• The Korean Journal of Ecology
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• v.19 no.6
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• pp.543-562
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• 1996

Zooplankton community structure and the factors correlated with community differences were examined in sandusky Bay (SB) and the open water of Lake Erie (LE, U.S.A.). SB zooplankton communities differed from those in LE by having a greater rotifer density and species richness. Keratella spp., Brachionus spp., and Pompholyx complanata dominated SB rotifers; Brachionus and Pompholyx were rarely seen in LE. Of 19 rotifer species observed, nine species were found only at SB sites. Ordination of zooplankton species abundance by detrended correspondence analysis (DCA) showed an overlap between SB and LE sites, but indicated a portion of the space that was occupied by only SB communities. The seasonal trajectories of zooplankton dynamics in the ordination space at SB sites differed from that of LE. The zooplankton most important in forcing site separation along a DCA Axis I at SB sites were Brachionus angularis, Pompholyx complanata, Keratella valga, Keratella quadrata, Filinia terminalis (rotifers), and Eubosmina coregoni and Daphnia (cladocerans). These species had axis scores which were significantly correlated (p<0.01) with bacterial density and bacterial phosphorus, total phosphorus, and algal density. Very high baterial density and very abundant bacterivorous rotifers in SB suggest that the transport of bacterial carbon through rotifers may be a relatively important link to higher trophic leaels. We believe that this "microbial carbon flow" from the base of the food web may be important in determining the suitability of SB as a spawning site and nursery for larval and juvenile fish.nile fish.

• Economic and Environmental Geology
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• v.54 no.4
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• pp.465-473
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• 2021

This numerical study aims at analyzing the effect of flow characteristics, caused by geometrical features such as intersecting angles, on solute mixing at fracture junctions. It showed that not only Pe, the ratio of advection to diffusion, but also the intersecting angles played an important role in solute mixing at the junction. For the intersection angles less than 90°, the fluid flowed to the outlet in the same direction as the injected flow direction, which increased the contact at the junction with the streamlines coming from the different inlets. On the other hand, for the intersecting angles greater than 90°, the fluid flowed out to the outlet opposite to the flow direction in the inlet, leading to minimizing the contact at the junction. Therefore, in the former case, solute mixing occurred even at high Pe, and in the latter case, solutes transport along the streamlines even at low Pe. For Pe < 1, the complete mixing model was known to occur, but for the intersecting angle greater than 150°, no complete solute mixing occurred. Overall, the transition from the complete mixing model to the streamline-routing model occurred for Pe = 0.1 - 100, but it highly depended on the intersecting angles. Specifically, the transition occurred at Pe = 0.1 - 10 for intersecting angles ≧ 150° and at Pe = 10 - 100 for intersecting angles ≦ 30°. For Pe > 100, the streamline-routing model was dominant regardless of intersecting angles. For Pe > 1,000, the complete streamline-routing model appeared only for the intersecting angles greater than 150°. For the intersecting angles less than 150°, the streamline-routing model dominated over the complete solute mixing, but solute mixing still occurred at the fracture junction.

• Korean Journal of Agricultural and Forest Meteorology
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• v.1 no.1
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• pp.29-35
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• 1999

Soil structure and organic matter have been known to strongly affect water flow and solute transport, yet little information is available concerning soil hydraulic properties related to soil physical and chemical properties in the forest site. The purpose of this study was to quantify the spatial variability and spatial correlation of the measured parameter values from the plots established with the rainfall simulator on Japanese larch(Larix leptolepis) dominated site in Kwangju. Kyunggi-Do. Measurement of soil water flux and retention were made with the inherent soil texture, soil structure, and organic matter. The method was based on the observation that when water was applied at a constant rate to the soil surface on each plot. The method was simple to apply and consists of following steps: (i) Wet the soil from a rainfall simulator with several known discharge rates on a relatively leveled soil surface with and without organic matter. (ii) Once the borders of the ponded zone were steady, saturated hydraulic conductivity( $K_{s}$) and the matric flux function(F) was evaluated from a regression of flux vs. the reciprocal of the ponded area. A conductivity of the form $K_{i+}$$_1$ $_{c}$= $K_{i}$( $_{c}$) [1-d /dz] where flux continuity implies. For this, continuity of matric potential at the interface at all times are as follows: $_1$( $Z_{c}$) = $_2$( $Z_{c}$) = $_{c}$ for steady state intake from water ponded on the soil surface. Results of this investigation showed the importance of understanding spatial variability in wide differences of water retention and saturated hydraulic conductivity with respect to pore geometry and organic matter contents which influenced the water flux throughout the soil profile.l profile.ile.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.5 no.2
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• pp.105-118
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• 2000

Anchored measurements (12.5 hr) of suspended sediment concentration and other hydrodynamic parameters were carried out at two stations located at the entrance to Hampyung Bay in summer (August 1999). Tidal variations in water temperature and salinity were in the range of 26.0-27.9$^{\circ}C$ and 30.9-31.5, respectively, indicating exchange offshore and offshore water mass. Active tidal mixing processes at the entrance appear to destroy the otherwise vertical stratification in temperature and salinity in spite of strong solar heating in summer. On the contrary, suspended sediment concentrations show a marked stratification with increasing concentrations toward bottom layer. Clastic particles in suspended sediments consist mostly of very fine to fine silt (4-16 ${\mu}$m) with a poorly-sorted value of 14.7-25.9 ${\mu}$m. However, at slack time with less turbulent energy, flocs larger than 40 ${\mu}$m are formed by cohesion and inter-collision of particles, resulting in a higher settling velocity. Strong ebb-dominated and weak flood dominated tidal currents, in the southwestern and the northeastern part, respectively, result in a seaward residual flow of -10${\sim}$-20 cm $s^{-1}$ at station H1 and a bayward residual flow less than 5.0 cm $s^{-1}$ at station H2. However, mean concentration of suspended sediments at station H1 is higher at flood (95.0-144.1 mg $1^{-1}$) than in ebb (75.8-120.9 mg $1^{-1}$). On the contrary, at the station H2, the trend is reversed with higher concentration at the ebb (84.7-158.4 mg $1^{-1}$) than that at the flood (53.0-107.9 mg $1^{-1}$). As a result, seaward net suspended sediment fluxes ($f_{s}$) are calculated to be -1.7 ${\sim}$-$15.610^{3}$ kg $m^{-2}$ $s^{-1}$ through the whole water column. However, the stations H1 and H2 show definitely different values of the flux with higher ones in the former than in the latter. Alternatively, depth-integrated net suspended sediment loads ($\c{Q}_{s}$) for one tidal cycle are also toward the offshore with ranges of 0.37${\times}$$10^{3}$ kg $m^{-1}$ and 0.21${\times}$$10^{3}$ kg $m^{-1}$, at station H1 and H2, respectively. This seaward transport of suspended sediment in summer suggests that summer-time erosion in the Hampyung muddy tidal flats is a rather exceptional phenomenon compared to the general deposition reported for many other tidal flats on the west coast of Korea.

• The Korean Journal of Petroleum Geology
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• v.10 no.1_2 s.11
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• pp.23-33
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• 2004

The Lago Sofia conglomerate in southern Chile is a lenticular unit encased within mudstone-dominated, deep-sea successions (Cerro Toro Formation, upper Cretaceous), extending from north to south for more than $120{\cal}km$. The Lago Sofia conglomerate is a unique example of long, gravelly deep-sea channels, which are rare in the modern environments. In the northern part (areas of Lago Pehoe and Laguna Goic), the conglomerate unit consists of 3-5 conglomerate bodies intervened by mudstone sequences. Paleocurrent data from these bodies indicate sediment transport to the east, south, and southeart. The conglomerate bodies in the northern Part are interpreted as the tributary channels that drained down the Paleoslope and converged to form N-S-trending trunk channels. In the southern part (Lago Sofia section), the conglomerate unit comprises a thick (> 300 m) conglomerate body, which probably formed in axial trunk channels of the N-5-trending foredeep trough. The well-exposed Lago Sofia section allowed for detailed investigation of sedimentary facies and large-scale architecture of the deepsea channel conglomerate. The conglomerate in Lago Sofia section comprises stratified conglomerate, massive-to-graded conglomerate, and diamictite, which represent bedload deposition under turbidity currents, deposition by high-density turbidity currents, and muddy debris flows, respectively. Paleocurrent data suggest that the debris flows originated from the failure of nearby channel banks or slopes flanking the channel system, whereas the turbidity currents flowed parallel to the orientation of the overall channel system. Architectural elements produced by turbidity currents represent vertical stacking of gravel sheets, lateral accretion of gravel bars, migration of gravel dunes, and filling of channel thalwegs and scoured hollows, similar to those in terrestrial gravel-bed braided rivers. Observations of large-scale stratal pattern reveal that the channel bodies are offset stacked toward the east, suggestive of an eastward migration of the axial trunk channel. The eastward channel migration is probably due to tectonic tilting related to the uplift of the Andean protocordillera just west of the Lago Sofia deep-sea channel system.

• Journal of Wetlands Research
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• v.25 no.2
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• pp.99-110
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• 2023

Non-point source (NP) pollutants in an agricultural landuse are discharged from a large area compared to those in other land uses, and thus effective source control measures are needed. To develop appropriate control measures, it is necessary to quantify discharge load of each source and evaluate the degree of water quality improvement by implementing different options of the control measures. This study used Hydrological Simulation Program-FORTRAN (HSPF) to quantify pollutant discharge loads from different sources and effects of different control measures on water quality improvements, thereby supporting decision making in developing appropirate pollutant control strategies. The study area is the Gyeseong river watershed in Changnyeong county, Gyeongsangnam-do, with agricultural areas occupying the largest proportion (26.13%) of the total area except for the forest area. The main pollutant sources include chemical and liquid fertilizers for agricultural activities, and manure produced from small scale livestock facilities and applied to agriculture lands or stacked near the facilities. Source loads of chemical fertilizers, liquid fertilizers and livestock manure of small scale livestock facilities, and point sources such as municipal wastewater treatment plants (WWTPs), community WWTPs, private sewage treament plants were considered in the HSPF model setup. Especially, NITR and PHOS modules were used to simulate detailed fate and transport processes including vegitation uptake, nutrient deposition, adsorption/desorption, and loss by deep percolation. The HSPF model was calibrated and validated based on the observed data from 2015 to 2020 at the outlet of the watershed. The calibrated model showed reasonably good performance in simulating the flow and water quality. Five Pollutants control scenarios were established from three sectors: agriculture pollution management (drainge outlet control, and replacement of controlled release fertilizers), livestock pollution management (liquid fertilizer reduction, and 'manure management of small scale livestock facilities) and private STP management. Each pollutant control measure was further divided into short-term, mid-term, and long-term scenarios based on the potential achievement period. The simulation results showed that the most effective control measure is the replacement of controlled release fertilizers followed by the drainge outlet control and the manure management of small scale livestock facilities. Furthermore, the simulation showed that application of all the control measures in the entire watershed can decrease the annual TN and TP loads at the outlet by 40.6% and 41.1%, respectively, and the annual average concentrations of TN and TP at the outlet by 35.1% and 29.2%, respectively. This study supports decision makers in priotizing different pollutant control measures based on their predicted performance on the water quality improvements in an agriculturally dominated watershed.