• Korean Journal of Ecology and Environment
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• v.37 no.4 s.109
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• pp.431-435
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• 2004

A nitrate-contaminated groundwater was hydrogeochemically investigated to estimate the factors controlling groundwater quality in an alluvial fan area. Even though monthly groundwater levels increased with monthly rainfalls, the monthly $NO_3^--N$ concentrations in groundwater showed a small variation, mostly exceeding a maximum contaminant level of 10 mg $L^{-1}$ in environmental quality standards for groundwater during 2003. The 2003 annual groundwater recharge was 1,730 mm =20,056 mm-18,326 mm. Where 20,056 mm and 18,326 mm are annual sum of daily increase and decrease in ground water level. However, the annual sum of increase in ground water level (20,056 mm) was approximately 10 times higher than annual rainfall. Moreover, the annual sum of daily ground water level decrease (-18,326mm) showed that a large amount of groundwater was discharged with $NO_3^-$-contamination. Hydrogeochemically, a large amount of groundwater input and output through the alluvial fan area were observed after rainfall with a considerably high concentration of $NO_3^-$. Consequently, this alluvial fan area including forest area reflects on the evidence under the condition of 'nitrogen excess' or 'nitrogen saturation'. In addition, such a large amount of groundwater outflow can cause environmental damage in surface water, associated with $NO_3^-$- contamination. This study also expects that this hydrogeochemical data will be useful for water management.

• Journal of the Mineralogical Society of Korea
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• v.26 no.2
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• pp.129-138
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• 2013

River bank filtration has been considered as a promising alternative water management scheme, in which groundwater is extracted from an aquifer near a river after infiltration of the river water into the aquifer, thereby improving and maintaining the quality of water recovered. Iron (Fe) associated with sediment in contact with groundwater and infiltrating surface water is an important factor in determining the quality of water recovered from the pumping wells in river bank filtration. This study reports the results of Fe speciation in the aquifer sediment samples collected from different depths at the river bank filtration site in Changwon, studied using four different chemical extraction methods, namely, ferrozine, oxalate, HCl, and DCB methods. Overall, the results show that Fe(II) as well as the total Fe content decreases with depth down to ~20 m and then increases further below. This trend is consistent with the redox characteristics suggested by visual observation. The silt/clay size fraction (${\phi}$ < 62.5 ${\mu}M$) has up to 2~10 times more Fe compared with the sand size fraction (62.5 ${\mu}M$ < ${\phi}$ < 2 mm), depending on the extraction method. Of the four extraction methods, DCB solution extracted the most Fe from the sediment samples. The amounts of Fe extracted by the different extraction methods can be a good indicator of the redox conditions along the depth of the aquifer.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.3
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• pp.31-38
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• 2014

Four actual cultivations were prepared and a variety of soybean was cultivated. A H-flume, an automatic water level gauge and an automatic water sampler were installed at the outlet of each plot equipped for the measurement of flow rate and its water quality. The amount of rainfall of the study area in 2013 was measured as 975.6 mm which was much lower than the annual average rainfall of 1,271.8 mm, resulting in less occurrences in rainfall-runoff events. Rainfall-runoff events were occurred three times during the rainfall event of 4~5 July, 23 and 24 August. The characteristics of NPS pollution discharge of the plots and the reduction effect of the selected BMPs were analyzed during these events. The reduction effect of straw mat and soil amendments (Polyacrylamide (PAM) and Gypsum) on runoff ratio ranged between 38.2 and 92.9% (average 71.6%). The NPS pollution load reduced between 27.7 and 95.1% (average 70.0%) by the application of rice straw mat and soil conditioner when compared with that of control plot. Soybean yield (2,133.3 kg/ha) of the straw mat covered plots increased by 14.3% when compared with control (1,866.7 kg/ha). The effect of straw mat on the yield was not economically viable if the material and accompanying labor costs were considered. The data collected and analyzed on different soil textures and crops in this study are expected to be a fundamental reference for the expansion of the results to the application nationwide and the development of NPS pollution management policies.

• Journal of The Korean Society of Agricultural Engineers
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• v.63 no.1
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• pp.89-102
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• 2021

Soils in agricultural lands contain large amount of organic matter and nutrients due to the injected fertilizers and manure. During heavy rain, surface water and base runoff pollutants flows into a nearby stream or lake with eroded soil from agricultural lands. On the other hands, agricultural lands near the lake are inundated due to the increase of the water level in the lake, leading to organic matter and nutrient release from the inundated soil. In this study, releasing rates of nutrient salts and organic substances were analyzed for the soil in the agricultural land, where cultivation activities has been carried out and periodically flooded, to account for the possibility of contamination from the inundated agricultural land in reservoir areas The experiment results have shown that COD was released from the soil in anaerobic conditions, and T-P was released in both anaerobic and aerobic conditions. However, in the case of T-N, it was found that the runoff by soil was not made before the rainfall occurred, and when the soil was impound due to rainfall, the elution occurred under the aerobic conditions. Through the results of this study, it was possible to account for the effect of flooded agricultural lands on the water quality in the lake, and this could be reflected in an efficient agricultural non-point pollution management policy. In order to determine the precise releasing rate for each agricultural land, it is believed that the leaching experiment for paddy fields and grasslands are needed.

• Korean Journal of Soil Science and Fertilizer
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• v.38 no.3
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• pp.164-171
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• 2005

The aim of this study was to evaluate the load of nutrient from paddy fields. Water management practices that can reduce eutrophication and meet water quality requirements will also be addressed. Continuous monitoring from May to September in 2002 and 2003 was conducted for water quantification and qualification at the intensive paddy fields in Icheon, Gyunggi province of Korea. Water balance and concentration variation of nitrogen and phosphorus in the water were independently compared for water quality assessment at each rice cultivation period. Rice land preparation and transplanting periods usually marked the highest water demand when compared to other periods of cultivation. Overall, a greater net irrigation ratio was observed during the transplanting period in 2002 (92.3%) and 2003 (87.2%). The measured total N loads of precipitation, irrigation, drainage, and percolation during the rice cultivation period were 9.9, 41.6, 22.1, and $5.5kg\;ha^{-1}$ for 2002 and 15.8, 55.4, 17.3, and $7.5kg\;ha^{-1}$ for 2003, respectively. The measured total P loads of precipitation, irrigation, drainage, and percolation during the rice cultivation period were 2.1, 13.0, 3.6, and $1.8kg\;ha^{-1}$ for 2002 and 1.6, 15.0, 5.0, and $1.2kg\;ha^{-1}$ for 2003, respectively. Daily nutrient load followed the pattern of surface drainage water, but this pattern was changed by rainfall events. The nutrient load in drainage water depends on rainfall and surface drainage water amount from the paddy fields. Interestingly, the load of total N and total P output was smaller than the input load due to the natural infiltration that Occurred during the rice cultivation period. It is concluded that the paddy fields have a beneficial effect on the ecosystem and can reduce eutrophication in the water.

• Journal of Energy Engineering
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• v.22 no.3
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• pp.287-293
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• 2013

This study was carried out to diminish the formation of scale in boilers which is one of the defect elements when they are operating. The defect relating to scale can cause a fatal impact on the explosion of boilers due to the overheating of their tubes, or it can affect the flow of water inside boilers with its bad circulation and result in a disparity of water inside the equipment. Heat transfer in the scale is low comparing to the boiler material, so it can lead to energy losses and has also impact on the global warming. In 2005, the Korean government introduced a system which requires boiler users to install the equipment which can prevent or eliminate the formation of scale to improve the management of water quality in boilers. The study on the techniques for preventing or eliminating the formation of scale started in 1821 and since then subsequently there have been lots of similar studies. The first one was about the scale reduction using potato starch. Since an ultrasonic scale preventer developed by a scientist from a Russian acoustic institute was introduced in1993, a variety of equipment of this kind have been disseminated in Korea. There has been a need to demonstrate the condition for the best performances of such equipment. Boilers are mostly composed of the main body and 288 the tube with a circular curved surface. I carried out a demonstration study on a circular tube which affects the scale defect the most among the boiler components. As a result of it, I found out the fact that the ultrasonic wave needs to reach a certain level of sound pressure and frequency to affect the formation of scale.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.2_2
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• pp.199-208
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• 2022

The steel wire or steel bar processing process applied to the manufacture of various bolts and power transmission shafts was improved by applying in-line phosphate film treatment technology. By applying a polymer lubricant for a non-reactive metal forming process and a non-reactive non-phosphorus lubricating coating agent, the film formation for each process time was comparatively analyzed and reviewed. Compared to the nine processes applied previously, the in-line phosphate film treatment technology applied with only two processes has been effectively improved in terms of reduction of treatment time, reduction of facility installation area, prevention of water pollution due to wastewater, and non-use of ozone-depleting substances. In addition, it was found that it can have an important effect on productivity improvement and price competitiveness from the simplification of quality control and process control as well as improvement of the working environment.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.5
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• pp.30-39
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• 2023

Large dams, which are critical infrastructures for disaster prevention, are exposed to various risks such as aging, floods, and earthquakes. Better dam safety inspection and diagnosis using digital transformation technologies are needed. Traditional visual inspection methods by human inspectors have several limitations, including many inaccessible areas, danger of working at heights, and know-how based subjective inspections. In this study, drone photogrammetry was performed on two large dams to evaluate the applicability of digital data-based dam safety inspection and propose a data management methodology for continuous use. High-quality 3D digital models with GSD (ground sampling distance) within 2.5 cm/pixel were generated by flat double grid missions and manual photography methods, despite reservoir water surface and electromagnetic interferences, and severe altitude differences ranging from 42 m to 99.9 m of dam heights. Geometry profiles of the as-built conditions were easily extracted from the generated 3D mesh models, orthomosaic images, and digital surface models. The effectiveness of monitoring dam deformation by photogrammetry was confirmed. Cracks and deterioration of dam concrete structures, such as spillways and intake towers, were detected and visualized efficiently using the digital 3D models. This can be used for safe inspection of inaccessible areas and avoiding risky tasks at heights. Furthermore, a methodology for mapping the inspection result onto the 3D digital model and structuring a relational database for managing deterioration information history was proposed. As a result of measuring the labor and time required for safety inspection at the SYG Dam spillway, the drone photogrammetry method was found to have a 48% productivity improvement effect compared to the conventional manpower visual inspection method. The drone photogrammetry-based dam safety inspection is considered very effective in improving work productivity and data reliability.

• Korean Journal of Environmental Biology
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• v.29 no.3
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• pp.212-224
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• 2011

The Yeongsan River estuary, located in the south west coast, was a typical estuary before a dike was constructed in December 1981. After the construction, the water quality and plankton communities are expected to change. We investigated the change of phytoplankton community and environmental properties in the Yeongsan River estuary by comparing the data collected recently with the results reported before and/or shortly after the construction. Concentrations of $NH_4$-N were significantly increased in the freshwater zone. Concentrations of DO at the surface, $NO_2+NO_3$ and $NH_4$-N were increased while the concentrations of $PO_4$ at the surface were decreased in the seawater zone. The number of green algae species was decreased in the freshwater zone. The number of diatom species was decreased while the numbers of green algae and dinoflagellates were increased in the seawater zone. This study can provide information for better management of the Yeongsan River estuary since no comparison study has been documented between the phytoplankton community before and after the construction of the dike in the estuary.

• Journal of Korea Water Resources Association
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• v.43 no.12
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• pp.1029-1038
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• 2010

In meteorology Korea has 2/3 of rain of annual total rainfall at the month of Jun through Sept and it has possibility to have serious flood damage because geographically it is composed of mountainous area with steep slope which account for 70% of its country. Also, the increase of impervious layer due to industrialization and urbanization causes direct runoff, which deteriorates contamination of rivers by moving the contaminated material on the surface at the beginning of rain. In particular, the area of leisure facilities needs the management of water quality absolutely because dense population requires space of park function and place to relax and increases moving capability of non-point pollution source. For disposition of rainfall & runoff, the standard of initial rainfall, which is to be used for the computation of disposition volume, is significant factors for the runoff study of non-point pollution source, Until now, a great deal of study has been done by many researchers. However, it is the current reality that the characteristics of runoff varies according to land protection comprising river basin and the standard of initial rainfall by each researcher is not clearly defined yet. Therefore, in this research, it is suggested that, with the introduction of SOM (Self-Organizing Map), the standard of initial rainfall be determined after analyzing each sectional data by executing pattern classification about runoff and water quality data measured at the test river basin for this research.