysical techniques coupled with sediment sampling the spatial and temporal distribution of groundwater composition beneath the riverbed was determined through detailed profiling contaminated fresh groundwater discharges through a narrow band of the riverbed at a distance approximately 88 105 m from the shoreline coinciding with the termination of a massive silty unit saline groundwater as part of a regional flow system dominates the riverbed sediments from 105 m beyond the shoreline towards the centre of channel three water types occur within the upper 2 m of the riverbed sediments a result of both mixing of river water contaminated fresh groundwater and saline groundwater and modification by cation exchange reactions the interaction of these waters produced distinct zones of ca hco 3 na cl and ca cl type waters the distribution of groundwater solutes indicates that during a single tidal cycle river water penetrates the riverbed to a depth of approximately 15 cm but the long term effects of tidal pumping of river water into the riverbed is observed to a depth of approximately 1 m below the river bed

influence of variable salinity conditions in a tidal creek on riparian groundwater flow and salinity dynamics while recent studies have revealed that tidal fluctuations in an estuary significantly affect groundwater flows and salt transport in the riparian zone only seawater salinity in the estuary has been considered a numerical study is conducted to investigate the influence of estuarine salinity variations on the groundwater flow and salt dynamics in the adjacent aquifer to extend our understanding of these complex and dynamic systems tidal salinity fluctuations synchronous with estuary stage were found to alter the magnitude and distribution of groundwater discharge to the estuary which subsequently impacted on groundwater salinity patterns and residence times especially in the riparian zone the effects of salinity fluctuations were not fully captured by adopting a constant time averaged estuarine salinity the modelling analysis also included an assessment of the impact of a seasonal freshwater flush in the estuary similar to that expected in tropical climates e g mean estuary level during flood significantly greater than average on adjacent groundwater flow and salinity conditions the three month freshwater flushing event temporarily disrupted the salt distribution and re circulation patterns predicted to occur under conditions of constant salinity and tidal water level fluctuations in the estuary the results indicate that the salinity variations in tidal estuaries impact significantly on estuary aquifer interaction and need to be accounted for to properly assess salinity and flow dynamics and groundwater residence times of riparian zones

nitrogen in rock occurrences and biogeochemical implications 1 there is a growing interest in the role of bedrock in global nitrogen cycling and potential for increased ecosystem sensitivity to human impacts in terrains with elevated background nitrogen concentrations nitrogen bearing rocks are globally distributed and comprise a potentially large pool of nitrogen in nutrient cycling that is frequently neglected because of a lack of routine analytical methods for quantification nitrogen in rock originates as organically bound nitrogen associated with sediment or in thermal waters representing a mixture of sedimentary mantle and meteoric sources of nitrogen rock nitrogen concentrations range from trace levels 200 mg n kg 1 in granites to ecologically significant concentrations exceeding 1000 mg n kg 1 in some sedimentary and metasedimentary rocks nitrate deposits accumulated in arid and semi arid regions are also a large potential pool nitrogen in rock has a potentially significant impact on localized nitrogen cycles elevated nitrogen concentrations in water and soil have been attributed to weathering of bedrock nitrogen in some environments nitrogen released from bedrock may contribute to nitrogen saturation of terrestrial ecosystems more nitrogen available than required by biota nitrogen saturation results in leaching of nitrate to surface and groundwaters and where soils are formed from ammonium rich bedrock the oxidation of ammonium to nitrate may result in soil acidification inhibiting revegetation in certain ecosystems collectively studies presented in this article reveal that geologic nitrogen may be a large and reactive pool with potential for amplification of human impacts on nitrogen cycling in terrestrial and aquatic ecosystems

ammonium contents of biotites from precambrian rocks in finland the significance of nh4 as a possible chemical fossil abstract the ammonium contents of biotites in precambrian rocks from finland have been determined to examine the possibility that ammonium in biotites represents a chemical fossil if biologic activity existed in precambrian sedimentary environments biotites formed from the sediments should contain distinctly larger quantities of nh 4 than biotites from igneous rocks biotites from svecokarelidic metasediments which were originally products of sedimentation about 2400 1900 ma ago have high nh 4 contents hundreds of ppm while biotites from svecokarelidic plutonic rocks of 1800 1900 ma old and postsvecokarelian rapakivi granites of 1650 1700 ma old have low nh 4 contents tens of ppm the results may indicate that biologic activity was plentiful during sedimentation of the svecokarelian strata this agrees with evidence for ancient life found in dolomites and greywacke slates of the svecokarelides biotites from presvecokarelidic schists of more than 2600 2800 ma old have only tens of ppm of nh 4 this value is at the same level as those of biotites from the rapakivi granites and the svecokarelidic plutonic rocks considering the rarity of fossils in presvecokarelidic rocks the low nh 4 content of biotite from a presvecokarelidic pelitic schist may indicate less biologic activity during the sedimentation of the original sediments these data emphasize that ammonium in biotites of precambrian metasediments may be a useful chemical fossil for identifying the geologic sites of ancient life

total nitrogen content of deep sea basalts abstract various models have been suggested concerning the origin and evolution of the earth s atmosphere an estimate of the nitrogen content of the mantle could further constrain atmospheric models total nitrogen content was determined by thermal neutron activation analysis via 14n n p 14c the 14c was converted to carbon dioxide and counted in miniature low level proportional counters the total nitrogen content of u s g s standards bcr 1 and g 2 as determined by different laboratories is variable probably due to atmospheric adsorption by the finely ground samples total nitrogen content was determined in deep sea basalt glasses from three regions east pacific rise 15 4 18 4 and 7 ppm 2 n mid atlantic rift famous region 22 5 18 3 and 10 2 ppm n and the juan de fuca ridge 17 4 ppm n matrix material from the same samples as the glasses was available from the east pacific rise 37 6 26 4 and 34 6 ppm n and the mid atlantic rift 39 4 ppm n which are about 50 to 100 greater than the associated glasses the increased matrix abundance may be due to incorporation of chemically bound nitrogen from sea water rather than dissolved molecular nitrogen the nitrogen content of the famous samples are inconsistent with the model of langmuir et al 1977 for petrogenesis based on trace element data factors which can affect the observed nitrogen content in the basalts and the interpretation in terms of the mantle nitrogen abundance are discussed e g partial melting and degassing of the basalts a lower limit of about 2 ppm n in the mantle can be estimated

interaction between shallow groundwater saline surface water and nutrient discharge in a seasonal estuary the swan canning system the swan and canning rivers converge to form an estuary that is seasonally forced by wet winter and dry summer conditions the estuary is also tidally forced due to its contact with the indian ocean the perception that the occurrence of nuisance algal blooms has increased in frequency and severity in recent years has prompted the present investigation into the interaction of the shallow groundwater system with the swan canning estuary the extent to which this interaction contributes to nutrient delivery to the river is a focus of the work groundwater interaction with the upper reaches of the swan river is shown to occur at three length scales i the scale of the river bed sediments i e 1000 m two dimensional groundwater flow modelling in plan covering the regionally advected groundwater flow domain of the upper swan river estuary from the causeway to guildford shows that there is a net groundwater discharge to the swan river of groundwater discharge of about 80 000 m3 day or about 29 million m3 year between 1987 and 1996 the average surface tributary inflow to the swan river was about 460 million m3 year thus groundwater discharge contributed approximately 6 of the total annual river flow this percentage is clearly small in comparison to the total river flow however in the six months from november to april in summer tributary flow into the swan river declines sharply to an average total of approximately 12 million m3 groundwater discharge during this six month period is approximately 14 million m3 or about 55 of the surface tributary flow and thus groundwater is a significant component of the total inflow to the swan canning estuary during this period nutrient concentrations particularly ammonium within the sediment pore fluids underlying the river are very high relative to concentrations in the river such that groundwater discharge rates of this magnitude are capable of introducing significant nutrient loadings to the river the nitrogen load to the swan river derived from regionally advected groundwater discharge is conservatively estimated at between 30 and 60 t year this ranks groundwater as one of the highest single inputs of nitrogen to the swan canning estuary when compared to surface water flows it contributes about 10 of the total nitrogen load entering this reach of the river seasonal and tidal variations increase the complexity of the system and may act to increase the presence and availability of groundwater derived nutrients in the river and estuary system field observations and results from numerical groundwater flow modelling show that groundwater preferentially discharges into the swan river along the outside of river meanders along the inside of meanders groundwater discharge is either very low or at times the flow direction reverses such that saline river water recharges the aquifer during the late spring summer and early autumn months short term high frequency fluctuations such as wave induced displacement seawater intrusion hyporheic flux and tidal fluctuations may cause small spatial scale mixing and perturbation of the nutrient rich groundwater and sediment porewater with either the river water directly or with fresher groundwater as it discharges to the river these short term fluctuations appear to cause nutrient release from the sediment pore fluids particularly in summer low flow periods such that they are a significant contributing factor in triggering algal blooms copyright 2001 john wiley sons ltd

groundwater flow and salt transport in a subterranean estuary driven by intensified wave conditions a numerical study based on a density dependent variably saturated groundwater flow model was conducted to investigate flow and salt transport in a nearshore aquifer under intensified wave conditions caused by offshore storms temporally varying onshore hydraulic gradients due to wave setup were determined as the seaward boundary condition for the simulated aquifer the results showed a rapid increase in influxes across the aquifer ocean interface in response to the wave event followed by a more gradual increase in effluxes the upper saline plume first widened horizontally as the wave setup point moved landward it then expanded vertically with recirculating seawater pushed downward by the wave induced hydraulic gradient the time for the salt distribution to return to the prestorm condition was up to a hundred days and correlated strongly with the time for seawater to recirculate through the aquifer the pathways of recirculating seawater and fresh groundwater were largely modified by the wave event these pathways crossed through the same spatial locations at similar times indicating significant salt freshwater mixing the flow and salt transport dynamics were more responsive to wave events of longer duration and higher intensity especially in more permeable aquifers with lower fresh groundwater discharge despite their larger response aquifers with higher permeability and beach slope recovered more rapidly postevent the rapid recovery of the flows compared with the salinity distribution should be considered in field data interpretation due to their long lasting impact wave events may significantly influence the geochemical conditions and the fate of chemicals in a subterranean estuary key points intensified waves perturb flow and transport in a subterranean estuary lengthy period months for salinity distribution to recover from a wave event exchange fluxes and flows respond and recover rapidly following a wave event

nitrogen in future biosphere studies this article suggests a theme for future nitrogen studies involving the functioning and evolution of the biosphere together with certain aspects of human biology it is hoped that this theme could be developed into a multi authored book at some point in the future although numerous new case studies may be required the biosphere can be considered to be a single interactive system comprised of numerous component parts including the atmosphere rain rivers lakes oceans continental ecosystems marine ecosystems soils and sediments in order to study the internal complexity of each of the components and the relationships that exist between them one can choose a common theme the author believes that nitrogen is a good prospect because of its ubiquitous nature and complex chemistry the burial of sedimentary volatiles in the continental crust has contributed to the long term chemical evolution of the exterior environments of the earth the most marked effects notably the accumulation of atmospheric oxygen have been due to the burial of reduced carbon an understanding of the passage of sedimentary volatiles through the crust will provide important constraints on the evolution of the biosphere and may lead to a more meaningful comparative planetology carbon is difficult to trace through crustal processes because its high temperature form graphite is incompatible with the crystal structures of silicate minerals however the high temperature form of sedimentary nitrogen ammonium readily enters into potassic minerals and it can be easily traced through crustal processes herein the fate of sedimentary nitrogen is traced from wet sediments through metamorphic rocks into granites and other crustal melts without the trapping of nitrogen in the crust and the liberation of oxygen that is a consequence of biological nitrogen fixation the n2 o2 of the atmosphere may have been about 82 9 to 16 3 and the total atmospheric pressure about 1 2 atm most of the changes in the oxygen content is due to dilution by nitrogen with only about 5 of the present atmospheric oxygen being a consequence of nitrogen fixation the ancient continental surfaces would have been volcanic deserts containing little 1 ppm or no nitrogen today nitrogen rich soils support continental ecosystems one can use nitrogen as a window to speculate on the colonisation of the continents by land plants herein nitrogen fixation by legumes is considered in detail and by drawing analogies with the present day the author speculates on the colonisation of the continents by land plants having speculated on the co evolution of the atmosphere soils and continental ecosystems one can place a human being in the centre of a tropical forest and begin to examine how they relate to the modern biosphere the chosen example is the metabolism of plant protein and the roles of glutamate dehydrogenase gdh vitamin b2 and flavin mononucleotide fmn the realisation of this theme would imply numerous new case studies notably those concerning the continental crust where nitrogen studies were linked to mineralogy petrology and other geochemical tracers including sr o al and k and where the short range order of 15n were taken into consideration

origin of natural gas from the ordovician paleo weathering crust and gas filling model in jingbian gas field ordos basin china abstract the ordos basin the second largest natural gas producing basin in china is one of the most tectonically stable sedimentary basins favorable to natural gas generation and preservation the origin and potential source of the jingbian gas field one of the five giant gas fields in the basin containing the ordovician paleo weathering crust as reservoir strata remains unclear the question is whether gas is generated from carboniferous permian coal measures or ordovician carbonates this study provides abundant gas geochemical evidence which clarifies its origin and source among 82 natural gas samples collected from the ordovician paleo weathering crust in the jingbian gas field c1 c4 gaseous hydrocarbons are dominant with low amounts of non hydrocarbons co2 h2s and n2 the content of c1 c4 ranges from 79 26 to 99 93 with a gas dryness c1 c1 4 of 0 981 0 999 suggesting that natural gases are dry and possibly originate from a high to over mature source the carbon isotopic compositions of methane and its homologues in natural gases from the ordovician paleo weathering crust vary widely with 13c1 13c2 and 13c3 values of 38 9 to 29 1 37 5 to 22 2 and 30 0 to 20 9 respectively the 13c2 and 13c3 values in the jingbian gas field are much more negative than those of typical coal type gas in sulige wushenqi yulin daniudi and kela2 gas fields the carbon isotopic signature suggests that the natural gas in the ordovician paleo weathering crust in the jingbian gas field most likely originates from ordovician carbonates containing sapropelic organic matter the measured d values of methane range from 177 to 155 and support our hypothesis of the natural gases originating from marine sapropelic organic matter the thermal maturity of the natural gases in the ordovician paleo weathering crust is at a high to over mature stage suggesting that the gases originated from secondary cracking of oil and gas at high temperature and pressure thermochemical sulfate reduction tsr might partially play a role in the alteration of gas dryness and 13c1 in those areas where gypsum is present as an effective cap rock mixing of high to over mature secondary cracking gas from the ordovician source and coal type gas from carboniferous permian coal in the jingbian gas field is minor

dynamic groundwater flows and geochemistry in a sandy nearshore aquifer over a wave event dynamic coastal forcing influences the transport of pollutants in nearshore aquifers and their ultimate flux to coastal waters in this study field data are presented that show for the first time the influence of a period of intensified wave conditions wave event on nearshore groundwater flows and geochemistry in a sandy beach field measurements at a freshwater beach allow wave effects to be quantified without other complex forcing that are present along marine shorelines e g tides pressure transducer data obtained over an isolated wave event reveal the development of transient groundwater flow recirculations the groundwater flows were simulated in feflow using a phase averaged wave setup approach to represent waves acting on the sediment water interface comparison of measured and simulated data indicates that consideration of wave setup alone is able to adequately capture wave induced perturbations in groundwater flows while prior studies have shown sharp ph and redox spatial zonations in nearshore aquifers this study reveals rapid temporal variations in conductivity ph and redox orp in shallow sediments up to 0 5 m depth in response to varying wave conditions comparison of head gradients with calculated conductivity and ph mixing ratios indicates the controlling effect of the wave induced water exchange and flows in driving the observed geochemical dynamics while we are not able to conclusively determine the extent to which temporal variations are caused by conservative mixing versus reactive processes the ph and orp variations observed will have significant implications for the fate of reactive pollutants discharging through sandy nearshore aquifers

mixing of surface and groundwater induced by riverbed dunes implications for hyporheic zone definitions and pollutant reactions 1 the hyporheic zone is often defined as where mixing of surface water and groundwater occurs in shallow sediments beneath and adjacent to rivers this mixing is credited with creating unique biogeochemical conditions that can attenuate contaminants from either upstream surface water or groundwater under gaining conditions however reactions of contaminants upwelling from groundwater may be more dependent on such mixing than contaminants from surface water we numerically modeled mixing between hyporheic flow paths induced by riverbed dunes and flow paths of adjacent upwelling of deeper groundwater results show that only 12 7 or less tracer mass upwelling from deeper groundwater dispersed across into hyporheic flow paths originating in surface water the spatial extent of a mixing defined hyporheic zone was smaller than a hyporheic zone defined as hydrologic flow paths leaving and returning to surface water mixing dependent reactions will therefore be localized within a thin mixing zone yet vary considerably with site conditions for example mixing in homogeneous sediments was controlled most by variation in hydraulic conductivity and upwelling flow rate which primarily affected mixing zone length by contrast introduction of heterogeneity increased mixing primarily by increasing mixing zone thickness consistent with studies of flow focusing in aquifers finally dispersivity is a critical parameter for which data are needed for shallow sediments our results help clarify hyporheic zone definitions and potential for mixing dependent reactions in particular the biogeochemically reactive portion of riverbed sediments from the perspective of upwelling contaminants does not necessarily spatially coincide with more traditional hydrologic conceptions of the hyporheic zone

application of ert and gpr for demarcating the saline water intrusion in coastal aquifers of southern india to investigate the pathways for saline water intrusion into fresh water aquifers the electrical resistivity tomography ert and ground penetrating radar gpr have been pooled for nagapattinam area of southern india the study area has two river sub basins uppanar river basin urb and cauvery river basin crb ert carried out in urb shows very low resistivity ranging from 0 003 to 1 5 m at shallow depth indicating saline water whereas the resistivity ranges away from the river stream are 1 7 5 0 m cauvery river basin shows resistivity range varying from 3 6 to 150 m indicating a salt fresh water mix similarly few gpr profiles were carried out along ert profiles to confirm the saline water intrusion and its pathway besides the hydrochemical study reveals the same signature of saline and fresh water zones in both river basins water samples collected during field investigation show high total dissolved solids tds content near urb and crb river course ert data was correlated with gpr data to distinguish fresh and saline water zones more accurately urb has more saline water zones at shallow depth nearer to river course and intermediate depth of saline water zones away from the river course while crb is having fresh water towards the inland

hydrochemical and isotopic characterisation of groundwaters to define aquifer type and connectivity in a subtropical coastal setting fraser coast queensland physico chemical parameters major ion chemistry and isotope composition of surface and groundwaters were determined in forested coastal catchments and adjacent coastal plains results showed obvious characterisation related to physical and hydrological setting and highly variable spatial differences reflecting the complexities of these areas all these coastal waters are dominated by na cl and fall on a common dilution line hydrochemical grouping is largely due to anionic differences cl so4 and hco3 although na and mg ratios also vary six major hydrochemical facies were determined for groundwaters compositional differences are largely related to aquifer material and level of confinement for coastal groundwaters important are tidal effects and proximity to the shoreline differentiation for surface waters is mainly by drainage morphology flow regime plus proximity to the coast connectivity between water bodies is reflected by minor base flow to catchment streams including with flood plain wetlands but mostly occurs in low lying zones where there is mixing of fresh and saline water within surface water and subterranean estuaries or by seawater intrusion enhanced by overuse oxygen and hydrogen isotopic data for confined and semi confined groundwaters along the coast indicates local recharge fresh surface waters in the elevated catchments are shown to be sourced further inland plus have experienced evaporation

impact of seasonal variations in hydrological stresses and spatial variations in geologic conditions on a tce plume at an industrial complex in wonju korea spatial and temporal variations in a trichloroethylene tce plume at an industrial complex in wonju korea were examined based on hydrogeological data and seven rounds of groundwater quality data collected over a year the site has considerable vertical heterogeneities the top layer of soil is covered by impermeable paving material at several locations followed by a series of reclaimed or residual soil layers and with weathered rocks to the crystalline biotite granite at the bottom areal heterogeneity in the surface conditions plays an important role in controlling groundwater recharge the heterogeneity structure is influenced by complex surface conditions paved with asphalt and concrete owing to the presence of limited recharge area and concentrated summer precipitation events the effects of seasonal variations on groundwater hydraulics tend to diminish with distance from the recharge area this result was established by analysing the influence of the contrasting surface recharge conditions between the near source zone and the far zone and the seasonally concentrated precipitation on the transport patterns of a tce plume in addition variations in the plume s downstream contaminant flux levels were also analysed along a transect line near the source zone the results show that the general tendency of the tce plume contaminant concentration and mass discharges were reproducible if we account for seasonal recharge variations and the associated changes in the groundwater level during recharge events the tce concentration variations appear to be influenced by leaching of the residual dense non aqueous phase liquid dnapl tce trapped in the unsaturated zone this result shows that seasonal variations in contaminant plume near the source zone is inevitable at this site and that these variations indicate the presence of residual dnapl at or above the water table at least in some isolated locations copyright 2011 john wiley sons ltd

intertidal and submarine groundwater discharge on the west coast of ireland submarine groundwater discharge is now a phenomenon of global interest as studies show that it represents both a significant proportion of the fresh water input to the ocean and a significant contribution to the loads of many substances at present little monitoring of groundwater in ireland is carried out at its point of entry to seawater and consequently the volumes of fresh water and the loads of nutrients and contaminants being carried into irish coastal waters by submarine and intertidal groundwater discharge sigd are unknown sigd is the principal source of fresh water entering irish coastal waters between the major west coast estuaries of the corrib and the shannon calculations of the volume of submarine sigd delivered to southern galway bay in winter indicate it equals 10e25 of the discharge of the r corrib and that its nutrient load may be of the same order of magnitude as that from the r corrib this coastal karst area includes important commercial shellfish waters which may be strongly impacted by sigd

hydro geophysical techniques for safe exploitation of the fresh groundwater resources in coastal area vertical disposition of the freshwater aquifer lens and their progressive change on lateral scale are relevant to understand the short circuiting of fresh and saline water at coastal areas since half of the world population dwells within 50 km of coast line the freshwater aquifers at coast are deteriorating at alarming rate there are well defined water well construction plans for coastal aquifer management but mostly fails while execution due to lack of precise knowledge of subsurface lithological layer setup in the present study an attempt has been made to investigate such precise information about subsurface lithological layer setup to protect the freshwater resources at coastal area applying noninvasive hydro geophysical technique integrated electrical parameters hydrochemistry topography and water table assessment have been applied to decipher the geometry of freshwater lens at cuddalore coast india results show in this study 1 the electrical resistivity 1 10 m of subsurface formation electrical conductivity 30 891 s cm of groundwater and water table 1 55 m above mean sea level msl confirms the zone of effluent contamination 2 the zone showing 1 10 m 6172 s cm water table 6 46 m below msl is attributed to the saline water intrusion 3 freshwater formations are identified in beach ridges underlain by clay layers with 30 60 m 453 s cm and water table above msl and 4 water well design is proposed to tap the freshwater aquifers avoiding vertical short circuiting of saline and freshwater

significance of microbial processes in gases of the south caspian basin abstract the south caspian basin has been a major petroleum producing province for more than a century while the basin s oil has been the focus of a number of studies the region s gas has been largely understudied this study examines 31 gas samples from 14 fields with the primary purpose of determining their mode s of formation and the role that microbial activity has had in their formation and alteration the basin s natural gas accumulations display significant differences in both molecular and isotopic composition gas wetness ranges from less than 1 at absheron to greater than 12 at guneshli methane carbon isotopic composition ranges from 57 to 37 relative to the pdb standard the stable carbon isotopic composition of the wet gas c 2 components also displays a very broad range e g c 2 ranges from 37 to 20 c 3 ranges from 31 to 10 and n c 4 ranges from 30 to 11 no strong depth related trends were observed in any of the geochemical attributes the absence of a trend implies that the gases have not been generated in situ but have migrated vertically been altered or represent a mixed product mixing is also suggested by the differences in the calculated thermal maturity levels between the c 2 components and methane in some accumulations e g karabagly as much as 55 of the methane may have a biogenic origin these data further indicate that among the gas samples studied those from bakhar appear to be the most mature with thermal maturity values consistent with the condensate window in several fields including guneshli and neftchala the wet gas components display evidence for microbial alteration this is largely manifested in anomalously heavy isotopic compositions of propane n butane and n pentane

ammonium halos in lithogeochemical exploration for gold at the horse canyon carbonate hosted deposit nevada u s a use and limitations abstract rock samples taken from the oxidized open pit to depths of 55 m of the carbonate hosted horse canyon gold deposit contain no nh4 samples from the unoxidized zone at the bottom of the pit in the protore however contain as much as 1 44 nh4 1 12 n the presence of nh4 was confirmed by mass spectrometry from these results it is concluded that samples from any oxidized environment e g outcrops soils likely will have lost all or most of any nh4 originaly present in minerals such as buddingtonite of nh4 containing clays this limits the use of nh4 halos in lithogeochemical exploration programs the most reliable application of lithogeochemical studies based on nh4 halos will likely be based on samples from drill cores and other situations where the samples have always been in a reducing environment analysis for nh4 by ir spectroscopy the method preferred by most previous workers is subject to several inherent problems the main one being the presence of the co32 ion whose absorbance at about 1430 cm 1 coincides with that used to determine nh4 the removal of co32 and other phases e g organic matter which may cause analytical difficulties by chemical treatment is not recommended because it is not possible to predict the effect of such treatment on any one of several possible minerals which may contain nh4 it is suggested that the most efficient method of analysis of rock samples for nh4 or n which can be assumed to represent nh4 will be to analyze the samples after heating to 550 c at which temperature all organic nh4 and n is removed by oxidation any remaining nh4 n determined on this residue can be assumed to originate in nh4 containing mineral structures

a comparison of peak and plate electrodes in electrical resistivity tomography application to the chalky groundwater of the beauvais aquifer northern part of the paris basin france electrical resistivity tomography was used in order to explore an experimental site of the lasalle beauvais polytechnic institute france the test was conducted along a profile line of 315 m length using 64 electrodes deployed at an inter electrode spacing of 5 m and the data were recorded using gradient wenner and pole dipole arrays the performance of plate electrodes non conventional flat based is compared with the performance of peak electrodes conventional spike the hydrogeophysical investigation of the chalk aquifer system of beauvais shows that the performance of plate electrodes is satisfactory leading to inversions of small root mean square errors peak and the plate electrodes were tested before and after injection of a salt tracer in the piezometer of the experimental site the study demonstrates the usefulness of plate electrodes efficient less time consuming and the possibility of aquifer characterization by a salt tracer copyright 2010 john wiley sons ltd

distribution of ammonium in minerals of metamorphic and granitic rocks abstract sixty nine analyses are given for nh4 in minerals of metamorphic and granitic rocks mostly from the ryoke belt japan the distribution of nh4 in coexisting minerals is quite systematic suggesting that nh4 is one of the stable geochemical components in high temperature processes biotite has the highest content of nh4 followed by muscovite k feldspar and plagioclase pure quartz is almost free from nh4 calcic plagioclase contains less nh4 than does sodic plagioclase the partition coefficients d pl bi d kf bi and d kf bi are on the average 0 11 0 38 and 0 43 respectively the fractionation of nh4 in these minerals is quite similar to that of rb but much smaller than that of cs distribution of nh4 as well as those of rb and cs appears to be explained by its ionic radius and the shortest cation o distances in alkali positions of minerals

urban groundwater baseflow influence upon inorganic river water quality the river tame headwaters catchment in the city of birmingham uk summary understanding the linkage between urban land groundwater baseflow and river contamination at the city scale is lacking this study evaluates the influence of inorganic major minor ions and metals groundwater contamination in the triassic sandstone quaternary deposits aquifer system underlying the city of birmingham uk upon the baseflow and water quality of the river tame baseflow water quality data have been collected from a riverbed piezometer network installed in the 7 4 km reach crossing the effluent unconfined sandstone aquifer and compared to river and aquifer water quality data overall the inorganic chemical quality of the baseflow was not as poor as potentially surmised from the urbanisation present baseflow impact upon river water quality was also low these conclusions were underpinned by evidences of limited river water quality changes along the reach some river concentrations being diluted by better quality baseflow only occasional breaching of water quality criteria limited impact upon river reach quality local to elevated baseflow dicharges natural attenuation occurrence within the riverbed and modest albeit somewhat uncertain baseflow mass fluxes baseflow fluxes to the reach were in the ranges 100 3500 t yr for major ions 1 50 t yr for minor ions and 1 500 kg yr for toxic metals with zinc and nickel most prominent the sporadic occurrence of elevated baseflow concentrations was ascribed to discrete groundwater plume discharges more detailed sub reach studies would be required to fully resolve discrete plume baseflow contributions and improve mass flux estimates not uncommonly the urban river studied was already contaminated and hence persistent baseflow fluxes may assume more importance if the river became cleaner through other control measures future research should hence consider the emergent significance of urban baseflows there are needs to conduct similar studies to investigate if city scale baseflow impacts are comparable elsewhere research the importance of spatially and temporally dynamic attenuation in the riverbed and develop improved baseflow mass flux estimation methods

tidal effects on sea water intrusion in unconfined aquifers abstract a variable density groundwater model is used to analyse the effects of tidal fluctuations on sea water intrusion in an unconfined aquifer it is shown that the tidal activity forces the sea water to intrude further inland and it also creates a thicker interface than would occur without tidal effects moreover the configuration of the interface is radically changed when the tidal fluctuations are included this is because of the dramatic changes in the flow pattern and velocity of the groundwater near the shoreline for aquifer depths much larger than tidal amplitudes the tidal fluctuation does not have much effect on how far the sea water intrudes into the aquifer nevertheless a significant change in the configuration of concentration contours because of the effect of tidal fluctuations is observed this change is more noticeable at the top of the aquifer near the water table than at the bottom of the aquifer and is caused by the infiltration of salt water into the top of the aquifer at higher tidal levels a flatter beach slope therefore intensifies this phenomenon the interface configurations do not change noticeably over the course of a tidal cycle neglecting tidal fluctuation effects results in an inaccurate evaluation of the water table elevation at the land end of the aquifer although no distinguishable difference is seen between the water tables near the shoreline where the landward boundary condition is a constant head the effects of tidal fluctuations on sea water intrusion are more pronounced than for cases where the landward boundary condition is a specified flux also it is shown that the effects of tidal fluctuations are more significant for a sloping beach than for a vertical shoreline and the salt water intrudes further inland for the sloping case

ammonium geochemistry in mineral exploration a comparison of results from the american cordilleras and the southwest pacific abstract ammonium concentrations in the host rocks to circum pacific epithermal precious metal and exhalative base metal deposits vary from 0 to 25 000 ppm high ammonium concentrations in mineralizing fluids are probably derived from the breakdown of organic matter in sediments or sedimentary rocks within the hydrothermal system shales are particularly good ammonium source rocks ammonium substitutes for k and other alkali elements in crystal lattices host rocks with k bearing minerals therefore have the highest potential for the development of ammonium haloes both surface and subsurface rocks can contain high concentrations of ammonium and substantial haloes have been found associated with precious metal veins particularly in the hanging wall such haloes are well developed at mines in mexico bolivia and peru and ammonium geochemistry thus provides a potentially useful exploration tool especially for vein type epithermal precious metal deposits

transient groundwater dynamics in a coastal aquifer the effects of tides the lunar cycle and the beach profile 1 detailed field measurements are combined with a numerical modeling to characterize the groundwater dynamics beneath the discharge zone at waquoit bay massachusetts groundwater salinity values revealed a saline circulation cell that overlaid the discharging freshwater and grew and disappeared with the lunar cycle the cell was initiated by a greater bay water infiltration during the new moon when high tides overtopped the mean high tide mark flooding the flatter beach berm and inundating a larger area of the beach the dynamics of this cell were further characterized by a tracer test and by constructing a density dependent flow model constrained to salinity and head data the numerical model captured the growing and diminishing behavior of the circulation cell and provided the estimates of freshwater and saline water fluxes and travel times furthermore the model enabled quantification of the relationship between the characteristics of the observed tidal cycle maximum minimum and mean tidal elevations and the different components of the groundwater circulation freshwater discharge intertidal saline cycling and deep saline cycling we found that 1 recharge to the intertidal saline cell is largely controlled by the high tide elevation 2 freshwater discharge is positively correlated to the low tide elevation whereas deep saline discharge from below the discharging freshwater is negatively correlated to the low tide elevation so when the low tide elevation is relatively high more freshwater discharges and less deep saltwater discharges in contrast when low tides are very low less freshwater discharges and more deep salt water discharges 3 offshore inflow of saline water is largely insensitive to tides and the lunar cycle

tidal effects on variations of fresh saltwater interface and groundwater flow in a multilayered coastal aquifer on a volcanic island jeju island korea summary we conducted various field studies at the seawater intrusion monitoring wells located in the eastern part of jeju island korea to observe the tidal effect on groundwater seawater flow in the coastal aquifer studies included monitoring the fluctuations of groundwater and tide levels electrical and temperature logging and 2 d heat pulse flowmeter tests according to time series analysis tidal effects on groundwater level reached up to 3 km inland from the coastline water level variation was more sensitive to tidal fluctuations near the coast and more related to rainfall toward inland areas temporal and spatial variations in the shape and location of the freshwater saltwater interface were analyzed using data from nine monitoring wells the results indicated that the interface toe is located at a distance of 6 8 km from the coastline and its location was related to geological layers present long term seasonal variations revealed no major changes in the interface minor variations were due to moving boundary conditions induced by tidal fluctuations using the two dimensional heat pulse flowmeter groundwater flow directions and velocities at four tidal stages were measured on three monitoring wells drilled into the multilayered aquifers this direct measurement enabled us to relate the differences of flow velocities and directions with geology and tidal fluctuations combining the results of ec logging and flowmeter tests we found a zone where freshwater and saltwater moved alternately in opposite directions as influenced by the tidal fluctuations integrating various physical logging and flowmeter data with water level fluctuations improved our understanding of the behavior of fresh and seawater flow in the coastal aquifers

natural gas genesis and sources in the zizhou gas field ordos basin china abstract the zizhou gas field is a large tight sandstone gas field in the ordos basin china based on the analysis of the geological background gas components light hydrocarbon composition carbon and hydrogen isotope values of alkane gases and the geochemical correlation between gases of the zizhou gas field and analogs from other fields in the basin we conclude that a most natural gases in the zizhou gas field are dry with a small content of wet gas b the gases have similar carbon isotopic and light hydrocarbon compositions to the analogs from other fields as well as much more positive 13c values and high contents of c5 7 i alkanes and methylcyclohexanes indicating typical coal derived gas c carbon isotopic reversal in some gas samples is due to mixing of coal derived gases of different maturities d the gases are sourced from mature to high mature carboniferous permian coal measures and e the gas reservoirs represent continuous accumulations

implications of anthropogenic river stage fluctuations on mass transport in a valley fill aquifer 1 in humid regions a strong coupling between surface water features and groundwater systems may exist in these environments the exchange of water and solute depends primarily on the hydraulic gradient between the reservoirs we hypothesize that daily changes in river stage associated with anthropogenic water releases such as those from a hydroelectric dam cause anomalous mixing in the near stream environment by creating large hydraulic head gradients between the stream and adjacent aquifer we present field observations of hydraulic gradient reversals in a shallow aquifer important physical processes observed in the field are explicitly reproduced in a physically based two dimensional numerical model of groundwater flow coupled to a simplistic surface water boundary condition mass transport simulations of a conservative solute introduced into the surface water are performed and examined relative to a stream condition without stage fluctuations simulations of 20 d for both fluctuating river stage and fixed high river stage show that more mass is introduced into the aquifer from the stream in the oscillating case even though the net water flux is zero enhanced transport by mechanical dispersion leads to mass being driven away from the hydraulic zone of influence of the river the modification of local hydraulic gradients is likely to be important for understanding dissolved mass transport in near stream aquifer environments and can influence exchange zone processes under conditions of high frequency stream stage changes

salt freshwater dynamics in a subterranean estuary over a spring neap tidal cycle this paper presents field measurements and numerical simulations of pore water salinities and groundwater flow in the intertidal zone of an unconfined coastal aquifer over a spring neap tidal cycle the study provides insight into the extent and time scales of mixing between fresh groundwater and recirculating seawater in a tidally influenced subterranean estuary salt freshwater dynamics in subterranean estuaries are currently not well understood despite their potentially important implications for fluxes of chemicals to coastal waters via submarine groundwater discharge the data and simulation results show that changes in the tidal shoreline excursion over the spring neap cycle induce significant variations in the intertidal salinity structure observed higher frequency salinity fluctuations demonstrate further the intensity and complexity of the salt freshwater mixing process in contrast with the salinity variations fresh groundwater was found to discharge around a distinct intertidal beach slope break throughout the spring neap period this suggests that the slope break may affect significantly groundwater flow and salt transport near the shore measurements of ph and dissolved oxygen distributions revealed important biogeochemical zonations in the system these zonations are expected to strongly influence the fate of many reactive chemicals in the nearshore aquifer and their subsequent discharge to coastal waters

gas maturity and alteration systematics across the western canada sedimentary basin from four mud gas isotope depth profiles abstract carbon isotope and molecular compositions of mississippian to upper cretaceous mud gases have been examined from four depth profiles across the western canada sedimentary basin wcsb the profiles range from the shallow oil sands in the east r 0 0 25 to the very mature sediments in the overthrust zone to the west r 0 2 5 in the undisturbed wcsb 13 c 1 13 c 2 and 13 c 2 13 c 3 cross plots show three maturity and alteration trends 1 pre cretaceous gas sourced from type ii kerogen 2 cretaceous colorado group gas and 3 lower cretaceous mannville group biodegraded gas a fourth set of distinctly different maturity trends is recognized for lower cretaceous gas sourced from type iii kerogen in the disturbed belt of the wcsb displacement of these latter maturity trends to high 13 c 2 values suggests that the sampled gas was trapped after earlier formed gas escaped probably as a result of overthrusting unusually 13 c enriched gas 13 c 1 34 13 c 2 13 and 13 c 3 0 from the gething formation in the disturbed belt is the result of late stage gas cracking in a closed system in general gas maturity is consistent with the maturity of the host sediments in the wcsb suggesting that migration and mixing of gases was not pervasive on a broad regional and stratigraphic scale the deep basin portion of the wcsb is an exception here extensive cross formational homogenization of gases has occurred in addition to updip migration along the most permeable stratigraphic units

application of light hydrocarbons c4 c13 to oil source rock correlations a study of the light hydrocarbon compositions of source rocks and test fluids from offshore mid norway abstract relatively little work has been published on the correlation between the light hydrocarbon distributions in reservoir fluids and their proposed source rocks philippi g t 1981 the aim of our work was to study this relationship in detail for samples from mid norway the main source rocks offshore mid norway are the marine shales of the late jurassic spekk formation and the coals and paralic shales of the early jurassic are formation reliable light hydrocarbon c 4 c 13 data for source rock samples were acquired by thermal extraction gc of the source rocks of these notably the hydrocarbons in the c 6 c 8 range routinely measured in test fluids were used to discriminate between the spekk and are formation samples a total of twenty six samples from the spekk formation and twenty four samples from the are formation at different maturity levels and facies were analyzed in general the two source rock types differ in their light hydrocarbon composition by the presence of relatively more aromatics and cyclohexanes in the are samples while the spekk samples are richer in cyclopentanes and acyclic hydrocarbons we show that source rock facies is a more important indicator of light hydrocarbon composition than maturity variation differences in the chemical composition which can be used to discriminate between the two source rocks were supported by differences in the carbon isotope composition of individual components of the same fraction as determined by ghm ir ms analysis of eleven samples further the light hydrocarbon compositions of reservoir fluids oils and condensates were compared with those for the source rock s sixty six gas chromatograms of oils and condensates representing most of the known petroleum accumulations in mid norway were collected of these five oil samples were selected for detailed isotopic analysis of individual components gc ir ms when using a classification scheme based on data from sediment samples data for the light hydrocarbon fraction of oils and condensates indicate that the spekk formation is the dominant source for most of the fields from mid norway with a significant contribution from the are formation being detected principally in one field differences in the chemical composition of the c 6 c 8 fractions were supported by differences in the carbon isotope composition of individual components which also discriminate between the oils although the classification diagrams used in this study are based on source rock data from mid norway the method can be applied to other areas providing that the diagrams are calibrated with source rock data from the area of interest

high ammonium contents in the 3800 ma isua supracrustal rocks central west greenland abstract ammonium contents of whole rock and biotite samples from the metasedimentary sequence of the 3800 ma isua supracrustal belt central greenland have been determined and compared with the ammonium contents of volcanic sedimentary metamorphic and granitic rocks from the late archaean early proterozoic a sample of the amitsoq gneiss has an nh4 content whole rock 9 ppm biotite 29 ppm that is similar to many younger igneous rocks ammonium contents of the supracrustal rocks vary with chemistry and mineralogy of the rock and most likely were inherited from the original sediments a series of carbonate bearing and basic plagioclase bearing biotite rich schists from sequence a have varying nh4 contents whole rock 6 24 ppm that increase with an increasing chemical clastic component and decreasing volcanogenic component biotites in these rocks together with biotites in mica schists of the same sequence have high nh4 contents which vary over a small range of 54 95 ppm suggesting that the nh4 in these rocks was contained mostly in authigenic clays of the original sediments all these data imply that clay minerals were the major sink of nh4 or other nitrogen compounds on the earth s surface at 3800 ma two samples of graphite bearing garnet staurolite mica schist from sequence b have remarkably high nh4 contents whole rock 68 and 86 ppm biotite 234 and 253 ppm which are as high as or even higher than those of common late archaean early proterozoic argillites it appears almost certain that the original thick clay rich bottom sediments contained a large amount of nh4 or other nitrogen compounds the most likely major source of nitrogen in these nh4 enriched graphite bearing mica schists might be organic nitrogen

petroleum and source rock characterization based on c7 star plot results examples from egypt the main types of egyptian oils condensates have been reviewed and characterized by light end hydrocarbon c7 based geochemical star plots the technique relies on high resolution gas chromatography of the c7 compounds and compositional differences are evaluated by using crossplots and multivariate polar plots c7 results of oils condensates are presented for the three main hydrocarbon provinces in egypt the gulf of suez the western desert and the nile delta and nearby mediterranean for the gulf of suez there are two main oil types which were derived from 1 cretaceous eocene carbonate rich and 2 miocene siliciclastic rich source rocks for the western desert there are three distinct oil types two of these oil types probably originated from middle jurassic carbonaceous marine shale rich source rocks whereas the third oil was produced from upper cretaceous argillaceous limestones for the nile delta there are two types of oil the majority of the oils condensates from this region are derived from tertiary shale rich source rocks but some may have a cretaceous jurassic source the given examples show that the c7 based star plot is very effective as a discriminating tool and that the c7 results are supportive and supplementary to other more standard geochemical oil condensate correlation methods the c7 data give reliable results over a wide range of thermal maturities but some compounds may be sensitive to evaporative fractionation water washing and biodegradation special attention is given to what extent the c7 data provide reliable information on source rock typing for the egyptian petroleums it appears that marine carbonate rich type ii derived oils have very different c7 compound concentrations than terrestrial clastic type iii ii derived oils for any oil condensate source correlation study be it on an exploratory regional or production field scale the light end c7 data may provide extremely useful geochemical information

precambrian ammonium biogeochemistry a study of the moine metasediments scotland abstract the content and isotopic composition of ammoniacal nitrogen have been determined in a suite of amphibolite facies metasediments of precambrian age whole rock samples and mica separates from the moine succession proterozoic of scotland were analysed by a combination of capacitance manometry and static vacuum mass spectrometry prior to the analyses the presence of the ammonium ion was confirmed by obtaining infrared ir absorption spectra from the micas principally biotites whole rock ammonium contents are high for amphibolite facies metasediments 140 422 ppm the ammonium ion was not detected in the ir absorption spectra of biotites from one schist however this sample contains neither garnet nor white mica for most of the samples the 15n values are very positive between 12 4 and 16 6 with one sample having a lower value of 8 4 the major variations between samples can be interpreted in terms of original sedimentary features for the ammonium bearing samples muscovites have concentrations between 365 and 633 ppm biotites between 845 and 1739 ppm for individual samples nh4 mu nh4 bi varies between 0 31 and 0 43 a much narrower range than has been reported previously there are no significant or consistent differences in 15n between co existing biotite and white mica nor between the 15n values of the mineral separates and their respective whole rock values the latter suggests minimal selective partitioning of isotopes between micas and plagioclase feldspar the only other potential host for ammonium in the rocks assuming that the ammonium has been derived from organic matter originally present at the time of deposition and by comparison with previous studies it can be inferred that the original 15n value of the moine sediments was somewhere between 5 and 10 similar to recent sediments this suggests that the nitrogen cycle in the proterozoic shelf sea from which the moine sediments were deposited was broadly similar to the present day overall the study underlines how under developed the n system is compared to other stable isotope systems notably c and s and we use the opportunity to highlight some areas that could be developed in the future however one aspect is clear future ammonium studies of metamorphic rocks will need to be performed at high resolution visible scale of heterogeneity with strong mineralogical petrological and field controls

quantitative analysis of seabed mixing and intertidal zone discharge in coastal aquifers 1 contaminant loading from an inland source zone to the nearshore marine environment is examined using a saturated unsaturated simulation model which incorporates both the influence of the growth and the extinction of the seepage face in the intertidal zone and the inclusion of hydromechanical stress coupling due to tidal loading the system analyzed represents a site where an unconfined aquifer extends offshore with a broad intertidal zone the volumetric discharge of groundwater in the intertidal zone dominates the discharge occurring beyond the low tide line for most of the cases examined within the intertidal zone the recirculated saline component of the discharge is greater than the freshwater component the majority of the contaminant mass exits through the seepage face located above the instantaneous tide line the peak contaminant loading rate occurs around the time of the falling midtide at low tide the contaminant loading rate is more than 2 orders of magnitude lower than the peak rates even though groundwater discharge rates are highest as low tide is approached sensitivity studies indicate that the relative proportion of recirculated intertidal zone discharge to fresh intertidal zone discharge is most sensitive to the magnitude of the freshwater flux the spatial variation of the outflow across the intertidal zone as influenced by anisotropy in hydraulic conductivity and tidal pumping as influenced by specific storage dilution of contaminant concentrations due to mixing with seawater beneath the sediment water interface is represented in terms of a dilution factor defined relative to the onshore source concentration for our base case the dilution factor for the contaminant concentration averaged over one tidal cycle at the high tide midtide and low tide lines was 1 3 3 9 and 560 respectively the key factors determining contaminant dilution at the sediment interface are location within the intertidal zone and the vertical extent of the contaminant plume as it enters the intertidal zone

nitrogen and argon signatures in 3 8 to 2 8 ga metasediments clues on the chemical state of the archean ocean and the deep biosphere abstract n and ar elemental and isotopic analyses were conducted on archean metasediments of isukasia west greenland and pilbara craton western australia in order to investigate the n isotopic evolution during the first half of earth s history the selected samples are deep sea sediments and hydrothermal deposits having ages from 3 8 to 2 8 ga and affected by different degrees of metamorphism the release patterns of n and ar obtained by high resolution stepped combustion show the occurrence of at least two trapped components the first is released at 600 c and it is likely contained in fluid inclusions n is released together with primordial 36ar and shows a 15n value of 1 3 1 0 close to that of modern atmospheric n2 15n 0 this component is well preserved in hydrothermal vent silica deposits of north pole pilbara craton and nitrogen may represent ammonium salt dissolved in deep sea hydrothermal fluids the second n component released at temperatures higher than 1000 c is accompanied by radiogenic 40ar and shows a 15n value of 7 4 1 0 in a kerogen rich chert from north pole pilbara craton this n is likely biogenic and negative 15n values may reflect a metabolic isotopic fractionation induced by chemosynthetic bacteria using inorganic nh4 contained in hydrothermal fluids this 15n depleted biogenic component may occur in isukasia banded iron formation 15n 1 7 but further data are needed to confirm such a hypothesis in all other samples metamorphic induced rayleigh distillation has altered the pristine n isotopic signature

methane dominated thermochemical sulphate reduction in the triassic feixianguan formation east sichuan basin china towards prediction of fatal h2s concentrations abstract new sour pools have recently found in the lower triassic feixianguan fm carbonate reservoirs in the east sichuan basin in china with h 2 s up to 17 4 by volume a recent blowout from a well drilled into this formation killed hundreds of people as a result of the percentage concentrations of h 2 s in order to assess the origin of fatal h 2 s as well as the cause of petroleum alteration h 2 s concentrations and the isotopes 34 s and 13 c have been collected and measured in gas samples from reservoirs anhydrite pyrite and elemental sulphur 34 s values have been measured for comparison the high concentrations of h 2 s gas are found to occur at depths 3000 m temperature now at 100 c in evaporated platform facies oolitic dolomite or limestone that contains anhydrite nodule occurrence within the reservoirs where h 2 s concentrations are greater than 10 its 34 s values lie between 12 0 and 13 2 cdt this is within the range of anhydrite 34 s values found within the feixianguan fm 11 0 to 21 7 average 15 5 3 5 cdt thus h 2 s must have been generated by thermochemical sulphate reduction tsr locally within the reservoirs burial history analysis and fluid inclusion data reveal that the temperature at which tsr occurred was greater than about 130 140 c suggesting that the present depth temperature minimum is an artifact of post tsr uplift both methane and ethane were actively involved in tsr since the petroleum became almost totally dry no alkanes except methane and methane 13 c values become significantly heavier as tsr proceeded methane 13 c difference thus reflects the extent of tsr while it is tempting to use a present day depth control 3000 m to predict the distribution of h 2 s in the feixianguan fm this is an invalid approach since tsr occurred when the formation was buried some 1000 2000 m deeper than it is at present the likelihood of differential uplift across the basin means that it is important to develop a basinal understanding of the thermal history of the feixianguan fm so that it is possible to determine which parts of the basin have been hotter than 130 140 c

heat transport dynamics at a sandy intertidal zone 1 intertidal zones are spatially complex and temporally dynamic environments coastal groundwater discharge including submarine groundwater discharge may provide stabilizing conditions for intertidal zone permeable sediments in this study we integrated detailed time series temperature observations porewater pressure measurements and two dimensional electrical resistivity tomography profiles to understand the coupled hydraulic thermal regime of a tropical sandy intertidal zone in a fringing coral reef lagoon rarotonga cook islands we found three heating patterns across the 15 m study transect over tidal and diel periods 1 a highly variable thermal regime dominated by swash infiltration and changes in saturation state in the upper foreshore with net heat import into the sediment 2 a groundwater supported underground stable cool region just seaward of the intertidal slope break also importing heat into the subsurface and 3 a zone of seawater recirculation that sustained consistently warm subsurface temperatures that exported heat across the sediment water interface simple calculations suggested thermal conduction as the main heat transport mechanism for the shallow intertidal sediment but deeper and or multidimensional groundwater flow was required to explain temperature patterns beyond 20 cm depth temperature differences between the distinct hydrodynamic zones of the foreshore site resulted in significant thermal gradients that persisted beyond tidal and diel periods the thermal buffering of intertidal zones by coastal groundwater systems both at surface seeps and in the shallow subsurface can be responsible for thermal refugia for some coastal organisms and hotspots for biogeochemical reactions

gas venting and subsurface charge in the green canyon area gulf of mexico continental slope evidence of a deep bacterial methane source abstract questions as to the role of modern carbon in methanogenesis and the maximum depth of methane sources in the gulf of mexico continental slope remain unanswered a research submersible was used to sample mixed bacterial and thermal gas 13 c of methane 62 8 d 176 venting to the water column from the gulf slope in green canyon gc 286 the 14 c value of the methane 998 is consistent with fossil carbon another gas vent on gc 185 is 100 methane 13 c 62 9 d 155 and may be from a bacterial source the 14 c 997 of this bacterial methane is also consistent with fossil carbon fossil bacterial methane and thermal hydrocarbons are present in pliocene to pleistocene reservoirs 3509 4184 m of genesis field gc 205 161 160 oil in these reservoirs is biodegraded but gas is not suggesting that gas charge to reservoirs continues presently at 3 4 km depth mixed thermal and bacterial methane may charge the deep reservoirs and fossil methane from depth may ultimately vent on the sea floor at gc 286 and gc 185 results of this study of green canyon suggest that bacterial methane in gas vents and in reservoirs is from deep fossil sources

fixed ammonium in clays associated with crude oils abstract the association of ammonium nh 4 silicates with organic rich sedimentary environments has stimulated interest in the chemical cycle of n and its possible application as an indicator of in situ organic maturation reactions or crude oil migration fixed nh 4 in clay minerals was determined from three hydrocarbon occurrences of similar depositional environment but different ages depth and thermal maturity to determine whether anomalously high nh 4 substitution occurs near mature hydrocarbons results show higher fixed nh 4 concentrations in marginally mature mudstones than in immature sediments the highest fixed nh 4 concentrations were found in clays from sandstone reservoirs containing migrated crude oil fixed nh 4 in clays from holocene oil seep sediments in the gulf of mexico continental slope offshore louisiana averages 0 08 wt and increases with depth in shallow cores 420 cm reflecting an early diagenetic trend that is apparently not influenced by migrating crude oil programmed pyrolysis shows that the sediments are thermally immature av t max 419 c high hydrogen index values av 359mg g are the result of biodegraded crude oil and a high oxygen index av 182mg g reflects the presence of authigenic carbonate fixed nh 4 averages 0 16 wt in wilcox group eocene mudstones enclosing two sandstone reservoirs at fordoche field onshore louisiana in comparison to these mudstones anomalously high nh 4 fixation appears to occur in reservoir clay minerals pyrolysis shows that the sediments are marginally mature for crude oil generation av t max 432 c average hydrogen index 187 mg g and oxygen index values 75 mg g are consistent with oil prone type ii and type iii kerogen increased pyrolysis production index values and solvent extraction shows the presence of migrated crude oil this suggests that a reaction which releases nh 3 during crude oil generation or migration is recorded bynh 4 substitution in clays fixed nh 4 and total organic carbon toc at fordoche field show no statistically significant correlation suggesting that nh 4 substitution in clay minerals is not simply related to the amount of organic matter in the section but is also influenced by the presence of crude oil once nh 4 has been fixed in clays it is a more stable hydrocarbon proximity indicator than pore fluid tracers because it is less influenced by later chemical or geological changes

hypoaigic influences on groundwater flux to a seasonally saline river hypoaigic zones are aquifer volumes close to and beneath the shores of saline surface water bodies and are characterized by the presence of time dependent natural convection and chemical stratification when transient and cyclic processes are involved there is significant potential for complex flow and reaction in the near shore aquifer presenting a unique challenge to pollutant risk assessment methodologies this work considers the nature of some hypoaigic processes generated by the seasonally saline canning river of western australia near a site contaminated by petroleum hydrocarbons a dissolved hydrocarbon plume migrates within the shallow superficial aquifer to the nearby bank of the canning river beneath the river bank a zone of complex fluid mixing is established by seasonal and tidal influences understanding this complexity and the subsequent ramifications for local biogeochemical conditions is critical to inferring the potential for degradation of advecting contaminants a range of modelling approaches throws light on the overall topographic controls of discharge to the river on the saline convection processes operating under the river bank on the potential for fluid mixing and on the various important time scales in the system saline distributions simulated within the aquifer hypoaigic zone are in at least qualitative agreement with previous field measurements at the site and are strongly affected by seasonal influences groundwater seepage velocities at the shoreline are found to be positively correlated with river salinity calculations of fluid age distributions throughout the system show sensitivity to dispersivity values however maximum fluid ages under the river appear to be diffusion limited to a few decades the saline convection cell in the aquifer defines a zone of strong dispersive dilution of aged many decades deep aquifer fluids with relatively young several months riverine fluids seasonal recharge and river salinity cycles induce regular perturbations to the convection cell yielding intra annual variations of 50 in seepage velocity and almost 30 in wedge penetration distance at the plume location

ammonium as a biomarker in precambrian metasediments abstract the following article assesses the potential of ammonium as a biomarker in precambrian metasediments a modern marine environment is considered to highlight the processes that contribute to the isotopic composition of organic nitrogen notably the roles played by nitrogen fixing organisms cyanobacteria and denitrifying bacteria the carbon and nitrogen biogeochemical cycles are compared and contrasted unlike carbon the major nitrogen isotope variations may be controlled by local environmental conditions such as season of the year and water depth however such local environmental factors may have been superimposed on more gradual changes related to the long term chemical evolution of the exterior environments of the earth the great potential of nitrogen as a biomarker is that the breakdown product of organic nitrogen ammonium behaves like a trace element and is stable in high temperature crustal processes thus ammonium may survive as a biomarker when all other evidence for former life has been destroyed and ammonium studies may be able to identify sedimentary pelitic components in high grade precambrian terrains previous results from precambrian rocks are reviewed to highlight that very little work has been completed to date and that only very general conclusions can be drawn much work needs to done in order to understand the basic biogeochemistry and geochemistry of crustal nitrogen and it is suggested that the best way to proceed is by numerous detailed case studies the interpretation of isotope ratios in ancient sediments usually assumes uniformitarianism and the justification of this approach is considered briefly overall this article highlights the under developed potential of precambrian ammonium biogeochemistry and suggests area for future research not only does the development of the subject have implications for the search for former life on mars but it may also open up new areas of precambrian research

salt intrusion in coastal and lowland areas of semarang city over a long term semarang coastal and lowland areas have experienced salt water intrusion this condition is accelerated due to land subsidence sea level rise and groundwater exploitation the purposes of this research paper were to highlight the salt water intrusion from 1995 until 2108 based on well log measurement and modfow numerical modeling in coastal and lowland of semarang city sea level rise projection also was considered for salt intrusion projection in the future modflow was used to compute the groundwater flow field mt3d for the salt transport and arcgis environments for coherent geographic visualization a calibration of the model was conducted based on observation best match the results obtained illustrate the development of a forward onshore sea salt water intrusion since 1995 it also showed the 2008 recorded sea water intrusion and provide groundwater sea water contamination projection for the years 2018 until 2108 moreover fresh water distribution near the coast in previous years developed into brackish water then into saline groundwater result showed the movement of saline groundwater from coastline to landward years by years from 2018 2028 2048 2068 2088 and 2108 following high hydraulic conductivity area salt intrusion was also driven by future sea level rise which result to the increase of the fresh water front forward move

stable carbon and hydrogen isotopes of natural gases sourced from the xujiahe formation in the sichuan basin china abstract the compound specific hydrogen and carbon stable isotope ratios of alkanes in natural gases from the xujiahe and jurassic formations in the western sichuan basin were investigated to distinguish between coal derived and oil associated gases all gases were determined to be coal derived and sourced from the xujiahe formation thermal maturities of the source rocks are expected to vary from 0 8 1 8 vitrinite reflectance ro according to the empirical relationship between the measured 13cch4 values and ro which is within the scope of the maturities of source rocks 0 7 2 1 in particular c1 3 alkanes of primary coal derived gases which have not undergone any secondary alteration become more enriched in deuterium with increasing molecular mass and the dch4 values increase with increasing thermal maturity of source rocks in the sichuan basin d values of coal derived gases sourced from terrigenous source rocks of the xujiahe formation are more negative than those of oil associated gases sourced from marine organic matter of the sinian permian and triassic formations

origine des nitrates dans les nappes de fissures de la zone tropicale humide exemple de la cote d ivoire abstract high nitrate contents up to 200 mg l 1 were observed in a sample of 230 tubewells reaching fissure groundwater beneath thick layers of weathered and decayed rock in a humid tropical zone with annual rainfall of over 1000 mm examination and comparison of the regions studied led to envisaging two possible sources of the nitrates first classic domestic pollution and second the leaching of the soil and rotting plant debris after local deforestation when villages or crops were established an attempt was made to distinguish between the two sources by using 15 n no 3 the results were rendered uncertain by the probable involvement of natural denitrification nevertheless this approach provides arguments in support of nitrates originating in processes connected with deforestation

interaction between shallow groundwater saline surface water and contaminant discharge at a seasonally and tidally forced estuarine boundary this paper presents findings from a 2 year field investigation of a dissolved hydrocarbon groundwater plume flowing towards a tidally and seasonally forced estuarine river system in perth western australia samples collected from transects of multiport wells along the riverbank and into the river enabled mapping of the fine scale 0 5 m vertical definition of the hydrocarbon plume and its longitudinal extent spear probing beneath the river sediments and water table and transient monitoring of multiport wells electrical conductivity was also carried out to define the zone of mixing between river water and groundwater the hyporheic zone and its variability the results showed that groundwater seepage into the estuarine surface sediments occurred in a zone less than 10 m from the high tide mark and that this distance and the hyporheic transition zone were influenced by tidal fluctuations and infiltration of river water into the sediments the dissolved btexn benzene toluene ethylbenzene the xylene isomers and naphthalene distributions indicated the behaviour of the hydrocarbon plume at the groundwater surface water transition zone to be strongly influenced by edge focussed discharge monitoring programs and risk assessment studies at similar contaminated sites should therefore focus efforts within the intertidal zone where contaminants are likely to impact the surface water and shallow sediment environments