Function Of Salinity Research Articles

Estimation of net accumulation and removal of fluorescent dissolved organic matter in different Baltic Sea water masses

This study aimed to detect non-conservative processes that affect the distribution of fluorescent dissolved organic matter (FDOM) in the Baltic Sea. An extensive data set comprised of 408 FDOM data, optical and physical profiles, and the development of a water masses balance model allowed us to ascertain the sources of mixing anomalies. These were seen as second-order deviations in the FDOM distribution as a function of salinity in three layers: surface water, Baltic Sea Winter Water, and deep water. The difference between modeled and measured FDOM values at three different excitation/emission wavelengths allowed to show the strength of non-conservative processes, such as photochemical and microbial decomposition (negative residual values) or extracellular release of dissolved organic matter from phytoplankton, heterotrophic uptake and release from anoxic sediments (positive residual values). Humic-like FDOM fractions displayed positive residuals in all seasons for intermediate and deep layers and negative residuals in surface waters. Largest accumulation rates of humic-like fractions were reached in the Gulf of Gdańsk during summer in intermediate and deep layers, while the greatest removal in surface waters was observed during spring in the Bornholm and Gotland Basins and during summer in the Gulf of Gdańsk, probably due to photodegradation. Positive residuals of the protein-like fraction were observed at the surface in summer and autumn in the Gulf of Gdańsk, probably linked to the abundance of phytoplankton and also due to the low molecular weight by-products of photodegradation of humic-like components. Spatial transects revealed an increase in humic-like residuals with depth and a strong correlation with apparent oxygen utilization, increasing with higher fluorescence and exhibiting an asymptotic trend. A relationship was found between the protein-like fractions and phytoplankton biomass proxies. A generalized concept for FDOM cycling in the Baltic Sea was proposed, highlighting photobleaching as the dominant non-linear process determining the efficiency of humic-like FDOM removal. The protein-like component was found to be more efficiently taken up by aerobic prokaryotes at the surface. Microbial utilization and reworking of organic matter, release from sediments, and a decade-long stagnation of bottom water masses, all contribute to the observed accumulation of FDOM in mesohaline deep waters below the permanent pycnocline in the Baltic Sea.

The Impact of Glucose-induced Priming on Nutrients Accumulation and Certain Primary Attributes of Brassica napus L. Under the Saline Regimes

In the present study, the response of primary attributes (seedling growth, percent emergence, seedling fresh and dry biomass, and seedling moisture contents) and nutrient contents (Calcium, Magneisum, Iron, Manganese, Zinc, Copper) of Brassica napus L. was evaluated as a function of glucose-induced priming and salinity. The priming comprised 30 minutes, 60 minutes and 90 minutes of seeds soaking in glucose solution (0.50 M) and salinity stress was simulated by the solutions of 0, 15, 18, 21, and 24 milli Molar (mM) NaCl. The results revealed that doses of salinity induced significant changes in the fresh weight of Brassica napus L. The response of selected nutrients (except Magnesium) as a function of salinity was also highly significant (P≤0.05 %). The salinity doses reduced plants' mineral contents (except Mn) compared to control. The priming of seeds for 90 minutes significantly (P≤0.05 %) enhanced certain early growth traits (plumule growth, radical growth, fresh weight and dry weight) of Brassica napus. On the other hand, for improving germination (%) and moisture contents (%) of Brassica napus, soaking durations of 30 minutes and 60 minutes are more suitable. The pre-soaking of seeds for 60 minutes increased the Calcium, Magnesium and Manganese contents (mg/litre) of Brassica napus. The Iron and Zinc contents (mg/litre) showed hype in seedlings raised from seeds primed for 30 minutes. The priming of seeds for 90 minutes was found to be stimulatory for Copper (mg/litre) only. The influence of factors interaction (treatments × priming durations) on the initial growth attributes and the studied minerals of Brassica napus L. was highly significant (P≤0.05 %). From the gathered evidence, the present study concludes glucose as a potent priming agent that can boost oil-yielding plants' performance under saline conditions.

Magnetotelluric images of the medium enthalpy Bakreswar geothermal province within a granitic gneissic complex, Eastern Indian Peninsula

AbstractThe Bakreswar geothermal province represents a medium enthalpy geothermal system with its Bakreswar and Tantloie hot springs. It lies within the Chotanagpur Granite Gneissic Complex in the eastern part of the Indian Peninsula. The province has a high heat flow and a high geothermal gradient of 90°C/km. Magnetotelluric data from 95 sites in a frequency range of 10 kHz–10 Hz were acquired over the Bakreswar geothermal province to obtain an electrical conductivity model and map the geothermal reservoir with its fluid pathways and related geological structures. Subsurface conductivity models obtained from three‐dimensional inversions of the Magnetotelluric data exhibit several prominent anomalies, which are supplemented by gravity results. The conductivity model maps three features which act as a conduit (a) a northwest–southeast trending feature, (b) an east–west trending feature to the south of the northwest–southeast trending feature (which lies 1 km north of the Oil and Natural Gas Corporation fault marked by previous studies) and (c) shallow conducting features close to Bakreswar hot spring. The northwest–southeast trending feature coincides with the boundary of the high‐density intrusive block. This northwest–southeast trending feature provides the pathway for the meteoric water to reach a maximum depth of 2.7 km, where it gets heated by interacting with deep‐seated structures and then it rises towards the surface. The radiogenic process occurring within the granites of Chotanagpur Granite Gneissic Complex provides the heat responsible for heating the meteoric water. The northwest–southeast and east–west trending features are responsible for the transport of meteoric water to deeper depths and then towards the shallow regions of the Earth. The near surface features close to the Bakreswar hot spring are responsible for carrying the water further towards the hot spring. The resistivity of these structures plotted as a function of salinity and temperatures for saline crustal fluids suggests the involvement of meteoric water. Further, applying Archie's law to this resistivity suggests that the conduit path has a porosity greater than 10%. This study successfully maps the anomalous structures which might foster the migration of geothermal fluid in Bakreswar geothermal province.

Transport Properties of NaCl in Aqueous Solution and Hydrogen Solubility in Brine.

Ion transport properties and hydrogen solubility in brine play pivotal roles in various engineering and scientific scopes including chemical, physical, geochemical, and geothermal domains. Molecular dynamics simulations were performed to obtain transport properties of NaCl in the binary H2O + NaCl system using different force fields. Brine density, ion diffusivity, molar conductivity, conductivity, and hydrogen solubilities were obtained as functions of temperature and salt concentration. We compared the performance of different force fields against the experimental correlation model and developed three mathematical models. The first was the modified brine density model based on the simulated brine density over a wide range of salinity levels, and the second and third analytical mathematical models were derived for the ion diffusivity and molar conductivity as a function of salinity and temperature. The results of this study illustrated that the modified brine density model not only produced the same results of the previous model for lower salinity levels but also applied well to predict the brine density for a higher salinity level. The derived mathematical models indicated that the ion diffusivity and molar conductivity decreased linearly with salinity, and the slope and y-intercept of the lines of diffusivity and molar conductivity versus temperature were third-order polynomials of temperature. The developed models provided the mechanism for the behavior of decreasing molar conductivity with increasing salinity and increasing conductivity with increasing salinity. The directions of the effect of salinity on the molar conductivity and conductivity were opposite. The molar conductivity increased with a decreasing salinity level. However, the conductivity increased with increasing salinity, as the contribution of the ion concentration or salinity level to conductivity dominated over that of the ion movement.

Intraregional variability of exotic and native zooplankton in Basque coast estuaries (inner Bay of Biscay): effect of secondary dispersion, estuary features and regional environmental gradients

The zooplankton of five estuaries of the Basque coast (southeast Bay of Biscay) was surveyed in summer 2019 to check the intraregional spread of exotic species and analyse the cross-estuary differences in brackish and neritic communities related to the arrival of exotic species and the summertime geographic gradient of water temperature. Results revealed that all the studied estuaries have been colonized by Oithona davisae but not by Acartia tonsa and Pseudodiaptomus marinus. Environmental constraints due to estuarine hydrological features partly explained such differences, and the role of secondary spread opportunities remained less clear. Cross-estuary differences in the brackish community mainly reflected changes in the dominance of the native species Acartia bifilosa relative to different exotic copepod species. The neritic holoplankton differed in the contribution of thermophilic species in agreement with the thermal west–east increase of surface water temperature in the inner Bay of Biscay in summer. The detection of large numbers of larvae of the exotic crab Rhithropanopeus harrisii only in one of the estuaries highlighted the role of exotic benthic species in enhancing intraregional differences in estuarine meroplankton. Differences in the dominance of neritic or brackish species as a function of salinity and distance from coastline were also explored.

Synthesis and molecular dynamics simulation of amphoteric hydrophobically associating polymer

To address the practical issues of poor temperature and salt tolerance of polymers, a new amphoteric monomer (E)-N-(docos-13-enoyl)-N-methylglycine named CQ was developed. The polymer CQMP was synthesized by acrylamide (AM) and CQ as an associative monomer and sodium p-styrene sulfonate (SSS) as a functional monomer in aqueous solution. The structure of the products was confirmed by FTIR, 1H NMR and TGA, while the micro-morphology of the polymer was observed by SEM. Taking HAPAM as a control, the properties of polymer in aqueous solution were studied as a function of salinity, shear rate, temperature, and polymer concentration. The oil displacement performance was also evaluated in detail. Additionally, the surface tension (SFT) and interfacial tension (IFT) of CQMP solution were measured. The critical micelle concentration (CMC) values of CQMP in aqueous solution and in NaCl solution are 2.13 g·L-1 and 1.79 g·L-1,respectively. The copolymer can reduce the interfacial tension between water and crude oil from Changqing Oilfield, with an IFT value of about 15.96 mN·m−1. The results indicate that the critical association concentration (CAC) is approximately 600 mg·L-1, and the polymer exhibits good salt tolerance and oil flooding performance. Furthermore, molecular dynamics simulation demonstrated that CQ can enhance intermolecular interactions while maintaining the same hydrophobic chain content, thereby reinforcing the polymer’s resistance temperature and salt. The laboratory flooding experiment showed that the enhance oil recovery of CQMP with 0.5 PV 3000 mg·L-1 was 12.23 % greater than that of HAPAM, which is promising for multiple applications in complex oil fields.

The impact of LNG offshore terminal on sea temperature and sea currents in the northern Adriatic Sea

The aim of this paper is to simulate the impact of a potential offshore LNG terminal on sea temperature (in autumn and spring/ summer) and sea currents (in autumn/winter) at three different depths (at the sea surface, at 25 m depth and at the seabed) in the northern Adriatic Sea from 14 November 2015 to 06 August 2016 using the Regional Ocean Modelling System (ROMS) model. The location of the potential offshore LNG terminal Istria (in the northern Adriatic Sea) was selected using the visual PROMETHEE method. The potential LNG terminal uses seawater for LNG heating and the seawater cooled to a temperature of 9°C returns to the marine environment. Although the differences in sea temperature with and without the discharge fit within normal temperature ranges, the simulations show that the discharge changed the speed and direction of sea currents at the sea surface not only in the wider northern Adriatic, but in the entire Adriatic. This is probably due to the specific circulation in the Adriatic, where cold water affects the geostrophic balance, an important part of the circulation field that depends on density (a function of salinity and temperature). Atmospheric conditions in the broader vicinity of the LNG terminal would also be affected by redistribution of air-sea fluxes due to changes in surface temperature. Changes in circulation would alter environmental conditions by redistributing nutrients, oxygen, etc. Further multi-year simulations of changes in the circulation system are needed, but other physical parameters (density, salinity, river inflow...) should also be included in the simulations to determine the cumulative impact of a potential LNG terminal on the marine environment.

Effect of salinity, mineralogy, and organic materials in hydrogen wetting and its implications for underground hydrogen storage (UHS)

Hydrogen is a green energy carrier, which appears to reshape the current energy supply chain. To develop a full-scale hydrogen supply chain, underground hydrogen storage has been proposed as a key method. However, one of the key hurdles in UHS is the fluid-rock interactions or hydrogen wetting. The interfacial reactions govern hydrogen wetting in underground reservoirs and thus determine the hydrogen flow and govern the amount of hydrogen trapping in porous media. Although the hydrogen wetting has been gaining attention, how the hydrogen wetting behaves in complicated underground circumstances remains in the shadow.To understand the nano-scale character of hydrogen wetting, a series of molecular dynamics (MD) simulations were performed to analyse the hydrogen distribution on kaolinite surface in function of salinity, mineralogy, and organic materials. We computed density distribution and the radial distribution function (RDF, g(r)) of each species. The results show that salinity can dramatically affect hydrogen distribution on the siloxane surface while negligible effects can be observed on aluminol (gibbsite) surfaces of kaolinite. Furthermore, the hydrogen distribution can be notably shaped by organic materials. Organic materials with acid functional group (–COOH) can generate a more hydrogen wetting surface than base functional group (–NH). This investigation reveals the governing mechanics of hydrogen-brine-kaolinite reactions at molecular scale, unravels the effects of hydrogen-brine-kaolinite reactions in hydrogen wetting and thus provides a paradigm to screen candidate sites for the UHS.

A laboratory study on the behavior of estuarine sediment flocculation as function of salinity, EPS and living algae

The interactions between organic and inorganic particles in the context of flocculation is an on-going topic of research. Most current researches do not distinguish between the effects of EPS (produced by microorganisms) and living microorganisms (like algae). In this study, the effect of salinity, EPS and living algae on sediment flocculation are investigated separately. Several types of measurements were performed, which can be divided into the following categories: sediment at different salinities, sediment in the presence of EPS at different salinities, sediment in the presence of living algae at a given salinity. Results show that increasing salinity enhances slightly sediment flocculation. In the presence of EPS there was hardly any flocculation in demi-water, but the flocculation was significant in saline water. The living algae cells were shown to flocculate with themselves and form large flocs. These algae flocs can bind to sediment particles to form larger flocs, both in demi-water and sea water. Size-wise algae-sediment flocs were largest, EPS-sediment flocs came second, and salt-sediment flocs were smallest.

Sodium incorporation in foraminiferal calcite: An evaluation of the Na/Ca salinity proxy and evidence for multiple Na-bearing phases

The ratio of sodium to calcium (Na/Ca) in foraminiferal calcite has been proposed as a proxy for salinity, yet relatively little is known about the incorporation of sodium into the shells of foraminifera. Ongoing debates include the location of Na in the calcite crystal lattice, the possibility that at least some Na might be complexed with organics, and the influence of spines/spine bases. We present new Na/Ca measurements, determined using both solution and laser ablation ICP-MS, of the planktonic foraminifera Globigerinoides ruber (white) from plankton tows and sediment traps spanning a wide salinity range (32.5–40.7 salinity units), laboratory cultures under varying carbonate chemistry, and globally-distributed core-top samples. Our results show that Na/Ca in recently living foraminifera measured by laser ablation ICP-MS is elevated by up to 5 mmol/mol (∼85%) relative to the same samples measured by solution ICP-MS (the same comparison for Mg/Ca shows excellent agreement between the techniques). Na/Ca in recently living foraminifera measured by laser ablation ICP-MS displays a significant relationship with salinity above ∼36 salinity units with a slope of ∼0.7 mmol/mol/salinity unit; however, only a weak relationship is observed between salinity and Na/Ca measured by solution ICP-MS. We propose that Na is incorporated in at least two discrete phases; a primary phase within the CaCO3 mineral, and a (or likely multiple) secondary phase(s). Possibilities for these secondary phases include residual metastable CaCO3, fluid inclusions, high Na/Ca spine bases, and organics. These secondary phases contribute to spatially-resolved analyses (i.e. laser ablation ICP-MS) of recently living foraminifera but are removed by crushing/oxidative cleaning for solution ICP-MS, and during early diagenesis, as evidenced by the agreement between laser analysis of coretop samples and Na/Ca measured by solution. The amount of one of these secondary phases, or the amount of Na within this phase, appears to vary as a function of salinity, and is likely the principal driver of the previously observed steep Na/Ca-salinity relationship in recently living foraminifera analysed by laser ablation. Overall, we find salinity, temperature, carbonate chemistry, and bottom water saturation state (Ωcalcite) all have a significant but relatively weak effect on Na/Ca in the primary calcite phase. As such, Na/Ca in planktonic foraminifera recovered from sediment cores is unlikely to find widespread utility as a salinity proxy.

Habitat and abundance of cetaceans in Atlantic Ocean continental slope waters off the eastern USA

This study quantifies the abundance and spatial distribution of the cetacean community occupying continental shelf edge and inner continental slope waters along the US southeast Atlantic coast. A shipboard visual line-transect survey was conducted between June and August of 2004 that included effort in waters >50m deep encompassing the shelf break and inner continental slope off the US east coast between 28°N and 38°N latitude. The abundance of nine cetacean taxa was estimated using line-transect distance analysis and an independent observer approach to correct for visibility bias. Canonical correspondence analysis was used to examine the spatial distribution of the cetaceans encountered during the survey as a function of surface temperature, surface salinity, surface fluorescence, bottom depth, and bottom slope. The abundance estimates for most species were much higher than those from a study of the area conducted in 1998. This is primarily due to increased coverage of the shelf-break region and correction for visibility bias. The multivariate analysis indicated four distinct groups of cetaceans that partitioned habitat as a function of salinity, depth, and a latitudinal gradient. These groups were associated with specific water masses and hydrographic features including mid-Atlantic shelf waters (Group I), the shelf break (Group II), mid-Atlantic slope waters (Group III), and south Atlantic slope water (Group IV). Areas where water masses converge such as the continental shelf break along the mid-Atlantic and near Cape Hatteras, North Carolina are therefore areas of both high diversity and density of cetaceans.

DISCOVR strain pipeline screening – Part I: Maximum specific growth rate as a function of temperature and salinity for 38 candidate microalgae for biofuels production

To identify high productivity strains for microalgal biofuels generation, the maximum specific growth rate of 38 strains was measured as a function of salinity (i.e., 5, 15, and 35 PSU) and temperature (i.e., at 8 temperatures along a linear gradient from ca. 5 to 45 °C) to determine the most suitable growth medium salinity and best growing season, respectively, for outdoor raceway pond cultivation. The following strains were evaluated: Agmenellum quadruplicatum UTEX 2268, Anabaena sp. ATCC 33081, Arthrospira fusiformis UTEX 2721, Arthrospira platensis UTEX 3086, Chlorella vulgaris NREL 4-C12, Chlorella autotrophica CCMP 243, Chlorella sorokiniana DOE1044, Chlorella sorokiniana DOE 1116, Chlorella sorokiniana DOE 1412 (UTEXB3016), Chlorella vulgaris LRB AZ-1201, Chlorococcum littorale UTEX 117, Chlorococcum sp. UTEX-B P7, Chloromonas reticulata CCALA 870, Coelastrella sp. DOE 0202, Cyanobacterium sp. AB1, Micractinium reisseri NREL 14-F2, Microchloropsis gaditana CCMP1894, Microchloropsis salina CCMP 1776, Monoraphidium sp. MONOR1, Monoraphidium minutum 26B-AM, Nannochloropsis oceanica CCAP 849/10, Oscillatoria cf. priestleyi CCMEE 5020.1-1, Picochlorum celeri TG2-WT-CSM/EMRE, Picochlorum oklahomensis CCMP 2329, Picochlorum renovo NREL 39-A8, Picochlorum soloecismus DOE 101, Porphyridium cruentum CCMP 675, Scenedesmus acutus LRB-AP-0401, Scenedesmus obliquus DOE 0152.z, Scenedesmus obliquus UTEX393,Scenedesmus rubescens NREL 46B-D3, Scenedesmus sp. IITRIND2, Stichococcus minor CCMP 819, Stichococcus minutus CCALA 727, Synechococcus elongatus UTEX2973.1, Tetraselmis striata LANL 1001, Tisochrysis lutea CCMP 1324, and Tribonema minus UTEXB3156. For each strain, the identity and the presence of bacterial cohorts was determined using 18S and 16S rDNA sequencing, respectively. The maximum specific growth rate versus temperature data were also used to determine the activation energies (Arrhenius equation) for most strains. For all strains, the measured salinity and temperature tolerance data were compared to those reported in the literature. The fastest growing strains were down-selected for subsequent biomass productivity measurements in climate-simulation photobioreactors, as reported in the next paper in the issue.

The characteristic curvature (Cc) definition and its use in assessing Cc for single ionic surfactants

AbstractThe hydrophilic–lipophilic‐difference (HLD) is a set of empirical equations that correlate the formulation conditions at phase inversion (HLD = 0). Based on partition studies for nonionic surfactants, the HLD can be interpreted as a normalized chemical potential difference between the surfactant dissolved in water and oil. The net‐average curvature (NAC) model extrapolates this interpretation into a curvature form that has been used to fit and predict the phase behavior of surfactant‐oil–water (SOW) systems. The curvature interpretation led to renaming the HLD surfactant parameter, sigma (σ), as the characteristic curvature (Cc). This work tests the validity of the curvature interpretation of the HLD, and the Cc concept, for single ionic surfactants and the use of this concept as a method to assess the Cc without the use of reference surfactants or alcohols. To this end, the net curvature of six anionic and two cationic surfactants was evaluated from solubilization data at the characteristic condition of 25°C, no added cosolvent, in the presence of an oil mixture with equivalent alkane carbon number (EACN) of zero, and as a function of salinity. These studies showed that the original HLD equation for ionic surfactant could not be interpreted as chemical potential or curvature because a salinity prefactor (coefficient) “bi” was missing. The revised equation, HLDbi = bi∙ln(S)‐kbi∙EACN+Ccbi ‐aTbi∙(T‐25°C), could now be interpreted as a curvature expression, and it was demonstrated that Cc could be obtained from curvature using the expression Cc = Ccbi/bi. This single surfactant method produces uncertainties that, for most surfactants, ranged from 0.2 to 1 Cc units, similar to the uncertainty obtained with the conventional method of Cc determination using mixtures of test and reference surfactants.

Copper(II) hydroxide/oxide-coated granular activated carbon forE. coliremoval in water

AbstractLow-cost granular filter media with hybrid bacterial adsorption and survival inhibition capability is highly desired for the development of a low-impact water filtration system. In addition to overall removal, a deeper understanding of the fate and transport behaviour of bacteria in such systems should also be obtained to guide system operation. In this study, copper(II) hydroxide nanoparticles-modified granular activated carbon via a single-step in situ coating was prepared and denoted as CuH-G. Copper release behaviour and Escherichia coli removal efficiency of CuH-G were studied in saturated columns as a function of salinity, flow rate, and hydraulic loading. Copper release decreased exponentially on increasing salinity in test water, which potentiates controlled copper release for desired bacteria inhibition efficiency. With an effective contact time of 3.7 min, CuH-G provided 3.0 and 1.6 log E. coli removal in test water of salinity 237 and 680 μS/cm, respectively. Copper leaching at these two salinities were 1.7 and 0.74 mg/l, respectively below the Australian Guidelines for Water Recycling: Augmentation of Drinking Water Supplies. Further study of E. coli transport and deposition behaviour in heat-treated CuH-G at 160 °C revealed that the observed removal was largely attributed to enhanced attachment during filtration and survival inhibition post filtration.

Interaction between Hydrated Smectite Clay Particles as a Function of Salinity (0-1 M) and Counterion Type (Na, K, Ca).

Swelling clay minerals control the hydrologic and mechanical properties of many soils, sediments, and sedimentary rocks. This important and well-known phenomenon remains challenging to predict because it emerges from complex multiscale couplings between aqueous chemistry and colloidal interaction mechanics in nanoporous clay assemblages, for which predictive models remain elusive. In particular, the predominant theory of colloidal interactions across fluid films, the widely used Derjaguin-Landau-Verwey-Overbeek model, fails to predict the ubiquitous existence of stable swelling states at interparticle distances below 3 nm that are stabilized by specific inter-atomic interactions in overlapping electrical double layers between the charged clay surfaces. Atomistic simulations have the potential to generate detailed insights into the mechanisms of these interactions. Recently, we developed a metadynamics-based molecular dynamics simulation methodology that can predict the free energy of interaction between parallel smectite clay particles in a wide range of interparticle distances (from 0.3 to 3 nm) and salinities (from 0.0 to 1.0 M NaCl). Here, we extend this work by characterizing the sensitivity of interparticle interactions to counterion type (Na, K, Ca). We establish a detailed picture of the free energy of interaction of parallel clay particles across water films as the sum of five interaction mechanisms with different sensitivities to salinity, counterion type, and interparticle distance.

Geochemistry of uranium in the Ganga (Hooghly) River estuary, India: The role of processes in the water column and below the sediment-water interface

In this study, we discuss the cycling of uranium (U) in the Ganga (Hooghly) River estuary through investigation of the composition of the water samples of six periods of contrasting water discharge, the bulk and exchangeable phases of the coexisting suspended particulate matter (SPM) and the bed sediments. In addition, we evaluate data on urban and industrial effluent waters that drain into the estuary. Similar U concentrations of freshwaters and effluent waters do not indicate the anthropogenic source to be an important contributor of U to the estuary. The removal of dissolved U in the low-salinity zones, observed for five of six study periods, is primarily linked to the cycling of the FeMn oxyhydroxide phases. The compositions of exchangeable phases of SPM provide supportive evidence for the removal of dissolved U. Mass balance calculations show that the degree of removal of dissolved U can be sustained by the observed enhancement of exchangeable U in the SPM. Loss of U from the bed sediments is inferred from the distributions of exchangeable U concentrations as a function of salinity. Multiple observations based on compositions of the exchangeable and bulk phases of bed sediments indicate mobilization and loss of both U and Mn through suboxic diagenesis in the sediment columns followed by tidally-induced sediment resuspension.We estimate that 40–60% of riverine U is removed in the low-salinity zone during the monsoon and post-monsoon periods. More importantly, the salinity range over which U removal occurs varies between the periods of similar water discharge. The estimated U flux from the estuary is ∼70% higher in 2012 than in 2013. A significant difference between the annual U fluxes, driven mainly by considerable variation in the magnitude of U removal, suggests that estimates of meaningful annual U fluxes would require data at higher temporal resolution. This study highlights the importance of processes operating in the water column and below the sediment-water interface in the cycling of U in the Hooghly River estuary, where the solute-particle interaction driven by high SPM load is known to influence the cycling of trace metals.

Photosynthetic, Respirational, and Growth Responses of Six Benthic Diatoms from the Antarctic Peninsula as Functions of Salinity and Temperature Variations.

Temperature and salinity are some of the most influential abiotic parameters shaping biota in aquatic ecosystems. In recent decades, climate change has had a crucial impact on both factors—especially around the Antarctic Peninsula—with increasing air and water temperature leading to glacial melting and the accompanying freshwater increase in coastal areas. Antarctic soft and hard bottoms are typically inhabited by microphytobenthic communities, which are often dominated by benthic diatoms. Their physiology and primary production are assumed to be negatively affected by increased temperatures and lower salinity. In this study, six representative benthic diatom strains were isolated from different aquatic habitats at King George Island, Antarctic Peninsula, and comprehensively identified based on molecular markers and morphological traits. Photosynthesis, respiration, and growth response patterns were investigated as functions of varying light availability, temperature, and salinity. Photosynthesis–irradiance curve measurements pointed to low light requirements, as light-saturated photosynthesis was reached at <70 µmol photons m−2 s−1. The marine isolates exhibited the highest effective quantum yield between 25 and 45 SA (absolute salinity), but also tolerance to lower and higher salinities at 1 SA and 55 SA, respectively, and in a few cases even <100 SA. In contrast, the limnic isolates showed the highest effective quantum yield at salinities ranging from 1 SA to 20 SA. Almost all isolates exhibited high effective quantum yields between 1.5 °C and 25 °C, pointing to a broad temperature tolerance, which was supported by measurements of the short-term temperature-dependent photosynthesis. All studied Antarctic benthic diatoms showed activity patterns over a broader environmental range than they usually experience in situ. Therefore, it is likely that their high ecophysiological plasticity represents an important trait to cope with climate change in the Antarctic Peninsula.

Comprehending the role of different mechanisms and drivers affecting the sea-surface pCO2 and the air-sea CO2 fluxes in the Bay of Bengal: A modeling study

We apply a coupled physical and biogeochemical (ROMS+PISCES) to understand the influence of distinct drivers and mechanisms on the sea-surface pCO2 and the air-sea CO2 flux of the Bay of Bengal (BoB). The model evaluation suggests that the model simulated sea-surface pCO2 is in accord with the observations. The north of BoB is found to be a sink for the atmospheric CO2, whereas the rest of the region acts as a source. The effect of dissolved inorganic carbon (DIC) and the total alkalinity (TALK) is found to be predominant but is contrasting in nature. Mixing-induced changes in DIC and TALK results in high pCO2 (+570μatm) and, consequently, the positive CO2 flux. The biological activity does draw down the surface pCO2 (−120μatm) but is insufficient in completely opposing the effect of mixing. The uptake of CO2 in the north is due to the CO2 solubility, which is a function of salinity and temperature. The northern rivers, having a high discharge rate, reduce the salinity and temperatures in the north, which possibly aids in this region to be a sink. In the northeast monsoon season, the impact of temperature and DIC is high and opposing. The TALK reduces the pCO2 in the northeast monsoon, but the magnitude is low. The pCO2 in the southwest monsoon is influenced primarily by temperature, whereas in the postmonsoon monsoon, the freshwater dominates. The pre-monsoon season experiences the TALK, temperature, and freshwater increase the pCO2 anomalies, and only the DIC reduces pCO2 anomalies.

Hydroponic cultivation of coriander intercropped with rocket subjected to saline and thermal stresses in the root-zone

An experiment was carried out in a randomized blocks design, aiming at evaluation of the cultivation of coriander intercropped with rocket subjected to saline and thermal stresses in the root-zone. Six treatments were evaluated, as follows: four treatments consisted of the combinations of two levels of electrical conductivity of water (ECw 0.3 and 6.5 dS m-1) with two root-zone temperatures - RZT (ambient: < 25 °C and constant at 30 °C). The respective waters were used to prepare the nutrient solution and to replenish the water consumed. In the other two treatments the cultivation was performed at ambient RZT, one with 0.3 dS m-1 level used to prepare the solution and 6.5 dS m-1 level to replenish the consumption, and other with 6.5 dS m-1 level used to prepare the solution and 0.3 dS m-1 level to replenish the water consumed. Plant height, stem diameter, water content in shoot, fresh and dry matter of shoot, and tolerance index of saline and thermal stresses were evaluated. The coriander was more tolerant to combined stresses than the rocket. For the isolated stresses, there was a greater reduction in the production of both crops as a function of salinity than by thermal stress.

H2−brine interfacial tension as a function of salinity, temperature, and pressure; implications for hydrogen geo-storage

Hydrogen as a clean fuel source compared to hydrocarbons has attracted many attentions to mitigate anthropogenic greenhouse gas emissions and meet global energy demand. However, high volatility and compressibility of hydrogen make a challenge for its storage. In this regard, the surface-based hydrogen storage facilities (e.g. aerospace, cryogenic tanks, high-pressure gas cylinders, etc.) have been in operation for decades. Moreover, H2 geo-storage is an effective way to store vast volume of hydrogen in deep underground formations where it can be withdrawn again to generate energy when the need arises. The interaction between the injected hydrogen and resident formation fluids (e.g. water), can strongly influence the H2-flow pattern and storage capacity. In this regard, interfacial tension (γ) between hydrogen and brine is a key parameter that influences hydrogen displacement within the geological porous medium. As there is a serious lack of literature on this important subject, we measured H2-brine interfacial tension at various geo-storage conditions for a wide range of pressure, temperature, and brine salinity, using the pendant drop technique. The results of the study indicate that γ declined linearly with increasing pressure when temperature and salinity are kept constant. Moreover, a linear reduction in γ with increasing temperature was observed under constant salinity and pressure conditions. The results also clearly demonstrate that γ increased linearly with brine molality over the whole range investigated. An empirical equation was also developed with which γ as a function of pressure, temperature, and brine molality can be predicted. The predictions for data points of this work had a maximum deviation of 2.13% from the experimental data. This work thus provides fundamental data for H2 geo-storage projects, and aids in the implementation of an industrial-scale hydrogen economy.