• 한국환경보건학회지
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• 제29권1호
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• pp.19-27
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• 2003

Coliforms is currently being used as the standard of environmental water qualify to evaluate the level of source water quality especially condition of fecal contamination. However, not properly applied to water quality management. So in this study, in addition to Coliforms, fecal contamination indicator bacteria turk at Feral Coliforms(FC), E. coli, Fecal streptococci(FS), Clostridium and environmental parameters related with it's distribution were investigated on a monthly basis in 6 water intakes of Han River. The mean of BOD, DO, SS and pH, benchmarks of source water management were maintained the second grade of environmental water quality standard applied to Han River but Coliforms exceeded it. Distribution of Coliforms ranged from 1.0×10¹ to 2.7 10/sup 5/ CFU/ml, FC ranged from ND to 5.3×10¹ CFU/ml, E. coli ranged from ND to 9.2×10¹ CFU/ml, FS ranged from ND to 2.5×10¹CFU/ml, they were steepy rise on July and August in common when rainfalls was heavy and water temperature was high, but Clostridium perfringens ranged from 1.7×10¹to 1.7×10¹CFU/ml not fluctuate by month. Statistical analysis of sampling data showed that most significant correlations occurred among FC and Coliforms(r = 0.840), E. coli(r = 0.792), FS(r = 0.687) and environmental parameters(temperature, turbidity, SS, rotor were all r > 0.60) while no significant correlation was observed between ammonia generally recognized fecal contamination indicator and bacteria. Identification of the coliforms showed that Enterobacter, Klebsiella, Citrobacter were comprised of 32%, 24%, 16% respectively, and E. coli were 7% of it. while E. coli was made up 85.9% of FC. The mean value of FC/Coliforms ratio, 5.2(0.1-42) were higher in Amsa, Guui than Jayang. Fecal coliforms, as those are able to reflect more particularly the extent of the fecal contamination, were considered useful in deciding the level of water treatment while monitoring the fecal contamination from the source of water supply. Therefore, it is expected that the water quality is going to be managed more efficiently by using fecal coliforms supplementarily to total coliforms which are current standard item of water-quality environment.

• 한국물환경학회지
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• 제39권1호
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• pp.20-29
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• 2023

This study analyzed the relationship between harmful cyanobacterial abundance and environmental factors in order to figure out the causes of the recent increase of cyanobacteria in Lake Dukdong from 2019 to 2021. Lake Dukdong, which is used as a drinking water source for Gyeongju City, has an algae alert system in place. Lake Dukdong has maintained good water quality, but algae alert level 1 (over 1,000 cells/mL) has been issued in recent years. As a result of Pearson correlation analysis (from May to Oct.), the cell density of Microcystis and Aphanizomenon, which form part of the most harmful cyanobacteria genus, were significantly positively correlated with the water temperature and water storage volume. T-test was performed to compare the data from 2016-2018 and 2019-2021 (from May to Oct.). The average density of harmful cyanobacteria cells increased about six-fold from 54 to 344 cells/mL. There were significant differences in water temperature, pH, total nitrogen (TN), total phosphorus (TP), TN/TP ratio, water storage volume, and cyanobacterial cell density. Water temperature increased from 19.2 to 22.8 ℃. TP concentration increased from 0.017 to 0.028 mg/L. The main cause of the recent increase of harmful cyanobacteria in Lake Dukdong is thought to be the increase in water temperature, TP concentration, and water storage volume from 2019 and 2021, resulting in more favorable conditions for cyanobacterial growth.

• Computers and Concrete
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• 제21권6호
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• pp.697-703
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• 2018

Compressive strength is one of the most important engineering properties of concrete, and testing of the compressive strength of concrete specimens is often costly and time consuming. In order to provide the time for concrete form removal, re-shoring to slab, project scheduling and quality control, it is necessary to predict the concrete strength based upon the early strength data. However, concrete compressive strength is affected by many factors, such as quality of raw materials, water cement ratio, ratio of fine aggregate to coarse aggregate, age of concrete, compaction of concrete, temperature, relative humidity and curing of concrete. The concrete compressive strength is a quite nonlinear function that changes depend on the materials used in the concrete and the time. This paper presents an adaptive neuro-fuzzy inference system (ANFIS) for the prediction of concrete compressive strength. The training of fuzzy system was performed by a hybrid method of gradient descent method and least squares algorithm, and the subtractive clustering algorithm (SCA) was utilized for optimizing the number of fuzzy rules. Experimental data on concrete compressive strength in the literature were used to validate and evaluate the performance of the proposed ANFIS model. Further, predictions from three models (the back propagation neural network model, the statistics model, and the ANFIS model) were compared with the experimental data. The results show that the proposed ANFIS model is a feasible, efficient, and accurate tool for predicting the concrete compressive strength.

• 한국물환경학회지
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• 제31권2호
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• pp.159-165
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• 2015

The organic matter sources of phytoplankton and related environmental factors influencing algal bloom in Paldang reservoir were studied using nitrogen and carbon isotope ratio(${\delta}^{15}N$, ${\delta}^{13}C$). Phytoplankton samples for stable isotope analysis were collected from four points in reservoir using a plankton net. Physicochemical water quality, algal taxa and hydrological data were collected from published monitoring material. Phytoplankton samples were analyzed by IRMS. CN ratio of each sample was very similar to that of phytoplankton from literature cited. ${\delta}^{15}N$ of each sample was decreased during July. Mixing and dilution of nitrogen sources due to increment of influx by concentrated rainfall were considered as the main reason for the decline of ${\delta}^{15}N$. Based on analyzed ${\delta}^{15}N$ value of each sample, nitrogen source of Bughan river sample was presumed to come from soil. The nitrogen sources of Namhan river and Kyeongan stream samples seemed to be sewage or animal waste. Low ${\delta}^{15}N$ value in August (2012) seemed to be influenced by isotope fractionation due to the blooming of nitrogen-fixation blue-green algae (Anabaena spp.). Variation in ${\delta}^{15}N$ values particularly by blue-green algal bloom was considered the important factor for estimating the organic matter sources of phytoplankton.

• 한국물환경학회지
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• 제33권2호
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• pp.130-139
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• 2017

With the need to evaluate accuracy of real-time measurement of cyanobacterial fluorescence to determine cyanobacterial blooms, this research examined 357 paired data (2013-2016) comprising both microscopic toxic cyanobacterial cell counts and concurrent real-time cyanobacterial concentrations at 2 sites (YS1 and YS2) in Yeongsan river. The increase in real-time cyanobacterial concentration was closely associated with the exceedance of 5,000 cyanobacterial cells/ml (odds ratio [OR] 1.07, 95% confidence interval [CI] 1.03-1.12) and 10,000 cells/ml (OR 1.08, 95% CI 1.04-1.12) at YS2 site. The area under the receiver operating characteristic (ROC) curve for the real-time cyanobacterial measurement at the YS2 site was 0.93, which indicates the measurement provides a high accurate detection of cyanobacterial blooms. On the ROC curve, the early alert levels of real-time cyanobacteria ranging $16-23{\mu}g$ chl-a/L would produce acceptable sensitivity of 79% and specificities greater than 90%. The real-time fluorescence measurement was found to be an accurate indicator of cyanobacteria and can serve as a tool for detecting toxic cyanobacterial bloom events in Youngsan river.

• 한국농공학회논문집
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• 제52권4호
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• pp.19-26
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• 2010

To provide the basic information for the water quality management of the Sumjin River Basin, delivery ratios for flow duration were studied. Using the day-interval data set of discharge and water quality observed from the Chooryeong-cheon watershed, the flow-duration and discharge-load relation curves for the watershed were established, then the load-duration curve was constructed. Delivery ratios for flow duration were also developed. Delivery ratios showed wide variation according to flow conditions. In general, delivery ratio of high flow condition showed higher value reflecting nonpoint source pollution contribution from the forest dominating watershed. To resolve this problem, a regression model explaining the relation between flow rate and delivery ratio was suggested. The delivery ratios for different flow regime could be used for pollutant load estimation and TMDL (Total maximum daily load) development.

• 한국환경과학회지
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• 제20권10호
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• pp.1285-1295
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• 2011

In this study, occurrence status of nonpoint pollutants and characteristics of discharge by each nonpoint pollutants were examined through monitoring on nonpoint pollutants caused when raining in vineyard belonging to the agricultural area of various land use patterns. Also, the first flush analysis limited to studies on the existing non-percolation area was applied to percolation area to ascertain availability and criteria of study. Various water quality and sluice of nonpoint pollutants were analyzed, based on which discharge of nonpoint pollutants in agricultural area was ascertained to be influenced greatly by artificial factors such as period, cultivation, management, etc. Meanwhile, the first flush phenomenon at agricultural area was ascertained to occur, and the first flush was quantified through calculation of the first flush ratio. If MFF30 is based, discharge load by each nonpoint pollutants caused when raining was investigated to include 40.8% on the basis of total discharge. In case of SS in pollutants showed the highest first flush phenomenon of 64.8%. Through such a result, calculation possibility of the initial rain criteria was ascertained, and it was determined that reliability-assured criteria were calculated through further monitoring.

• 한국환경과학회지
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• 제11권7호
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• pp.621-626
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• 2002

Depth-area-duration(DAD) relations are important to hydrological plans and designs for the water resources as well as the flood defence. And these relations have been still in analysis and use today because they can be applied to readily available data. In this paper, rational and consistent DAD models were developed using the multiple regression analysis and basic relationships of area ratio-runoff volume about heavy rainfall occurring in the Im-Jin river basin, 1999. In addition, revised DAD models and curves that can convert a maximum point rainfall to mean area rainfall were developed and evaluated. As results, these models seem to have predictive value in order to plan and design hydrological structures of flood defence in the Im-Jin river basin.

• 한국수자원학회논문집
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• 제45권12호
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• pp.1227-1241
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• 2012

본 연구에서는 목자판과 수면이 포함되어 있는 시차를 가진 두 영상에 대해 직사각형 검사영역을 설정하고 그 상관계수를 분석하여 수면을 판단하는 새로운 수면인식 기법을 제안하였다. 상관계수의 수직적인 값들로부터 임계치, 첨두값, 기울기, 분산비 등 4가지 방법을 이용하여 수면의 위치를 판정하였다. 흔들림 등으로 인해 두 영상의 위치가 불일치하여 생기는 문제를 제거하기 위해 추가로 영상의 흔들림을 보정하는 알고리즘과 통계적 필터링 기법을 적용하였다. 저수시에 촬영한 28개 지점의 영상에 개발한 수면 인식 방법을 적용하였다. 이 방법으로 계산한 수면은 목측 수면과의 평균상대오차가 3.4~5.7 cm 정도로 나타났다. 수면의 요동이 있을 경우, 이 방법은 기존 방법을 보완하여 영상수위계의 수위 측정성능을 높이는데 활용될 수 있을 것이다.

• 물과 미래
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• 제14권1호
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• pp.39-49
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• 1981

하천 재해 방지 및 하천 유지의 관점에서 반드시 구명되어야 하는 하천 사행에 관한 연구는 자연 현상에 대한 관점에서 출발하여, 금세기초부터 체계적이고 과학적인 연구가 진행되어 왔다. 그 발생 원인은 정설이 확립되지 않은 가운데 복합적인 여러 요인에 의하여 사행은 생성, 발달되며, mechanism의 고찰과 함께 계량형태학적 분석으로 사행 특성이 일부 밝혀지고 있다. 본 연구에서는 유로연장 30km 이상의 67개 대상하천에서 사행특성인자인 사행파장(M$$)과 사행대(M$$) 등의 관계를 구명하여 유량과의 상관성을 분석하였다. 또한 하천의 기점에서 종점까지의 직선 거리에 대한 유로 연장의 비인 유로형상계수(L$$)를 처음으로 제안했으며, 유로 연장에 대한 만곡부연장의 비인 Tortuosity(t)와 더불어, 유로연장, 사행경사, Horton의 유역형상계수 등과 상관분석 및 복합회귀분석을 시행한 결과 L$$와 T가 하천사행의 한 척도가 됨을 밝혔다. 사행 유로부와 직유로부에서 유속과 수면경사, 하상굴곡도(degre of sinuosity)를 비교 검토한 결과, 사행 유로부가 직유로부보다 하상의 안정성이 높음을 알았다. 하천 수계별 사행파장과 사행대의 상관식은 각기 선형관계와 역함수관계로 대별되었으며, 남한강 수계의 경우에는 선형관계, 낙동강, 금강 수계의 경우에는 역함수 관계식을 제시하였다.