• Journal of Wetlands Research
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• v.21 no.3
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• pp.215-223
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• 2019

In this study, we analyzed the water quality characteristics of major tributaries of Nakdong River through statistical analysis such as correlation analysis, principal component and factor analysis, and cluster analysis. Organic matter and nutrients are highly correlated, and are high in spring and autumn, and seasonal water quality management is required. Principal component and factor analysis showed that 82% of total variance could be explained by 4 principal components such as organic matter, nutrients, nature, and weather. BOD, COD, TOC, and TP items were analyzed as major influencing factors. As a result of the cluster analysis, the four clusters were classified according to seasonal organic matter and nutrient pollution. Kumho River watershed showed high pollution characteristics in all seasons. Therefore, effective management of water quality in tributary streams requires measures in consideration of spatio-temporal characteristics and multivariate statistical techniques may be useful in water quality management and policy formulation.

• Journal of Environmental Policy
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• v.12 no.1
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• pp.59-74
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• 2013

The weakness of current water quality monitoring system was reviewed to manage Nakdong river's water quality. The current monitoring system has sampling periods lasting for a week to 10 days, but these-SAMpling periods may not accurately measure the real level of water quality. Therefore, daily sampling and analysis of water samples for nine factors was performed from May 1st 2011 to Sep. 30st 2011 to check the water quality changes at three-SAMpling points, Munsanri (the upper side of Kangjung-Koryung weir), Kangchang (the outlet of the Kumho River) and Samunjin (the lower side of Kangjung-Koryung weir). As demonstrated by the results, concentrations of all nine factors dramatically changed on a daily basis, so daily sampling and analysis of water quality samples may be needed instead of weekly sampling and analysis of water quality samples to ensure the proper management of the Nakdong River's water quality. However, daily observations for all water sampling points are not possible because costs and labors are limited, so that new methods which could support the current monitoring system should be developed.

• Journal of Korea Water Resources Association
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• v.53 no.2
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• pp.141-154
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• 2020

The accidents of toxic chemical spill into rivers are increasing in recent years due to expansion of heavy industries in Korea. In order to respond to the chemical spills, accident response systems have been established for both main rivers and tributary rivers. However, since these accident response system adopted the water quality models imported from the foreign countries, it is difficult to acquire the model parameters and to calibrate and validate the water quality models. Therefore, this study developed a depth-averaged two-dimensional river water quality model to analyze the behavior of hazardous chemicals in rivers and proposed an efficient simulation execution framework by identifying the significant reaction mechanisms considering the characteristics of the toxic chemicals. The depth-averaged two-dimensional river water quality model CTM-2D was upgraded by adding reaction terms representing mechanisms of the adsorption, desorption, and volatilization of toxic chemicals. In order to verify the model, the analytical solution was compared with the numerical solution, and results showed that the error was less than 0.1%. In addition, the model was applied to a virtual scenario which is a water pollution accident at the confluence of the Nakdong River - Kumho River, and model results showed that an efficient simulation could be carried out by activating only significant reactions which were assessed by the sensitivity analysis.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.2
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• pp.89-96
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• 2017

This study analyzed the characteristics of water quality and the correlation between Chl-a and water quality factors among four weirs located in the middle and downstream of Nakdong River for five years. The concentration of nutrients and Chl-a from DS to CH was higher than that of GG, which is considered to be due to the influx of Kumho River located at upstream of DS. There was a significant correlationship between Chl-a and most of the water quality factors for all season data. Based on the comparison results between all season data and summer season data, a negative correlation between Chl-a and nutrients ($PO_4-P$, $NH_3-N$) was increased. Based on analysis on summer in 2015 with relatively low precipitation and high algal blooms, the correlation between Chl-a and $PO_4-P$ at all sites were increased. Therefore phosphorus is an important factor in the river on summer season. And PCA results showed the first factor was classified as T-N, $NO_3-N$ for all seasons, and the first factor was classified as T-P, $PO_4-P$ for summer seasons. Consequently, the middle and downstream of Nakdong River were most affected by nutrients, especially it was affected by phosphorous pollutants rather than nitrogen pollutants during summer seasons.

• Journal of the Korean Chemical Society
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• v.45 no.1
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• pp.14-24
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• 2001

In order to study the long-term change of water quality, water analysis for 9 items was conducted at 13 sites surrounding the Kumho river system for 18 times from September 1993 to August 1999. Analytical items for the study of water quality are as follows; water temperature, pH, BOD, COD, DO, SS, electrical conductivity, oil and grease, ABS and phenol. The six year term was divided into Part I(second study) and Part Ⅱ(third study), which covers the term from September 1993 to August 1996 and the term from September 1996 to August 1999, respectively. The mean values obtained for three years for water temperature, pH, BOD, COD, DO, SS, electrical conductivity, oil and grease, ABS and phenol for the Part I period showed 18.4$^{\circ}C$, 7.9, 4.88 ppm, 9.66 ppm, 9.0 ppm, 618.0 umho/cm, 6.9 ppm, 2.63 ppm, 3.57 ppm and 0.98 ppm, respectively. The mean values obtained for water temperature, pH, BOD, COD, DO, SS, electrical conductivity, oil and grease, ABS and phenol for the Part Ⅱ period showed 18.0$^{\circ}C$, 8.0, 2.86 ppm, 7.40 ppm, 8.94 ppm, 541.0 umho/cm, 6.0 ppm, 5.43 ppm, 0.94 ppm and 0.01 ppm respectively. The values of BOD, COD, SS, electrical conductivity, ABS and phenol in the second period were found to be decreased by 1/1.71, 1/1.31, 1/4.15, 1/3.80 and 1/98, respectively. The values of water temperature, pH and DO were nearly constant. However, the concentrations of oil and grease were found to be increased about 2.06 times in the second period.

• Journal of Korean Society on Water Environment
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• v.26 no.4
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• pp.629-636
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• 2010

According to the spatial movements of the Nak-dong river watershed, the changes in heavy metal concentrations were simulated by WASP7.3. The risk assessment was performed using the predicted data of WASP7.3. The target heavy metal was manganese (Mn). In the simulated manganese data of WASP7.3, the average concentration by regions was from 0.03 mg/L to 0.07 mg/L. It is lower than drinking water standard in korea. The risk assessment was presented that it was high at the junction of Nak-dong river and Kumho river. It was influenced by the discharge of industrial complexes and large cities which were located in the junction. In comparison of drinking water standard and predicted data of WASP7.3 risk assessment, whole watershed was also low level at predicted data. However, to keep the similar risk value ($10^{-7}$) in adults and children anywhere, it requires the additional treatment of the point source discharges. It was also reflected by regions. Through this study, it was possible to evaluate heavy metal influence in unattainable monitoring regions and to estimate heavy metal addition and reduction by locations. Therefore, the outcomes of WASP7.3 can connect with the risk assessment and it can evaluate the safety of human by regions.

• Journal of Environmental Health Sciences
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• v.25 no.3
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• pp.36-43
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• 1999

The present study was performed to investigate biodegradation rate of dichlorvos and methidathion. In the biodegradation test of two pesticides by the modified river die-away method from June 17 to August 22, 1998, the biodegradation rate constants and half-life were determined in Nakdong(A) and Kumho River(B). Biodegradation rate of dichlorvos was 4.51% in A sampling point, 6.88% in B sampling point after 7 days. Biodegradation rate constants and half-life of dichlorvos were 0.0066 and 105 days in A sampling point, 0.0102 and 67.9 days in B sampling point, respectively. Biodegradation rate of methidathion was 23% in A sampling point, 36% in B sampling point after 7 days. Biodegradation rate constants and half-life of methidathion were 0.0377 and 18.4 days in A sampling point, 0.0641 and 10.8 days in B sampling point, respectively. Biodegradation rate of methidathion was faster than that of dichlorvos. This suggested that the difference in biodegradation of pesticides was due to difference in the water quality and standard plate counts in the Nackdong and Kumho Rivers. The result of correlation analysis between biodegradation rate constants of the pesticides and water quality(DO, BOD, SS, ABS, NH$_3$-N, and NO$_3$-N) showed significant correlation with BOD, SS and NH$_3$-N at the 5% significant level. A significant linear equation was obtained from regression analysis at the 5% significant level, whereas, dependent variables were BOD, SS and NH$_3$-N, and the biodegradation rate constant was independent variable. It is suggested that dichlorvos will be mainly degraded by hydrolysis, and for methidathion was both hydrolysis and biodegradation. A significant QSAR equation was obtained from regression analysis at the 10% significant level, whereas, dependent variable is biodegradation rate constants of BPMC, chlorothalonil, dichlorvos and methidathion, vapor pressures, partition coefficients and water solubilities of the pesticides are independent variables. Also, a significant linear equation was obtained from regression analysis at the 1% significant level, whereas, dependent variable is biodegradation rate constants of BPMC, chlorothalonil, dichlorvos and methidathion, hydrolysis rate constants of the pesticides are independent variables. It is suggested that the pesticides will be degraded by main degradation factor when the pesticides was affected both hydrolysis and biodegradation.

• Journal of Food Hygiene and Safety
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• v.14 no.3
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• pp.249-254
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• 1999

The present study was performed to investigate biodegradation rate of BPMC(2-sec-butylphenyl methyl carbamate) and chlorothalonil. In the biodegradation test of two pesticides by the modified river die-away method from June 17 to August 22, 1998, the biodegradation rate constants and half-life were determined in Nakdong(A) and Kumho River(B). Bio- degradation rate of BPMC was 27% in A sampling point, 40% in B sampling point after 7 days. Biodegradation rate constants and half-life of BPMC were 0.0460 and 15.1 days in A sampling point, 0.0749 and 9.3 days in B sampling point, respectively. Biodegradation rate of chlorothalonil was 100% in A and B sampling points after 7 days. Biodegradation rate constants and half-life of chlorothalonil were 0.1416 and 4.9 hours in A sampling point, 0.1803 and 3.8 hours in B sampling point, respectively. Biodegradation rate of chlorothalonil was faster than that of BPMC. Correlation analysis between biodegradation rate constants of pesticides and water quality(DO, BOD, SS, ABS, $NH_3-N\;and\;NO_3-N$) showed significant correlation with BOD, SS and $NH_3-N$. Furthermore, regression analysis with BOD, SS and $NH_3-N$ as independent variable and biodegradation rate constant as independent variable showed a significant linear equation. These results suggested that BPMC and chlorothalonil were mainly degraded by biodegradation, and the difference in biodegradation of two pesticides was due to difference of water quality.