Search

Urbanization and climate change have deteriorated the runoff water circulation and quality in urban areas worldwide. Consequently, low-impact development (LID) and green infrastructure (GI) techniques have been applied to manage impermeable land and non-point source pollutants. Herein, the impacts of urban characteristics, sewer system type, and precipitation intensity on surface runoff were analyzed using the Storm Water Management Model (SWMM) to derive an effective water circulation strategy for urban and complex areas through the optimal allocation of LID/GI strategies. The runoff rates were estimated to be 77.9%, 37.8%, and 61.7% for urban areas with separated and combined sewer systems and complex areas with combined sewer systems, respectively. During low rainfall, runoff was intercepted in areas with combined sewer systems, and runoff and pollutant load were lower than that in areas with separated sewer system. In contrast, wastewater was diluted during heavy rainfall; however, the total pollutant load was higher than in separated areas. The analysis of scenarios according to the regional distribution of each LID type resulted in high efficiency when combined sewers were applied during the distributed placement of catchment areas. Additionally, LID infrastructure was applied in areas with separated sewers when the placement was concentrated at the end of the basin.

It is difficult to accurately identify and manage the paths of nonpoint source (NPS) pollution in rural watersheds because their discharge patterns vary depending on season, region, and agricultural characteristics. In this study, flow and water quality during rainfall events were monitored in Songya watershed, an impaired, rural area in South Korea. A method of identifying priority management areas was proposed through scientific objectification and quantification of key factors controlling NPS, such as land use, agricultural type, and load. For the load calculation, a watershed model was developed using Hydrological Simulation Program Fortran (HSPF). Three priority management areas—Mulhan Stream, Osan Stream, and the upstream area of Songya Stream—were selected. Using the developed model, constructed wetlands with the capacity of 1000 m3 were applied at the lower reach of each priority management subbasin and the impacts on NPS pollution reduction were tested. The simulated results showed that BOD and TP concentrations at the outlet of Songya watershed were lowered by 9.2% and 6.0%, respectively. It is expected that the method proposed in this study for identifying priority management areas and implementing best management practice in agricultural watersheds can be applied to similar areas which struggled with NPS pollution.

The negative changes in the hydrological cycle are increasing due to climate change and urbanization, resulting in deterioration of water quality and environmental issues. Although Low-Impact Development (LID) techniques studies have been conducted to solve this problem, the spatial distribution of LID facilities and sewer types has received less attention. In this study, it is proposed to analyze the effects of sewer type, the spatial distribution of LID facilities, and LID type on runoff and water quality using the Storm Water Management Model and to identify effective ways of improving the hydrological cycle and Non-Point Source (NPS) pollution associated with urbanization. As a result of the runoff reduction analysis, 68% of the rainfall was discharged at the outlet for separate sewers, 79% for combined sewers without storage tank, and 49% for combined sewers with storage tank. The LID scenario results showed the distributed LID application method has higher reduction efficiency of runoff and NPS pollution than the intensive application method. Moreover, intensive application of LID in downstream areas resulted in higher runoff reduction efficiency than the application of LID in upstream areas. It will be used not only in the hydrological cycle plan but also in NPS pollution management.

In this study, we investigated the interrelationships between organic matter and water quality indices in the total maximum daily load basins, namely, Churyeongcheon and Yocheon of the Seomjin River system, and identified trends. Churyeong A and Yocheon B, the basins being analyzed, have high proportions of nonpoint pollution sources and pollutant loads from terrestrial sources. During the study period, biochemical oxygen demand (BOD) decreased in both basins, whereas chemical oxygen demand (COD) and total organic carbon (TOC) increased in Churyeong A and decreased in Yocheon B. The increase in organic matter in Churyeong A correlated with the flow rate, whereas organic matter in Yocheon B showed little correlation with flow rate. Variations in organic matter (BOD, COD, and TOC) in Churyeong A exhibited seasonality under the influence of increased flow rate. Organic matter in Yocheon B was affected by increased flow rate, wherein with time, BOD decreased and COD and TOC increased. This study provides basic data that can be used as a reference to facilitate continuous water management and appropriate strategy implementation by analyzing the influencing factors and trends of organic matter using long-term measurement data.

Lake sediments are important sinks of various pollutants and preserve historical pollution records caused by anthropogenic activities. Recently, the sediments of Lake Jangseong, South Korea were first detected with high concentrations of organic matter (ignition loss [IL]; total organic carbon [TOC]), nutrients (total nitrogen [TN]; total phosphorus [TP]), and some heavy metals (Zn, Cu, Cd, and Hg). Here, we identified the origins of these concentrations accumulated in the sediments using extensive surveys and various assessments. Sediment pollution assessed by sediment quality guidelines, pollution load index, and potential ecological risk index was found to be of serious concern for IL, TN, TP, and Cd. Thus, we assessed pollution sources through spatial, grid, and vertical distributions and found that the high pollutant concentrations detected in 2020 were confirmed only at a certain location in the lake. Additionally, similar results were detected in the sedimentary layer below a sediment core at a depth of 15.0 cm. The high pollutant concentrations locally occurred around a "hotspot" site that was previously frequently used for aquaculture activities, indicating that the pollutants were accumulated in sediments owing to past cage fish farming rather than from influx of externally sourced pollution. Furthermore, chemical fractionation of phosphorus and heavy metals and assessment of stable isotopes (

In 2020, organic matter, nutrient, and some heavy metal concentrations in the sediments of Lake Jangseong, South Korea were found to be approximately 1.4 to 14 times higher than the average over the previous 5 years. Here, the origins of high concentrations of ignition loss (IL), total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), Zn, Cu, Cd, and Hg accumulated in the sediments were identified through extensive survey strategies and various assessment techniques. Sediment pollution assessed by sediment quality guidelines, pollution load index, and potential ecological risk index was found to be of serious concern for IL, TN, TP, and Cd. Thus, we assessed pollution sources through spatial, grid, and vertical distributions and found that the high pollutant concentrations detected in 2020 were confirmed only at certain location in the lake. Additionally, similar results were detected in the sedimentary layer below a sediment core at a depth of 15.0 cm. The high pollutant concentrations locally occurred around a “hotspot” site that was previously frequently used for aquaculture activities, indicating that the pollutants were accumulated in sediments owing to past cage fish farming rather than from influx of externally sourced pollution. Furthermore, chemical fractionation of phosphorus and heavy metals and assessment of stable isotopes (13C and 15N) of organic matter suggested that the pollutants in the sediments at the “hotspot” sites had different origins than those found at other sites. Accordingly, the by-products discharged after cage fish farming, such as residual feed, fish meal, and waste, accumulated in the sediments and were then exposed to natural internal disturbances caused by the effects of climate change-induced drought. This local distribution and the phosphorus and heavy metal chemical fraction results with low elution potential indicated that the pollutants in the sediments of Lake Jangseong had negligible impact on water quality.

The Seungchon and Juksan Weirs were constructed in 2012 through four major river projects to control floods and secure water in the Yeongsan River. However, anthropogenic changes in the environment can lead to loss of biodiversity and longitudinal connectivity and the deterioration of ecosystem health. The objective of this study is to evaluate the effects of physical and chemical changes in the Yeongsan River on aquatic habitats through an integrated (water quality–aquatic habitat) model (i.e., Delft3D and HABITAT). The target species used to simulate habitat suitability included Squalidus chankaensis tsuchigae (an endemic fish), Cyprinus carpio, and Micropterus salmoides (an invasive species of fish). Based on the results, maintaining the lowest water level in one of the two weirs was predicted to improve the habitat of the target species. In particular, the habitat area was greatly improved, especially when the Juksan Weir was completely opened. Furthermore, resistance to environmental changes due to habitat area changes indicates that invasive species adapt more to environmental changes than endemic species. This study suggests that physical and chemical changes in the environment can predict the impact on the health of the aquatic ecosystems, which will be useful in establishing an integrated water management plan. These results can be used as basic data for supporting water management policy, to apply an aquatic ecology prediction model suitable for the Yeongsan River system, and to present a management plan for improving the health of an aquatic ecosystem.

To determine the high-priority tributaries that require water quality improvement in the Nakdong River, which is an important drinking water resource for southeastern Korea, data collected at 28 tributaries between 2013 and 2017 were analyzed. To analyze the water quality characteristics of the tributary streams, principal component analysis and factor analysis were performed. COD (chemical oxygen demand), TOC (total organic carbon), TP (total phosphorus), SS (suspended solids), and BOD (biochemical oxygen demand) were classified as the primary factors. In the self-organizing maps analysis using the unsupervised learning neural network model, the first factor showed a highly relevant pattern. To perform the grade classification, 11 parameters were selected. Six parameters are concentrations of the main parameters for the water quality standard assessment in South Korea. We added the pollution load densities for the selected five primary factors. Joochungang showed the highest pollution load density despite its small watershed area. According to the results of the grade classification method, Joochungang, Topyeongcheon, Hwapocheon, Chacheon, Gwangyeocheon, and Geumhogang were selected as tributaries requiring high-priority water quality management measures. From this study, it was concluded that neural network models and grade classification methods could be utilized to identify the high-priority tributaries for more directed and effective water quality management.

This study identifies the impact of river sediments on coastal ecosystems in the southwestern coastal region of Korea. Surface sediments were analyzed for their spatial distributions of organic matter, nutrients, and heavy metal concentrations. Furthermore, pollutants were identified according to the pollution load index (PLI) and potential ecological risk index (RI). Concentrations did not show serious pollution levels compared to generalized guidelines; however, some sites exceeded the PLI pollution standard, and were also identified as potential ecological risks. Through cluster analyses the sediment sites were classified into three groups: rivers with relatively high concentrations of organic matter and nutrients, rivers affected largely by artificial heavy metal pollution, and rivers with low levels of pollution by organic matter, nutrients, and heavy metals. It is evident that continuous monitoring and management are required to prevent major pollution from industrial complexes, agriculture, and commercial activities in the regions near these rivers.

A dual isotopes approach and the Bayesian isotope mixing model were applied to trace nitrogen pollution sources and to quantify their relative contribution to river water quality. We focused on two points to enhance the applicability of the method: 1) Direct measurement on the end-members to distinguish “sewage” and “manure” which used to be grouped in one pollution source as their isotope ranges overlap; 2) The Lagrangian sampling method was applied to consider the transport of nitrogen pollutants in a long river so that any fractionation process can be dealt with in the given Bayesian modeling framework. The results of the analysis confirmed the NO3− isotope composition in the river of interest to be within the range of NO3− with origins in “NH4+ in fertilizer”, “Soil N”, and “Manure and sewage” pollution. This suggests that nitrogen pollution is mostly attributed to anthropogenic sources. The δ18O NO3 value follows the range +2.5∼+15.0‰, implying that NO3− in the river is mainly derived from nitrification, and possible nitrification in groundwater or waterfront other than surface water. The ratio of the concentration of δ15N NO3 to that of δ18O NO3, and the corresponding regression equation indicates that the denitrification effect in surface water was insignificant during the study period. From the results of the contribution ratio of each source, improving the water quality of the discharge from the sewage treatment plants was proved to be the key factor to reduce nitrogen pollution in the river.

We investigated particle size distribution and heavy metal concentrations in surface sediments of streams and lakes in the Seomjin River Basin by comparison with Sediment Quality Guidelines (SQGs). Origins were identified using statistical and geochemical approaches. Sand was prevalent in mean particle size of surface sediments (except lakes). Mean concentrations of Pb, Zn, Cd, and Hg were similar for the Seomjin and Boseong rivers, while those of Cu, As, Cr, and Ni were approximately 1.5-2.0 times higher in the Boseong. SQGs revealed no serious pollution in the basin's site concentrations, although As and Ni levels in the Boseong had some potential for benthos toxicity. Correlation and principal component/factor analysis showed that concentrations of Cu, As, Cr, and Ni were dominant from geological origins rather than anthropogenic. The reducible fraction bound to Fe and Mn-oxides was prevalent in Pb, while the water- and acid-soluble fractions were easily exchangeable or bound to high Cd carbonates. The fraction bound to the highest lattice in residual prevailed in Zn, Cu, Cr, and Ni, accounting for 64%, 65%, 87%, and 86%, respectively. Similarly, results indicated geological origins. Risk assessment to benthos based on labile fractions (F1 + F2 + F3) were Cd (72%) Pb (66%) Zn (36%) ≈ Cu (35%) Ni (14%) ≈ Cr (13%). While Cd and Pb showed the highest risk, their concentrations were relatively lower. However, Cr and Ni showed the highest concentrations but low risk levels, suggesting their pollution is unlikely to have adverse effects on benthos.

Data assimilation in complex water quality modeling is inevitably multivariate because several water quality variables interact and correlate. In ensemble Kalman filter applications, determining which variables to include and the structure of the relationships among these variables is important to achieve accurate forecast results. In this study, various analysis methods with different combinations of variables and interaction structures were evaluated under two different simulation conditions: synthetic and real. In the former, a synthetic experimental setting was formulated to ensure that issues, including incorrect model error assumption problem, spurious correlation between variables, and observational data inconsistency, would not distort the analysis results. The latter did not have such considerations. Therefore, this process could demonstrate the undistorted effects of the different analysis methods on the assimilated outputs and how these effects might diminish in real applications. Under synthetic conditions, updating a single active variable was found to improve the accuracy of the other active variables, and updating multiple active variables in a multivariate manner mutually enhanced the accuracy of the variables if proper ensemble covariance and observation data consistency were ensured. The results of the real case indicated a weakened mutual enhancement effect, and the methods in which variable localization were applied yielded the best analysis results. However, the multivariate analysis methods produced more accurate forecasting results, indicating that these methods could be superior. Therefore, it is suggested that multivariate analysis methods be considered first for water quality modeling, and the application of variable localization should be considered if significant spurious correlations and data inconsistency are present.

We investigated the spatial and temporal patterns of water quality in the Gangjung-Goryoung weir that is located in the middle area of the Nakdong river, Korea. The monitoring results indicated that there are discernible vertical differences in water quality during the pre- and post-monsoon periods (May to September). During this period, it was observed that the weak thermal stratification formed at the maximum level, and pH, Chl-a, and DO concentrations in the surface layer were higher than those in the bottom layer. This vertical difference was especially noticeable for DO concentrations: there were DO depletions at the bottom layer in late June to early August. During the summer monsoon period with heavy rainfall, there was a decline in vertical differences in water quality. From this study, it was suggested that continuous monitoring of vertical profiles could become a useful tool for identifying the spatial and temporal distributions of water quality and for developing the best management policy for water quality in the Nakdong river.Key words: Algal bloom, DO depletion, Gangjung-Goryoung weir, Nakdong river, Thermal stratification

M-type hexaferrites with the magnetoplumbite structure are industrially mass produced uniaxial magnets that possess the simplest crystal structure among various hexaferrites. Herein we present an intriguing phenomenon of relaxor-like ferroelectricity observed in a M-type hexaferrite PbFe6Ga6O19 (PFGO) single crystal. The unique feature of the present discovery is that the improper polarization (∼30 nC cm−2 at 5 K) with a direction parallel to hexagonal [ 1 1 ¯ 0 ] arises from the collinear Si · Sj-type spin exchange coupling. This collinear coupling, in turn, is triggered by selective local spin reversal of the Fe3+ magnetic moment at the octahedral 2a sublattice. The frequency-dependent dielectric data indicated relaxor-like responses of PFGO with the Vogel–Fulcher freezing temperature of ∼17 K. This freezing temperature for the polar-cluster reorientation coincided with the onset of a rapid decrease in polarization with temperature.

Antiferromagnetic YFeO3, belonging to a family of centrosymmetric orthoferrites (space group Pbnm), is known to be nonferroelectric. Here we report, contrary to this common knowledge, that an epitaxial YFeO3 thin film fabricated by adopting a hexagonal template is characterized by a six-fold hexagonal symmetry and exhibits ferroelectricity with a ferroelectric Curie temperature (Tc) of ∼460 K. According to first-principles calculations, the P63/mmc–P63cm structural phase transition at Tc by the freezing-in of the zone-boundary K3 phonon is primarily responsible for the observed room-temperature ferroelectricity and the asymmetric Y 4 d z 2 – O 2 p z orbital overlapping along the c-axis of P63cm over the Γ–M first Brillouin zone is the electronic origin of this artificially imposed ferroelectricity. For temperatures between 115 K (Neel point) and 20 K, the present thin film interestingly shows meta-magnetism-like responses.

We have studied magnetic structure and properties of Ga-substituted Pb-hexaferrites having the stoichiometry of PbFe 12− x Ga x O 19 with x =6 (i.e., Fe:Ga=1:1). According to the neutron diffraction results, this compound is characterized by a collinear spin structure below its Curie temperature (∼325 K). Analysis of the neutron diffraction patterns further indicates that the magnetic-moment direction of Fe 3+ ions located at the octahedral 2a sublattice is downward while that of the unsubstituted PbFe 12 O 19 is upward at room temperature. With decreasing temperature, the Fe 3+ magnetic moment at the octahedral 2a sublattice undergoes a reorientation to the upward direction while that of the unsubstituted PbFe 12 O 19 remains upward down to 5 K. This selective local spin reversal at the 2a sublattice of PbFe 6 Ga 6 O 19 was attributed to the weakening of the superexchange interaction between the octahedral 2a site and the tetrahedral 4 f IV site upon the preferential substitution of Ga ions for Fe ions at these two neighboring sites. Comparison of the neutron diffraction results with dc magnetization responses and ac susceptibilities further indicates that the paramagnetic–ferrimagnetic transition at ∼325 K ( T c ) is followed by the local spin reversal at lower temperatures.

Spinal arachnoiditis is a rare disease caused by fibrosis and adhesion of the arachnoid membrane due to chronic inflammation. The causes of arachnoiditis are infection, spinal surgery, intraspinal injection of steroid or myelography dye, and spinal anesthesia.Case report.A 60-year-old woman presented with progressive weakness and sensory change of both legs and urinary symptoms. She had received a single caudal block 6 months before symptom onset. Magnetic resonance imaging of the thoraco-lumbar spine showed an intradural extramedullary tumor at the T5-T7 level. She underwent laminectomy and tumor resection. The pathological finding was arachnoiditis. After surgery, a rehabilitation program of strengthening exercises of both lower extremities and gait training was started. At 2-month follow-up, she was able to walk with orthoses and performed daily activities with minimal assistance.Symptoms of spinal arachnoiditis occurred 6 months after a single caudal block in this woman. Clinicians should be aware of this possible delayed complication.

A three-dimensional hydrodynamic and water quality model was applied to Lake Paldang, a lake in South Korea that is stratified by incoming flows. The spatial and temporal patterns of phytoplankton growth in this lake were determined from the model. The model was calibrated and verified using data measured under different hydrological conditions. The model results were in reasonable agreement with the field measurements, in both the calibration and verification phases. The distributions of water quality and residence time in the lake and phytoplankton response to changes in nutrient loads were examined with the model, and the influence of the hydrodynamics on phytoplankton response was analyzed. The simulation results indicated that Lake Paldang is an essentially phosphorus-limited system, but that phytoplankton growth is limited by low water temperature and short residence time during the winter and the summer monsoon period, respectively. The results of sensitivity analyses also suggested that the hydrodynamics within the lake may have an indirect influence on phytoplankton responses to changes in the limiting nutrient loads, and that reducing phosphorus loading from Kyoungan Stream should be a high priority policy for controlling algal blooms during the pre- and post-monsoon periods. From this study, it was concluded that the three-dimensional water quality model incorporating hydrodynamic processes could successfully simulate phytoplankton response to changes in nutrient loads and that it could become a useful tool for identifying the essential factors determining phytoplankton growth and for developing the best management policy for algal blooms in Lake Paldang.

The effect of carbo-nitride precipitation on the recrystallization behavior of Ti-stabilized extra low carbon steels was investigated. The precipitation behavior of titanium carbo-nitride was analyzed using transmission electron microscopy (TEM), a chemical extraction method, and the small angle neutron scattering (SANS) method. The recrystallization temperature was varied from 590°C to 680°C depending on the alloy chemistry and hot rolling process. The total amount of precipitates in the hot bands did not significantly affect the recrystallization temperature of the alloys. Isothermal annealing treatment showed a plateau in the stress relaxation curves, i.e. a delay in the recovery, when precipitation occurred during the annealing treatment. A model developed to explain the dynamic interaction of the precipitation with the recovery in the microalloyed austenite was successfully adopted to simulate the delay of the recovery during the recrystallization treatment of the cold rolled Ti-stabilized extra low carbon steels.

BACKGROUND The patients with brain lesion have a high risk of pulmonary complication due to restrictive pulmonary impairment. OBJECTIVE To investigate the effectiveness of active pulmonary rehabilitation on pulmonary functional improvement in these patients. METHODS Twnety-two patients of hemiplegia or quadriplegia with brain lesion were recruited who had restrictive pulmonary impairment. The patients were randomly assigned to an experimental group that receive active pulmonary rehabilitation training and a control group without it. The active pulmonary rehabilitation training is composed of air-stacking exercise by ambu-bagging and functional electrical stimulation (FES) on phrenic nerve and abdominal muscle. We examined respiration function test of all patients composed of peak cough flow (PCF), pulmonary function test (PFT), diaphragmatic motion evaluation and oxygen saturation (SaO2) at the beginning and 4 weeks after treatment. RESULTS There was no significant difference in pulmonary function between experimental group and control group at the beginning. After 4 weeks treatment, FVC and FEV1 of PFT, PCF, diaphragmatic motion, SaO2 have significantly improved (p < 0.05) in experimental group, but no significant changes were detected in control group. CONCLUSIONS It is suggested that active pulmonary rehabilitation with air-stacking exercise and FES would be useful to improve pulmonary function in patients with brain lesion.

Objective To identify factors affecting test results of the quiet standing balance evaluation conducted by posturography and to investigate the standardized method by comparing results according to feet width. Method The study cohort consisted of 100 healthy individuals. We assessed the quiet standing balance of subjects by using 3 different methods: standing on a force plate with feet width the same as shoulder width (test 1); with feet width the same as half the shoulder width (test 2); with feet width determined by the subject's comfort (test 3). Subjects underwent each test with their eyes open and closed for 30 seconds each time. Parameters for measuring standing balance included the mean mediolateral and anteroposterior extent, speed, and the velocity moment of center of pressure (COP) movement. Results All parameters showed better results when the subject's eyes were open rather than closed, and the mean AP extent and speed increased as the age of the subjects increased (p