• Journal of Korean Society of Environmental Engineers
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• v.35 no.8
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• pp.554-563
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• 2013

The purpose of this study is to evaluate the possibility of nutrient release at up and downstream of Kangchun weir, upstream of Yuju and Ipo weir in Namhan River. For this survey, we measured basic characteristics of the sediments (water content, ignition loss, TOC, TP, SRP, TN, phosphorus fractionation) and conducted nutrients release experiments under both aerobic and anaerobic condition. The overlying water from the sediment-water column was analyzed for nutrients (i.e. TP, $PO_4$-P, TN, $NO_3$-N, $NH_3$-N) everyday for 18days. Result of soil texture experiment showed that sediments are Sand. SRP concentration before the release experiment was different with the value after the release experiment. According to this result, we can find that there were more activated release processes in anaerobic condition. $PO_4$-P increased from 1 to 8 days and remained at the maximum value (7~8 days) afterward. The rapidly increase of $PO_4$-P was observed from 1 to 2~3 days whereas the TP continuously increase from 1 to 18 days. The $PO_4$-P release rate calculated by up to 7~8 days data highly correlated with initial SRP concentration with $R^2$=0.8502. $NO_3$-N release rate appears constantly decreasing trend as -5.7~-3.08 $mg/m^2{\cdot}day$, otherwise the $NH_3$-N release rate, by-product of a organic matter decomposition using nitrate as electron acceptor, was 0.57~2.41 $mg/m^2{\cdot}day$. Substantial portion in TN can be induced by organic nitrogen which originated from the tributary passing through non-point pollutant source. Compared with other similar researches, phosphorus and nitrogen release rates obtained in this study can be considered as relatively low values. Since this study targeted the sediments accumulated by one time of flooding season, there are limitation to generalize theses results. Therefore, it is necessary to consistently monitor and investigate the accumulation of nutrients in the sediment for understanding the effect of weir construction on the overlying water quality.

• Asian Journal of Turfgrass Science
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• v.24 no.1
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• pp.45-49
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• 2010

Research on nitrate-nitrogen ($NO_3-N$) leaching in turfgrass indicates that in most cases leaching poses minimal risk to the environment. Although there have been many studies investigating $NO_3-N$ leaching, there has been little research to investigate the effect of compaction level and rootzone mix on nitrogen (N) leaching. The research objective is to determine the effect of compaction level and rootzone mix on nitrogen leaching. The four rootzone mixes are 76.0:24.0, 80.8:19.2, 87.0:13.0 and 93.7:6.3 % (sand:soil). The four levels of compaction energies are 1.6, 3.0, 6.1, and 9.1 J $cm^{-2}$. Nitrogen was applied using urea at a rate of 147 kg $ha^{-1}$ split among three applications. Rootzone was packed into a polyvinylchloride pipe with a perforated bottom to facilitate drainage. Rootzone depth was 30 cm over a 5 cm gravel layer. Each column was sodded with Poa pratensis L. Hoagland solution designed for coolseason grasses, minus N, was used to ensure adequate nutrition in the rootzone. Turf grass quality and clipping yield were recorded from each tube at two-week intervals. The clippings were oven-dried at a temperature of $67^{\circ}C$ for 24 h and weighed. At the end of the study, root dry weight was determined by washing and oven-drying samples at $67^{\circ}C$ for 24 h. Leachate solution was collected weekly for analysis. More than 6.1 J $cm^{-2}$ of compaction energy increased possibilities of surface runoff. The compaction energy between 3.0 and 6.1 J $cm^{-2}$ produced more clipping dry weight and less N leaching than 9.1 J $cm^{-2}$.

• Korean Journal of Soil Science and Fertilizer
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• v.42 no.6
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• pp.454-459
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• 2009

In order to identify the effect of soil salinity on saturated hydraulic conductivity in reclaimed paddy soils, we established the soil columns uniformly packed with soils collected at every 20 cm up to 60 cm from the reclaimed paddy area with high and low salinity which has been cultivated rice plants for the last 30 years. The soil textures were sandy loam and loamy sand for high-salinity and low-salinity topsoils, respectively. For high-salinity and low-salinity soils the ECes were ranged from 25.2 to $37.8dS\;m^{-1}$ and 3.0 to $3.4dS\;m^{-1}$ while the ESPs were ranged from 7.70 to 20.84 % and from 5.12 to 11.33 %, respectively. The bulk densities of the soil columns were adjusted to $1.15{\pm}0.03g\;cm^{-3}$. The results of the soil column experiments shows that the stabilized saturated hydraulic conductivity of low-salinity soil was $0.62cm\;hr^{-1}$ at the topsoil while there were little water flow at the bottom of the soil columns packed with high-salinity soils. After removal of $Na^+$ ions with $1N\;NH_4OAc$ from the high-salinity soil, Ksat of the saline soil was drastically increased to $0.23cm\;hr^{-1}$. Soil columns of high-salinity topsoil treated with four different concentration of NaCl influent after removal of soluble and exchangeable cations with $1N\;NH_4OAc$ show Ksat in the range of $0.1{\sim}0.15cm\;hr^{-1}$ and the Ksat slightly decreased as the concentration of NaCl influent was increasing. Conclusively, we could assume that $Na^+$ can be significantly contributed to the saturated hydraulic conductivity in newly reclaimed sandy soil.

• Economic and Environmental Geology
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• v.41 no.6
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• pp.685-693
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• 2008

The rates of oxidative degradation of perchloroethene (PCE) and trichloroethene (TCE) using $KMnO_4$ solution were evaluated under the flow condition using a bench-scale transport experimental setup. Parameters which are considered to affect the reaction rates tested in this study were the contact time (or retention time), and the concentration of oxidizing agent. A glass column packed with coarse sand was used for simulating the aquifer condition. Contact time between reactants was controlled by changing the flow rate of the solution through the column. The inflow concentrations of PCE and TCE were controlled constant within the range of $0.11{\sim}0.21\;mM$ and $1.3{\sim}1.5\;mM$, respectively. And the contact time was $14{\sim}125$ min for PCE and $15{\sim}36$ min for TCE. The $KMnO_4$ concentration was controlled constant during experiment in the range of $0.6{\sim}2.5\;mM$. It was found that the reduction of PCE and TCE concentrations were inversely proportional to the contact time. The exact reaction order for the PCE and TCE degradation reaction could not be determined under the experimental condition used in this study. However, the estimated reaction rate constants assuming pseudo-1st order reaction agree with those reported based on batch studies. TCE degradation rate was proportional to $KMnO_4$ concentration. This was considered to be the result of using high inflow concentrations of reactant, which might be the case at the vicinity of the source zones in aquifer. The results of this study, performed using a dynamic flow system, are expected to provide useful information for designing and implementing a field scale oxidative removal process for PCE/TCE-contaminated sites.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.20 no.1
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• pp.43-52
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• 2015

The growth and population dynamics of eelgrass (Zostera marina) due to changes in sediment composition were examined in the lower intertidal zone of the Seomjin Estuary, Korea. We surveyed environmental factors such as water temperature, underwater irradiance, main types and organic content of sediment, tidal exposure, and nutrient concentrations in the water column and sediment pore water, in relation to the shoot density, biomass, morphological characteristics, and growth of Z. marina inhabiting lower intertidal zones. The survey was conducted monthly from May to December of 2004 and 2009. The water temperature showed obvious seasonal trends in both study years. Underwater irradiance was significantly higher in 2009 than in 2004. Tidal exposure was not significantly different between 2004 and 2009. The sediment was muddy-sand in 2004 but became sandy and with a significantly lower organic content in 2009. Water column $NH_4{^+}$ concentrations were significantly higher in 2004 than in 2009. Sediment pore water $NO_3{^-}+NO_2{^-}$ concentrations were significantly higher in 2009 than in 2004. Other nutrient concentrations did not differ significantly between 2004 and 2009. Morphological characteristics, including eelgrass length and leaf width were significantly lower in 2009 than in 2004. Eelgrass shoot height, leaf length, and sheath length showed typical seasonal patterns, increasing in early summer and decreasing in autumn, in both years. Vegetative shoot density was not significantly different between 2004 and 2009, while the biomass of individual plant parts and the total biomass were significantly lower in 2009. Eelgrass leaf productivity did not differ between years, but leaf turnover time was significantly shorter in 2009 than in 2004. Eelgrass downsizing and decreased turnover time in 2009 compared to 2004 indicate more effective adaptations to the stress of long-term changes in sediment composition. Overall, results suggest that changes in sediment composition can be a limiting factor for seagrass growth in the intertidal zone.

• Korean Journal of Weed Science
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• v.18 no.3
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• pp.225-236
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• 1998

KSC-13906 [Erythro N-{(4,6-dimethoxypyrimidin-2-yl)aminocarbonyl} -2-(2-fluoro-1-hydroxy-n-propyl) benzenesulfonamide, US Patent 5,461,025] was investigated how can control phytotoxicity fluctuation and what a good method apply to new rice herbicide. The growth inhibition was observed when the rice plants was transplanted at a shallow depth(0 - 1cm) and leaching was low(0 - 1cm/ day) from the paddy soil. KSC-13906 appeared to move readily down into the paddy soil with water by 3cm depth in the soil column(${\phi}$ 10cm) filled with loamy sand soil under 3cm/day of leaching condition. Artificial control releasing pattern, designed as treated with KSC-13906 of 9 or 18g ai/ha either at a once or daily treated dividing volume of 1/20, 1/25 and 1/30 of the total volume, increased the safety of KSC-13906 to direct seeded and transplanted rice. The safety of KSC-13906 was also enhanced when KSC-13906 was mixed with dymron. For example, the mixture of KSC-13906 and dymron effectively reduced injury of direct seeded rice plants at 18 and 500g ai/ha, respectively, treated 7 days after transplanting. However, combination of KSC-13906 and several herbicides didn't show any synergistic effetct on herbicidal activity and safening effect on rice. However, the combination of KSC-13906+dymron (9~12+250~500g ai/ha) or KSC-13906+mefenacet+dymron(9+250+250g ai/ha) controlled almost all weeds in paddy field without causing any injury to rice and thus the combination would successfully be used as an oneshot herbicide in rice culture.