• Title/Summary/Keyword: Sediment flux

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A Study on the Characteristics of Pollutant Loads in Kamak Bay Watershed (駕莫灣 流域의 汚染負荷 特性에 관한 硏究)

  • 이대인;조현서
    • Journal of Environmental Science International
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    • v.11 no.9
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    • pp.945-954
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    • 2002
  • The objective okgf this study is understanding and evaluation of temporal and spatial variation of pollutant loads by input sources for water quality management in Kamak Bay. Flow rate of rivers and ditches ranges from about $2,592-63,072m^3/d$ in October to $864-55,296m^3/d$ in January. In particular, the R2 predominated flow rate among input sources. Total COD, BOD, DIN and DIP loadings in January were about 896kg/d, 718kg/d, 2,152kg/d, and 154kg/d, respectively, which exceeded those of October. Lower POC/TOC levels are estimated in R2, and also in October. Temporal variation of pollutant loads were closely related to the human activity. Total discharging loadings of BOD, TN and TP by unit loading estimation were 4,993.0kg/d, 2,558.7kg/d, and 289.2kg/d, respectively, and were mainly affected by the population. Runoff ratio of BOD was about 0.14 in January Mean $NH_4^+_-N$ and $PO_4\;^{3-}-P$ loadings from sediment were 16.23mg/$m^2$/d and 7.26mg/$m^2$/d, respectively. For the improvement of water quality in this area, not only pollutant loads of rivers and ditches but also benthic flux from sediment should be reduced within the limits of the environmental capacity.

Effects of streambed geomorphology on nitrous oxide flux are influenced by carbon availability (하상 미지형에 따른 N2O 발생량 변화 효과에 대한 탄소 가용성의 영향)

  • Ko, Jongmin;Kim, Youngsun;Ji, Un;Kang, Hojeong
    • Journal of Korea Water Resources Association
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    • v.52 no.11
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    • pp.917-929
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    • 2019
  • Denitrification in streams is of great importance because it is essential for amelioration of water quality and accurate estimation of $N_2O$ budgets. Denitrification is a major biological source or sink of $N_2O$, an important greenhouse gas, which is a multi-step respiratory process that converts nitrate ($NO_3{^-}$) to gaseous forms of nitrogen ($N_2$ or $N_2O$). In aquatic ecosystems, the complex interactions of water flooding condition, substrate supply, hydrodynamic and biogeochemical properties modulate the extent of multi-step reactions required for $N_2O$ flux. Although water flow in streambed and residence time affect reaction output, effects of a complex interaction of hydrodynamic, geomorphology and biogeochemical controls on the magnitude of denitrification in streams are still illusive. In this work, we built a two-dimensional water flow channel and measured $N_2O$ flux from channel sediment with different bed geomorphology by using static closed chambers. Two independent experiments were conducted with identical flume and geomorphology but sediment with differences in dissolved organic carbon (DOC). The experiment flume was a circulation channel through which the effluent flows back, and the size of it was $37m{\times}1.2m{\times}1m$. Five days before the experiment began, urea fertilizer (46% N) was added to sediment with the rate of $0.5kg\;N/m^2$. A sand dune (1 m length and 0.15 m height) was made at the middle of channel to simulate variations in microtopography. In high- DOC experiment, $N_2O$ flux increases in the direction of flow, while the highest flux ($14.6{\pm}8.40{\mu}g\;N_2O-N/m^2\;hr$) was measured in the slope on the back side of the sand dune. followed by decreases afterward. In contrast, low DOC sediment did not show the geomorphological variations. We found that even though topographic variation influenced $N_2O$ flux and chemical properties, this effect is highly constrained by carbon availability.

Intercomparison and Determination of Sediment by Instrumental Neutron Activation Analysis (중성자방사화분석을 이용한 퇴적물의 정량 및 비교연구)

  • 정용삼;문종화;정영주;박용준;이길용;윤윤열;이수형;김경태
    • Journal of the Korean Society of Groundwater Environment
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    • v.5 no.2
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    • pp.116-121
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    • 1998
  • For the application of study on pollution and conservation of environment determination of 33 elemental concetrations in different sediment samples were carried out using instrumental neutron activation analysis (INAA). For verification and evaluation of the analytical method, three standard reference materials (two NIST SRMs and one NRCC CRM) were chosen and the accuracy and precision of the analysis were estimated by comparison to the certified values. Under the optimum condition, the analytical procedure to apply a practical sample was estimated. Neutron irradiation of sample was done at the irradiation facilities (neutron flux, 1-3${\times}$10$\^$13/n/$\textrm{cm}^2$$.$s) of the TRIGA MARK-III and HANARO research reactor in the Korea Atomic Energy Research Institute. In addition, analysis of two IAEA's sediment was performed according to the pre-established analytical method. The analytical results of elements such as Al, As, Co, Cr, Fe, Sb and Zn by INAA were intercompared with those of WD-XRF, ICP-MS and AAS, and are relatively agreed with each other.

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Tidal Current and Suspended Sediment Transport in the Keum Estuary,West Coast of Korea (錦江 鹽河口에서의 潮流와 浮游堆積物 이동)

  • 오임상;나태경
    • 한국해양학회지
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    • v.30 no.3
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    • pp.147-162
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    • 1995
  • The circulation due to tidal current and river discharge, and the associated suspended suspended sediment transport in macrotidal Keum Estuary, were studied through a series of field measurements of tidal currents and suspended sediment concentration at three anchored stations from 1990 through 1992. From the measurements, the following results were obtained. At the seaward entrance of the estuary, the veritical profiles of the ebb and flood currents were almost symmetric. At the southern channel the flood current was dominant in the whole water column, but in the northern channel the ebb current was dominant in the surface and bottom layers and the flood current was dominant in the intermediate layer. The maximum velocity of the tidal current in the southern channel was 174 cm/s during flood tide in the intermediate layer. The maximum velocity, 148 cm/s in the northern channel also appeared during flood tide in the intermediate layer. However, in the surface and bottom layers, the maximum velocities were 110.6 cm/s during ebb tide and 92.1 cm/s during flood tide, respectively. The type of the Keum Estuary can be categorized to 'Type 3' of Hansen and Rattray's scheme. The water column of the estuary during the flood tide becomes stratified, and after high water the ebb current reduces the density difference and the water column becomes turbulent. The lower layer of the water column is generally turbulent. The largest sediment flux 20.61 ton/s was found in the southern channel during flood current in the lowest river discharge (May, 1991), while the smallest flux, 0.65 ton/s in the northern channel in the lowest tidal range (July, 1992). The stronger bottom shear velocity for the present study area seems to erode the bottom sediments during the flood tide, and the relatively long duration of the ebb tide to transport the suspended sediments. Under normal river discharge conditions, the suspended sediments are transported mainly through the southern channel. However, under high river discharge condition the suspended sediment transport is dominant through the northern channel.

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Seasonal Variations of Sediment Oxygen Demand and Denitrification in Kanghwa Tidal Flat Sediments (강화도 갯벌 퇴적물의 산소요구량과 탈질소화의 계절 변화)

  • An, Soon-Mo
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.10 no.1
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    • pp.47-55
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    • 2005
  • Seasonal variations of remineralization and inorganic nitrogen removal capacity were measured from Dec. 2001 to Apr. 2004 in a tidal flat located in south-western pan of Gwanghwa island, Korea by measuring the sediment oxygen demand (SOD) and denitrification. SOD was higher in muddy sediment (Dong-Mak; three year average=$683;m^{-2}d^{-1}$) than sandy sediment(Yeocha; three year average=$457;m^{-2}d^{-1}$). The SOD was high in summer and tended to be lower in winter. During the sediment incubation in Apr. 2002, production of oxygen from sediment was observed implying active benthic photosynthesis. Denitrification was also higher in muddy sediment (Dong-Mak: $5.4;m^{-2}d^{-1}$) than sandy sediment (Yeocha; $3.4;m^{-2}d^{-1}$). The denitrification rate corresponds to the carbon remineralization rate of 9.3 and $5.9\;mg-C\;m^{-2}d^{-1}$ in Dong-Mak and Yeocha, respectively. The denitrification rates were lower compared to rates observed in other coastal area $(0{\sim}200\;{\mu}mole\;m^{-2}h^{-1})$. Although Kwanghwa tidal flat sediments are replete in organic matter, remineralization activity seems to be limited by the availability of labile organic matter. The Kwangwha tidal flat may have potential to effectively remove large load of organic matter. Net remineralization rates were 196 and $132\;mg-C\;m^{-2}d^{-1}$ in Dong-Mak and Yeocha, respectively.

Chemical Fluxes at the Sediment-Water Interface Below Marine Fish Cages on the Coastal Waters off Tong-Young, South Coast of Korea (남해안 통영지역 가두리양식장 해수-퇴적물 경계면에서의 chemical fluxes)

  • Shim, Jeong-Hee;Kang, Young-Chul;Choi, Jin-Woo
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.2 no.2
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    • pp.151-159
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    • 1997
  • Benthic respiration and chemical fluxes were measured at the sediment-water interface underlying the marine fish cages floating on the open coastal waters off Tong-Young, the South Coast of Korea. The effects of cage farming on coastal benthic environment and on mass balance of organic carbon in the benthic boundary layer under the marine fish cages are addressed. In a growing season of caged fishes of June, 1995, benthic chambers and sediment traps were deployed on the sediment-water interfaces of the two sites chosen for this study: 1) Cage Site, directly underlying the fish cages of the farm at 18 m water depth, and 2) Control Site, about 100 m away from the farm at 32 m water depth. Benthic respiration rates and chemical fluxes were calculated from the evolution of dissolved oxygen and chemicals in the chamber water, and mass balance of organic carbon in the benthic boundary layer was constructed based on the vertical flux of particulate organic matter (POM) and chemical fluxes out of the sediment. High organic dumping (6400 mg C $m^{-2}d^{-1}$) and high benthic respiration (230 mmol $O_2\;m^{-2}d^{-1}$) were observed at the Cage Site. Equivalent to 40% of vertical flux of organic carbon into the Cage Site seemed to be decomposed concurrently and released back to overlying waters (2400 mg C $m^{-2}d^{-1}$). Consequently, up to 4000 mg C $m^{-2}d^{-1}$ of organic carbon could be buried into the farm sediment (equivalent to 60% of organic carbon flux into the Cage Site). At the Control Site, relatively less input of organic carbon (4000 mg C $m^{-2}d^{-1}$) and low benthic respiration rate (75 mmol $O_2\;m^{-2}d^{-1}$) were observed despite short distance away from the cages. The influence of cage farming on benthic chemical fluxes might be restricted and concentrated in the sea bottom just below the fish cages in spite of massive organic dumping and high current regime around the fish cage farm.

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Behavior of Currents and Suspended Sediments around a Silt Screen

  • Jin, Jae-Youll;Chae, Jang-Won;Song, Won-Oh;Park, Jin-Soon;Kim, Sung-Eun;Jeong, Weon-Mu;Yum, Ki-Dai;Oh, Jae-Kyung
    • Ocean and Polar Research
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    • v.25 no.spc3
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    • pp.399-408
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    • 2003
  • The behavior of Suspended Sediment Concentrations (SSC) around a silt screen in a microtidal coastal area was hydrodynamically measured. The current speed at the mid-layer about 30m downstream of the screen reduces to about half that at the same distance upstream. It was caused by the contraction of the vertical section due to the screen. Even during a relatively weak storm period the SSC increases to that of the value caused by dredging. Section-averaged SSC at the downstream of the screen is higher by about 60% than that at the upstream, suggesting that the silt screen plays an adverse effect rather than a constructive role in the reduction of SSC generated by dredging.

The Analysis of Inflowing Sediments Behavior around the Sandbar in Nakdong River Estuary (낙동강 하구역 사주 주변에서의 퇴적물질의 유압거동 해석)

  • KIM KYUNG-HOI;LEE IN-CHEOL
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2004.11a
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    • pp.133-136
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    • 2004
  • In-situ collection experiments were performed to analyze inflowing sedilnents behavior as a basic study of topographical change in Nakdong River Estuary. Sediment rate and bed load flux ranged from 0.0004 to $0.472\;g/cm^2/day\;and\;0.0005\~1.7579\;g/cm^2/day$, respectively. The settling velocity of suspended particulate matter was estimated in tire range of $0.339\~1.010\;cm/sec$, The grain size analysis shows that surface sediments in backside of sandbar and bed load in front of dike have a similar grain size distribution. It is considered that the source of surface sediments in backside of sandbar were flowed in from Nakdong River. In order to verify the characteristics of inflowing sediments behavior, detailed surveys around Nakdong River Estuary need to be carried out, continuously.

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Applicability Study of Numerical Model for Sedimentation in Navigation Channel (항로매몰 예측을 위한 수치모형의 적용성 검토)

  • 김규한;배기성;백승화
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.8 no.1
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    • pp.1-9
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    • 1996
  • A numerical model for predicting depositional processes of navigation channels caused by waves and currents is proposed. In the model, non-equilibrium concentrations of suspended sediment are numerically solved by using the split-operator approach. The calculated concentrations across a channel show good agreements with the measured concentrations in experiments. Based on the calculated concentrations, differences of upward and downward sediment fluxes are estimated to predict topographic changes. The Predicted topographic change across the channel coincides fairly well with the measured profile provided that the currents are relatively stronger than waves.

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Correlation Analysis of Signal to Noise Ratio (SNR) and Suspended Sediment Concentration (SSC) in Laboratory Conditions (실험수로에서 신호대잡음비와 부유사농도의 상관관계 분석)

  • Seo, Kanghyeon;Kim, Dongsu;Son, Geunsoo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.37 no.5
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    • pp.775-786
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    • 2017
  • Monitoring sediment flux is crucial especially for maintaining river systems to understand morphological behaviors. Recently, hydroacoustic backscatter (or SNR) as a surrogate to empirically estimate suspended sediment concentration has been increasingly highlighted for more efficient acquisition of sediment dataset, which is difficult throughout direct sediment sampling. However, relevant contemporary researches have focused on wide range solution applicable for large natural rivers where H-ADCPs with relatively low acoustic frequency have been widely utilized to seamlessly measure streamflow discharge. In this regard, this study aimed at investigating hydroacoustical characteristics based on a very recently released H-ADCP (SonTek SL-3000) with high acoustic frequency of 3 MHz in order to capitalize its capacity to be applied for suspended sediment monitoring in laboratory conditions. SL-3000 was tested in a laboratory flume to collect SNR in conjunction with LISST-100X for actual sediment concentration and particle distribution in both sand and silt sediment injection in various amount. Conventional algorithms to correct signal attenuations for water and sediment were carefully tested to validate whether they can be applied for SL-3000. As result of analyzing the SNR-SSC correlation trand, through further study in the future, it is confirmed that SSC can be observed indirectly by using the SNR.