Brackish Water Layer Research Articles

Carbon dioxide sequestration in brackish water: Principles, techniques and environmental benefits

Carbon dioxide storage is a technology to separate carbon dioxide gas from the atmosphere and inject it into the brackish water layer to achieve the purpose of carbon dioxide emission reduction. In this way, carbon dioxide is dissolved in salt water and then sequestered in deep underground water layers, preventing it from being released into the atmosphere and causing a greenhouse effect. This technology can effectively reduce carbon dioxide emissions, but also can use geological structures for storage, has great potential application prospects. It is important to note that further research and practice is needed to address possible environmental risks and costs.

Changes in the salt concentration distribution in surface water (seawater) due to seawater recirculation in a porous medium under tidal fluctuations

Many studies have used numerical simulations and experiments to simulate saltwater intrusion in a nearshore aquifer. Thus, it is known that seawater recirculation occurs in a porous medium just below a sloping beach, and a saltwater wedge occurs in the medium below where the slope intersects the water level at low tide. This study investigated the salt distribution in the surface water when subterranean recirculation of seawater is occurring and there is a saltwater wedge in an underlying porous medium, along with the relationships between the seawater recirculation and the tidal amplitude and beach gradient. The salt distribution in a subterranean aquifer and in surface seawater where the shore sloped gently seaward with a constant slope of 1/10 or 1/5 under tidal amplitudes of 0.5, 1.0, or 2.0 m was numerically simulated by the ASGMF method, which couples water pressure and water flow in a porous medium with those in the overlying surface water and can simulate variable-density flows and the salt concentration distribution in both the porous medium and the surface water. The results showed that the recirculation of seawater depended on the tidal amplitude, being greater when the amplitude exceeded 1.0 m, but that it was unlikely to occur when the beach gradient was steep. Thus, the aspect ratio (width to depth) of the seawater recirculation decreased as the tidal amplitude increased above 1.0 m. Furthermore, the simulated surface water level was often lower than the tidal water level; thus, the surface water level was not consistent with the tidal water level imposed at the right boundary of the simulation domain but varied slightly under the influence of water flow in the surface water and gas flow in the atmosphere. The salt concentration in the surface water was not always the same as the seawater salt concentration because a thin freshwater layer and a brackish water layer of mixed freshwater and saltwater overlay the seawater.

Interannual variability in mesoscale distribution of Dinophysis acuminata and D. acuta in Northwestern Patagonian fjords

Dinophysis acuminata and D. acuta, which produce diarrheogenic toxins and pectenotoxins in southern Chile, display site-specific differences in interannual variability (2006 – 2018) in Reloncaví, Pitipalena and Puyuhuapi fjords (41 – 46 °S), Chilean Patagonia. Linear Models show decreasing trends in rainfall and river discharge. Latitudinal decreasing gradients in SST temperature and vertical salinity gradients were observed. A brackish water layer (FW salinity <11 psu), permanently present in Reloncaví, decreased in thickness with time in Pitipalena and was usually absent in Puyuhuapi, the only fjord where D. acuta reached bloom (>103 cells L‒1) densities every season. Dinophysis acuminata, associated with toxin profiles in shellfish that include only pectenotoxins, bloomed everywhere with a poleward increasing gradient. Absence of the FW layer provides a possible index of risk for D. acuta blooms. An apparent poleward shift of D. acuta populations, responsible for DSP outbreaks in Reloncaví in the 1970s, and the recent EU deregulation of pectenotoxins will have a positive impact on the mussel industry in Los Lagos Region. Changes to ongoing monitoring protocols to improve risk assessment capabilities are suggested.

Stygobitic crustaceans in an anchialine cave with an archeological heritage at Vodeni Rat (Island of Sveti Klement, Hvar, Croatia)

A group of four amphoras found in the anchialine cave of Vodeni Rat in the Croatian island of Sveti Klement, on a rocky ledge at 24 m water depth, indicates that a freshwater source was exploited at the bottom of this karstic pit by islanders and/or passing-by sailors from the late Roman Republican Period to the Early Medieval Period. In other words, prior to the 4th–7th century CE, Vodeni Rat was not an anchialine cave but a Pleistocene karstic pit with a freshwater pool at the bottom. Seawater started to infiltrate this cavity via newly opened fissures in the surrounding limestone after the 4th–7th century CE, as the archeometric age of the youngest intact amphora found down in the pit suggests. At present, the 29-m-deep water body is stratified, with a saline water layer at the bottom, a freshwater layer at the surface, and a transitional brackish water layer in the middle. Our study of the physical and biological characteristics of the cave water column revealed diversified and highly partitioned populations of stygobitic crustaceans including ostracods, copepods, amphipods, and thermosbaenaceans. Some species known to be exclusively endemic of highly saline habitats were collected from the bottom saline layer, whereas others known to be of freshwater origin were found in the upper water layer. This suggests that the freshwater dwellers were already present in this cave prior to the early medieval event that caused seepage of seawater into this karstic pit.

ГЕТЕРОТРОФНЫЙ МИКРОПЛАНКТОН ЮЖНОЙ ОКОНЕЧНОСТИ ЖЕЛОБА СВЯТОЙ АННЫ В ОСЕННИЙ ПЕРИОД (КАРСКОЕ МОРЕ)

The paper concerns the pelagic microbial community of the southern part of the St.Anna trough in the late vegetation period. in 2007 and 2011. The abundance, biomass and production of bacterioplankton, as well as the abundance and species composition of heterotrophic flagellates and ciliates were analyzed. The abundance and bacterial production values observed in the trough were significantly lower than the values typical of the surface brackish water layer above the Kara Sea shelf. The bacterioplankton abundance values of the upper warm layer in 2007 were several times lower than in 2011 (10-60*103 cells/ml and 24-147*103 cells/ml, respectively). In the deeper water layers, this difference diminished. The interannual differences in the values of bacterioplankton production were also most pronounced in the upper 60-meter layer: 0-0.17 and 0.05-0.87 mgC/m3 per day in 2007 and 2011, respectively. The distribution of the abundance of heterotrophic flagellates and ciliates is significantly influenced by the contour current along the slope of the trench. In the area of its influence in 2007, high values of the number of flagellates (154 ± 29 cells/ml) were observed throughout the water column, whereas in 2011 maximal values were confined to the upper 50-meter layer, exceeding almost twice the abundance at neighboring stations (810 ± 102 and 481 ± 61 cells/ml, respectively).The results of multifactor analysis showed that the number of heterotrophic flagellates, as well as the number of protozoan species decreased with depth. However in the euphotic layer there was a difference between two years of observations: in 2007, the abundance of consumers depended on the state of primary producers, whereas in 2011 the main factor affecting their abundance was the number of bacteria. Analysis of the species composition of heterotrophic flagellates suggests that the complex vertical hydrophysical structure of the water column does not affect substantially the microbial community of the region. However the influence of main currents of the area under consideration may be traced regarding the distribution of the abundance and species composition of heterotrophic microorganisms.

A PRELIMINARY STUDY ON AQUIFER IDENTIFICATION BASED ON GEO-ELECTRICAL DATA IN BANDA ACEH, INDONESIA

The aquifers exploration has been conducted at the western part of Banda Aceh, Indonesia. This research aims to explore the aquifer layer beneath the surface and to obtain the cross-section model of the aquifer. The Vertical Electrical Sounding (VES) method was applied to investigate the aquifer layer. The VES method worked as the current penetrated into the ground using of two electrodes and the potential response due to its current being measured by another two electrodes. Ten grid points of VES has performed in western part of Krueng Aceh of Banda Aceh using the ARES (Automatic Resistivity Meter). The Res1Dinv and curve matching computer software used in VES data processing and analysis. The result shows the resistivity value of aquifer in Banda Aceh city at the range of 1 – 12 Ωm for freshwater, and 0.1 – 0.6 for brackish water layer. The first aquifer (water table) found at a depth of 0.5 to 2 meters beneath the surface. The 2-meters water table mostly located near the coastal zone or downstream zone of Krueng Aceh basin and shallow depth of 0.5 meters on the upstream. More than one aquifer layers were found beneath the surface, they were separated by aquitard layer consisting of silt to clay layers.

Bacterioplankton of the Kara Sea shelf

The principal zones of the Kara Sea shelf are distinguished on the basis of structural and functional characteristics of bacterioplankton. Estuarine regions are characterized by elevated bacterial abundance and production rates, while the adjacent shelf has high abundance but lower production values. The southwestern part of the Kara Sea has relatively low bacterial abundance; here, the activity of microorganisms depends on the availability of allochthonous organic matter. In the northern part of the Kara Sea shelf, high bacterial abundance and growth rates are observed in the upper brackish water layer. The upper water layer above the slope of the St. Anna Trough is characterized by low numbers of bacteria, and production rates decrease almost to zero values. It has been shown that the analysis of bacterial abundance in the upper mixed layer is enough for the characterization of quantitative changes in bacterial community of the shelf zone.

Находки видов Chaetoceros (Bacillariophyta) в озере Могильное (остров Кильдин, Баренцево море)

New data on morphology of two Chaetoceros species found in a unique subpolar meromectic lake Mogilnoye are presented. The species Chaetoceros muelleri dominates in upper brackishwater layer and in sediments as resting spores.

Quantification of the surface brackish water layer and frontal zones in southern Chilean fjords between Boca del Guafo (43°30′S) and Estero Elefantes (46°30′S)

The southern Chilean region between the Boca del Guafo passage and Estero Elefantes contains one of the estuarine zones with the greatest freshwater influence on the planet. At the surface, plumes of freshwater from the fjord heads to their mouths, emptying into the Moraleda–Costa–Elefantes channel system and then the coastal ocean. The influence of this freshwater on the region’s estuarine dynamics, coastal ecology, and biogeochemical processes has only recently begun to be elucidated. Using hydrographic data from the CIMAR-Fiordos cruises (1998–2001), this study quantifies the equivalent height of freshwater, emphasizing the role it plays in the potential energy anomaly and front locations, as well as its relationship with river discharges. Using a criterion of equivalent height of freshwater >15% (density <1021 kg/m 3 and salinity <28), the brackish layer was found to be 1–15 m thick (except in Estero Elefantes), with horizontal extensions on the order of 100 km. The limits of this layer tended to coincide with frontal zones having potential energy anomaly gradients >0.005 J/m 4. The frontal zones were located in the extreme southeast of Jacaf Channel, at the head of Ventisquero Sound, in the central part of the Puyuguapi and Moraleda channels, and at the head and mouth of Aysén Fjord. The equivalent height of freshwater and potential energy anomaly showed a good correlation with the accumulated (5-day) river discharges ( r 2=0.87), which were greatest toward the fjord heads in spring. The brackish surface water had short residence times (3.5 days) in Aysen Fjord, unlike the deep layer, which other authors report to have a longer residence time (near 1 year).

Prymnesium parvum: The Norwegian Experience1

Johnsen, Torbjørn M., Wenche Eikrem, Christine D. Olseng, Knut E. Tollefsen, and Vilhelm Bjerknes, 2010. Prymnesium parvum: The Norwegian Experience. Journal of the American Water Resources Association (JAWRA) 46(1):6‐13. DOI: 10.1111/j.1752‐1688.2009.00386.xAbstract: In Norwegian waters, Prymnesium parvum has been reported from Oslofjorden in the south to Spitzbergen in the north. However, blooms of P. parvum have only been reported from the Sandsfjorden system in Ryfylke, Western Norway where the salinity of the permanent brackish layer (2‐5 m) typically is in the range of 4‐7 psu during the summer months. The first bloom on record occurred in 1989, and it killed 750 metric tons of caged salmon and trout which was a significant economic loss to the fish farming industry. Toxic blooms occurred as well in subsequent years and the number of fish farms in the area decreased considerably as did the occurrence of P. parvum. In 2005, fish farming was reintroduced to the area and again, in 2007 a toxic bloom of P. parvum killed 135 metric tons of caged fish. The Norwegian Institute for Water Research has, in collaboration with “Erfjord Stamfisk” fish farm, set up a monitoring program that includes light microscopy cell counts of Prymnesium, water quality measurements, and observation of the caged fish. A submergible fish net was mounted over the fish pens and during the toxic outbreak of P. parvum in July‐August 2007, which was as previous years confined to the upper brackish water layer, the fish nets were lowered to 10 m depths below the surface and fish feeding was temporarily stopped. Despite substantial weight loss, the fish survived the toxic bloom and the economic loss was minimal. Monitoring of P. parvum bloom dynamics in 2007 revealed that populations were initially dominated by the nonmotile forms which were gradually replaced by the flagellated forms. Toxicity was observed when the flagellated cells dominated populations in the summer. Chrysochromulina, solitary small Chaetoceros species, and small centric diatoms co‐existed with P. parvum during the monitoring period (June‐October).

Effect of river run-off on the distribution of marine invertebrate larvae in the southern Kara Sea (Russian Arctic)

Within the generally oligotroph Arctic marine environment river outlets are favoured by many planktonic and benthic organisms due to their high input of organic carbon. The retention of pelagic larvae within nursery grounds and/or the ability to return to their parental grounds prior to settlement is one important factor for the persistence of benthic communities in such river influenced areas. The southern Kara Sea is strongly controlled by high freshwater inputs from the Ob and Yenisei Rivers, which create a pronounced bi-layered pycnocline with a warm fresh/brackish water layer on top and a cold high saline marine layer below. The dispersal of five meroplanktonic species and settled juveniles (the brittle star Ophiocten sericeum, and the polychaetes Micronephtys minuta, Nereimyra aphroditoides, Phyllodoce groenlandica and Prionospio cirrifera) in relation to the adult distribution patterns was investigated. For all apart from P. cirrifera the highest densities of larvae were found in the upper brackish water layer. To assess size-at-settlement, the body sizes of larvae and newly settled juveniles were estimated and compared. Dispersal patterns ranged from virtually no adaption to river run-off as in the common, stenohaline O. sericeum and M. minuta (7 ind. m − 3 , 459 μm) to local retention as in N. aphroditoides (7 ind. m − 3 , 541 μm) and P. groenlandica (0.5 ind. m − 3 , 1121 μm) retained by horizontal eddies created by the outflow. Adults of P. cirrifera, which were exclusively restricted to the estuary of the Yenisei River, showed a well adapted reproductive behaviour to ensure a high retention potential of their progenies. The larvae (1.5 ind. m − 3 , 1513 μm) were only present in the lower water layers, most probably taking advantage of the prevailing near bottom counter current retaining them within their hatching areas.

Analysis by simulation of a solar still integrated in a greenhouse roof

This paper presents a simulation model for fresh water production and derived performance parameters for a water desalination system integrated in a greenhouse roof. Several typical daily weather patterns taken from a 10-year period for three arid regions in Tunisia were analyzed. The simulation model is based on a set of heat balance equations including material layers and a brackish water layer. The equations are solved with the more general PC-program, Engineering Equation Solver. For calculation of solar irradiation, the simulation code TRNSYS (Transient System Simulation) was used in the model. The influence of solar irradiation, optical material properties and process parameters on the fresh water production and total light transmission was studied. The most important conclusion is that the roof-integrated still concept has a fresh water production capacity on a sufficient level for irrigation of plants in greenhouse environments. As about 40% of the solar irradiation has to be transmitted, the thermal efficiency is around one-third of the efficiency for tilted types of conventional stills. Further research and technical development are needed in order to optimize the thermal and optical performance of the concept. The solar energy yield could be improved through better design of the greenhouse shape and more selective absorbers.

Biotransformation of nonylphenol polyethoxylate surfactants by estuarine mixed bacterial cultures

Biotransformation of nonylphenol polyethoxylates (NPnEOs), a major class of non-ionic surfactants, was studied under laboratory conditions by using a static die-away method. The experiments were performed with autochthonous bacterial cultures that originated from two essentially different estuarine compartments, i.e., from the brackish water and saline water layers of the highly stratified Krka River estuary, Croatia. Highly specific HPLC methods were applied to study biotransformation kinetics of individual NPnEO oligomers in the range of 1–16 EO units. Mixed bacterial cultures from the brackish water layer exhibited a significantly greater ability to transform NPnEO than that from the saline water layer. The results suggest, however, that this difference should not be interpreted as a salinity effect, but rather as a consequence of a better preadaptation of the brackish water bacteria to NPnEOs in their natural habitat. The biodegradation rates, calculated by presuming first-order kinetics, showed a strong temperature dependence. The estimated overall half-lives of NPnEOs under winter temperature conditions (13°C) ranged from 23–69 days, while the half-lives determined under summer temperature conditions (22.5°C) ranged from 2.5–35 days. Transformation kinetics of larger, more hydrophilic, oligomers of NPnEOs was faster than that of the lower ones. In fact, the elimination of higher NPnEOs was followed by a significant formation of the short-chain NPnEOs (nEO = 1–4). The main lipophilic intermediate formed during the experiments was nonylphenol diethoxylate (NP2EO), whose concentration in the medium increased by a factor of 10–20. Its relatively fast accumulation was followed by a rather slow degradation. Consequently, residual concentrations of NP2EO were detected in the medium even after 30 days.

Input and distribution of alkylphenol polyethoxylates in a stratified estuary

The behaviour and fate of nonylphenol polyethoxylate surfactants (NPnEO) in the Krka River estuary were studied during 1990–1991. The study comprised determination of NPnEO input via municipal wastewaters and their subsequent distribution in the water column of the estuary. All quantitative determinations were performed by high-performance liquid chromatography using both normal-phase and reversed-phase systems. The concentrations of NPnEO in untreated municipal wastewaters varied in a wide range of 70 to 2960 μg/l. The oligomer distribution in all of the analysed wastewater samples was rather uniform characterised by a maximum at NP10EO which indicated heavy-duty detergents as the predominant source of NPnEO in the investigated area. Hydrophobic partitioning between dissolved and solid phase was found to play a significant role in wastewaters, as indicated by a relatively high percentage (6–60%) of NPnEO associated with wastewater suspended solids and by different oligomer distribution patterns in the two phases. The most important features of the NPnEO distribution in the estuary were: (1) exponential decrease of concentrations with increasing distance from sewage outlets, and (2) a rather complex vertical distribution pattern which reflected the basic hydrographic properties of this strongly stratified estuary. An efficient initial dilution was found to be the chief mechanism that was responsible for rather low NPnEO concentrations in estuarine waters. However, significant concentration differences were observed between the brackish water layer (1.1–6 μg/l) and saline water layers (0.1–0.7 μg/l). This suggested that the wastewater plume spreads into the estuary predominantly in the brackish water layer while the underlying saline water layer remains much less affected. However, NPnEO concentration maxima were observed at the two estuarine phase boundaries: air-brackish water (17 μg/l) and brackish water-saline water (9 μg/l). Relatively small changes of the oligomer distribution pattern in the water column, compared to that originally found in wastewaters, indicated that biodegradation played only a limited role as the mass balance determining process in the estuary.

Exchange of water in a stratified estuary with an application to Krka (Adriatic Sea)

A method of computing the exchange time of freshwater and marine water in a stratified estuary is presented. The method is based on the inflow of the river and its tributaries, the depth of the halocline and salinity in the upper brackish water layer. Exchange time of freshwater and seawater in the Krka Estuary is shorter during winter than during summer. During winter the exchange time of freshwater is between 6 and 20 days, whereas during summer it is up to 80 days. The exchange time of marine water during winter is from 50 to 100 days, whereas during summer it lengthens to 250 days. The renewal time of water in the Krka Estuary as a whole may be approximated by the exchange time.

Effects of wind on a stratified estuary

Before the onset of wind in the Krka Estuary, a sharp halocline extends from 2.5 to 4 m below the surface, separating the upper brackish water layer from the lower marine layer. Strong wind (20 m s −1) induces a tilt of the halocline surface so that downwind (5-km wind fetch) the halocline is pushed to 4.6 m below the surface. Wind-driven surface currents induce a vertical gyre within the upper layer and a gyre in the opposite direction in the lower marine layer. As a consequence, the halocline close to the coast on the downwind side is not only deeper but is also steepened. The entrainment of marine water into the upper brackish water layer is intensified on the windward side. The possible role of wind in oxygenating the bottom layer is discussed.

Subsurface temperature maximum in a stratified estuary

A subsurface temperature maximum recorded in the highly stratified Krka Estuary is described. The maximum is located on the lower edge of a steep halocline and reaches the highest temperature in the Adriatic Sea. Temperatures of up to 31 °C were recorded. The development of the maximum and its persistence during summer is the consequence of a relatively thin and transparent brackish water layer while the entrainment of the seawater is weak. The maximum may be recorded from the middle of April until the end of October.

Stable-isotope (18O/16O) Tracing of Fresh, Brackish, and Sea Ice in Multi-year Land-fast Sea Ice, Ellesmere Island,Canada

AbstractIce salinity and 18O/16O ratios were measured on 12 ice cores drilled from thick, multi-year land-fast sea ice (MLSI) off the north coast of Ellesmere Island, Canada. Fresh, brackish, and sea ice were identified in the ice cores using the 18O/16O ratios. Two cases are considered: case 1, which assumes that no isotopic fractionation occurs on freezing; and, case 2, which assumes that a maximum isotopic fractionation factor (a) of 1.003 applies. The amount of each ice type is variable among the cores, but overall the 12 cores comprise 29.6% brackish ice, 70.0% sea ice, and 0.4% fresh ice in case 1, and 42.3% brackish ice, 57.3% sea ice, and 0.4% fresh ice in case 2. The data suggest that time-dependent brackish sea-water stratification below the ice is quite common and is often associated with the inverted bottom topography. However, the stratification is not always confined to small, areally limited under-ice melt pools in inverted depressions, and neither is it a summer-only phenomenon. Brackish ice growth apparently occurs in a brackish water layer that in some instances underlies the ice sheet year-round. For both case 1 and case 2 the salinity distribution in brackish ice is positively skewed, with 50% of salinity values occurring in the range 0–0.49‰. Sea-ice salinity values are more evenly distributed. In case 1, brackish ice has mean salinity and mean δ18O values of 0.66 and –19.9‰, respectively, compared to mean values of 1.88 and –6.5‰ for the sea ice. In case 2, brackish ice has mean salinity and mean S18O values of 0.75 and –18.1% compared to mean values of 2.03 and –5.2‰ for the sea ice. The salinity of brackish ice and sea ice, ice-growth mechanisms, and the inclusion of brine in the sub-structure are discussed briefly.

Stratified Condition of Lake Kaiike, a Small Coastal Lake on Kamikoshiki Island, Kagoshima Prefecture

Vertical distributions of chlorinity, water temperature, dissolved oxygen and hydrogen sulfide have been obtained from Lake Kaiike, a small coastal lake on Kamikoshiki Island, Kagoshima Prefecture, during April, 1976 and October, 1977. Lake Kaiike (surface area : 0.15 km2; maximum depth : 11.6 m) is stratified between brackish water layer above (chlorinity, 6.6-12.2 ‰) and saline layer below (chlorinity, more than 17 ‰). During the spring and autumn, high temperature of up to 39°C were found in the boundary. In the lower water layer an anoxic condition prevailed throughout the year and a noticeable amount of hydrogen sulfide was contained. From autumn to winter the lake was exposed to wind-induced mixing process and the stratified condition was somewhat altered. With the gradual rise of sea level during spring to summer seawater intruded into the bottom by seepage through the gravel bar.

Fronts in fjords

Abstract Severa1 types of fronts have been observed in the surface waters of Norwegian fjords: shear fronts along river jets, tidal/wind induced river fronts, river-river fronts and wind-driven foam fronts. A river jet spreading over a layered fjord mixes predominantly with the surface water. Farther seaward, wind and tide drive the river plume. In most Norwegian fjords wind mixing causes an entrainment of deeper water to the river plume. In the absence of wind and tide, a geostrophic balance in the top brackish water layer controls the velocity of a river plume in wide fjords. For narrow fjords, topography plays a significant role for the residence time of river water in the basin. River fronts are permanent features of the surface waters. Foam fronts, related to slicks, are observed during the spring and summer months at wind speeds less than those for the better-known windrows.