• Korean Journal of Ecology and Environment
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• v.49 no.4
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• pp.245-257
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• 2016

Although rivers cover only 0.5% of the total land area on the Earth, they are windows that show the integrated effects of watershed biogeochemistry. Studies on the loads and properties of riverine carbon have been conducted because they are directly linked with drinking water quality, and because regional or global net ecosystem production (NEP) can be overestimated, unless riverine carbon loads are subtracted. Globally, ${\sim}0.8-1.5Pg\;yr^{-1}$ and ${\sim}0.62-2.1Pg\;yr^{-1}$ of carbon are transported from terrestrial ecosystems to the ocean via rivers and from inland waters to the atmosphere, respectively. Concentrations, ${\delta}^{13}C$, and fluorescence spectra of riverine carbon have been investigated in South Korea to understand the spatiotemporal changes in the sources. Precipitation as well as land use/land cover can strongly influence the composition of riverine carbon, thus shifting the ratios among DIC, DOC, and POC, which could affect the concentrations, loads, and the degradability of adsorbed organic and inorganic toxic materials. A variety of analyses including $^{14}C$ and high resolution mass spectroscopy need to be employed to precisely define the sources and to quantify the degradability of riverine carbon. Long-term data on concentrations of major ions including alkalinity and daily discharge have been used to show direct evidence of ecosystem changes in the US. The current database managed by the Korean government could be improved further by integrating the data collected by individual researchers, and by adding the major components ions including DIC, DOC, and POC into the database.

• Journal of the Korean Geosynthetics Society
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• v.14 no.2
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• pp.11-21
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• 2015

According to the damage investigation in 2002, the failures of river levee were caused by overflow, erosion, and unstable body conditions due to piping, inappropriate embanking materials, and poor compaction. Especially, overflow was identified as a main reason that induces levee failure by 39.5% from the distribution of failure types. The major parameters, such as levee collapsing angle (${\theta}$), levee collapsing rate (k) affect inundation velocity and area size during the analysis of inundation modeling, however, domestic research effort on this area is still insufficient. In this paper authors conducted levee failure experiments of 4 levee height types, 0.20 m, 0.25 m, 0.30 m, and 0.40 m based on theassumption of Froude Similarity (${\lambda}_{Fr}=1$). As a result, the authors suggested a levee failure mechanism according to the levee heights (H), a collapse extension lengthwhich is around, levee collapse angle (${\theta}$), levee collapse rate (k).

• Journal of Korean Society of Forest Science
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• v.81 no.4
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• pp.346-356
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• 1992

The extensive Snake River floodplain in Northwest United States has experienced major changes in water channels and vegetation types due to floodings. To detect the change of wetland cover-types for the period of 1985 and 1988, post-classification comparison and image differencing change detection techniques were evaluated using Landsat-5 TM digital data. Differenced infrared-band images indicated better accuracy indices than any visible-band images. A thresholding technique was applied to identify the change and no change categories from the transformed images produced by image differencing. The problems in using different accuracy indices, including the Kappa coefficient of agreement, overall accuracy, producer's accuracy, user's accuracy, and average accuracy(based on both the producer's and user's accuracy approaches) in determining an optimal threshold level, were examined.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.16 no.2
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• pp.41-52
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• 2013

Anyang Stream Restoration Movement was started from 2001 for the construction of ecological city. The facilities for reuse of treated sewerage have been used since 2003 for improvement of water quality, maintenance of water quantity, river ecological restoration, and hydrophilic space. Thus, the Anyang city has been gradually transformed to eco-friendly city after the construction of Anyang stream and Hakui stream as natural rivers. In this study, biological and chemical methods as well as ecological indicators for Anyang mainstream and major tributaries were monitored for four years in between 2008 and 2012. The water quality and the diversity of species in most of the streams were found to be good except Anyang main stream. It appears that the influence of seasonal drying stream is almost disappeared except Sammak stream. Thus, the values for BOD (Biochemical Oxygen Demand) and BIP (Biological Index of Pollution) for Anyang main stream were found to be 5.27~3.42mg/l and 4.51~5.50, respectively. This is considered to be caused by the reused water quality of treated wastewater being exceeded the design criteria or by the non-point source of contaminants around the stream. However, entire section of tributaries shows I, II grade as a good water quality.

• Journal of Korean Society on Water Environment
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• v.36 no.3
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• pp.245-254
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• 2020

Water quality improvement projects are being implemented without predicting the effect of water quality improvement on Lake Sapgyo. As the method of selecting the target stream for the effective conduct of water quality improvement projects the method of rating the streams were studied. To build a stream grading method, 60 major streams in the Lake Sapgyo system were monitored. The selection method of rivers subject to priority management for water quality improvement was applied to the stream grading method using the Analytic Hierarchy Process (AHP). The analysis of importance by site by stream grading method revealed the following: water quality (36.0%), flow (26.1%), travel load (13.4%), TMDL density (12.0%), TMDL (8.9%), and area (3.7%). The pollution level of the river was scored by using the stream grading method, and the ranking of 51 streams was calculated. Based on this, the group was classified into six grades (A-F). Among the groups, the F and E groups were selected as the priority management streams. Cheonan-Cheon (Cheonan City) was selected as the first stream to establish water quality improvement measures in the Lake Sapgyo system, and Seowoo-Cheon (Dangjin City) was selected as the second site, and Oncheon-Cheon (Asan City) was selected as the third site. Each local government is expected to improve the water quality improvement effect with limited resources when establishing and implementing water quality improvement measures for the streams (F group, E group) to be managed in this study.

• Journal of environmental and Sanitary engineering
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• v.16 no.3
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• pp.96-103
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• 2001

This study was carried out to investigate the major factors for the removal of NOMs (Natural Organic Matters) by alum ferric chloride and blended coagulants that consisted of alum and ferric chloride. Investigated factors were pH, the dosage of coagulant, alkalinity, hardness and bloc strength. The particle size contained in the test water came from the Han River was also measured. DOC(Dissolved Organic Carbon) removal at pH 6 was two to three times higher than at pH 8.5. The blended coagulant showed 9 to 10 percent higher DOC removal efficiency and 2 to 4 percent higher turbidity under the same condition. Alkalinity consumption of alum, ferric chloride and blended coagulant was 81%, 90% and 86% of theoretical value, respectively. The limit concentration of alkalinity to avoid pin floe was 10 mg $CaCO_3/L$ when alum was used. Hardness had no apparent effect on coagulation. The residual turbidity and $UV_{254}$ showed a tendency of increasing with floc strength($sec^{-1}$) increase. The order of floe strength was the following; alum >blended coagulant > ferric chloride. The particle counter test showed 89 percent of the small particle size(SPS, $1~5{\;}{\mu}textrm{m}$) and 11 percent of the medium to large particle size(M.LPS, $5~125{\;}{\mu}textrm{m}$). At PH7.85, the particle removal efficiencies of SPS($1~5{\;}{\mu}textrm{m}$) and M.LPS($5~125{\;}{\mu}textrm{m}$) in the coagulation process were 81% and 95%, respectively.

• Journal of Ecology and Environment
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• v.39 no.1
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• pp.71-80
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• 2016

The main goal of this study is to develop a multi-metric fishway assessment model (M_m-FA) and evaluate the efficiency of fishway. The M_m-FA model has three major fishway components with nine metrics: structural characteristics, hydraulic/hydrologic features, and biological attributes. The model was developed for diagnosing and assessing fishway efficiency and tested to Juksan Weir at the Yeongsan River Watershed. Structural characteristics of fishway included slope of the fishway (M₁), ratios of fishway width to stream width (M₂), and the proportion of orifice clogging and orifice size (M₃). Hydraulic/hydrologic characteristics included depth of fishway entrance head (M₄), depth of exit tail (M₅), and current velocity of inner fishway (M₆). Biological characteristics included fish species ratio of inner fishway to upper-lower weir (M₇), fish length distribution (M₈), and the proportion of migratory fish species to the total number of species (M₉). Overall, the assessment of fishway efficiency showed the total score of the M_m-FA model was 25 in the Juksan Weir, indicating "good condition" by the criteria of the five-level classification system. The M_m-FA model may be used as a key tool for the assessment of fishway efficiency, especially on the 16 weirs constructed for the "Four Rivers Restoration Project" after a partial calibration of M_m-FA model.

• Journal of Korean Society on Water Environment
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• v.20 no.5
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• pp.415-421
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• 2004

Litter wastes on highway runoff are gradually being considered one of the major pollutants of concern in protecting the integrity of receiving waters for beneficial use. The California State Water Resources Control Board has identified in their 303(d) list at least 36 water bodies where trash or litter is considered a pollutant of concern. The first TMDL adopted by the Region 4 (Los Angeles area) of the California State Water Quality Control Board was for trash in the Los Angeles River. The first flush characteristic study was developed to obtain first flush water quality and litter data from representative stormwater runoff from standard highway drainage outfalls in the Los Angeles area. Total captured gross pollutants in stormwater runoff were monitored at six Southern California highway sites over two years. The gross pollutants were 90% vegetation and 10% litter. Approximately 50% of the litter was composed of biodegradable materials. The event mean concentrations show an increasing trend with antecedent dry days and a decreasing trend with total runoff volume or total rainfall. Event mean concentrations were ranged 0.0021 to 0.259g/L for wet gross pollutants and 0.0001 to 0.027g/L for wet litters. The first flush phenomenon was evaluated and the impacts of various parameters such as rainfall intensity, drainage area, peak flow rate, and antecedent dry period on litter volume and loading rates were evaluated. First flush phenomenon was generally observed for litter concentrations, but was not apparent with litter mass loading rates. Litter volume and loading rates appear to be directly related to peak storm intensity, antecedent dry days and total flow volume.

• Journal of Korean Society on Water Environment
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• v.25 no.4
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• pp.560-567
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• 2009

Treated or untreated wastewater may be a major source of refractory organic matters (R-OM) in drinking water sources. For this study, spectroscopic characteristics of wastewater OM were investigated using the samples from 20 wastewater treatment plants, which are located at the upstream of the lake Paldang, to suggest a estimate index for R-OM in wastewater. R-OM was quantified by measuring total organic carbon (TOC) concentration of the wastewater samples remaining after 28-day dark incubation. Among the traditional OM indices such as chemical oxygen demand (COD) and initial TOC, CODMn showed the lowest correlation coefficients with R-TOC of the samples. The ratios of carbonaceous biochemical oxygen demand (CBOD) to $COD_{Cr}$ had a better correlation with the percent distribution of R-OM than $BOD/COD_{Cr}$ ratios. terrestrial humic-like fluorescence (THLF) exhibited the highest correlation coefficient with R-TOC among the indices obtained from the synchronous fluorescence spectra of the samples. Milori index, one of the humification indices, showed a good correlation with the percent distribution of wastewater. This study demonstrated that fluorescence properties might be a better indices to estimate the concentrations and the distributions of wastewater OM compared to the specific UV absorbance (SUVA) values. Some useful formulas based on OM spectroscopic characteristics were finally suggested to predict R-OM in wastewater.

• Journal of the korean society of oceanography
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• v.35 no.4
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• pp.179-191
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• 2000

Both acid-leached and residual Pb in surface sediments of the Yellow Sea are analyzed in order to explain the spatial distribution of Pb contents and to determine a major controlling factor of its geographical distribution. Leached and residual Pb contents in surface sediments, which may have a different origin, show mirrored geographical distribution. Sediments with high residual Pb ( ${\sim}$20 ${\mu}$g/g; northeastern sand) contain low leached Pb (6-8 ${\mu}$g/g) while sediments with high leached Pb ( ${\sim}$20 ${\mu}$g/g; central mud) contain low residual Pb. As a result, total Pb shows little variation spatially. The mirrored distribution of both species also leads the grain-size dependence of Pb contents to be unclear although the grain-size dependence of other trace metals (Cr, Co, Ni etc.) has been well reported in this shelf. High leached Pb contents (>15 ${\mu}$g/g) were also observed in sediments off the Changjiang River mouth and off the Kyunggi Bay where they can be interpreted as the results of diagenetic accumulation and anthropogenic pollution, respectively. Residual Pb enriched in sands of the northeastern area might be from K-feldspar, which in turn allows the suggestion that northeastern sands may have originated from coastal erosion of granitic landmass or directly from nearby rivers.