• Ecology and Resilient Infrastructure
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• 제3권4호
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• pp.215-220
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• 2016

A new immobilization technique of nanoscale $TiO_2$ powder to expanded polystyrene (EPS) balls with temperature-controlled melting method was developed, and the photocatalytic activity of $TiO_2$ powder-embedded EPS balls were evaluated using methylene blue (MB) solution under ultraviolet irradiation (${\lambda}=254nm$). Based on the scanning electron microscope (SEM) images and associated energy-dispersive X-ray spectroscopy (EDX) analysis, the components of the intact EPS balls were mainly carbon and oxygen, whereas those of $TiO_2$-immobilized EPS balls were carbon, oxygen, and titanium, indicating that relatively homogenous patches of $TiO_2$ and glycerin film were coated on the surface of EPS balls. Based on the comparison of degradation efficiencies of MB between intact and $TiO_2$-immobilized EPS balls under UVC illumination, the degradation efficiencies of MB can be significantly improved using $TiO_2$-immobilized EPS balls, and surface reactions in heterogeneous photocatalysis were more dominant than photo-induced radical reactions in aqueous solutions. Thus, $TiO_2$-immobilized EPS balls were found to be an effective photocatalyst for photodegradation of organic compounds in aqueous solutions without further processes (i.e., separation, recycling, and regeneration of $TiO_2$ powder). Further study is in progress to evaluate the feasibility for usage of buoyant $TiO_2$-immobilized EPS to inhibit the excessive growth of algae in rivers and lakes.

• 한국물환경학회지
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• 제33권3호
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• pp.326-333
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• 2017

The lakes and reservoirs have been reported as important sources of carbon emissions to the atmosphere in many countries. Although field experiments and theoretical investigations based on the fundamental gas exchange theory have proposed the quantitative amounts of Net Atmospheric Flux (NAF) in various climate regions, there are still large uncertainties at the global scale estimation. Mechanistic models can be used for understanding and estimating the temporal and spatial variations of the NAFs considering complicated hydrodynamic and biogeochemical processes in a reservoir, but these models require extensive and expensive datasets and model parameters. On the other hand, data driven machine learning (ML) algorithms are likely to be alternative tools to estimate the NAFs in responding to independent environmental variables. The objective of this study was to develop random forest (RF) and multi-layer artificial neural network (ANN) models for the estimation of the daily $CO_2$ NAFs in Daecheong Reservoir located in Geum River of Korea, and compare the models performance against the multiple linear regression (MLR) model that proposed in the previous study (Chung et al., 2016). As a result, the RF and ANN models showed much enhanced performance in the estimation of the high NAF values, while MLR model significantly under estimated them. Across validation with 10-fold random samplings was applied to evaluate the performance of three models, and indicated that the ANN model is best, and followed by RF and MLR models.

• 생태와환경
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• 제38권2호통권112호
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• pp.261-270
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• 2005

매년 남조 Microcystis aeruginosa가 대발생하는 인공연못에 100 L mesocosm를 설치하고 생물제재 (Xantobacter autotrophycus + casitone)를 혼합 처리한 결과, 환경요인의 변화(pH, DO감소, 영양염 증가)와 함께 식물플랑크톤 군집의 뚜렷한 변화가 관찰되었다. 생물제재 처리후 M. aeruginosa는 점차 감소하여 8일에는 관찰되지 않았고, 식물플랑크톤 총 밀도의 약 60% 이상이 감소하였다. 또한 남조의 소멸과 함께 조체성 독소의 감소 및 용존성 독소가 증가하였으며, 뚜렷한 영양물질의 증가에도 불가하고 현존량이 증가하는 종은 나타나지 않았다. 이러한 영양물질이나 용존성 독소의 증가는 생물제재를 이용한 남조류 제어가 상수원 저수지와 같은 장소보다는 규모가 작은 연못이나 저수지 등에 적합하며, 생물제재 처리 이후 수질변화에 대한 적극적인 수질관리 대책이 마련되어야 할 것으로 판단되었다.

• 생태와환경
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• 제38권2호통권112호
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• pp.188-195
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• 2005

2000년부터 2004년까지 5년간 횡성호 일대의 어류군집 동태를 조사한 결과는 다음과 같다. 조사기간동안 출현한 어류는 총 10과 39종이었으며 이 중 한국고유종은 Rhodeus pseudosericeus 등을 포함하여 총 17종 (43.59%) 이었다. 우점종은 Acheilognathus lanceolatus (20.10%), Zacco platypus (15.94%), Z. temmincki (6.92%), Carassius cuvieri (6.33%), A. rhombeus (6.18%), Pungtungia herzi (5.13%), Pseudorasbora parva (4.93) 등이었다. 조사시기별 출현종을 근거로 생활형에 따른 어류군집은 담수가 되면서 점차 저서성 어종의 수가 감소하였고 부유성 어종이 증가하는 것으로 나타났다. 또한 조사시기별 유사도 분석을 한 결과 각 조사시기는 비가중치 평균연결법 (UPGMA)에 의해 3개의 그룹으로 나누어졌다. 한편 다른 인공호와 본 조사의 어류상을 근거로 유사도 분석을　한 결과 수계에 따라 2개의 그룹으로 나누어졌으며 같은 수계 내에서 다시 3개의 그룹으로 나누어졌다. 이 중 횡성호 어류군집의 현재 상태는 북한강 중류의 춘천-청평호와 유사한 것으로 나타났다.

• Toxicological Research
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• 제29권1호
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• pp.69-79
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• 2013

The purpose of this study was to investigate the current status of metal pollution in the sediment from rivers, lakes, and streams in active gold mining districts in Ghana. Two hundred and fifty surface sediment samples from 99 locations were collected and analyzed for concentrations of As, Hg, Cr, Co, Cu, Fe, Zn, Pb, Cd, Ni, and Mn using inductively coupled plasma-mass spectroscopy (ICP-MS). Metal concentrations were then used to assess the human health risks to resident children and adults in central tendency exposure (CTE) and reasonable maximum exposure (RME) scenarios. The concentrations of Pb, Cd, and As were almost twice the threshold values established by the Hong Kong Interim Sediment Quality Guidelines (ISQG). Hg, Cu, and Cr concentrations in sediment were 14, 20, and 26 times higher than the Canadian Freshwater Sediment Guidelines for these elements. Also, the concentrations of Pb, Cu, Cr, and Hg were 3, 11, 12, and 16 times more than the Australian and New Zealand Environment and Conservation Council (ANZECC) sediment guideline values. The results of the human health risk assessment indicate that for ingestion of sediment under the central tendency exposure (CTE) scenario, the cancer risks for child and adult residents from exposure to As were $4.18{\times}10^{-6}$ and $1.84{\times}10^{-7}$, respectively. This suggests that up to 4 children out of one million equally exposed children would contract cancer if exposed continuously to As over 70 years (the assumed lifetime). The hazard index for child residents following exposure to Cr(VI) in the RME scenario was 4.2. This is greater than the United States Environmental Protection Agency (USEPA) threshold of 1, indicating that adverse health effects to children from exposure to Cr(VI) are possible. This study demonstrates the urgent need to control industrial emissions and the severe heavy metal pollution in gold mining environments.

• 한국물환경학회지
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• 제30권5호
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• pp.524-531
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• 2014

Korea has been trying to manage water quality of rivers and lakes in many ways. Ministry of Environment is making continuous efforts of operation control improvement such as strengthening effluent standards in sewage treatment plants and expanding Tele-Monitoring System (TMS). However, evaluation method for operations of sewage treatment plants and establishment system of effluent standards are inadequate. The objective of this study is to evaluate for operations of sewage treatment plants using statistics technique such as frequency analysis, percentile, normal distribution analysis. We used the effluent data (BOD, COD, SS) collected at 299 plants in 2012. The values were very low by comparison with standards. The Data followed a normal distribution. We think that distribution characteristics are closely related with effluent standards, especially T-P and BOD. Statistics technique attempted in this study can be used to evaluate for operations of sewage treatment plants and assess the appropriateness of effluent standards based on TBEL(Technology-based effluent limitation). And, this technique can be used to figure out the overall level of plants, the status of each plant and the favorable treatment process for each item (BOD, COD etc.). Data acquired through this method can be used to improve facilities and operation techniques and decide on a sewerage policy.

• 한국물환경학회지
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• 제36권1호
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• pp.1-13
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• 2020

The purpose of this study was to investigate the thermal and chemical stratification in Lake Paldang 2013-2018 weekly using Schmidt's stability index (SSI) and the index of chemical stratification (IC-i). The annual average for SSI was 19.1 g cm/㎠ with the maximum value of 45.3 g cm/㎠ in the summer and the minimum value of 4.8 g cm/㎠ in fall-winter showing seasonal differences as well as increased vertical mixing in the summer. The lake stability increased higher in 2016 as compared with the other period. The most influential factors of thermal stratification were temperature and heavy rainfall. Especially, high water temperature and a prolonged residence duration caused by reduced rainfall and inflows could result in an increase of the stratification period. While decreasing inflow and outflow at the end of the rainfall, the thermal stratification was restrengthened within 7-14 days, and then stabilized rapidly before the rainfall. IC-DO increased with high air temperature in the spring and fall-winter. However increasing sunshine duration and residence time and decreasing rate of outflow caused an increase of IC-DO in the summer. Rainfall (less than 800 mm/year) and discharge (less than 200 CMS) significantly declined in 2015 resulting in IC-DO (0.77) increased more than three times over the other years and bottom water hypoxia occurred. The SSI and IC-i used in this study could be applied to other lakes to understand changes in stratification and mixing dynamics.

• Journal of Microbiology
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• 제34권2호
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• pp.131-136
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• 1996

In order to known the extend of contribution to the degradation of organic materials and nutrient recycling by sulfate-reducing bacteria (SRB) and methane-producing bacteria (MPB) in sediment, the distribution and activity of these two groups of microorganisms were studied montly in 1994 at two sites, one littoral (Sanggulri) and the other profunndal (DAM), in Lake Soyang. In the seasonal distribution of two microorganisms, SRB were 1.07 $\times$ 10$^{3}$-2.42 $\times$ 10$^{5}$ cells/g-dry weight at Sanggulri, 2.40 $\times$ 10$^{5}$ -1.29 $\times$ 10$^{6}$ at Dam and MPB were 0.52 $\times$ 10$^{3}$ cells/g-dry weight at Sangguri and 1.44 $\times$ 10$^{3}$-6.89 $\times$ 10$^{3}$ at Dam. In these results, the density of SRB in Lake Soyang is much higher than other lakes. These high values might be due to higher sulfate concentration, 0.69-4.05 mM, than normal freshwater, 0.01-1.2 mM. And a good correlation of SRB and chlorophyll a concentration implied that the important environmental factor on distribution of SRB might be the concentration of available organic matter. In a comparison of sulfate-reducing rate and methane producing rate in 1995, the activity of SRB for the degradation of organic matter was higher than MPB by factor of 359. Conclusively SRB superior to MPB in the distribution and activity are more important annearobic bacteria in Lake Soyang sediments.

• 미생물학회지
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• 제44권3호
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• pp.251-257
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• 2008

대청호와 용담호로부터 조류 독소인 microcystin을 생산하는 남조세균을 분리하고, 이의 16S rRNA와 microcystin 생합성 유전자(mcyA)를 분석하였다. 분리된 조류 중 대청호에서 분리된 DC-2와 총담호에서 분리된 YD-1, YD-6은 16S rRNA와 mcyA 유전자 염기서열을분석한 결과 Microcystis aeruginosa에 속하는 것으로 판단되었다. 용담호에서 분리된 YDS2-3의 경우, mcyA 유전자는 M. aeruginosa와 매우 유사하나 16S rRNA 유전자는 매우 상이한 것으로 나타나 Microcystis 속에 속하는 새로운 종일 가능성 이 있는 것으로 판단되었다. 대청호와 용담호 시료로부터 mcyA 유전자 library를 구축하여 분리된 조류의 유전자와 비교한 결과, DC-2의 mcyA 유전자가 두 호수에서 가장 우점하는 것과 일치하였다. 본 연구에서 분리된 조류는 독성 조류의 모니터링 및 제어에 관한 연구에 활용될 수 있을 것으로 사료된다.

• 환경생물
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• 제38권3호
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• pp.433-449
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• 2020

Nine fish and one clam species were collected from freshwater environments in Korea, including four lakes, two streams, and the Nakdong River, to investigate the host-associated bacteria. Hundreds of bacterial strains were isolated from the samples using a cell sorter and a dilution plating method. After identification of the bacterial strains using 16S rRNA gene sequences, 42 strains with greater than 98.7% sequence similarity with validly published species were determined to be unrecorded bacterial species in Korea. These strains were phylogenetically diverse and assigned to four phyla, six classes, 17 orders, 27 families, and 32 genera. At the genus level, the unrecorded species were classified as Corynebacterium, Mycobacterium, Mycolicibacterium, Gordonia, Williamsia, Modestobacter, Brachybacterium, Sanquibacter, Arthrobacter, and Mycolicibacterium of the class Actinobacteria; Empedobacter, and Flavobacterium of the class Flavobacteriia; Fictibacillus, Psychrobacillus, Cohnella, Paenibacillus, Rummeliibacillus, Enterococcus, and Vagococcus of the class Bacilli; Aquamicrobium, Paracoccus, and Sphingomonas of the class Alphaproteobacteria; Achromobacter, Delftia, and Deefgea of the class Betaproteobacteria; and Aeromonas, Providencia, Yersinia, Marinomonas, Acinetobacter, and Pseudomonas of the class Gammaproteobacteria. The 42 unrecorded species were subjected to further taxonomic characterization using gram staining, cellular and colony morphological determination, biochemical analyses, and phylogenetic analyses. This paper provides detailed descriptions of the 42 previously unrecorded bacterial species.