• Journal of the korean society of oceanography
• /
• v.39 no.1
• /
• pp.96-106
• /
• 2004

A total of 116 surface sediment samples were obtained on the Yellow Sea and analyzed for grain size and geochemical elements in order to interpret the present sediment transportation. Thirty-nine cores and 3,070 line-km shallow seismic profiles are analyzed for sedimentary records of Yellow Sea in the past. Results show that the boundary of sediment transport between Korean side and Chinese side is about between $123^{\circ}E$ and $124^{\circ}E$. The similar result is produced from Shi et al. (in this publication). Two cyclonic patterns of surface sediments are recognized in the northeastern and southwestern Yellow Sea, while the strong front zone of the mud patch and sandy sediments are found in the southeastern Yellow Sea (the southwestern part of Korean coasts). The formation of fine-particle sediment packages, called for Northwest Mudbelt Deposit (NWMD), Hucksan Mudbelt Deposit (HSMD) and Jeju Mudbelt Deposit (JJMD), are resulted from eddies (gyres) of water circulations in the Yellow Sea. NWMD has been formed by cyclonic (anticlockwise) eddy. NWMD is composed of thick, homogeneous, relatively semi-consolidated gray clay-dominated deposit. On the other hand, HSMD and JJMD are formed by anticyclonic (clockwise) eddies. They are thick, homogeneous, organic-rich gray, silt-dominated deposit. Both core and surface sediments show that the middle zone across Chinese and Korean side contains bimodal frequency of grain-size distribution, indicating that two different transport mechanisms exist. These mud packages are surrounded by sand deposits from both Korea and China seas, indicating that Yellow Sea, which is the shallow sea and epicontinental shelf, is formed mostly by sand deposits including relict sands. The seismic profiles show such as small erosional/non-depositional channels, sand-ridges and sand-waves, Pleistocene-channelfilled deposits, a series of channels in the N-S major channel system, and thick Holocene sediment package, indicating that more complex sedimentary history exists in the Yellow Sea.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.58 no.6
• /
• pp.1-8
• /
• 2016

Crop damages due to agricultural drought has been increased in recent years. In Korea, water resources are limited indicating that proper management plans against agricultural drought are required for better water-use efficiency in agriculture. In this study, irrigation intervals and amounts for various crops and soil physical properties (sandy and silt loams) were estimated using the IWMM model. Five different crops (soybean, radish, potato, barley and maize) at the Bangdong-ri site in Chuncheon were selected to test the IWMM model. IWMM assessed agricultural drought conditions using the soil moisture deficit index (SMDI), and irrigation intervals and amounts were determined based on the degree of agricultural drought (SMDI). Additionally, we tested the effects of surface irrigation and sprinkler irrigation methods and various irrigation intervals of 2, 3, 5 and 7 days. In our findings, the irrigation intervals of 5 and 7 days showed the minimum rrigation amounts than others. When we considered that the intervals of 3 or 5 days are usually preferred to fields, the interval of 5 days was determined in our study. The estimated irrigation amounts for different crops were shown as maize > radish > barley > soybean > potato, respectively. The irrigation amounts for maize and barley were highly affected by soil properties, but other crops have less differences. Also, small differences in irrigation amounts were shown between the surface and sprinkler irrigation methods. These might be due to the lack of consideration of water loss (e.g., evapotranspiration, infiltration, etc.) in IWMM indicating model structural uncertainties. Thus, possible water loss (e.g., evapotranspiration, infiltration) need to be considered in application to fields. Overall, IWMM performed well in determining the irrigation intervals and amounts based on the degree of agricultural drought conditions (SMDI). Thus, the IWMM model can be useful for efficient agricultural water resources management in regions at where available water resources are limited.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.59 no.2
• /
• pp.37-47
• /
• 2017

In this study, we analyzed the variability of irrigation water amounts based on the combination of various crops and soil textures using the Irrigation Water Management Model (IWMM). IWMM evaluates the degree of agricultural drought using the Soil Moisture Deficit Index (SMDI). When crops are damaged by the water scarcity under the drought condition indicating that the SMDI values are in negative (SMDI<0), IWMM irrigates appropriate water amounts that can shift the negative SMDI values to "0" to crop fields. To test the IWMM model, we selected the Bandong-ri (BDR) and Jucheon (JC) sites in Gangwon-do and Jeollabuk-do provinces. We derived the soil hydraulic properties using the near-surface data assimilation scheme form the Time Domain Reflectrometry (TDR)-based soil moisture measurements. The daily root zone soil moisture dynamics (R: 0.792/0.588 and RMSE: 0.013/0.018 for BDR/JC) estimated by the derived soil parameters were matched well with the TDR-based measurements for validation. During the long-term (2001~2015) period, IWMM irrigated the minimum water amounts to crop fields, while there were no irrigation events during the rainy days. Also, Sandy Loam (SL) and Silt (Si) soils require more irrigation water amounts than others, while the irrigation water were higher in the order of radish, wheat, soybean, and potato, respectively. Thus, the IWMM model can provide efficient irrigation water amounts to crop fields and be useful for regions at where limited water resources are available.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.48 no.4
• /
• pp.555-563
• /
• 2015

Organic matter and trace metals were investigated in surface sediments of Gomso Bay, where there is dense Manila clam Ruditapes philippinarum farming activity, to evaluate contamination of sediments in intertidal shellfish farming area. We measured mean grain size (Mz), chemical oxygen demand (COD), ignition loss (IL), acid volatile sulfide (AVS), total organic carbon (TOC), and total nitrogen (TN), and trace metals (As, Cd, Cr, Cu, Fe, Hg, Mn, Pb and Zn) in intertidal and sublittoral sediments. The intertidal sediments were mainly composed of coarser sediments (sand, silty sand, and sandy silt), with Mz values ranging from 2.61 to 4.79 Ø. Mz and the content of organic matter in sediments were lower in the intertidal zone than in the sublittoral zone. The mean metal concentrations in surface sediments decreased in the order Fe > Mn > Zn > Cr > Pb > Cu > As > Cd > Hg. The metal concentrations in surface sediments showed a significant positive correlation with Mz and organic matter content, indicating that metal concentrations in the surface sediments of Gomso Bay are controlled by Mz and organic matter. The concentrations of organic matter and trace metals in the study region were lower than or similar to those in other intertidal zones in western coast and much lower than those reported in other shellfish farming areas in Korea. Our results suggest that intertidal Manila clam farming sediments from Gomso Bay are not contaminated by organic matter and trace metals.

• Ocean and Polar Research
• /
• v.26 no.1
• /
• pp.23-32
• /
• 2004

As a baseline survey for long-term monitoring on environmental change around the Antarctic King Sejong Station, distribution pattern of Deschampsia antarctica Desv., a flowering plant newly colonized were investigated qualitatively and quantitatively in both austral summer 2002 and 2003. Dispersal of the seeds and vegetative leaves by skuas might lead to the colonization into this area from neighbors in Maxwell Bay. The pioneer populations were observed around ponds and a stream of the Sejong Point in January 2002, and the maximum dispersal area was four times expanded after a year. Most of the populations were formed on the stable and well-drained substrate, which consisted of moss carpet of Sanionia georgico-uncinata (65%) and pebbles (25%), while only a few young individuals were observed on the unstable and watertight silt-sandy area. Especially, S. georgico-uncinata was being effectively utilized as their primary substrate with the soft, coarse and water-contained leaves. Also the perennial mature plants of D. antarctica were mainly formed on the moss carpet rather than pebbles. A few individuals were grown on other mosses of Polytrichastrum alpinum, Bryum pseudotriquetrum, Pohlia cruda, and Conostomum magellanicum and on a liverwort of Cephaloziella varians. We expect that dispersal of D. antarctica and the following succession to grass field will be countinuously and dynamically proceeded in this area, with the characteristics of ecological niche against the initial moss populations, on the similar continuity of environmental conditions. The continuous observations are needed with establishment of database on environmental change of micro-habitats, e.g. the water content and nutrients of soil and the underground temperature and permafrost.

• Journal of Korean Society of Environmental Engineers
• /
• v.32 no.1
• /
• pp.9-16
• /
• 2010

The purpose of this study is to clarify the origin of organic matters on sediment and the characteristics of seasonal variation at an estuarine tidal flat. Silt-clay content (<63 ${\mu}m$), chlorophyll a, TOC, C/N ratio and the stable isotope ratio of carbon and nitrogen were measured at tidal flat around the estuary of the Nanakita River. As a result, organic matters originating from marine organic matter and bethic microalgae greatly contributed to sedimentation of organic matters at Stn.A, sandy tidal flat, though terrigenous organic matters did at Stn.C, muddy tidal flat. Furthermore, it was revealed that the volume and origin of organic matters in the sediments depended on seasonal variation, and the factors were different from the Stns, i.e. bentic microalgae and event for Stn.A, and the eventual sedimentation of organic matters originating from terrestrial plants, respectively.

• Korean Journal of Soil Science and Fertilizer
• /
• v.44 no.2
• /
• pp.236-241
• /
• 2011

Soil microbial diversity was responsible for a strong effect on the chemical properties of orchard soils. This study evaluated a relationship between soil chemical properties and soil microbial diversities at 25 sites in orchard soils in Gyeongnam Province. The average nutrients in the orchard soils were 2.6 times for available phosphorous, 2.3 times for exchangeable potassium and 1.3 times for exchangeable calcium higher compared to recommend concentrations in the orchard soils. Contents of available phosphorous and organic matter in the inclined piedmont soils were higher than those in the other topographical soils (p<0.05). Populations of fungi and fluorescence Pseudomonas sp. in the silt loam soils were significantly higher than those in the sandy loam soils (p<0.05). In principal component analysis of chemical properties and microbial populations in the upland soils, our findings suggested that population of bacteria should be considered as potential factor responsible for the clear orchard soils differentiation. The soil organic matter was significantly negative correlation with population of bacteria whereas was positive correlation with population of fungi in orchard soils.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.31 no.5
• /
• pp.1-10
• /
• 2003

The purpose of this study was to verify the shore margin protection effect of a root system developed from direct sticking of Salix gracilistyla Miq., focusing on the reinforcement of soil shear strength. The materials were 20cm long sticks whose average diameter and weight were 7.52mm and 14.58g respectively, and sandy loam(Sand 60.36%, Silt 28%, Clay 11.64%), whose maximum dry weight(${\gamma}$$_{dmax}$) was 1.59gf/㎤ at the water ratio( $W_{opt}$) 13.8%. The direct shearing test(KS F 2343) was applied to cylindric columms(diameter 132mm) of pure soil and two years old root reinforced soil. At each condition of vertical stress, 10N/$ extrm{cm}^2$, 14.41N/$\textrm{cm}^2$ and 18.82 N/$\textrm{cm}^2$, five soil+root columns were sheared. After shear tests, the root area ratio and soil moisture on the shear plane were measured. The results of this research were as follows: 1. The average of root area ratio was 1.86% and the soil moisture 14.67%. 2. Two years old root system was found to increase the soil shear strength of pure soil in terms of Cohesion(C) and Inner friction Angle($\phi$) as follows. 3. The relationship between root area ratio and the increased shear strength can be presented with the following equation, $\Delta$S ≒ 0.33ㆍ TrㆍAs/A $\Delta$S : Increased Shear Strength Tr : Average Tension Strength of Root, Ar/A : Root Area Ratioioage Tension Strength of Root, Ar/A : Root Area Ratio

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.46 no.5
• /
• pp.626-637
• /
• 2013

We measured the grain size, ignition loss (IL), chemical oxygen demand (COD), acid volatile sulfide (AVS) and trace metals (Al, Fe, Cu, Pb, Zn, Cd, Cr, Mn, Hg, and As) of intertidal surface sediment collected from 11 islands (62 stations) in the southern region of Jeollanam Province. The objective of this research was to evaluate the organic matter and trace metals contaminations of sediments from coastal island tidal flats. Surface sediment texture was characterized as follows: mud, sandy silt, muddy sand, and slightly gravelly sand facies. The finer sediments are mainly dominated in the northern part of each island. The concentrations of IL, COD, AVS and some trace metals (Al, Fe, Zn, Cr, Cu, and Hg) were higher in the northwestern part of Wan Island and the area between Gogeum and Sinji Islands, and were associated with relatively finer sediment, as compared to other locations. The concentrations of Mn, Pb, Cd, and As were higher in the northwestern and southeastern parts of Geoguem and Pyungil Islands, but were not correlated with mean grain size. Based on sediment quality guidelines (SQGs), the concentrations of trace metals were lower than the values of effect range low (ERL), used in United States, and threshold effects level (TEL), used in Korea, with exception of As. Similarly, the intertidal sediments were moderately contaminated with As, based on the the enrichment factor (EF) and the geoaccumulation index ($I_{geo}$). The high concentration of As in intertidal sediments from this study region may be due to the input of naturally or artificially contaminated submarine groundwater, contaminated waste from seaweed aquaculture operations and/or land-based seaweed processing facilities. Further studies are needed to identify the sources of As in this study region, and to determine the effects of As contamination on coastal ecosystem.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.8 no.2
• /
• pp.59-66
• /
• 1988

At the present time, annually about 2 million tons of coal ashes are generated from thermal power plants in Korea, however, they are dumped into ash ponds mixed with sea water very expensively. In this thesis, engineering characteristics of bituminous and anthracite ashes are studied to utilize them as construction materials. The coal ash is non-plactic material and its grain size falls in the range of silt, but it has better soil engineering characteristics than general soils of same grain size. For example, the permeability, shearing strength, CBR, and consolidation properties match to that of sandy soils, moreover, strengthening by hydration can be expected with the lapse of year because of CaO presence in the components. So, utilizing those coal ashes in a productive way as reclamation or banking materials is expected.