• Title/Summary/Keyword: 미소환경

Search Result 322, Processing Time 0.023 seconds

Level and Fate of Arsenic(As) in the Namdae Stream (강릉 남대천 수계의 비소(As) 농도 분포 및 거동특성 연구)

  • Yoon, Yi-Yong;Kim, Kyung-Tae
    • Journal of Korean Society of Environmental Engineers
    • /
    • v.22 no.1
    • /
    • pp.149-157
    • /
    • 2000
  • This paper presents the first results of dissolved arsenic in the Kangnung Namdae stream. The distribution of As concentrations measured in 28 August (high water flow) and in 21 November 1997 (low water flow) differs from those of other metals measured during the same period; The concentrations of Doam-dam are lower than those of Obong-dam and accumulation in the downstream in the period of low water flow is not pronounced. The As concentration in the downstream under the low water flow is lower than under high water flow, reciprocally to other metals. Freshwater concentrations are comparable with those measured in pristine river and lower than the world average and the diffrence of concentrations measured during two period is minute. Therefore, the As concentrations in the Namdae stream are background level and the source of As contamination does not exist. In the mixing zone between the freshwater and Donghae seawater, As behave conservatively, indicating the absence of any significant removal or mobilization processes. A first estimation of total dissolved As input from Namdae stream to Donghae coastal sea shows 65.12 kg/yr.

  • PDF

Community Structure of Plankton in Eutrophic Water Systems with Different Residence Time (체류시간이 서로 다른 부영양 수계에서 플랑크톤군집의 생태학적 특성)

  • Lee, Uk-Se;Han, Myeong-Su
    • Korean Journal of Ecology and Environment
    • /
    • v.37 no.3 s.108
    • /
    • pp.263-271
    • /
    • 2004
  • To collect the basic ecological information about the microbial food webs in eutrophic water system with different residence time, the monthly variation of bacterioplankon (bacteria and small-sized cyanobacteria) and nanoplankton (phytoplankton and protists) were examined from December 2000 to September 2001. Kyungan stream is shorter in resident time (ca.5.4 d) than Seokchon reservoir (ca.72 d), even though they showed the same pattern in precipitation. With the basic environments, we examined the biomass (standing crops and its carbon content) of each plankton collected from the surface water. Large-sized planktons flourished in the time of low temperature, while small planktons were in the time of the high temperature period. Especially, in the Kyungan stream with much disturbance by rainfall and outflow, high diversity showed in term of species and cell morphology, compared to that of Seokchon lake. The time-lag relationship remarkably showed between phytoplankton and bacteria in Seokchon reservoir, and between protists and bacteria in Kyungan stream, respectively.

The Process Grandchildren's Growth: - Based on the Life History Approach - (조손가족 손자녀의 성장과정에 관한 생애사 연구)

  • Yoon, Ju Young;Koh, Bo Sun
    • Korean Journal of Family Social Work
    • /
    • no.56
    • /
    • pp.69-104
    • /
    • 2017
  • This research aims to understand in depth and contextually of the grandchildren 's growth with their grandparents. The data were collected through in-depth interviews with observation and documents and analyzed using life history approach. The life history method was based on Mandelbaum(1973)'s framework including 'life dimensions', 'turning points', and 'adaptations'. After the analysis, central themes in each domain emerge as follows; 'social prejudice', 'growing poverty', 'a painstaking smile', 'more polite and honest', and 'being alone' in life dimensions, 'parentless children', 'a painful memory, outcast', and 'going to college' in turning points, and 'a willing person, parents', 'a blessed person', 'self-reliance and scale of economic life', and 'diligence and inborn cheerfulness' in adaptations, respectively. Based on these results, several intervention strategies and implications for healthy growth of grandchildren.

Evaluation on Compression Wave Velocities and Moduli of Gyeongju Compacted Bentonite (경주 압축 벤토나이트의 압축파속도와 탄성계수 산정 연구)

  • Balagosa, Jebie;Yoon, Seok;Choo, Yun Wook
    • Journal of the Korean Geotechnical Society
    • /
    • v.35 no.7
    • /
    • pp.41-50
    • /
    • 2019
  • Gyeongju bentonite is a buffer material primarily considered in Korea and it is highly compacted as a part of an engineered barrier system (EBS) of high-level radioactive waste repository. The compacted bentonite undergoes swelling stress by groundwater penetration and thermal stress by decay heat from a canister. Therefore, the mechanical properties of the compacted bentonite buffer material is crucial for the performance assessment of EBS. This paper aims to evaluate deformation properties of Gyeongju compacted bentonite using seismic methods. Two sets of compacted bentonite specimens were prepared having dry densities of $1.59g/cm^3$ and $1.75g/cm^3$ with water contents of 10.6% and 8.7%. Free-free resonant column tests were performed to measure constrained and unconstrained compression wave velocities. With the measured wave velocities, Young's modulus ($E_{max}$) and constrained modulus ($M_{max}$), material damping ratio ($D_{min}$), and Poisson's ratio at small strain were determined. As results, this paper evaluates the deformation properties of Gyeongju compacted bentonite and compares them with the results of previous researches.

Hydration and Mechanical Properties of High-volume Fly Ash Concrete with Nano-silica (나노 실리카를 혼입한 하이볼륨 플라이애시 콘크리트의 수화도 및 역학적 특성)

  • Cha, Soo-Won;Lee, Geon-Wook;Choi, Young-Cheol
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.26 no.6
    • /
    • pp.112-119
    • /
    • 2022
  • Recently, as carbon neutrality has been important factor in the construction industry, many studies have been conducted on the high-volume fly ash concrete. High volume fly ash concrete(HVFC) is usually made by replacing more than 50% of cement with fly ash. However, HVFC has a disadvantage of low compressive strength in early age. To overcome this shortcoming of HVFC, improve this, interest in techonolgy using nanomaterials is increasing. Nano silica is expected to improve the early age strength of HVFC as a pozzolanic material. This study investigated the effect of nano silica on the early hydration reaction and microstructure of HVFC. The early hydration reaction of HFVC was analyzed through setting time, isothermal calorimeter, compressive strength and thermal weight analysis. In addition, the microstructure of HVFC was measured by mercury intrusion porosimetry. From the test results, it was confirmed that nano silica increased the early age strength and improve the microstructure of HVFC.

Comparative Study on Cross-anisotrupic Elasticity of Granular Soils Based on Lab-scale Triaxial Experiment and Discrete Element Analysis (실내 삼축시험과 개별요소법(DEM)을 이용한 사질토 직교 이방 탄성 특성의 미시역학적 비교 분석)

  • Jung, Young-Hoon;Lee, Jae-Hoon;Chung, Choong-Ki
    • Journal of the Korean Geotechnical Society
    • /
    • v.23 no.8
    • /
    • pp.59-68
    • /
    • 2007
  • The comparative study using the lab-scale experiment and the discrete element analysis is attempted to analyze the cross-anisotropic elasticity of granular soils. The lab-scale experiment consists of the small stress-controlled triaxial cyclic tests and the bender element tests. In the discrete element analysis the simulations of lab-scale cyclic tests are conducted in the various directions. Good agreement between the experimental data and the simulation on the elastic properties in the axial and shear directions confirms the usefulness of the discrete element method. The comparative analysis of the difference in the experimental data and the simulation of radial cyclic tests shows that the discrete element method can successfully be used to check the reasonable magnitude of each measurement in the experiments.

Development of multi-depth and artificial intelligence smart measuring device for analyzing surface water-groundwater correlation characteristics (지표수-지하수 연계 특성 분석용 다심도 및 인공지능 스마트 계측장치 개발)

  • Lim, Woo-Seok;Hwang, Chan-Ik;Choi, Myoung-Rak;Kim, Gyoo-Bum
    • Proceedings of the Korea Water Resources Association Conference
    • /
    • 2020.06a
    • /
    • pp.380-380
    • /
    • 2020
  • 가뭄 피해 극복을 위한 인공 함양지 통합관리시스템의 일부로써 지표수-지하수 연계 특성 분석용 의사결정을 전달하는 인공지능 스마트 계측기의 필요성이 꾸준히 제기되어 왔으나 실용성과 효율성을 동시에 갖춘 계측기는 시장에 출시되지 않았다. 기존의 계측기는 단순 측정이 목적이었으며 분석을 위해서는 일정 기간 직접 계측하여 분석하거나, 계측데이터를 원격 망을 통하여 서버로 전송하고 관리자가 데이터를 해석하는 방식을 취하였다. 또한, 수질 계측과 수질의 미소 변동성을 동시에 계측하여 수질 변화상태를 판단 할 수 있는 수질 계측기는 상품화되지 않아 다목적 수질 분석에 한계점을 갖고 있다. 이러한 한계점이 기존의 지하수 수질 계측기로는 불가능한 수중 라돈을 채수 없이 계측 가능하도록 하고, 순간 수질 변화 및 수질 변화 요인분석이 가능한 계측을 위하여 라돈, 전도도, 수위, 수온 및 필름형 pH 센서를 개발하여 적용한 다항목 계측기로 통합하는 연구가 필요한 이유이다. 개발한 계측기는 빅데이터 기반의 지능형 수질 변동성 분석 알고리즘을 내장하고 수직 깊이 방향의 다중심도 계측이 가능하도록 핵심적인 통신 연결성을 확보하였고 다양한 수질에서 견딜 수 있으며 특히 인공함양에서 발생하는 철, 망간에 부식되지 않는 재질을 이용하여 설계한 '지표수-지하수 연계 특성 분석용 다심도 및 인공지능 스마트 계측장치'이다. 본 장치는 기존 지하수 수질 계측기에서는 불가능하였던 순간 수위변화 및 수위변화 요인분석이 가능한 계측을 위하여 초당 측정 샘플링 주파수(10Hz)를 높인 계측회로를 개발하여 적용하였다.

  • PDF

Estimation on Physical Microhabitat Suitability for Species of the Mayfly Genus Ephemera (Ephemeroptera: Ephemeridae) Using Probability Distribution Models (확률분포모형을 이용한 하루살이속(Ephemera) 종들의 물리적 미소서식처 적합도 평가)

  • Dongsoo Kong;Jeaha Song
    • Journal of Korean Society on Water Environment
    • /
    • v.39 no.5
    • /
    • pp.396-412
    • /
    • 2023
  • Species from the mayfly genus Ephemera (Order Ephemeroptera) was assessed for their physical microhabitat suitability (namely E. strigata, E. separigata, and E. orientalis-sachalinensis). Probability distribution models (Exponential, Normal, Lognormal, Logistic, Weibull, Gamma, Beta, and Gumbel) based on the data collected from 23,957 sampling units of 6,787 sites in Korea from 2010 to 2021 were used. Mode and standard deviation calculated from the best-fitting models to species distribution along a water depth gradient were 265 cm and 159 cm in E. orientalis-sachalinensis; 10 cm and 83 cm in E. strigata; 20 cm and 15 cm in E. separigata, respectively. The current velocity gradient was 22 cm/s and 40 cm/s in E. orientalis-sachalinensis; 60 cm/s and 53 cm/s in E. strigata; 82 cm/s and 25 cm/s in E. separigata, respectively. The mean diameter (phi scale) of substrate grains were -3.6 and 2.2 in E. orientalis-sachalinensis; -7.4 and 1.5 in E. strigata; -5.8 and 0.9 in E. separigata, respectively. Habitat suitability range of E. orientalis-sachalinensis was estimated to be 161~369 cm (water depth), 5~44 cm/s (current velocity), -5.2~-2.0 (mean diameter); 3~34 cm (water depth), 36~94 cm/s (current velocity), -8.1~-6.3 (mean diameter) for E. strigata; 12~32 cm (water depth), 63~96 cm/s (current velocity), -6.3~-5.2 (mean diameter) for E. separigata. In relative comparison, E. orientalis-sachalinensis was estimated to be rheophobic, eurybathophilic, and eurypsephophilic; E. strigata to be euryrheophilic, bathophobic, and lithophilic; E. separigata to be stenomesorheophilic, stenobathophobic, stenolithophilic.

Evaluation of Hydration Characteristics and NOx-removal Performances of Cement Paste Containing Refined TiO2 Obtained from Waste Sludge (폐수 슬러지에서 정제된 TiO2를 혼입한 시멘트 페이스트의 수화특성 및 질소산화물 제거 성능 평가)

  • Yoon, Hyunno;Seo, Joonho;Kim, Seonhyeok;Bae, Jinho;Kil, Taegeon;Lee, Haeng-Ki
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.41 no.4
    • /
    • pp.357-364
    • /
    • 2021
  • The present study investigated the hydration properties and NOx-removal performances of the cement pastes containing three different types of TiO2. Two commercially available TiO2 (P-25 and NP-400) and refined TiO2 (GST) obtained from waste sludge were incorporated to cement paste at levels of 0, 5, 10, and 20 wt%. Isothermal calorimetry test results indicated that the TiO2 incorporation induced a notable influence on the reaction kinetics of cement paste, showing the highest cumulative heat release in the samples containing P-25, followed by NP-400 and GST. Quantitative X-ray diffractometry as calculated by the Rietveld method identified that the incorporated TiO2 promoted the formation of C-S-H, ultimately leading to the enhancement in the 28 day-compressive strength of cement pastes. As revealed by SEM/EDS analysis, the content of distributed Ti elements on the surface of the samples was in the order of P-25, GST, and NP-400. Regardless, the NOx-removal performance was the highest in the sample containing P-25, followed by NP-400 and GST.

Water Temperature and Sound Environment Characteristics of Huanren Brown Frog Oviposition Sites (계곡산개구리 산란지의 수온 및 음환경 특성)

  • Ki, Kyong-Seok;Gim, Ji-Youn;Lee, Jae-Yoon
    • Korean Journal of Environment and Ecology
    • /
    • v.30 no.3
    • /
    • pp.344-352
    • /
    • 2016
  • The goal of this study was to identify the water temperature and sound environment of oviposition sites of the Huanren brown frog (Rana huanrensis), which breeds in valleys in early spring. The study was conducted in Chiak National Park, central Korea, between March 23 and April 24, 2015. Correlation analysis of the physical factors of oviposition sites revealed that the number of egg clutches was positively correlated (p < 0.05) with the water temperature and negatively correlated (p < 0.05) with the sound volume of the oviposition sites. However, no correlation was found between clutch number and the total area or depth of water. The water temperature of the oviposition sites was $2.2^{\circ}C$ higher on average than that of the mainstream (p < 0.001). To avoid the low early spring temperatures, R. huanrensis spawned in sites with accumulated water, in which the depths were less than 10cm and the temperature was relatively high. Further, eggs were spawned in clusters in small spaces to maximize the thermal insulation effect. In terms of noise levels, oviposition sites were found to be 6.9 dB quieter than the mainstream (p<0.001). In conclusion, R. huanrensis was found to spawn in warm, quiet, and small oviposition sites in valleys to avoid low early spring temperatures and loud water noise. This study is significant because it is the first to characterize the sound environment of amphibian oviposition sites.