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Role of hemoglobin in hemoglobin-based remediation of the crude oil-contaminated soil
Hong, Jin-Kyung,Jho, Eun Hea,Choi, Hyo Sub,Kang, Guyoung Elsevier 2018 Science of the Total Environment Vol.627 No.-
<P><B>Abstract</B></P> <P>This study investigated the changes in the indigenous microbial community structure with hemoglobin (Hb) application to determine the role of Hb in Hb-based remediation of crude oil-contaminated soil. The phylogenetic diversity of the bacterial community showed that the Hb addition selected surfactants-producing species, thereby, promoting TPH degradation. The significant increase in the CO<SUB>2</SUB> generation, which can be related to the increase in the bacterial abundance inferred from the 16S rRNA gene copy number, supports the enhanced TPH degradation with Hb application. The similar residual TPH concentrations in the presence of only hydrogen peroxide (H<SUB>2</SUB>O<SUB>2</SUB>) and both Hb and H<SUB>2</SUB>O<SUB>2</SUB> suggested that the role of Hb as a catalyst was not as significant as the role of Hb as a nutrient. Also, in the presence of H<SUB>2</SUB>O<SUB>2</SUB>, a greater recovery of the microbial community structure was observed with the double Hb injection than the single Hb injection. Overall, this study shows that the Hb-based remediation strategies via microbial metabolism can be successfully applied to remediate the crude-oil contaminated Kuwaiti soil.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hemoglobin (Hb) imposed a selective force on surfactant-producing bacterial species. </LI> <LI> Hb application promoted TPH removal in the aged crude oil-contaminated soil. </LI> <LI> Hb-based biocatalytic reaction removed TPH from the crude oil-contaminated soil. </LI> <LI> Bacterial community structure recovered better after the biocatalytic reaction. </LI> <LI> Hb-based remediation can be a viable option for crude oil-contaminated soils. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Rheological properties of loose sands subjected to upward flow
Kang, Hyo Sub,Kim, Yun Tae Canadian Science Publishing 2017 Canadian geotechnical journal: Revue canadienne de Vol.54 No.5
<P> The objective of this study was to investigate the rheological properties of loose sands subjected to upward flow by using a vane-type rheometer that controlled upward flow in the loose sand specimens. Various hydraulic gradients (i.e., i = 0-2.0) were applied to loose sands. The rheological properties of the loose sands, such as yield stress and viscosity, were determined based on the Bingham and Herschel-Bulkley models. The experimental results showed that the flow behavior of loose sand samples exhibited a shear thickening when the Herschel-Bulkley model was applied (i.e., nondimensional flow index n @@>@@ 1) and exhibited a Bingham-like within a limited shear rate range (i.e., 1∼30 1/s). The latter is clearly shown for a relatively high shear rate. As the hydraulic gradient was increased, the flow characteristics were close to the Bingham fluid. Yield stress showed a tendency to decrease linearly as hydraulic gradient was increased. However, the viscosity of the loose sands maintained a constant value irrespective of hydraulic gradient. The test results indicated that the pore fluid pressure resulting from upward flow in a soil sample affects yield stress, which contributes to the initiation of debris flow mobilization. As a result, it was possible to estimate the rheological properties of soil at the condition of liquefaction (critical hydraulic gradient), or initial occurrence of debris flow. </P>
광역 토사재해 물리적 취약성 평가를 위한 Flow-R 모델의 매개변수 분석
강효섭(Kang, Hyo-Sub),김윤태(Kim, Yun-Tae) 한국방재학회 2017 한국방재학회논문집 Vol.17 No.4
This study analyzed effects of input parameters (maximum velocity and travel angle) of Flow-R model on debris flow mobility and deposition, which are essential to evaluate physical vulnerability of debris flow disasters in regional scale. The characteristics of debris flow spreading area and the maximum kinetic energy were analyzed through sensitivity analysis according to input parameters. Back analysis was carried out using total 11 cases of debris flow disasters in 2011, and the reasonable values of input parameters were determined through a comparison with investigated debris flow spreading areas. The results of numerical analysis showed that debris flow spreading area and kinetic energy increased with an increase in maximum velocity, but they converged to asymptote values at critical maximum velocity. The debris flow spreading area decreases with an increase in travel angle. Several case studies showed that travel angles of the 11 debris flow disaster regions were ranged from 10° to 22°, with an average of 15°, and the maximum velocities from 11 m/s to 35 m/s, with an average value of 22 m/s. The estimated travel angle and maximum velocity were compared with the results of previous researches. 본 연구는 광역 토사재해 물리적 취약성 평가를 위해 필요한 Flow-R 입력 매개변수(토석류 최대속도, 이동각)가 토석류의 거동특성에 미치는 영향에 대한 분석을 수행하였다. 입력 매개변수에 따른 민감도 분석을 통해 토석류 확산면적과 최대 운동에너지 변화 특성을 분석하였다. 2011년에 발생한 총 11개 토석류 재해 사례에 대해 Flow-R 모델을 이용하여 역해석을 수행하였고, 조사된 토석류 재해영역과의 비교를 통해 합리적인 입력 매개변수를 산정하였다. 최대속도가 증가함에 따라 토석류 확산범위가 증가하는 것으로 나타났으며, 한계 최대속도 이상에서는 토석류 확산범위가 수렴하는 것으로 나타났다. 이동각이 증가함에 따라 토석류 확산면적은 감소하는 것으로 나타났다. 사례 분석을 통해 산정된 총 11개 토석류 재해지역의 이동각은 10°~22°범위를 나타내며, 평균값은 약 15°로 분석되었다. 역해석을 통해 얻어진 한계 최대속도 값은 11 m/s에서 35 m/s범위를 나타내며, 평균 값은 약 22 m/s로 분석되었다. 산정된 이동각과 최대속도를 기존 연구결과와 비교하였다.
토석류 재해지역 풍화토의 체적농도에 따른 유변물성 특성
강효섭(Kang Hyo Sub),정진호(Jeong Jin Ho),김윤태(Kim Yun Tae) 한국방재학회 2017 한국방재학회논문집 Vol.17 No.2
본 연구는 토석류 재해가 발생된 세 지역(서울 우면산, 춘천 마적산, 용원 문수산)의 풍화토 시료를 이용하여 토석류 유변물성 특성을 조사하였다. 유변물성 실험 시 입자크기의 한계점을 극복하기 위해 대형 베인 레오메타를 이용하여 다양한 함수비(체적농도)에 대한 유변물성 특성을 분석하였다. 유변물성 실험 결과 전단응력과 전단변형률속도 관계는 선형적인 관계 즉, Bingham 모델을 따르는 것으로 나타났다. 함수비가 증가(혹은 체적농도가 감소)함에 따라 동일한 전단변형률속도에서 전단응력은 감소하는 경향을 나타내며, 유동곡선의 기울기 또한 감소하고 있음을 알 수 있다. 작은 함수비와 체적농도의 변화에도 항복응력과 점성 값은 큰 차이를 보인다. 이와 같은 결과로부터 흙의 함수비가 유변물성에 크게 영향을 줌을 알 수 있다. 유변물성과 체적농도의 관계에서 동일 항복응력과 점성에 대응하는 세 지역 풍화토의 체적농도 값은 큰 차이를 보였다. 토석류의 항복응력, 점성과 같은 유변물성 값은 풍화토 시료의 토질 특성(세립분 함량과 액성한계)에 영향을 받고 있음을 관찰하였다. In this study, the characteristics rheological properties are investigated using three samples of weathered soils collected from Woomyun Mt. in Seoul, Munsu Mt. in Yongin, and Majeok Mt. in Chuncheon were debris flow disasters occurred. Several series of rheometer tests were performed to investigate rheological properties of weathered soil samples with various water content (i.e. volumetric concentration of sediment). A large vane rheometer were used to overcome the limitation of commercial equipment on the particle size of weathered soil. Test results indicated that general shape of flow curves for weathered soil samples had characteristics of a Bingham fluid, with a linear relationship between shear stress and shear rate. At the same shear rate, shear stress of weathered soil decreased and slope of flow curve decreased with an increase in water content (or decrease in volumetric concentration of sediment). Also, the yield stress and viscosity give a large difference with a small change in volumetric concentration of sediment (Cu). The results indicated that the water content in soil samples influenced significantly the rheological properties such as yield stress and viscosity. The volumetric concentration of three weathered soil samples showed a significant differences at a given yield stress and viscosity. The results indicated that the soil properties (fine grained soil content, liquid limit) affected significantly the yield stress and viscosity of debris flow.