• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.4
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• pp.129-134
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• 2009

As a result of improved wastewater treatment facilities, the point source pollution emitted from human and municipal wastes is greatly decreasing. Conversely, the non-point source (NPS) pollution emanated from city streets, rural homes, suburban development, animal feedlot, croplands, and forestry is rapidly increasing. Practically, the main concern of the government is to control NPS pollutants by means of establishing a long term plan in order to protect the aqua-ecosystem. Studies have been conducted to assess the intensity of NPS from various landuses. In Korea, the data on NPS pollutant loadings are limited to few and broadly categorized landuses unlike in USA wherein specific landuses are available. This research aims to characterize the wash-off characteristics of NPS pollutants from forest landuse. Two sites were monitored during 15 storm events from 04/2008 to 10/2008. Mean $BOD_5$ EMCs are 1.13 mg/L and 0.91 mg/L for the two sites, respectively. The results of this research will be a helpful contribution for the assessment of total NPS pollutant loadings.

• Journal of Wetlands Research
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• v.11 no.3
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• pp.145-151
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• 2009

Recently the water quality management policy has been changed from managing the point source to controlling the nonpoint sources (NPSs) because of TMDL program. Most NPSs are accumulated on the surface during dry periods. These accumulated pollutants are washed-off during a storm event and highly impairing the water quality of the receiving water bodies. Usually NPS has high uncertainty and is hard to control because of the variability of the rainfall and watershed characteristics. Also, NPS is derived from various land uses. The Ministry of Environment (MOE) is studying and monitoring the pollutant loads from each land use since 2007 to determine the unit pollutant loads. This research was a part of long-term monitoring program conducted to characterize the washoff and provide the mean EMC of artificial grassland. The average EMCs result of BOD, COD, DOC, SS, TN, NH4-N, NO3-N, TP, and PO4-P of the artificial grassland were deterined to 8.2, 17.5, 11.3, 110.1, 3.07, 0.20, 0.75, 0.86 and 0.08 mg/L, respectively. The results of statistical analysis conducted showed a low correlation to the contaminants.

• Journal of Korean Society on Water Environment
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• v.25 no.5
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• pp.713-719
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• 2009

A natural wetland in the Nakdong River basin which effectively removes non-point source pollutants was investigated for 2 years to understand wetland topography, vegetation types, and water quality characteristics. The water depth of the natural wetland was in the range of 0.5~1.9 m which is suitable for the growth of non-emergent hydrophytes. The wetland has a high length to width ratio (3.3:1) and a relatively large wetland to watershed area ratio (0.057). A broad-crested weir at the outlet increases the retention time of the wetland whose hydrology is mainly dependent on storm events. The concentrations of dissolved oxygen in the growing season and the winter season showed anoxic and oxic conditions, respectively. Diurnal variations of DO and pH in the growing season were also observed due to weather change and submerged plants. COD and TP concentrations were low in the winter season due to low inflow rate and increased retention time. Increased TP concentrations in the spring season were caused by degradation of dead wetland plants. Nitrogen in the wetland was mostly in organic nitrogen form (>75%). During the growing season, ammonium concentration was high but nitrate nitrogen concentration was low, possibly due to anoxic and low pH conditions which are adverse conditions for ammonificaiton and nitrification. The results of this study can be used as preliminary data for design, operation, monitoring and management of a constructed wetland which is designed to treat diffuse pollutants in the Nakdong river watershed.

• Journal of Wetlands Research
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• v.18 no.1
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• pp.84-93
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• 2016

As a transition region between ocean and land, coastal wetlands are significant ecosystems that maintain water quality, provide natural habitat for a variety of species, and slow down erosion. The energy of coastal waves and storm surges are reduced by vegetation cover, which also helps to maintain wetlands through increased sediment deposition. Wave attenuation by vegetation is a highly dynamic process and its quantification is important for understanding shore protection and modeling coastal hydrodynamics. In this study, laboratory experiments were used to quantify wave attenuation as a function of vegetation type as well as wave conditions. Wave attenuation characteristics were investigated under regular waves for rigid model vegetation. Laboratory hydraulic test and numerical analysis were conducted to investigate regular wave attenuation through emergent vegetation with wave steepness ak and relative water depth kh. The normalized wave attenuation was analyzed to the decay equation of Dalrymple et al.(1984) to determine the vegetation transmission coefficients, damping factor and drag coefficients. It was found that drag coefficient was better correlated to Keulegan-Carpenter number than Reynolds number and that the damping increased as wave steepness increased.

• Journal of Environmental Science International
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• v.20 no.8
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• pp.977-986
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• 2011

This study analyzed the characteristics of stormwater runoff in the orchard areas and quantitatively estimated effluence of nonpoint source pollutants for the volume of runoff. Two target areas under vine cultivation were each $2,000m^2$ and $1,800m^2$, located in Gyeongju City. Since grape was the only crop on the target area, the characteristics of stormwater runoff at vineyard could be evaluated independently. A total of 51 rainfall events in the vineyard area during two years(2008-2009) was surveyed, and 19 of them became stormwater runoff, with rainfall ranging 16.5 - 79.7 mm and antecedent dry period of 1-13 days. The pollutant runoff loads by volume of stormwater runoff showed BOD ranging 19.5 - 45.3% in 30% of runoff volume. The average pollution discharge rate was 32.4%, indicating small first flush effect of BOD. The range of SS concentrations was 5 - 52.0% in 10% of runoff volume, showing the average 28.7% of discharge rate, about 3 times more than rainfall effluent. TOC and TN appeared to be similar to the results of BOD, the average discharge rate of 30.9% and 30.6% for TOC and TN, respectively, for 30% of stormwater runoff volume. Average discharge rate of COD and TP in the same runoff volume was 35.1% and 36%, respectively, showing comparatively high discharge ratio. As the targeted vineyard area was permeable land, the pollution load ratio against rainfall-runoff volume appeared to be 1:1, implying no strong first flush effect for all the survey items.

• Journal of Wetlands Research
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• v.14 no.4
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• pp.657-665
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• 2012

The development projects distort the natural water circulation system and increase the non-point source pollution by changing the natural cover type. The low impact development (LID) techniques are considering as new development approach to decrease the ecological- and hydrological impacts from high imperviousness rate. The high imperviousness rate is because of the construction of building, parking lot and road for human activities. Knowing the basic characteristics of rood runoff can give the direction for setting up the water management strategy. The monitoring results show the pollutant EMCs of roof runoff are 3~13 times lower than EMCs of the road and parking lot. The pollutant sources from roof runoff are mainly from leafs, cigarette butts, atmospheric deposition and materials of the roof. The EMC is occurred around 15minutes later after starting runoff and more than 8 storm events are needed to have the average EMCs.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.3
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• pp.329-341
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• 2005

The purpose of this study is to study the $PM_{2.5}$ source characteristics affecting the Seoul area using a chemical mass balance (CMB) receptor model. This study was also to evaluate the $PM_{2.5}$ source profiles, which were directly measured and developed. Asian Dust Storm usually occurred in the spring, and very high $PM_{2.5}$ concentrations were observed in the fall among the sampling periods. So the ambient data collected in the spring and fall were evaluated. The CMB model results as well as the $PM_{2.5}$ source profiles were validated using the diagnostic categories, such as: source contribution estimate, t-statistic, R-square, Chi-square, and percent of total mass explained. In the spring months, the magnitude of $PM_{2.5}$ mass contributors was in the following order: Chinese aerosol $(31.7\%)>$ secondary aerosols ($22.3\%$: ammonium sulfate $13.4\%$ and ammonium nitrate $8.9\%)>$ vehicles ($16.1\%$: gasoline vehicle $1.4\%$ and diesel vehicles $14.7\%)>$biomass burning $(15.5\%)>$ geological material $(10.5\%)$. In the fall months, the general trend of the $PM_{2.5}$ mass contributors was the following: biomass burning $(31.1\%)>$ vehicles ($26.9\%$: gasoline vehicle $5.1\%$ and diesel vehicles $21.8\%)>$ secondary aerosols ($23.0\%$: ammonium sulfate $9.1\%$ and ammonium nitrate $13.9\%)>$ Chinese aerosol $(10.7\%)$. The results show that the $PM_{2.5}$ mass in the Seoul area was mainly affected by the Chinese area.

• Journal of Korea Water Resources Association
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• v.45 no.6
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• pp.531-544
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• 2012

This study suggested the parameter estimation method for given rainfall events to be properly expressed by the beta distribution. For this purpose, this study compared the characteristics of probability density function with the parameter proposed considering the cases with and without addition to the rainfall peak, and the cases of using the real hyetograph and the rearranged hyetograph about the rainfall peak. As an example, this study analyzed the independent rainfall events at Seoul in 2010 and the annual maximum independent rainfall events from 1961 to 2010. The results derived are as follows. First, this study confirmed the necessity of additional consideration on rainfall peak to mimic the real hyetograph of rainfall events by the beta distribution. Second, this study confirmed the case of using rearranged hyetograph about the rainfall peak derived a better beta distribution to well mimic the characteristics of real rainfall than the case using the real hyetograph.

• Journal of Korea Water Resources Association
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• v.39 no.10 s.171
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• pp.813-822
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• 2006

By analyzing the concurrent rainfall data from rainfall gauges positioned in the Youngsan River basin, the areal reduction factors related to the rainfall characteristics of the Youngsan River basin are estimated. The estimated values are compared with the values of the Han River basin, and show that the rate of decrease of the areal reduction factors of the Youngsan River basin are smaller than those of the Han River basin as the basin area is increasing. That is especially true for short-term duration storm events. These findings reveal that the spatial variations in the Youngsan River basin's storms are smaller than the spatial variations of the storms In the Han River basin, due to the size of the two basin areas in addition to the topological characteristics that affect the rainfall distributions.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.6
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• pp.119-124
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• 2009

In this study, the characteristics of estimating methodology for RUSLE factors such as soil erodibility factor, slope length-steepness factor, and cover management factor were reviewed and then the relative error according to each methodology was analyzed. RUSLE was applied to experimental watershed for 42 storm events and their results were compared with measured sediment yield to examine the applicability of RUSLE. As a result, this paper found that it should be necessary to consider vegetation effect for forest application of RUSLE as cover management was the most sensitive factor. Also, soil erodbility factor was calculated from data of soil series by National Academy of Agricultural Science caused sediment yield to be overestimated because there were big differences between the soil series and on-site soil texture. The 22.7% of maximum relative error was shown according to selecting the rain energy equation. In addition, it will be necessary to verify the RUSLE factors with more data in order to improve their accuracy.