Pore Water Salinity Research Articles

The quest for an extraterrestrial component in Muong Nong-type and splash-form Australasian tektites from Laos using highly siderophile elements and Re-Os isotope systematics

Abstract Extremely low and variable concentrations of osmium (Os) and other highly siderophile elements (HSE) in most tektites make it challenging to establish direct links between these impact-related materials and their possible extraterrestrial contribution. New Os concentrations (2–43 ppt) and 187Os/188Os ratios (0.131–0.68) in a suite of fifteen well-characterized Australasian tektites from Laos (Muong Nong and splash-form types) with variable Ni enrichment indicate a maximum of ∼0.005% addition of a chondritic impactor. This is similar to some Australasian tektites from Vietnam with similarly low siderophile contents, but significantly lower than found in previous studies of more Ni-rich Australasian splash-form tektites and microtektites from different parts of the Australasian strewn field (e.g., Indonesia, South China Sea). The contents of HSE and Re–Os isotopic compositions of layered Muong Nong-type Australasian tektites are highly variable, suggesting mingling of crustal-derived (siderophile element-poor) and extraterrestrial (siderophile element-rich) materials. The absence of a direct correlation between HSE and Ni contents is interpreted to result from a fractionation process related to their different vaporization/condensation temperatures. The low Os abundance in most of the analyzed Australasian tektites, combined with non-radiogenic 187Os/188Os far below average upper continental crust, may provide a direct test to distinguish continental versus seawater impact scenario. In the absence of any specific low-Os target, a particular process of Os loss following impact is required. We envisage a scenario where evaporative loss of >>90% Os in the form of Os oxides from the overheated tektite melt is aided by volatile species derived from dissociated seawater and/or saline pore water embedded in sediments off-shore Indochina, consistent with elevated contents of halogens in Australasian tektites. This water-assisted Os loss could also play significant role for Central European tektites, while the continental surface with limited amount of water would prevent from more efficient HSE loss as could be the case for Ivory Coast tektites.

Allochthonous sources of iodine and organic carbon in an eastern Ontario aquifer

Regional geochemical characterization of groundwaters in a bedrock aquifer in the Ottawa – St. Lawrence Lowlands of eastern Ontario has identified an iodine (I) anomaly, with values regularly exceeding 150 μg/L and a maximum observed concentration of 10 812 μg/L. The spatial distribution, enrichment mechanisms, and sources of I and organic matter were investigated using geochemical and isotopic data. High-I groundwaters (>150 μg/L) are prevalent in Na–Cl-type groundwaters at low bedrock elevations in areas overlain by thick layers of glacial sediments. I is thought to be linked to massive muds in the glacial sediments overlying the aquifer, deposited during the postglacial incursion of the Champlain Sea 12–10 ka BP. Principal component analysis of I and 18 other chemical parameters revealed correlations among I, salinity, and indicators of microbial oxidation of organic matter, suggesting that the intrusion of saline pore waters affected by decomposition of organic matter such as marine phytoplankton in the massive muds is the dominant process controlling I enrichment in groundwater. 129I/127I ratios in the pre-modern waters vary between near-marine values of 460 × 10−14 and 5 × 10−14, demonstrating that older allochthonous I derived from the surrounding Paleozoic sedimentary terrain also contributed to the I pool in the Champlain Sea basin. 14C ages and δ13C signatures for dissolved organic carbon in groundwater and disseminated organic carbon within the glaciomarine muds highlight an allochthonous source of terrestrial organic carbon predating the Champlain Sea incursion, likely transported via glacial meltwaters in tandem with I to the Champlain Sea basin.

Porewater salinity effect on flocculation and desiccation cracking behaviour of kaolin and bentonite considering working condition

Cracking behaviour of clays at a local working climate and soils' evolution under seepage boundary is very important for the geological engineering. In coastal regions, pore water salinity is incorporated into above processes. In this study, the properties of typical clays (kaolin and bentonite) in saline environments, including the consistency limits, particle sedimentation and crack pattern, were investigated. The consistency limits of kaolin remain constant regardless of the pore water salinity, while the liquid limits of bentonite noticeably decrease with increasing salinity. Flocculation of kaolin occurs in both distilled water and NaCl solution, whereas the fine particles in bentonite disperse in distilled water but aggregate in saline water. At the end of the evaporation process, the total crack area of bentonite is obviously decreased, and the total crack length increases with pore water salinity, whilst that of kaolin is not influenced. In the subsequent wetting process, the bentonite clods disperse easily in saline environment, but the collapse of kaolin clods is not significantly influenced by the water salinity. The above observations are explained by the initial aggregation of clay platelets for the interactive forces between particles.

Effect of Pore-Water Salinity on the Electrical Resistivity of Partially Saturated Compacted Clay Liners

The aim of this paper is to investigate the effect of pore-water salinity on the electrical resistivity (ER) of different compacted clay liners (CCLs) in terms of its mineralogical composition. For this purpose, an experimental programme was conducted where ERs of different kaolin-dominant CCL specimens, reconstituted using water having different concentrations of NaCl (0 M, 0.5 M, and 1.0 M), were measured. The kaolin-dominant CCL specimens tested in this study include pure kaolin, three different kaolin-bentonite mixtures, and three different kaolin-sand mixtures. The experimental results show that the ERs of CCL specimens decrease as the salt concentrations in pore water, moisture content, and dry density increase. At constant density and moisture content, the test results also indicate that increasing the sand content in kaolin-dominant CCL specimens increases its ER regardless of the water salinity level. This behaviour could be attributed to the lower surface conduction of sand compared to kaolin. However, at constant density and moisture content, increasing the bentonite content in kaolin-dominant CCL specimens decreases its ER in the distilled water environment as surface conduction of bentonite is higher compared to that of kaolin. On the contrary, in saltwater environments, ER increases as the bentonite content increases. This behaviour could be explained in terms of the expected aggregated microstructure of bentonite in the saltwater environment that could reduce the number and area of interparticle contacts, and consequently, increase the ER of CCL specimens.

Geotechnical characterization and collapsibility of a natural dispersive loess

During preliminary investigation phase of the national Chabahar-Zahedan railway line, serious geotechnical problems including non-uniform settlements, tensile cracks, and local collapse were reported in parts of the path near the coastline. A follow-up field investigation revealed that the in-situ soil at construction site has a metastable structure being sensitive to saturation and loading. Therefore, a comprehensive series of physical, chemical, electro-chemical, and geotechnical tests were conducted to classify and characterize the soil properties and behavior in its natural state. The natural soil was classified as a clayey loess with moderately dispersive to dispersive characteristics. Given its significant collapse potential, the soil was assigned into the category with “severe trouble” for construction purposes. Importantly, our tests revealed that a threefold reduction in pore water salinity results in >4% rise in collapse potential of similar specimens. Reduction in salt concentration increases the thickness of diffuse double layer and hence collapsibility. In addition, strain softening shear behavior was observed for elevated confining stresses under undrained triaxial stress state. In fact, this brittle type failure mechanism associated with continuous generation of pore water pressure is undesirable as catastrophic failures could happen with no advance warning.

Impacts of salinity level and flood irrigation on Cd mobility through a Cd-contaminated soil, Thailand: experimental and modeling techniques

The objective of this research was to investigate the effects of salinity levels and pore water velocity (PV) on the sorption, fate, and transport of Cd through contaminated soil in low-lying areas along Mae Tao Creek, Tak Province, Thailand. Soil samples collected from a depth of 15 cm from the rice field were air-dried, ground, and sieved through a 2-mm sieve prior to the experiments. Batch sorption/desorption experiments were conducted under three salinity levels, 1, 10, and 100 mM, using CaCl2 as salt. The six columns for the Cd transport experiments were performed with low and high pore water velocities (2 and 9 cm/h) and salinity levels of 1, 10, and 100 mM. Effects on Cd rate-limited sorption and transport behavior were evaluated using the sorption isotherms, PHREEQC geochemical modeling, and mathematical model, HYDRUS-1D. For the batch experiments, the Freundlich isotherm was found to be the best sorption isotherm to explain the Cd sorption (R2 > 0.93, p value < 0.05). The Langmuir two-site model (TSM) well explained the breakthrough curves of the column experiments with Langmuir sorption coefficient (KL) ranging from 0.09 to 4.03 l/g. Salinity levels appeared to significantly increase the equilibrium fraction site (f) and first-order rate constant (α) on Cd sorption and transport over the salinity levels of 10–100 mM due to the competitive effect and the dominant species of Cd. Solute transport parameters in the TSM can be used as an efficient decision support tool to predict Cd movement through contaminated sandy loam soils under a flood irrigation area.

Hydrogeochemical features of pore-waters of bottom sediments of the shelf and limans of the Northwestern Black Sea region

The article presents information on the chemical composition and salinity of pore-waters of the Holocene bottom sediments in the shelf and limans from the Northwestern Black Sea region. The specific features of the water quality distribution laterally and in depth are considered. The peculiarities of the structure of hydrogeochemical sections confirm the transgressive-regressive character of the sea level change. Analysis of the geological structure, hydrogeochemical and paleoclimatic features allowed to substantiate the hypothesis of the use of limans as sources of salt in the Holocene period. Based on the information on the hydrochemical features of bottom sediments and changes in sea level, the reconstructions of paleogeographic sedimentation environments during the late Pleistocene-Holocene time on the northwestern shelf and limans of the Black Sea are presented.

Influence of structure on the compression behaviour of two very stiff fissured high plasticity Eocene clays

A series of one-dimensional compression tests have been performed on reconstituted specimens of Søvind Marl. A clear correlation is obtained between the location and the gradient of the intrinsic compression lines and the void ratio at the liquid limit. The found correlation has subsequently been used to normalise the compression curves of 12 one-dimensional compression tests on intact specimens of Søvind Marl and Little Belt Clay obtained from various depths at two sites at Aarhus Harbour. Søvind Marl and Little Belt Clay are both marine sedimentary clays of Eocene age, which can be characterised as very stiff fissured clays with a very high plasticity. From a comparison of the reconstituted and intact compression paths the influence of structure is analysed and discussed in the paper. The majority of intact specimens of Søvind Marl and Little Belt Clay from Aarhus Harbour show similar behaviour; a very stiff recompression path and yielding at high stress level after crossing the intrinsic compression line. The displayed behaviour indicates an insignificant influence of fissuring on the pre-yield behaviour. Post-yield the compression paths indicate a stable structure dominated by fabric rather than metastable interparticle bonds. The paper furthermore highlights the importance of considering the effect of pore water salinity when assessing the influence of structure on the compression behaviour of smectite rich natural marine clays.

Effect of evaporative drying on complex conductivity spectra of sandstones

Dehydration is a common process occurring in natural environments, rocks, and building materials. Suitable methods for monitoring the changing moisture content should be identified. We have investigated the impact of dehydration of sandstones on complex conductivity spectra. Spectral induced polarization measurements were performed on five sandstone samples during evaporative drying. The complex conductivity spectra indicate considerable changes with decreasing saturation. The relationship between conductivity and saturation can be described by a power law known as the second empirical Archie equation. Separate saturation exponents have been determined for the real and imaginary parts of conductivity. The imaginary part of conductivity indicates higher saturation exponents for the investigated sandstones compared to the real part. Obviously, the saturation exponents depend on the method used for changing water saturation. Evaporative drying, which is used in our experiments, causes an increase of pore-water salinity and results in lower saturation exponents for the real part of conductivity but higher exponents for the imaginary part in comparison with the classical imbibition/drainage technique. We evaluate a theoretical approach that considers the influence of pore water salinity on the saturation exponents of the real and imaginary parts of conductivity. The complex conductivity spectra are processed by a Debye decomposition procedure. The resulting integrating parameters such as direct current resistivity, total chargeability, normalized chargeability, and mean relaxation time indicate a power law dependence on saturation. Our experiments indicate that the imaginary part of conductivity and normalized chargeability have a high sensitivity related to the drying process of rocks and might be suitable indicators to monitor the changes of moisture content in sandstones.

Porewater salinity in a southeastern United States salt marsh: controls and interannual variation.

In coastal marsh ecosystems, porewater salinity strongly affects vegetation distribution and productivity. To simulate marsh porewater salinity, an integrated, spatially explicit model was developed, accounting for tidal inundation, evaporation, and precipitation, as well as lateral and vertical exchanges in both surface waters and the subsurface. It was applied to the Duplin River marsh, Sapelo Island, USA, over a 3-year period, which covered both drought and wet conditions. Simulated porewater salinity in the low and high marsh correlated with Duplin River salinity, with evapotranspiration and precipitation leading to substantial variations in porewater salinities across seasons, in particular in the high marsh. The model revealed substantial interannual variability in marsh soil conditions, and—due to its process-based approach linked to external forcings—can be used to explore effects of sea level rise and changes in hydrological forcings on marsh soil conditions.

Large-volume basaltic hyaloclastite eruption along a propagating land/lake lithosphere fracture at Lake Van (Eastern Anatolia): impact of volcanism on the evolution of Lake Van V

The Incekaya hyaloclastite cone (eastern Anatolia, Turkey), the focal point along a major eruptive fissure, was the main source of an unusually large explosive basaltic eruption. The ca. 80 ka-old eruption began onshore with scoria cones from a 5 km N-S fracture propagating toward Lake Van (surface area of 3755 km2). At the intersection with the fault-bounded lake basin, a ca. 400-m-high subaerial hyaloclastite edifice formed, which can be crudely subdivided into a main lower massive bulk of hydrothermally altered lithic-rich hyaloclastites (CL) topped unconformably by a > 30-m-thick, well-bedded fallout tephra (CU). The CU tephras are correlated with (1) widespread onshore hyaloclastite fallout deposits mostly west-southwest of the cone and (2) a ca. 2-m-thick, ca 80-ka-old bedded hyaloclastite (V-60), part of a 220 m ICDP (International Continental Scientific Drilling Program) core, drilled in Lake Van, 27 km N of Incekaya. The hyaloclastite unit was seismically identified as being the most widespread and well-defined reflector throughout much of western Lake Van. A minimum volume of > 9 km3 fallout hyaloclastite tephra is estimated when the area of the seismic reflector is extrapolated to the coast and 2 km inland. Seismic reflectors also suggest at least two (hyaloclastite?) intralake cones rising up to 388 m above the lake sediment surface 1.5 km NW off Incekaya cone and were possibly erupted along the same fracture. The total volume of hyaloclastites includes (a) subaerial Incekaya cone, (b) the inferred subaqueous continuation of the cone(s), (c) the bedded intralake and onshore deposits, and, tentatively, (d) a widespread (seismically defined) mass flow deposits directly beneath Incekaya reflector of roughly 20 km3 and may represent the deposits of explosively erupted basaltic magma. Sideromelane shards, the main clast type, are dominantly angular, and most show ≪ 50 vol.% vesicles. Less common tachylite clasts are poorly vesicular (< 50 vol.%). Structural transitions and interlayering between tachylite and sideromelane are ubiquitous. Fluidal and pumiceous lapilli are present in the basal massive facies. Bulk rock and glass compositions indicate constant composition of the slightly evolved Al-rich basalt magma. Olivine (Fo78–82) and plagioclase (An70–80) microphenocrysts, many skeletal with growth features, and microlites make up < 1 vol.% and suggest rapid magma ascent. The high explosive energy of the eruption is interpreted to be due to (1) high magma discharge rates and shearing in the eruptive jet and (2) magma-water interaction conditions. Approximate temporal coincidences with the Incekaya eruption include the following: (a) an abrupt cessation in the supply of evolved tephra from the adjacent Suphan Volcano to the lake sediments, which ended abruptly for ca. 60 ky, (b) an extreme fall in lake level by ca. 150 m, and (c) a drastic increase in pore water salinity (Na+ and Cl− (g/L)) and pH.

Methane sources and sinks in continental sedimentary systems: New insights from paired clumped isotopologues 13CH3D and 12CH2D2

Stable isotope compositions of methane (δ13C and δD) and of short-chain alkanes are commonly used to trace the origin and fate of carbon in the continental crust. In continental sedimentary systems, methane is typically produced through thermogenic cracking of organic matter and/or through microbial methanogenesis. However, secondary processes such as mixing, migration or biodegradation can alter the original isotopic and composition of the gas, making the identification and the quantification of primary sources challenging. The recently resolved methane ‘clumped’ isotopologues Δ13CH3D and Δ12CH2D2 are unique indicators of whether methane is at thermodynamic isotopic equilibrium or not, thereby providing insights into formation temperatures and/or into kinetic processes controlling methane generation processes, including microbial methanogenesis.In this study, we report the first systematic use of methane Δ13CH3D and Δ12CH2D2 in the context of continental sedimentary basins. We investigated sedimentary formations from the Southwest Ontario and Michigan Basins, where the presence of both microbial and thermogenic methane was previously proposed. Methane from the Silurian strata coexist with highly saline brines, and clumped isotopologues exhibit large offsets from thermodynamic equilibrium, with Δ12CH2D2 values as low as −23‰. Together with conventional δ13C and δD values, the variability in Δ13CH3D and Δ12CH2D2 to first order reflects a mixing relationship between near-equilibrated thermogenic methane similar to gases from deeper Cambrian and Middle Ordovician units, and a source characterized by a substantial departure from equilibrium that could be associated with microbial methanogenesis. In contrast, methane from the Devonian-age Antrim Shale, associated with less saline porewaters, reveals Δ13CH3D and Δ12CH2D2 values that are approaching low temperature thermodynamic equilibrium. While microbial methanogenesis remains an important contributor to the methane budget in the Antrim Shale, it is suggested that Anaerobic Oxidation of Methane (AOM) could contribute to reprocessing methane isotopologues, yielding Δ13CH3D and Δ12CH2D2 signatures approaching thermodynamic equilibrium.

Salinity and Macrocomponent Composition of Pore Water of the Bazhenov, Achimov, and Georgiev Formations from Analysis of Aqueous Extracts

This paper presents a reliable dataset on formation water salinity (mineralization) and salt composition for low-permeable (tight) shale rocks of the Bazhenov, Achimov and Georgiev formations for the first time. The data were obtained via laboratory analysis of aqueous extracts from rock samples before and after hydrocarbon extraction (cleaning). Thermodynamic modeling of the obtained solutions with a number of minerals was carried out and a correlation analysis of the Na/Cl, Ca/SO4, Mg/SO4, Ca/Cl, Ca/HCO3, and Fe/SO4 ratios was performed. It was established that the concentrations of certain macro-components, including Ca, Mg, Fe, hydrocarbonate, and sulfate ion in pore water cannot be reliably determined using aqueous-extract data, while at the same time, a reliable estimate of the minimal formation water salinity could be made. The need to use non-extracted core samples with the maximum preserved residual water saturation to study a pore water composition of tight shale rocks is shown.

Saltwater Intrusion Modifies Microbial Community Structure and Decreases Denitrification in Tidal Freshwater Marshes

Environmental changes can alter the interactions between biotic and abiotic ecosystem components in tidal wetlands and therefore impact important ecosystem functions. The objective of this study was to determine how saltwater intrusion affects wetland nutrient biogeochemistry, with a specific focus on the soil microbial communities and physicochemical parameters that control nitrate removal. Our work took place in a tidal freshwater marsh in South Carolina, USA, where a 3.5-year saltwater intrusion experiment increased porewater salinities from freshwater to oligohaline levels. We measured rates of denitrification, soil oxygen demand, and dissimilatory nitrate reduction to ammonium (DNRA) and used molecular genetic techniques to assess the abundance and community structure of soil microbes. In soils exposed to elevated salinities, rates of denitrification were reduced by about 70% due to changes in the soil physicochemical environment (higher salinity, higher carbon:nitrogen ratio) and shifts in the community composition of denitrifiers. Saltwater intrusion also affected the microbial community responsible for DNRA, increasing the abundance of genes associated with this process and shifting microbial community composition. Though rates of DNRA were below detection, the microbial community response may be a precursor to increased rates of DNRA with continued saltwater intrusion. Overall, saltwater intrusion reduces the ability of tidal freshwater marshes to convert reactive nitrogen to dinitrogen gas and therefore negatively affects their water quality functions. Continued study of the interrelationships between biotic communities, the abiotic environment, and biogeochemical transformations will lead to a better understanding of how the progressive replacement of tidal freshwater marshes with brackish analogues will affect the overall functioning of the coastal landscape.

Pore water salinity effect on the intrinsic compression behaviour of artificial soft soils

The framework of the intrinsic compression behaviour of normally consolidated soft clay proposed by Burland (1990) is widely adopted in engineering practices. However, further investigations should be conducted on its validity in the coastal and offshore environments to verify the effect of pore water salinity. In the present work, oedometer tests were performed on remoulded artificial soft clays (mixtures of kaolin and bentonite with 0%, 5%, 10%, and 20% of bentonite by mass). The artificial clays were salinized with sodium chloride solutions at concentrations 0 mol/L (distilled water), 0.17 mol/L, 0.51 mol/L, 0.86 mol/L, and 1.70 mol/L at water contents equal to 1.0–1.5 times of the liquid limits. The results showed that the ‘intrinsic’ properties of clays, including the compression index Cc⁎(100–1000 kPa), void ratio e100*, and compression line based on the void index Iv, changed with the pore water salinity. Following the empirical correlation proposed by previous researchers, the decrease in Cc⁎ caused by pore water salinity could be generally characterised by the liquid limit and void ratio at the liquid limit (eL). The dispersed correlation between the predicted e100⁎ and the experimental results in this study were caused by the significant changes in e0/eL controlled by pore water salinity. The relationships between void index Iv and vertical stress σv’ deviated from the intrinsic compression line (ICL) under the saline environment. For the artificial clay rich in smectite, the slopes of Iv–log σv’ before yielding increased with pore water salinity at the initial water content. Pore water salinity affected the intrinsic compression behaviour of soft clays primarily composed of kaolinite to a lesser extent.

Hydro-geochemical characteristics of the groundwater resources in the southern part of the Red River’s Delta plain, Vietnam

In this study, the origin and recharge areas as well as the chemistry of the groundwater in the southern part of the Red River Delta plain, in Thai Binh, Nam Dinh and Ninh Binh provinces (North Vietnam) was investigated by using isotopic techniques combined with geochemical analysis. Groundwaters under the study were those that are available in the Holocene, Pleistocene, Neogene and Triassic aquifers. Groundwater in the Holocene aquifer is brackish of Na–Cl type with an electric conductivity as high as up to 6000 µS cm−1. The water in the shallow aquifer comprises three end-members: the local precipitation, Red River’s water and intruded seawater. Groundwater in the Pleistocene, Neogene and Triassic aquifers in the Southwest of the study region is fresh containing less than 1 g L−1 of total dissolved solids and is characterized by the Ca–Na–HCO3 type. However, groundwater in the deep aquifers in the Northeast area is brackish of Na–Ca–Cl–HCO3 ion type containing more than 1 g L−1 TDS. The chemistry of groundwater in the study region is controlled by three processes, namely the incongruent dissolution of the biogenic high Mg-calcite, the reduction of sulphate and iron oxyhydroxide with organic matters present in the aquifers. The salinity in deep aquifers in the NE was attributed to the diffusion of saline pore water from aquifer or/and aquitard deposits to the recharge water. Groundwater in the Pleistocene, Neogene and Triassic aquifers in the study region seem to have meteoric origin with long traveling time and it mixed with the saline pore water that migrated from the aquifers sediments, as it was evident from the water isotopic compositions. The isotopic compositions of water (δ2H and δ18O) in the Neogene and Triassic aquifers are similar to that found in the Pleistocene aquifer suggesting the aquifers are hydraulically connected to each other due to the over-extraction rate of fresh water from the latter aquifer. Recharge area of groundwater in the Pleistocene and Neogene aquifers is suggested to be from the NW extension of the region and out crops at a highland at an altitude of 140–160-m above sea level (masl). The recharge water flows from northwesterly towards southeasterly to the sea coast. The results of the 14C-dating for groundwater combined with the hydraulic heads distribution in the deep aquifers revealed that the saline groundwater is flowing from the NE and backwards from the sea side to the production well field in the center of the region due to the high rate of groundwater mining. In order to mitigate the saltwater intrusion and avoid deterioration of the quality of the groundwater that is currently being mined and supplied to the local population, it needs to develop and implement an appropriate strategy for the groundwater resource management in the region.

The coupled effect of salt precipitation and fines mobilization on CO2 injectivity in sandstone

AbstractAppreciable CO2 injectivity is required to inject large volumes of CO2 through a minimum number of wells. In situ geochemical CO2‐brine‐rock reactions may dissolve sandstone rock minerals, and consequently release fine particles into the pore fluid. If the fine particles (‘fines’) are mobilized during CO2 injection, well injectivity could be severely impaired. The transport of fines under CO2 injection conditions involves the complex multiphase flow of dry supercritical CO2, saline formation brine, and fine particles. While transported fines could plug narrow pore channels, the saline pore water could be vaporized by supercritical CO2 to precipitate solid salt into the pores. To understand the impact of mineral dissolution on CO2 injectivity, it is important to consider the coupled effect of fine particle mobilization and salt precipitation. We conducted core‐flood experiments and theoretical modelling to investigate the coupled effect of the fines mobilization and salt precipitation on CO2 injectivity. We found that salt precipitation could increase CO2 injectivity impairment induced by the fines mobilization. The deposited salt reduces the flow area, making the pores more susceptible to particle entrapment. Injectivity impairment increased with decreasing initial rock permeability and increasing saturating brine salinity. Irreducible brine saturation and pore size distribution were identified as parameters that strongly determine the contribution of salt precipitation during the transport of fines. Injectivity impairment was also slightly higher when the rock was first exposed to salt precipitation, before the entrapment of fines. The current findings highlight the complexity and uniqueness of fines transportation under CO2 injection conditions and the impact of mineral dissolution on CO2 injectivity. © 2018 Society of Chemical Industry and John Wiley &amp; Sons, Ltd.

Composition of Pore Solutions. A Study Using the Indirect Method of Water Extracts

We have compared quantitative characteristics of the macro- and microcomponent composition of pore solutions in bottom sediments obtained by their direct analysis and those calculated on the basis of the composition of water extracts taking into account water content of the samples. In the result of the study it was shown that the method of water extracts may be used to determine salinity and chemical composition of natural pore waters in low-permeable argillaceous deposits with different lithification rates. It was also shown that an analysis of water extracts does not allow determining the exact composition of the natural pore solution, but may be used for the evaluation (within the measurement error) of chlorine, sodium, and bromine content.

The water extracts method as the possible method of the pore solutions’ composition investigation

The quantitative characteristics of the macro- and micro-component composition of the pore solutions of the see bottom sediments according to the direct analysis and the calculations from the water extracts are presented. The conclusion about the possibility of the water extracts method using to determine the salinity and chemical composition of the nature pore waters of the low permeable clay deposits of the different lithification stages was made. It was found that the water extracts solutions does not allow to accurately determine the composition of the natural pore solution, but its make it possible to estimate the content of chlorine, sodium and bromine within the error of the determination.

Climate drivers of Zizaniopsis miliacea biomass in a Georgia, U.S.A. tidal fresh marsh

AbstractTidal fresh marshes are at least as productive as nearby salt marshes, but much less is known about controls on primary production in tidal fresh vs. salt marshes. We studied a tidal fresh marsh in Georgia, U.S.A., dominated by the C3 grass Zizaniopsis miliacea. We documented seasonal variation in Z. miliacea above‐ground biomass and below‐ground macro‐organic matter over 1 yr, and annual variation in end‐of‐season aboveground biomass over 15 yr in creekbank and midmarsh zones. Aboveground biomass showed a distinct peak in July and October. Belowground macro‐organic matter was much greater than aboveground biomass and peaked in October. Overall productivity was similar to that of salt marshes downstream. Z. miliacea end‐of‐season above‐ground biomass showed a classic hump‐shaped “subsidy‐stress” relationship with plot elevation, but on average the creekbank supported about twofold more above‐ground biomass than the midmarsh, and both zones varied in biomass about 1.7‐fold among years. Annual variation in above‐ground biomass was negatively correlated with maximum and mean temperature in both zones, and positively with river discharge in the creekbank zone. Sea level, precipitation and water column salinity showed biologically plausible trends with respect to biomass. The responses of Z. miliacea to abiotic drivers were muted compared with the responses of nearby salt marshes dominated by Spartina alterniflora. Temperature was more important for Z. miliacea, whereas drivers of porewater salinity were more important in the salt marsh. Likely future changes in temperature, precipitation, and river discharge may pose a threat to the high productivity of tidal fresh marshes.