• Journal of The Korean Society of Agricultural Engineers
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• v.65 no.1
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• pp.73-81
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• 2023

To understand salinity status of fresh water and paddy soils and the susceptibility of rice to salinity stress of Gunnae reclaimed tidelands, salinity monitoring was conducted in rainy and dry seasons. For fresh water, a high salinity was observed at the sampling location near the sluice gate and decreased with distance from the gate. This spatial pattern of fresh water salinity indicates the necessity of spatial distribution of salinity in the assessment of salinity status of fresh water. Interestingly, there was significant correlation between rainfall amount and salinity, implying that salinity of fresh water varies with rainfall and thus it may be possible to predict salinity of water using rainfall. Soil salinity also higher near the gate, reflecting the influence of high saline water. In addition, the groundwater salinity also high to threat rice growth. Though soil salinity status indicated low possibility of sodium injury, there was changes in soil salinity status during the course of rice growth, suggesting that more intensive monitoring of soil salinity may be necessary for soil salinity assessment. Our study suggests the necessity of intensive salinity monitoring to understand the spatio-temporal variations of salinity of water and soil of reclaimed tideland areas.

• Fisheries and Aquatic Sciences
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• v.12 no.3
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• pp.209-218
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• 2009

We examined physiological and histological responses related to the survival, oxygen consumption, excretion, and O/N ratio of the ark shell, Scapharca subcrenata, as a result of salinity changes. The 20-day $LS_{50}$ (median lethal salinity) at $15^{\circ}C$ was 13.87 practical salinity units (psu; confidence limits 10.30-18.74 psu), whereas the 14-day $LS_{50}$ at $25^{\circ}C$ was 12.59 psu (confidence limits 8.03-18.16 psu). In conditions of decreasing salinity, the osmolarity of individuals acclimated within 5 h above 26.4 psu but required more than 60 h below 13.2 psu. Oxygen consumption and ammonia excretion rates varied irregularly as salinity decreased. The O/N ratio was 19 and 27 at water temperatures of $15^{\circ}C$ and $25^{\circ}C$, respectively, but decreased to 1-10 as salinity declined. The effects of decreasing salinity were observed in the histological changes to each organ of S. subcrenata. As salinity decreased, cilia fell off, the epithelial layer underwent necrosis and vacuolation, the connective tissue layers of the mantle and visceral mass were destroyed, and hemocytes increased in the gills. The results of this study could prove important in investigating causes of mass mortality and managing shellfish aquaculture farms.

• Journal of Ocean Engineering and Technology
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• v.32 no.5
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• pp.361-366
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• 2018

The present study analyzed the variation factors in inducing a salinity change using the existing observation network in the section between the Nakdong River Estuary Barrage and Changnyeong-Haman Weir, and also examined the seasonal changes in precipitation, salinity, and discharge. Furthermore, this study analyzed the causes of a salinity increase by collecting observational data during a period when abnormal salinity occurred, and further investigated the salinity transfer time in a section of approximately 5.3 km from the Nakdong River Estuary Barrage to Nakdong River Bridge to understand the behavioral characteristics of the salinity moving upstream. The study results would make it possible to control the increase in salinity and block salt water from moving upstream by understanding the salinity variation characteristics according to the discharge amount. This will provide stability in collecting water from various residential, agricultural, and industrial sources through water intake facilities scattered near the Nakdong River Estuary Barrage.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.3
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• pp.310-320
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• 2008

Water temperature and salinity variation patterns were analysed using the CTD data measured in the Yeochari, Dongmakri and Donggeomdo intertidal zone, south of Ganghwado. Only the data during the submersion period of the measurement stations were used in this analysis. It is clearly shown that the correlation between air and water temperatures is very low and the water temperature variation shows clearly the opposite patterns as the tidal elevation increases and decreases. Whereas, the salinity change shows the similar pattern of the tidal elevation change pattern because the salinity change pattern could be described as the increasing function from the shoreline to offshore regions due to the continuous ground-water inflow in the adjacent watersheds. The salinity is increased from the submersion time to the high tide and decreased from the high tide to the exposure time.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.2
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• pp.116-121
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• 2004

Physiological responses and tolerance limit of hybrid striped bass $(Morone\;Chrysops\;male{\times}\;M.\;saxatilis\;female),$ were investigated on salinity changes from 33 psu to 0 psu and from 0 to psu 33 psu in two separate trials, respectively. In the acute salinity decrease from sea water (33 psu) to fresh water (0 psu), plasma level of cortisol, glucose, total protein, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were not affected, however, $Na^+,\;Cl^-$ and osmolality significantly decreased. In the acute salinity increase from fresh water to sea water (33 psu), plasma cortisol level did not change. Glucose and total protein concentrations in plasma and hematocrit (Hct) decreased, whereas AST, ALT, $Na^+,\;Cl^-$ and osmolality increased. The hybrid striped bass can overcome the acute changes of salinity, from 0 psu to 33 psu or from 33 psu to 0 psu, But salinity decrease stressed the fish much more than salinity increase.

• Journal of the Korea Organic Resources Recycling Association
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• v.8 no.2
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• pp.124-129
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• 2000

The purpose of this study is to estimate the degradation rate and process efficiency of the composting according to the salinity concentration. The samples of food waste for this study were collected in Pocheon-Gun, Kyungki-Do. The collected samples were adjusted to the optimum range of moisture content, pH and C/N ratio. After that, adding the saline, the samples with 3 different salinity concentrations(1%, 5% and 10%) were made. Then each sample was fed into the reactor with temperature controller. During the aerobic composting process, the change of the physical and chemical properties of the sample as temperature, pH, C/N ratio and $CO_2$ and $O_2$ concentration in the reactor were measured. From the experiment of this study, the result are following. The highest temperatures are $59^{\circ}C$ at RUN 1(1% salinity conc.), $49^{\circ}C$ at RUN 2(5% salinity conc.) and $45^{\circ}C$ at RUN 3(10% salinity conc.). The change of $CO_2$ production and $O_2$ consumption have the positive correlation with the change of the temperature. $CO_2$ production and $O_2$ consumption are peaked at the low salinity concentration. During composting, Run 1, RUN 2 and RUN 3 are increased pH to 8.9, 8.6 and 7.2 and slowly decreased C/N ratio to 18.9, 19.1 and 22.1 and moisture content to 51.1%, 53.7% and 55.0%, respectively. It is supposed that increasing salinity concentration causes the retarding of the microbial degradation activities during the composting. And for the efficient composting, the salinity concentration in the sample hat to be maintained below 5%.

• Korean Journal of Animal Reproduction
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• v.16 no.4
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• pp.363-376
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• 1993

This study was taken to examine serum components concentrations and electrophoretic patterns of female tilapia(Oreochromis niloticus) living in 0$\textperthousand$, 10$\textperthousand$, 20$\textperthousand$, and 30$\textperthousand$ salt concentrations, respectively. The results obtained in these experiments were summarized as follows. The level of albumin and total protein showed changes in each salinity, but didn't significantly(P<0.05) change in Oreochromis niloticus. The level of BUN didn't significantly(P<0.05) change. When fish were adapted from 0$\textperthousand$ to 10$\textperthousand$, 20$\textperthousand$ and 30$\textperthousand$, each calcium level in every salinity groups showed less than that of control, and didn't significantly change in 10$\textperthousand$, 20$\textperthousand$, 30$\textperthousand$ salinity. The level of calcium didn't significantly(P<0.05) change in each salinity. In 20$\textperthousand$ salinity, the level of cholesterol was at the highest peak. When fish were adapted from 0$\textperthousand$ to 10$\textperthousand$, 20$\textperthousand$ and 30$\textperthousand$, each glucose level gradually decreased. When fish were adapted from 0$\textperthousand$ to 10$\textperthousand$, 20$\textperthousand$ and 30$\textperthousand$, each glucose level gradually decreased. When fish were adapted from 0$\textperthousand$ to 10$\textperthousand$, 20$\textperthousand$ and 30$\textperthousand$. In 30$\textperthousand$ salinity, the level of alkaline phosphatase was at the highest peak. The level of serum enzyme such as SGOT and SGPT was higher in seawater-adapted group than in freshwater group. The level of phosphorus chnage significantly(P<0.05) in each salinity. Correlation coefficient between serum albumin and glucose in 0$\textperthousand$ was ＋0.924. Correlation coefficient between serum SGOT and SGPT of individuals in 0$\textperthousand$ was ＋0.917. Fraction 1 of transferrin patterns of tilapia(Oreochromis niloticus) adapted in seawater was much thicker than that of transferrin patterns of individuals adapted in freshwater. Also fraction No. a wasn't observed in some individuals adapted in freshwater. These results showed that transferrin adapted in seawater relatively increased. Slight differences, that is, showed to be observed in total iron binding capacityand iron saturatin rate between tilapia adapted in freshwater and in seawater. The increase in total iron binding capacity was attributed to a rise in transferrin pressent in the first fraction of serum protein adapted in seawater. Accordingly, the serum iron levles seemed to be related to salinity($\textperthousand$).

• Journal of Korean Society of Water and Wastewater
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• v.34 no.6
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• pp.403-410
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• 2020

The difficulty of securing freshwater sources is increasing with global climate change. On the other hand, seawater is less affected by climate change and regarded as a stable water source. For utilizing seawater as freshwater, seawater desalination technologies should be employed to reduce the concentration of salts. However, current desalination technologies might accelerate climate change and create problems for the ecosystem. The desalination technologies consume higher energy than conventional water treatment technologies, increase carbon footprint with high electricity use, and discharge high salinity of concentrate to the ocean. Thus, it is critical to developing green desalination technologies for sustainable desalination in the era of climate change. The energy consumption of desalination can be lowered by minimizing pump irreversibility, reducing feed salinity, and harvesting osmotic energy. Also, the carbon footprint can be reduced by employing renewable energy sources to the desalination system. Furthermore, the volume of concentrate discharge can be minimized by recovering valuable minerals from high-salinity concentrate. The future green seawater desalination can be achieved by the advancement of desalination technologies, the employment of renewable energy, and the utilization of concentrate.

• Korean Journal of Environmental Biology
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• v.26 no.3
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• pp.138-144
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• 2008

The effects of salinity on oxygen consumption, operculum movement number and ammonia nitrogen excretion were examined in cultured tilapia, Oreochromis mossambicus (total length 10$\pm$1.0 cm, total weight 17.3$\pm$4.2 g). The fish were exposured to certain salinities (0, 3, 9, 15, 21, 27 and 32 psu) step by step with 3 psu$\cdot$d$^{-1}$ and changed rapidly from certain salinity to another salinity. The oxygen consumption of the fish which was transferred step by step showed increasing tendency in the range of 3 $\sim$ 27 psu, but markedly appeared very low value at 32 psu. The tolerance limit in tilapia by salinity change without acclimation was shown 23.3 psu from 96-h TL$_{50}$. The oxygen consumption, operculum movement and ammonia nitrogen excretion of fish which was transferred rapidly from certain salinity to each salinity (0, 9, 15, 21 and 32 psu) showed a changing point at 15 psu; they showed increasing and/or decreasing pattern before 15 psu, and showed decreasing pattern after 15 psu. From these results, it was concluded that the appropriate salinity without physiological change for Java tilapia was below 15 psu.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.207-207
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• 2021

The Vietnamese Mekong Delta(VMD) covers an area of 62,250 km² in the lowest basin of the Mekong Delta where more than half of the country's total rice production takes place. In 2016, an estimated 1.29 million tonnes of Vietnam's rice were lost to the country's biggest drought in 90 year and particularly in VMD, at least 221,000 hectares of rice paddies were hit by the drought and related saltwater intrusion from the South China Sea. In this study, 3D numerical simulations using Delft3D hydrodynamic models with calibration and validation process were performed to examine flow characteristics, climate change scenarios, water level changes, and salinity concentrations in the nine major estuaries and coastal zones of VMD during the 21^st century. The river flows and their interactions with ocean currents were modeled by Delft3D and since the water levels and saltwater intrusion in the area are sensitive to the climate conditions and upstream dam operations, the hydrodynamic models considered discharges from the dams and climate data provided by the Coupled Model Intercomparison Project Phase 6(CMIP6). The models were calibrated and verified using observational water levels, salinity distribution, and climate change data and scenarios. The results agreed well with the observed data during calibration and validation periods. The calibrated models will be used to make predictions about the future salinity intrusion events, focusing on the impacts of sea level rise due to global warming and weather elements.