Flow Salinity Research Articles

Modelling the shelf circulation off eastern Tasmania

The marine waters across Tasmanian's eastern continental shelf are biologically productive and home to economically important fisheries and aquaculture industries. However, the marine climate there is poorly understood. We use a high-resolution (∼2km in the horizontal), three-dimensional ocean model for eastern Tasmania (ETAS) to examine the simulated mean state and seasonal cycle of temperature, salinity and three-dimensional flow field, and the evaluation of daily model outputs against in situ and remote observations for the 1993–2014 period. We also use the model to examine the roles of river input and tidal forcing. The model is evaluated against remotely-sensed sea surface temperature and in-situ observations of sea level and subsurface temperature, salinity, and currents. The mean state demonstrates the influence of two well-known boundary currents (the East Australian Current, EAC, and the Zeehan Current, ZC) as well as the effects of local freshwater input from river runoff. The EAC is dominant in summer and the ZC in winter; the influence of the EAC also increases northwards and in the offshore direction. In addition, the model indicates the presence of a semi-permanent subsurface (50–100m depth) northward flow trapped near the coast. Cool freshwater runoff from the Derwent and Huon Rivers directly impacts the temperature and salinity in their estuaries but has little influence further across the shelf. Tidal forcing impacts the mean state through tide-river interactions which flush Frederick Henry Bay and Norfolk Bay with freshwater. Tidal forcing also impacts the variability of temperature all along the coastline, most likely due to changes in the turbulent mixing near to the coast. The ETAS model output data are available as a high-resolution representation of the mean state, seasonal variations, and interannual variability of Tasmania's eastern continental shelf marine climate.

Occurrence of natural radioactivity and corresponding health risk in groundwater with an elevated radiation background in Juban District, Yemen

This study aims to investigate the occurrence of natural radiation in groundwater with an elevated background level in Juban District, Yemen, and to assess the corresponding health risk. The mean concentrations of U, Th, and K in groundwater were 11.25, 0.15, and 17.35 mg l−1, respectively. The mean activity concentrations of 226Ra, 228Ra, and 40K were 94, 216, and 3306 mBq l−1, respectively. 65 % of the groundwater samples were above the WHO guidance level for 228Ra in water. The maximum concentrations of 226Ra, Th, and 228Ra were found around the fault zones in the basement aquifer while the concentrations of U increase down-gradient of Juan District. The principal factors controlling the occurrence and concentrations of radionuclides are aquifer type, leaching behaviour, characteristics of fracture systems, salinity, and water flow path. The annual effective doses due to ingestion of the water were estimated for infant and adult groups. The mean annual effective dose for infants was 1.97 mSv year−1 which is almost twenty times the WHO guideline level for drinking water. The ingestion dose deduced for adults and infants is dominated by 228Ra, where the average contribution from 228Ra in infants amounted to 90 % and in adults 76 %.

Scottish saline lagoons: Impacts and challenges of climate change

The majority of Scotland's saline lagoons are located on the low-lying coastlines of the Western Isles and the northern archipelagos of Orkney and Shetland, where recorded annual relative sea level rise rates are among the highest in Scotland. The sediment-impounded lagoons of Orkney and Shetland will either lose their impoundment and become incorporated in marine coastal waters, or become increasingly saline, as relative sea levels rise. The rock-basin lagoons of the Western Isles will retain their restricted exchange with the sea but will also become more saline with rising sea level. Specialist lagoonal organisms tend to have wide salinity tolerances but may succumb to competition from marine counterparts. In all areas, there are sufficient fresh-water inland water bodies with potential to be captured as lagoons to compensate for loss of extent and number, but the specialist lagoon biota tend to have limited dispersal powers. It is thus possible that they will be unable to transfer to their analogue sites before existing lagoons become fully marine, giving conservation managers the problem of deciding on management options: leave natural processes to operate without interference, manage the saline inflow to maintain the current salinity regime, or translocate lagoon organisms perceived as threatened by rising salinities. Timing of conversion and capture is unpredictable due to local topography and complications caused by variable stratification.

Hydrodynamic and Salinity Intrusion Model in Selangor River Estuary

A multi-dimensional hydrodynamic and transport model has been used to develop the hydrodynamic and salinity intrusion model for Selangor River Estuary. Delft3D-FLOW was applied to the study area using a curvilinear, boundary fitted grid. External boundary forces included ocean water level, salinity, and stream flow. The hydrodynamic and salinity transport used for the simulation was calibrated and confirmed using data on November 2005 and from May to June 2014. A 13-day period for November 2005 data and a 6-day period of May to June 2014 data were chosen as the calibration and confirmation period because of the availability of data from the field-monitoring program conducted. From the calibration results, it shows that the model was well suited to predict the hydrodynamic and salinity intrusion characteristics of the study area.

Flood regime as a driver of the distribution of mangrove and salt marsh species in a subtropical estuary

Tidal patterns of the subtropical Paranaguá Estuarine Complex, in southern Brazil, are strongly affected by episodic cold fronts and by the coastal geometry and bottom topography, resulting in high temporal variability and marked gradients in flood regime. We delimit tolerance ranges of submersion and exposure for representative plant and animal species from local mangroves and salt marshes, through a quantitative analysis of flooding patterns in three estuarine sectors. Our results are consistent with flood regime being the leading factor on how species are distributed over the intertidal flats of the PEC. Subleading factors might be related to salinity, sediment composition and nutrient flow.

Changes in the non-crustacean zooplankton community in the middle Adriatic Sea during the Eastern Mediterranean Transient

Background and Purpose: Here we presented changes in the non-crustacean zooplankton community in the years characterized by the large scale changes in the thermohaline circulation in the East Mediterranean known as the Eastern Mediterranean transient (EMT) and stronger inflow of colder and less saline Modified Atlantic Water (MAW) into the Adriatic Sea. Material and Method: Monthly samplings from February 1995 to February 1996, were performed at fixed station Stoncica near the Island of Vis in the open oligotrophic Middle Adriatic waters. Zooplankton samples, taken vertically from 100 m to the surface using a Nansen net with 125-µm mesh size were analyzed in detail for the following zooplankton taxa: Hydromedusae, Calycophorae, Ctenophora, Pteropoda, Heteropoda, Polychaeta and Chaetognatha. Results and Conclusions: Among the investigated non-crustacean zooplankton three species were registered for the first time, while one species reappeared after years of absence. Compared with earlier data there was a dramatic change in dominant species of calycophoran medusae, pteropods and polychaetes. Data presented herein provide baseline information that is essential for the evaluation of impact of hydroclimatic changes on the zooplankton community, which started in the East Mediterranean in the 1990s and are still on going. Keywords : zooplankton, hydroclimatic changes, Middle Adriatic

Changes in the non-crustacean zooplankton community in the middle Adriatic Sea during the East Mediterranean Transient

Background and Purpose: Here we presented changes in the non-crustacean zooplankton community in the years characterized by the large scale changes in the thermohaline circulation in the East Mediterranean known as the Eastern Mediterranean transient (EMT) and stronger inflow of colder and less saline Modified Atlantic Water (MAW) into the Adriatic Sea. Material and Method: Monthly samplings from February 1995 to February 1996, were performed at fixed station Stončica near the Island of Vis in the open oligotrophic Middle Adriatic waters. Zooplankton samples, taken vertically from 100 m to the surface using a Nansen net with 125-µm mesh size were analyzed in detail for the following zooplankton taxa: Hydromedusae, Calycophorae, Ctenophora, Pteropoda, Heteropoda, Polychaeta and Chaetognatha. Results and Conclusions: Among the investigated non-crustacean zooplankton three species were registered for the first time, while one species reappeared after years of absence. Compared with earlier data there was a dramatic change in dominant species of calycophoran medusae, pteropods and polychaetes. Data presented herein provide baseline information that is essential for the evaluation of impact of hydroclimatic changes on the zooplankton community, which started in the East Mediterranean in the 1990s and are still on going. Keywords: zooplankton, hydroclimatic changes, Middle Adriatic

Cycling of calcite and hydrous metal oxides and chemical changes of major element and REE chemistry in monomictic hardwater lake: Impact on sedimentation

The variation of major and rare earth elements and yttrium (REY) in the monomictic hardwater Lake Tiberias during the wet and dry seasons of the hydrological year was studied in two profiles. The average volume and Cl concentration of the known and unknown saline inflows of 1.6×107m3 and 1.2×109mol are derived by closing both balances. This brine corresponds to a mixture of 83% of groundwater from Cretaceous aquifers and 17% of very saline deep brine. Taking cycling of calcite in the hypolimnion into account, the settling rate of authigenic calcite is estimated to be 3.3molm−2a−1.In the stratified lake of the dry season dissolved inorganic carbon increases by 490μM at the thermo-/chemocline due to microbial reduction of SO42−, NO3−, chemical reduction of Fe(III) and MnO2 colloids, and cycling of calcite in the hypolimnion. REY distribution in the stratified water column is dominantly controlled by coprecipitation with calcite, hydrous ferric oxides and MnO2 in the epilimnion and cycling of these compounds in the hypolimnion. The positive Ce anomaly in the hypolimnetic water is produced by cycling of MnO2. The simulation of the increase of REY in the hypolimnion reveals that hydrous ferric and manganese oxides only play a negligible role except Ce. Only about 10% of REY from cycled matter enhance REY in solution. Most of the released REY are adsorbed by particular matter and thus settling on the floor of the lake.Different from Na, U, SO42− and SiO2, the other elements, in particular REY, increase in the mixed water column from the top to the lower third and mostly decrease thereafter toward the bottom in the mixed lake during the wet season. The behavior of REY is caused by some cycling of calcite and pH-dependent re-equilibration of REY bound to hydrous ferric and manganese oxides adsorbed by particular matter.

环境因子及规格对菲律宾蛤仔幼贝潜沙行为的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 环境因子及规格对菲律宾蛤仔幼贝潜沙行为的影响 DOI: 10.5846/stxb201404150728 作者: 作者单位: 大连海洋大学水产与生命学院,辽宁省贝类良种繁育工程技术研究中心,大连海洋大学水产与生命学院,辽宁省贝类良种繁育工程技术研究中心,大连海洋大学水产与生命学院,辽宁省贝类良种繁育工程技术研究中心,大连海洋大学水产与生命学院,辽宁省贝类良种繁育工程技术研究中心,大连海洋大学,大连海洋大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家高科技研究发展计划(2012AA10A400-2); 国家贝类产业技术体系建设专项(CARS-48) Effects of environmental factors and clam size on the burrowing behavior of Manila clam Ruditapes philippinarum Author: Affiliation: College of Fisheries and Life Science, Dalian Ocean University,Liaoning shellfish breeding Engineering Technology Research Center,College of Fisheries and Life Science, Dalian Ocean University,Liaoning shellfish breeding Engineering Technology Research Center,College of Fisheries and Life Science, Dalian Ocean University,Liaoning shellfish breeding Engineering Technology Research Center,College of Fisheries and Life Science, Dalian Ocean University,Liaoning shellfish breeding Engineering Technology Research Center,Dalian Ocean University,Dalian Ocean University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:作为埋栖型滩涂贝类的典型代表种类,菲律宾蛤仔Ruditapes philippinarum具有很强的潜沙行为。为了进一步了解其生态行为学,在室内实验室条件下,模拟了常见环境因子温度、盐度、pH值以及流速和规格大小对蛤仔幼贝(6-12 mm)潜沙速度的影响。结果表明,温度10-30 ℃,盐度25-30,pH值在6.0-9.0范围内蛤仔幼贝均能100%潜沙;在试验观察的4-5 h内,盐度由30突变至10时没有蛤仔潜沙,突变至20时有20%-30%潜沙(20 ℃,庄河蛤仔)或100%潜沙(15 ℃,福建蛤仔);pH值由8.0突变至10.0时不能潜沙;以暂养海水的温度(15或20 ℃)、盐度(30)和pH值(8.0)为中心,随着各个指标向两侧突变潜沙时间延长;流速为3、4和5 cm/s时,随流速增大潜沙速度加快;在规格6、9 mm和12 mm的幼贝中,以12 mm潜沙速度最快。若以半数潜沙时间(ET50)为判定指标,则适宜潜沙温度为15-20 ℃,盐度为25-30,pH值为7-9(莆田蛤仔)和8.0(庄河蛤仔)。在适宜条件下,蛤仔幼贝1 min内开始潜沙,3 min内有半数潜沙,5 min便全部潜沙。研究发现环境突变对蛤仔潜沙有明显影响,在天然海区放养蛤仔时应该注意购买地和放养海区温度、盐度和pH值的差异,并且选取10 mm以上幼贝放养效果较好。所得结论对完善菲律宾蛤仔幼贝的行为学及其底播养殖技术提供了有意义的参考。 Abstract:The Manila clam, Ruditapes philippinarum, which is widely distributed along the coasts of China, is an economically important marine bivalve species in China's aquaculture industry. Global production of this species was 3.6 million metric tons in 2010. China is the largest producer of Manila clams, producing approximately 3.0 million metric tons annually, which accounts for about 90% of global production. In this study, the effects of clam size and sudden changes in environmental factors such as temperature, salinity, pH, and water flow rate on the burrowing speed of juvenile clams were studied under laboratory conditions. The burrowing rate of juvenile R. philippinarum was 100% at temperatures of 10-30℃, at salinity between 25 and 30, and at pH between 6.0 and 9.0. When salinity was suddenly changed from 30 to 10, 4-5 h into the experiment, burrowing ceased. When salinity was suddenly changed from 30 to 20, burrowing rate declined to 20-30% (T = 20℃,Zhuanghe clam) or 100% (T = 15℃, Fujian clam). There was no burrowing when pH was changed from 8.0 to 10.0. Using seawater (T = 15 or 20℃, salinity = 30, and pH = 8.0) as a control, burrowing time was prolonged when each variable was changed. Burrowing speed increased as the flow rate was increased from 3 to 4 and then 5 cm/s. The burrowing speed of 12 mm clams was the fastest among the three different shell sizes of juvenile R. philippinarum tested (6 mm, 9 mm, and 12 mm). Using ET50 as an index, the optimum burrowing conditions were:T = 15-20℃, salinity = 25-30,pH = 7-9 (Putian clam) or 8.0 (Zhuanghe clam). Under these optimum conditions, some juvenile clams started burrowing after 1 min, 50% of the clams started burrowing after 3 min, and all clams began to burrow after 5 min. This study shows that abrupt changes in environmental factors had obvious effects on the burrowing behavior of Manila clams. Therefore, we suggest that it is important to pay attention to differences in environmental variables, such as temperature, salinity, and pH, between the place of purchase and the area where clams are to be reared. In addition, it is advisable to introduce clams to the farm when water flow is moderate and the shell length is more than 10 mm. 参考文献 相似文献 引证文献

Influence of sea level rise on saline water intrusion in the Yangtze River Estuary, China

The Yangtze River Estuary (YRE) is vulnerable to the accelerated sea level rise (SLR). In this study, a three-dimensional hydrodynamic and salinity transport model, with a high resolution unstructured mesh and spatially varying bottom roughness, is applied to quantify the influences of SLR on saline water intrusion in the YRE. The model has well been validated through observation data of tidal level, flow velocity and direction, and salinity. The performances of four scenarios of the present sea level (PSL) as well as 0.5, 1 and 2m SLR reveal that (1) the isohaline shifts upstream nonlinearly in the YRE with SLR, and non-uniform in the spatial distribution under the same SLR. The isohalines of 1, 2 and 5psu near the north bank of the South Branch intrude farther upstream than those near the south bank, and the upstream advance distance of 0.45psu isohaline is much longer than those of 1, 2 and 5psu isohalines under the same SLR. (2) The spillover of saline water from the North Branch into the South Branch intensifies with SLR, while the salinity in the lower reach of the North Branch is reduced due to increased low salinity flow from the South Branch and the North Channel caused by SLR. (3) The durations of undrinkable water increase at four reservoirs with SLR, and four reservoirs cannot intake raw drinking-water in the dry season in the 2m SLR scenario. (4) A regression analysis obtains a quantitative quadratic expression between salinity and SLR. Finally, the effects of the operation of the Three Gorges Reservoir and more SLR scenarios on the salinity, and two different approaches for SLR simulations are also discussed.

Characteristics of a landscape water with high salinity in a coastal city of China and measures for eutrophication control

Eutrophication of landscape waters is drawing public concerns in China but few studies have been conducted on the problem associated with high water salinity as what happens at Sino-Singapore Tianjin Eco-city in Tianjin, a coastal metropolis of northern China. In order to find ways for eutrophication control, a comparative study was conducted on three landscape water bodies, namely Qingjing Lake, Jiyun River and Jiyun River Oxbow, which are under varied conditions of salinity, organic, and nutrients intrusion. The spatial and temporal variations of water quality were revealed by water sampling and analyses, and correlative relationships were obtained between water salinity and other parameters related to eutrophication. By utilizing a trophic level index (TLI), the eutrophication status of the three landscape water bodies in different seasons could further be evaluated. As a result, water temperature, as expected, showed the strongest effect on eutrophication because higher TLI together with higher Chl-a concentrations tended to occur in later spring and summer seasons, while nutrient concentration, especially TP, was also the determinative factor to the eutrophication status. Of the three water bodies, the Jiyun River Oxbow showed a salinity as high as 20g/L or more in contrast with the other two water bodies with salinity as 4–5g/L. Although its TP concentration was usually very low (about 0.1mg/L), it was under a moderate eutrophication status almost in all seasons, indicating that high salinity tends to induce alga growth. Dilution of saline inflow and nutrients reduction could thus be proposed as the main measures for eutrophication control of landscape waters in the study area.

Extreme saline water advection into the Don River delta and ice advections into Kerch Strait

Analysis of such extreme natural phenomena as inflow of saline transformed waters from the Black Sea into the Don River delta, ice drift, and some others, which have been observed in the Sea of Azov in the recent years, is performed. The process and consequences of the ice movement from the Sea of Azov into Kerch Strait under the effect of hurricane-force NE winds is characterized. Data on the salinity and water level changes during the intensive westerly winds are given. The relationship between salinity and water level during episodes of the surges and downsurges is found. Recommendations for organizing the monitoring measures, intended to increase the accuracy of forecasting emergency situations in the Gulf of Taganrog, Sea of Azov, are presented.

Emergy analysis to evaluate the sustainability of two oyster aquaculture systems in the Chesapeake Bay

Oyster aquaculture is a growing industry in Maryland, USA and other coastal regions with significant estuaries that naturally provide the necessary salinity, food resources, and water flow for oyster growth. Although scientists, industry, and policy-makers promote oyster aquaculture as a sustainable business, studies to determine the environmental sustainability of oyster farming have focused on local environmental impacts without an analysis of the resources required and the overall ecological support needed to maintain a productive oyster farm. Since oyster aquaculture is a coupling of the human economy and the estuarine environment, understanding the sustainability of oyster aquaculture requires quantifying both the efforts of humans and the work of nature required to operate the farms. Emergy analysis, a quantitative tool for evaluating the energy and resources needed to support a process or product, converts the work of nature and human effort into a single metric, the solar emjoule (sej) for ease of comparison. The conversion allows the direct comparison of system flows of differing inputs, outputs and environmental impacts. This study compares two oyster (Crassostrea virginica) aquaculture farms in the Chesapeake Bay (Maryland, USA) that use differing methods of cultivation – floating rafts and on-bottom cages – through an emergy analysis. Our results showed that both farms are intensive systems driven primarily by imported emergy from the economy such as human labor, hatchery products, fuels, goods, and services. In comparison with other aquaculture products, cage- and raft-grown oyster production is supported by a higher percent of local renewable emergy (23% and 28%, respectively), in the form of particulate organic matter and estuarine water circulation. Our results showed a lower environmental loading ratio (3.2 and 2.5, respectively) than other forms of aquaculture; however the emergy yield ratio (1.3 and 1.4) was comparable to other aquaculture products. Between the two methods of rearing oysters, floating cage aquaculture had a lower environmental impact and a higher percentage of renewable emergy due to closer proximity to shore, which reduced motor fuel use, labor, and services. However floating cage used more emergy from hatchery products, due to the purchase of larger spat. Overall, we determined that oyster aquaculture has a lower global environmental impact, higher sustainability rating, and a higher net benefit to society than other forms of aquaculture. Reducing fuel use by locating aquaculture zone close to shore in floating cages and reducing electricity use by accessing natural water flows to drive upweller systems during the nursery stage are two opportunities to enhance sustainability of oyster aquaculture systems.

A multiple habitat restoration strategy in a semi-enclosed Florida embayment, combining hydrologic restoration, mangrove propagule plantings and oyster substrate additions

Abstract Habitat loss and disturbance are ranked globally as the greatest threats to biodiversity. Development and coastal population growth are the leading causes for habitat losses. Recently, the restoration of marine habitats has increased, especially with the goal of increasing non-consumptive ecosystem services derived from mangrove and submerged aquatic vegetation (SAV) along with biogenic oyster reefs. Habitats reside in landscapes dominated by multiple species. Rather than focusing on a single habitat such as oysters or mangroves or SAV, we took an approach restoring multiple adjacent habitats to accelerate restoration in a Florida embayment that had been significantly degraded prior to the restoration of natural tidally generated flows. After a multiple habitat die-off, a project was initiated in 2006 to reintroduce tidal flushing. The re-introduction of tidal flushing, however, did not result in immediate recovery of mangrove shorelines or oyster-dominated reefs. There was a lack of mangrove propagule production and significant substrate limitation in areas with appropriate salinity, sediment and tidal flows. From 2009–2012, red mangrove (Rhizophora mangle) propagules were collected (over 500,000) and planted for a total area of 3.24 ha. From 2009–2010, five intertidal reefs were constructed by adding bagged and fossil shell (54 MT) for Crassostrea virginica larvae to recruit onto totaling over 779 m2. Monitoring of planted mangrove versus unplanted shorelines demonstrated that prop root and drop root densities were higher where propagules were planted (28 m−2) versus unplanted (2.3 m−2). Oyster densities and mean sizes (multiple year classes) at new and natural reefs were measured after 8, 12, and 24, and 36 months. An initial settlement pulse was observed in the first 8 months followed by an increase in the density of greater than 1-year old oysters. Xanthid crab densities (Eurypanopeus depressus and Panopeus spp.) in restored reefs and natural reefs were similar, while Petrolisthes armatus densities were lower in restored reefs. Whole reef seston filtration rates over restored reefs were −26 to 157 L m−2 h−1 when measured at 4, 15, 28, and 40 months. A multiple habitat approach may be useful in accelerating the natural ecological succession, especially if the project site has reached a degraded, alternate ecological state. These results suggest a multiple habitat approach can be useful in providing non-provisioning ecosystem services to a Florida embayment.

Spatio-temporal variations in underwater light climate, thermal and chemical characteristics of the tropical soda lake, Lake Shala, Ethiopia

Although soda lakes are highly sensitive to environmental changes and suited for the study of vital ecological processes owing to their unique biological and physicochemical properties and closed nature, there are limited studies on and knowledge of their basic ecology. In this study, temporal and vertical fluctuations of underwater light climate, thermal and chemical characteristics of the soda lake Lake Shala were studied using data collected on 11 occasions over an annual cycle. Measured parameters of underwater light climate depicted light-limited conditions with slight temporal variations, which are attributable to non-biological turbidity and high water column mixing depth. Its water column exhibited superficial thermal stratification with turbulently mixing and well-oxygenated conditions. Alkalinity, pH and conductivity were high but exhibited small temporal and vertical variations. These parameters increased slightly during the rainy season, possibly due to saline inflows associated with precipitation. Most of the major algal nutrients showed small temporal and vertical variations. NO3 − and NH3 in the euphotic zone were often very low or undetectable, while soluble reactive phosphate and total phosphorus were very high throughout the study period. The concentration of SiO2 was remarkably low, which was probably associated with biological uptake and some chemical processes within the lake. In general, physicochemical parameters of Lake Shala exhibited small temporal and vertical variations despite the current threat of environmental degradation, possibly because of the high resilience of the lake associated with its low productivity and voluminous nature.

Optimization of operating variables in a pilot-scale reverse osmosis membrane process for reclamation of tunnel construction wastewater

The goal of this study was to investigate the individual and combined effects of temperature, salinity, and pressure on permeate flux and salt rejection of the reverse osmosis (RO) process used for reclamation of tunnel construction wastewater. Regardless of changes in temperature, higher operating pressures enhanced both permeate flux and salt rejection, while effects of temperatures on performance varied depending on the operating pressures. Increasing temperatures to less than 35 bar did not improve the permeate flux and salt rejection, while to more than 50 bar led to higher rejection as well as more permeate flux of reclaimed wastewater. Based on analysis of model equations developed, the extent of flux and salt rejection required for reuse of the reclaimed wastewater occurred under different optimal conditions depending on variations in seasons and salinity of wastewater. In particular, it was necessary to add additional pressure exceeding 50 bar or increase the temperature to over 20°C when wastewater of more than 20‰ salinity flows into the treatment system. Adjustment of influential variables can provide an implementable approach to improve operation of the RO process as well as optimize a process for practical construction on-site applications.

Fresh oxygen for the Baltic Sea — An exceptional saline inflow after a decade of stagnation

The ecological state of the Baltic Sea depends crucially on sufficiently frequent, strong deep water renewal on the periodic deep water renewal events by inflow of oxygen rich saline water from the North Sea. Due to the strong density stratification these inflows are the only source for deep water ventilation. Since the early eighties of the last century the frequency of inflow events has dropped drastically from 5 to 7 major inflows per decade to only one inflow per decade. Wide spread anoxic conditions became the usual state in the central Baltic. The rare major Baltic inflow (MBI) events in 1993 and 2003 could interrupt the anoxic bottom conditions only temporarily. After more than 10years without a major Baltic inflow events, in December 2014 a strong MBI brought large amounts of saline and well oxygenated water into the Baltic Sea. Based on observations and numerical modeling, the inflow was classified as one of the rare very strong events. The inflow volume and the amount of salt transported into the Baltic were estimated to be with 198km3 and 4Gt, respectively. The strength of the MBI exceeded considerably the previous 2003 event. In the list of the MBIs since 1880, the 2014 inflow is the third strongest event together with the MBI in 1913. This inflow event will most probably turn the entire Baltic deep water from anoxic to oxic conditions, with substantial spread consequences for marine life and biogeochemical cycles.

Numerical simulation of the hydrodynamics and turbulent mixing process in a drinking water storage tank

ABSTRACTJet-mixing and residence time in a rectangular water storage tank with a constant water level are investigated using the tools of Computational Fluid Dynamics (CFD). A set of Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations using a realisable k-ε model for different inlet configurations has been used. Numerical simulations were validated by means of experimental measurements. A saline inflow was simulated and the computed salinity in the outflow was compared with the measured values, with the aim of improving the tank performance based only on simple modifications of the inlet position and inflow rate. The results show that the URANS technique is able to adequately capture the experimental dilution curve measured at the outlet of the tank. The residence time is mainly influenced by advective transport. Modifications of the horizontal angle and Reynolds number of the inflow jet produce changes in the mixing characteristics when different performance indexes are compared.

Relationship between coral distributions and physical variables in Amitori Bay, Iriomote Island, Japan

AbstractThe relationship between coral distributions and physical variables was investigated in Amitori Bay, Iriomote Island, Japan. Field observations were conducted to obtain data on coral distributions, sea temperature, sea salinity, wind speed, and river flow rate. The observed data were then used in ocean and wave model numerical simulations and soil particle tracking analysis to obtain the spatial and temporal distributions of wave height and the numbers of soil particles. The main results of this study indicate that wave height and the number of soil particles have a significant correlation with coral distribution. Higher wave heights result in greater coverage of tabular coral and lower coverage of branching coral. A greater number of soil particles relates to lesser coverage of tabular coral. On the contrary, the number of soil particles is not correlated with branching coral coverage. The potential habitats for tabular corals largely depend on the species. Acropora hyacinthus is distributed in conditions with low numbers of soil particles, A. digitifera is distributed in conditions with low numbers of soil particles and high wave heights, and A. millepora is distributed in conditions with high numbers of soil particles and low wave heights. Averages of diversity index of the coral types at the mouth and inner parts of the bay are lower than average of the whole region, but average of diversity index at the intermediate part of the bay with the intermediate physical disturbances is higher than it, which seems to support the intermediate disturbance hypothesis.

Possible conduit-matrix water exchange signatures outlined at a karst spring.

During a significant flood event, reversible water exchanges may occur between a karst conduit and its adjacent porous rock (frequently designated as "matrix"): while the flood pulse rises, some conduit-derived water is forced into the matrix; then, as the flood recedes, the same water flows back into the stream passage. The present note addresses such a karst setting in the Carpathian Mountains (Romania), where in addition, a usually stable flux of chloride originating in a natural saline inflow, was being mixed with a variable flow of karst freshwater. For that particular case, with the above-mentioned process of matrix storage/release from storage assumedly taking place downstream of the mixing site, two distinct chemical signatures could be noticed during a flood event: an initial depletion in the spring flow chloride flux, subsequently followed by a comparable chloride flux enrichment (the depletion and the enrichment being outlined with respect to the essentially stable chloride flux value that had been noticed to persist at the spring over a long period of flow rate recession). Concomitantly with such flood-induced fluctuations in thespring chloride flux, thespring discharge displayed, for long periods, abnormally slow variations: the latter likely indicated that the springsupply rate actual oscillations were buffered by the reversible water exchanges which took place between the karst conduit and its adjacent matrix. On the whole, these results show that conduit-matrix water exchanges could be interpreted by simple mass balance calculations that involved fluxes of a conservative tracer (the chloride ion in that particular case).