• Fisheries and Aquatic Sciences
• /
• v.11 no.2
• /
• pp.103-112
• /
• 2008

Compressional sound velocities of shelf sediments in the South Sea of Korea, were measured in situ and in the laboratory for six cores. In situ sound velocity was measured using the Acoustic Lance (frequency of 7.5-15 kHz), while laboratory velocity was measured by the pulse transmission technique (frequency of 1MHz). Physical properties were relatively uniform with sediment depth, suggesting little effect of sediment compaction and/or consolidation. Average in situ velocity at each core site ranged from 1,457 to 1,488 m/s, which was less than the laboratory velocity of 1,503 and 1,604m/s. In muddy sediments the laboratory velocity was 39-47 m/s higher than in situ velocity. In sandy sediments, the difference was greater by an average of 116 m/s. Although the velocity data were corrected by the velocity ratio method based on bottom water temperature, the laboratory velocity was still higher than the in situ velocity (11-21 m/s in muddy sediments and 91 m/s in sandy sediments). This discrepancy may be caused by sediment disturbance during core collection and/or by the pressure of Acoustic Lance insertion, but it was most likely due to the frequency difference between in situ and laboratory measurement systems. Thus, when correcting laboratory velocity to in situ velocity, it is important to consider both temperature and frequency.

• Korean Journal of Microbiology
• /
• v.21 no.2
• /
• pp.79-85
• /
• 1983

Ammonia oxidation activity of polluted water samples in Jinhae Bay and isolated strain from the seawater was investigated, and effects of environmental factors such as temperature, salinity, substrate concentration to the ammonia oxidation were also investigated. The ammonia oxidation activities of sediments, 0.01-0.04mg eq. $NO_2-N/l/h$, were exceptionally higher than that of sea water, $0.5{\sim}1{\mu}g$ eq. $NO_2-N/l/h$. the activities of muddy sediments at station 4 and 2 were 0.03~0.04mg eq. $NO_2-N/l/h$ and that of sandy sediment at station 3 was 0.002mg eq. $NO_2-N/l/h$. In the case of sea water, the activity of polluted area, station 1, was 2 times higher than that of offshore, station 4. The isolated strain reached log phase after 30days culturs and its oxidation activity was $2{\sim}3{\mu}g$ eq. $NO_2-N/day$. The maximum oxidation of ammonia by IA 13 strain occured at 30mg/l oxidation increased with the salinity rising up to 100% seawater concentraion. And temperature for maximum oxidation of ammonia was $35^{\circ}C$. the oxidation increased with the salinity rising up to 100% seawater concentration.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2023.05a
• /
• pp.399-399
• /
• 2023

한강상류 비점오염원관리지역은 장기간 나지로 방치되고 있는 고랭지밭이 집중 분포하고 있어, 강우시 다량의 흙탕물 발생으로 인해 하천 환경오염 및 상·하류 지역사회간 갈등 문제가 지속적으로 발생하고 있다. 이러한 강우시 흙탕물로 인해 하류지역 주민들은 심각한 피해를 호소하므로 상·하류 지역간 갈등을 해소하기 위해서라도 상류지역에서 발생한 흙탕물이 어디까지 도달하는지에 대한 과학적 평가가 요구된다. 하지만, 상류부터 하류 사이에는 많은 유입 지류하천이 존재하고 있어, 실측을 통해 흙탕물의 거동을 파악하기에는 한계가 있다. 이러한 한계를 극복하고 유사거동을 파악하기 위해서는 강우시 실측 모니터링과 수질 모델링을 통한 흙탕물 거동 특성 평가가 필요하다. 현재, 자운지구에서 발생한 흙탕물은 내린천을 거쳐 소양호까지 영향을 미치고 있으나, 실제 상류유역에서 발생한 흙탕물이 하류 유역에 미치는 영향을 정량적으로 평가하고 흙탕물의 거동특성을 파악한 연구는 전무하다. 이에 본 연구에서는 자운지구를 포함한 내린천유역을 대상으로 강우시 실측 모니터링을 수행하고 수질 모델링을 통해 흙탕물의 거동특성을 평가하였다. 강우시 실측 모니터링 자료와 SWAT 모형을 활용하여 흙탕물 거동특성을 분석한 결과, 상류유역에 해당하는 자운지구에서 발생한 유사가 하류지역인 내린천까지 이동하고 있는 것으로 모의가 되었으며, 내린천의 유사 이동량은 448,986 ton으로 이중 자운지구에서 발생한 유사량은 9.7%의 기여도를 가지는 것으로 분석되었다.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.46 no.3
• /
• pp.215-220
• /
• 2001

Biochemical responses of rice to the flooding stress with different water turbidities and flooding time were evaluated. About 20% decrease of soluble protein was occurred with flooding stress. The decreasing rate was higher as flooding time and higher turbidity increased. Especially, dramatic decrease of soluble protein content was observed after 36 hrs of flooding. No protein subunit change was found before and after flooding. However, subunit product of 53 Kd increased from the beginning of flooding and subunit of 28 Kd was increased 48 hrs and 54 hrs after flooding. Lipid peroxidation increased about 150% by flooding. There was no significant difference in lipid peroxidation between clear and sub-muddy water, However, the lipid peroxidation was increased up to 180% at 60hrs of flooding. The malondialdehyde content (MDA) was higher in muddy water at the beginning of flooding and increased about 190-200% 36 hrs after flooding. Catalase activity increased with increasing turbidity and flooding time. Forty eight hours of flooding time provided a criteria for dramatic increase of catalase activity. In general, increase of saturated fatty acids and decrease of unsaturated fatty acids occurred with flooding treatment. Among unsaturated fatty acids, monounsaturated increased and polyunsaturated decreased. Double bond index(DBI) decreased as flooding time was extended and turbidity increased.

• Proceedings of the Korean Society of Crop Science Conference
• /
• 2017.06a
• /
• pp.227-227
• /
• 2017

This study was conducted to analyze the reduction of quality and ripening rate of rice due to submergence during ripening stage and identify the physiological cause. Korean japonica type rice cultivars, Nampyeong was used in the experiment. The following 7, 14 day after heading, they were then moved into submergence treatment facility and we conducted the tests under three different submergence conditions - T1(clear water and overhead submergence), T2(Muddy water and exposure of Flag leaf end ), T3(Muddy water and overhead submergence), and the treatment lasted for 4days. The decrease of ripening rate was most severe in T3 treatment at 7days after heading, and the decrease of head rice ratio was most severe in T3 treatment at 14days after heading. Meanwhile the starch synthesis was inhibited, as the supply of assimilation products was inhibited in grain during the submergence treatment. And in stem, sucrose content was increased because the soluble carbohydrates accumulated before heading were decomposed. These changes may be due to the consumption of respiratory substrate in anaerobic conditions and the inhibition of the production of photosynthetic products by light interception. In order to see what kind of reaction occurs at the molecular level, we examined the degree of RNA expression in grain, stem and leaf. First, the expression of rna associated with starch synthesis in grain was decreased in all submergence treatment. and especially Ospul(DBE) was more decreased in 14days after heading treatment than 7days after heading treatment. This difference can explain the result that the decrease of head rice ratio was more severe at 14days after heading. And in stem, the expression of rna associated with the supply of assimilation products was decreased in submergence treatment. Finally in leaf, the expression of rna(ADH, ALDH) associated with anaerobic respiration was increased, while the expression of rna associated with photosynthesis was decreased. These results of physiological analysis can used to develop the cultivation technique and to offer the information for breeding the cultivars with tolerant characteristics to submergence stress during ripening stage in rice.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.8 no.3
• /
• pp.65-73
• /
• 2005

Because the geological features of Imha basin are composed of clay and shale layer, much soil particle flows into reservoir in shape of muddy water when it rains a lot. Therefore, turbidity data can be indirect-index to estimate the soil erosion of Imha basin. This study evaluated annual soil erosion using GIS-based soil erosion model and applied rainfall weighting value method by time-series rainfall data to estimate monthly soil erosion. In view of 2003 turbidity data, monthly soil erosion with rainfall weighting value is more efficient than monthly soil erosion with rainfall data.

• The Korean Journal of Ceramics
• /
• v.2 no.4
• /
• pp.212-215
• /
• 1996

This paper focuses the strength and wear resistance of CVD diamond films. The strength of free-standing CVD diamond films synthesized by microwave plasm CVD, DC plasma CVD, RF plasma CVD and arc discharge plasma jet CVD has been measured by three-point bending test. The wear resistance of CVD diamod films has been evaluated by the pin-on-disk type testing. diamond films coated on the base of sintered tungsten carbide pin by hot filament CVD have been rubbed with a sintered diamond disk in muddy water. Volume removed wear of CVD diamond has been compared with stellite, WC alloy and bearing steel.

• Animal Systematics, Evolution and Diversity
• /
• v.36 no.3
• /
• pp.264-267
• /
• 2020

Thaumatometra tenuis (A. H. Clark, 1907), an unstalked crinoid that lives on the muddy bottoms of the deep sea, is re-described with images in this study. This species distributes in the cold water zone of the northwestern Pacific and had been reported at the end of 1800s from South Korea but had not been found thereafter. So we thought that this species was no longer living in Korea. In March 2019, a large number of T. tenuis were found near the Sokcho-si, Gangwon-do, Korea. So the presence of T. tenuis in Korea is reconfirmed. This species, markedly fragile overall, is characterized by long segments of cirri and pinnules, and P₁ composed of 35 segments.

• Journal of the Korean earth science society
• /
• v.44 no.4
• /
• pp.264-274
• /
• 2023

The Korea Strait comprises a continental shelf in a shallow sea that experienced glacio-eustastic sea-level changes during the Quaternary period. A long core of 76.6 m in length was acquired at the South Sea Drilling Project site (SSDP-101; 34°19.666'E and 128°16.335'N) with a 60 m water deep. The uppermost massive sand beds were interpreted as sandy sediments of the nearshore marine sand ridge in the shallow sea during the transgression of sea level, whereas the lower parts of alternating sandy and muddy beds were interpreted as deposits in marsh, estuary, and tidal flat environments. A three-layered geoacoustic model was reconstructed for the sedimentary succession in the high-resolution seismic profile based on a 140-grain size and sediment type of core SSDP-101. For the actual underwater simulation and experiments, the in-situ P-wave speeds were calculated using the sound speed ratio of the Hamilton method.

• Journal of Species Research
• /
• v.13 no.3
• /
• pp.326-328
• /
• 2024

The beetle family Georissidae, represented by Georissus kurosawai Nakane, is identified for the first time in Korea. Worldwide, the family Georissidae Laporte contains 83 described species in the only genus Georissus Latreille. This beetles usually inhabits sandy or muddy banks of streams, rivers, and standing water, and some species live in tidal flats and leaf litter. Mostly, adults are covered by a layer of mud or sand grains dorsally and are attracted to light. They are characterized by the combination of the following characters: prosternum reduced, procoxae enlarged, metacoxae separate, ventral hydrofuge pubescence absent, elytra punctatostriate and without scutellary stria, metathoracic anepisterna concealed, and sternite III enlarged. Habitus and aedeagus photograph, mtDNA sequence, and habitat information are provided.