• Journal of Korean Society on Water Environment
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• v.31 no.1
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• pp.55-66
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• 2015

It has been well known that it is not easy to quantify pollutant loads driven by non-point source pollution due to various factors affecting generation and transport mechanism of it. Especially pollutant loads through baseflow have been investigated by limited number of researchers. Thus in this study, the Web-based WAPLE (WHAT-Pollutant Load Estimation) system was developed and applied at study watersheds to quantify baseflow contribution of pollutant. In YbB watershed, baseflow contribution with WWTP discharge is responsible for 49.5% of total pollutant loads at the watershed. Among these, pollutant loads through baseflow (excluding any WWTP discharge) is responsible for 61.7% of it. In GbA watershed, it was found that 58.4% is contributed by baseflow with WWTP discharge 2.9% and 97.1% is by baseflow. For NbB watershed (without WWTP discharge), 52.3% of pollutant load is transported through baseflow. As shown in this study, it was found that over 50.0% of TN (Total Nitrogen) pollutant loads are contributed by non-direct runoff. Thus pollutant loads contributed by baseflow and WWTP discharge as well as direct runoff contribution should be quantified to develop and implement watershed-specific Best Management Practices during dry period.

• Journal of the Korean Association of Geographic Information Studies
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• v.3 no.1
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• pp.12-22
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• 2000

Recently urbanization and industrialization around the Nak-dong river watershed have lead to the regional environmental problems. In this viewpoint, we took up variables which were related to watershed environment, and found out spatial and environmental properties of the Nak-dong river using factor analysis, ANOVA test and geographic information system. The results may be summarized as follows; three common factors which were named as urban, agricultural and industrial pollutant factor extracted from statistical methods. Spatial distribution of watershed environment could be found by connection attributes of factor scores derived from factor analysis to digital map using GIS. According to the results, distribution of pollutant sources were concentrated in the main stream of the Nak-dong river and its tributaries, Kum-ho river. So it is necessary to manage the watershed environment in due consideration of environmental carrying capacity.

• Journal of Korean Society on Water Environment
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• v.30 no.4
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• pp.441-451
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• 2014

Streamflow is typically divided into two components that are direct runoff and baseflow, it is required to analyze and estimate behaviors of those two flow components to understand watershed characteristics so that watershed management plan can be effective in pollutant reductions. Since pollutant load behaviors in a stream or river are variable by flow component behaviors, best management practices need to be applied in a watershed based on the pollutant load behaviors varying with flow components. Thus, baseflow behaviors were analyzed separating baseflow from streamflow data collected from fifteen streamflow gaging stations in the 4 major river watersheds which are the Han river, Nakdong river, Guem river, and Yeongsan Somjin river watersheds. Moreover, precipitation trends throughout the 4 River Systems were investigated, thus daily precipitation data were collected from sixty-five locations. The Hank river watershed displayed the largest precipitation (925.2 mm) in summer but the lowest precipitation (71.8 mm) in winter, indicating the watershed has the most fluctuating precipitation characteristic. While the precipitation trends in the Four River Systems varied, a distinct feature in baseflow trends was not found, moreover baseflow percentages to streamflow were typically greater than 50% in the Four River Systems. As shown in this study, it would be expected significant amount of pollutants could be contributed to the stream in the form of baseflow at the watershed.

• Journal of the Korean Association of Geographic Information Studies
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• v.6 no.4
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• pp.85-98
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• 2003

There has recently been an increasing interest of the watershed management as a solution to a wide range of problems related water environment, therefore this study attempted to construct the environment information system to monitor the Geumho River watershed, and to evaluate the impacts of the watershed characteristics on stream water quality. A detailed GIS database to analyze the environmental characteristics at the subwatershed units, including 1:25,000 scale topographical maps, detailed soil maps, land use, 10m-resolution DEMs, roads, streams, vegetation index(NDVI) calculated from Landsat TM imagery, rainfall, and soil loss using RUSLE, is compiled for the study area. The set of variables representing watershed urbanization or industrialization, residential and commercial landuse, industrial landuse, and road area have significantly negative(-) relationship with water quality variables(BOD, COD, SS, T-N, T-P). On the other hand, watershed indicators related to natural environmental conditions, forest cover and vegetation index(NDVI) in each subwatershed were significantly positive(+) relationship with water quality. Three other variables, agricultural landuse, amount of fertilizer and pesticides, and potential soil loss, were not significant in explaining the correlations between watershed environment and stream water quality.

• Journal of Korean Society on Water Environment
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• v.25 no.2
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• pp.256-267
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• 2009

A method of estimating pollutant delivery ratios considering watershed physical and meteorological characteristics and flow conditions using SWAT-K watershed model was described, and pollutant delivery characteristics during dry and rainy seasons, for monthly and seasonally, and with flow regimes were investigated for the Chungju dam watershed. Delivery ratios for sediment, T-N, and T-P showed higher values over 100% during dry and winter seasons with low pollutant loads and flows, and showed relatively uniform ones under 100% during rainy and summer seasons with concentrated loads and flows. It was found that mainly wet flows during summer seasons played very important roles in investigating the delivery characteristics of total or nonpoint pollutant loads, because more than 90% of total loads were influenced by nonpoint source, and discharged with the flows. From the results, we could find out the delivery characteristics with various watershed and flow conditions which are difficult to consider by actual measurement, and could get a foothold of estimating more reasonable and scientific allocated loads for water quality standard using the reliable method of estimating delivery ratios with a watershed model.

• Journal of Korean Society on Water Environment
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• v.20 no.1
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• pp.63-71
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• 2004

The long-tenn trend analyses of water qualities were performed for 49 monitoring stations located in Nakdong River. Water quality parameters used in this study are the monthly data of BOD(Biological Oxygen Demand), TN(Total Nitrogen) and TP(Total Phosphorus) measured from 1990 to 1999. The long-tenn trends were analyzed by Seasonal Mann-Kendall Test and Locally WEighted Scatter plot Smoother(LOWESS). Nakdong river was divided into four subbasins, including upstream watershed, midstream watershed, western downstream watershed and eastern downstream watershed. The results of Seasonal Mann-Kendall Test indicated that there would be no trends of BOD in upstream watershed, western and eastern downstream watershed. Trends of BOD were downward in midstream watershed. For TN and TP, there were upward trends in all of watersheds. But LOWESS curves suggested that BOD, TN and TP concentrations generally increased between 1990 and 1996, then resumed decreasing.

• Journal of Korean Society on Water Environment
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• v.31 no.6
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• pp.700-714
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• 2015

The characteristic of the water quality and pollutant discharge was analyzed at the units watershed of the total amount management in Han-river basin, and after classified in a similar area by multivariate statistical analysis, the main trend such as the water quality trend and pollutant discharge characteristic were analyzed. As a result of this study, the density of the pollutant at the unit watershed is not necessarily identified as discharge density, and the primary management watershed and targeted substances were analyzed depending on the operating status of the environmental infrastructure in watershed and the main pollution factor and discharge path per pollutants. As a result of cluster analysis, watersheds were classified into four groups according to discharge characteristics. It will be used when selecting target area of primary management that is appropriate to the characteristics of each river and establishing efficient water quality improvement plans.

• Journal of Korean Society on Water Environment
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• v.30 no.3
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• pp.261-268
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• 2014

Four clays (both natural and commercial types) mainly used in Korea were tested for removal efficiency of Microcystis spp. and ecotoxicity on Daphnia magna and Vibrio fischeri. Four clays (clay A~D) were composed of 91.9~100% of sand (0.02~0.2 mm in particle size). Clay D consisted of lager particles than other clays. Major elements of the four clays were $SiO_2$ (45.3~62.8%), $Al_2O_3$ (18.5~29.7%) and $Fe_2O_3$ (5.4~7.9%). They contained kaolinite (clay mineral), quartz, muscovite, and so on. Clay C and D contained montmorillonite, one of the clay minerals improving clay-cell aggregation. For clay A, B and C, removal efficiency of Microcystis spp. was over 60% at 2 g/L. It reached about 100% at over 5 g/L. For clay D, it was over 60% and 95~100% at 5 g/L and 20 g/L respectively. After adding clays, pH decreased. The greatest drop of pH appeared at clay C. Except for addition of 100 g/L clay C, ecotoxicity on D. magna and V. fischeri didn't appeared at all dose of clays.

• Journal of Korean Society on Water Environment
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• v.32 no.6
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• pp.670-699
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• 2016

In this study, 16 antibiotics were selected from among the top 30 veterinary antibiotics sold in South Korea in 2014, as well as from among the pharmaceuticals targeted by EPA method 1694, in order to review analytical methods for the detection of trace levels of antibiotics in environmental samples: surface water, soils, animal origin foods, and manures. LC-MS/MS was heavily used. In the chromatography for the detection of the selected antibiotics, the $C_{18}$ column was mostly used at the temperature of $30{\sim}40^{\circ}C$. Water and methanol/acetonitrile were commonly chosen as a nonpolar and a polar mobile phase, respectively. Gradient elution was applied to separate multiclass antibiotics. Volatile additives, such as formic acid, acetic acid, and ammonium acetate were mixed with the mobile phase to improve the ionization efficiency of analytes and the sensitivity in MS detection. Electrospray ionization (ESI) was widely used in the LC-MS/MS and positive ionization was preferred to determine the selected antibiotics. A protonated $[M+H]^+$ molecule was selected as a precursor ion, and its two transitions were analyzed, one for quantitative measurement and the other for confirmation. This study reviewed linearity of the calibration curve, recovery, repeatability, method detection limits (MDLs), and method quantification limits (MQLs) for each target compound used to validate the developed analytical methods.

• Journal of Korean Society on Water Environment
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• v.32 no.6
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• pp.600-627
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• 2016

Korea is one of the countries with a large veterinary antibiotics market, although antimicrobial resistance in bacteria is becoming a serious issue in many countries. The Korean government started to take interest in estimating the effects of livestock manure on rivers and agricultural soils and in monitoring of heavy metals, organic pollutants and antibiotics in the ambient water and soil. In this paper, pre-treatment methods to separate the selected antibiotics from solid samples were reviewed. It is essential to select an efficient and appropriate procedure for pre-treatment due to the high proportion of proteins and organics in biosolid samples. Pre-treatment consists of extraction followed by clean-up. Initially, homogenized samples were extracted by sonication, mechanical agitation or pressurized liquid extraction with methanol/acetonitrile/water mixture under acidic/basic conditions depending on the compound. However, aminoglycosides and colistin were extracted with 5% trichloroacetic acid and HCl, respectively. Since the ${\beta}-lactams$ are easily decomposed in acidic and basic conditions, they were extracted in neutral pH. Filtration with a membrane (pore size, $0.2{\mu}m$) or solid phase extraction with HLB and methanol, as eluents, was normally applied for the clean-up. At least, three different pre-treatment procedures should be adopted to screen all the selected antibiotics in solid samples.