• Korean Journal of Remote Sensing
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• v.25 no.2
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• pp.155-163
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• 2009

An abundance of internal waves is observed by SAR in the Yellow Sea during summer. They are small scaled internal waves and are not relatively studied well compared to the ones in the East/South China Sea. These internal waves should be considered in the study of physio-biological properties of the Yellow Sea because the mixing of the stratified surface water caused by internal waves during summer is important for ocean biological environment, and they also affect the sediment transport and acoustic signal transmission in the continental shelf region. To understand the characteristics of internal waves, it is important to get the spatio-temporal information of internal waves simultaneously by executing in-situ measurements as well as the SAR observation. This study tracks the internal waves observed by SAR in the time series of temperature profile data by analyzing simultaneously acquired in-situ measurement data and RADARSAT SAR image on 29 May 2002.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.4
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• pp.456-463
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• 1996

The purpose of the present study is to estimate the regional and seasonal variations of dissolved inorganic nitrogen (DIN) flux across the sediment-water interface of the inner and central areas of Hiroshima Bay from August 1994 to May 1995. In addition it compares the measured methods and estimates the effect of DIN released from sediment to the primary production of Hiroshima Bay. One method used in this study is to calculate DIN flux from a concentration gradient between sediment porewaters and the overlying water, and the other method is to measure DIN flux from the sediment-core experiment. The fluxes of $NH_{4}^{+}-N\;and\;NO_{2}^{+}\;+\;NO_{3}^{-}-N$ in the inner area were higher than those in central area, all of which showed seasonal variation. $NH_{4}^{+}-N$ flux was maximum in August, while $NO_{2}^{-}\;+\;NO_{3}^{-}-N$ flux was high in January compared with the other seasons. The calculated $NH_{4}^{+}-N\;and\;NO_{2}^{-}+NO_{3}^{-}-N$ fluxes from sediments were $18.2\~60.8\;{\mu}g-at/m^2{\cdot}hr\;and\;0.24\~18.2\;{\mu}g-at/m^2{\cdot}hr$, respectively. The measured $NH_{4}^{+}-N\;and\;NO_{2}^{-}+NO_{3}^{-}-N$ fluxes across the sediment-water interface were $2.00\~111\;{\mu}g-at/m^2{\cdot}hr\;and\;-265\~82.9\;{\mu}g-at/m^2{\cdot}hr$, respectively. The former was lower than the tatter. The calculated $NH_{4}^{+}-N$ flux showed closer relation to environmental factors (dissolved of gen in the overlying water, temperature and redox condition of the sediments) than the measured one did. On the other hand, in the case of $NO_{2}^{-}+NO_{3}^{-}-N$ flux both the calculated and the measured showed little relation to environmental factors, while they turned out to have stronger relation with their concentration in sediments. DIN released from the sediment is expected to support about $25\%\~67\%$ of the primary production in Hiroshima Bay.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.21 no.3
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• pp.91-102
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• 2016

The spatio-temporal variations of the dissolved methane concentration were investigated and the methane budget was estimated in the Nakdong Estuary in January, September, and November of 2014. Dissolved methane showed seasonal variation (21~874 nM) with high concentration in summer due to enhanced temperature and fresh water discharge. Decreasing trends of dissolved methane from the river to the estuary were consistent in all seasons showing the main source of the estuarine methane is river discharge. However, the decreasing trends were modified seasonally due to the local sources such as organic-rich sediments in intertidal zone or near the estuarine barrage. Dissolved methane concentration in the Nakdong Estuary was high, compared to other estuaries probably due to the well developed wetland in Nakdong-river system and stagnation effect from barrages and dams. Dominant sink for the Nakdong estuarine methane was outflux into the atmosphere. Relatively long residence time (produced by barrier island and estuarine dam) in the estuary might provide the enough time for the outgassing.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.23 no.3
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• pp.225-237
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• 1990

Various chemical constituents were measured from April to August 1988 at the down-ward 20 stations of Keum River, which is located in the Midwest of Korea, to understand the characteristics of water quality with respect to spatio-temporal variations of each constituent. The 24-hrs continuous measurements with 2-hrs interval were made simultaneously at station 2 near the estuary weir and station 9(Ganggyeong) of 35 km upstream from the weir in April. By the results observed for one day in April at station 2, salinity has a range of $7.88\~22.14\%_{\circ}$ and its temporal variability is identical to the pattern of tidal cycle in the neigh-bouring Kunsan Harbor. However, turbidity shows relatively high values only at an interval of 4~5 hours after the lowest salinity time, though hourly fluctuation of pH is very small. Silicate and dissolved inorganic nitrogen have inversively linear correlationships with salinity, implying the concentration of the two nutrients strongly regulated by estuarine mixing of sea and river waters. In contrast, phosphate sustains roughly a constant level over a wide salinity range and distinctly lower values than those corresponding to nitrate in the oceans. Such distributions of phosphate have been observed in some estuaries, and interpreted as driven by removal of dissolved phosphate into bottom sediments and the bufforing of phosphate by particulate matter. COD values at station 2 are relatively high in day-time(particularly afternoon) and in high-salinity periods. At station 9, saltwater intrusion was never found but water level changed to the extent of 2.5 m for one day. Although each parameter at this station exhibits very slight variations in their abundance for 24 hours compared with station 2, the contents of COD, silicate and ammonia are significantly higher than at station 2. Concentration of suspended matter is relatively high in the brackish water region up to $\~20$ km above the river mouth, probably due to strong tidal stirring of the bottom de-posits. Also, relatively high pH, COD and $O_2$ saturation at the upward stations of $40\~50$ km from the weir are presumably attributable to active photosynthesis of plants in the region. In general, COD and nutrients except phosphate are higher values at the upper stations than in the estuary zone, and show the highest abundances in July nearly at all stations. Finally, in the estuarine region tidal mixing of sea-river waters seems to be an important factor controlling the distributions of turbidity, COD, silicate and nitrate as well as salinity. However, water quality in the upward fresh-water zone is remarkably variable according to months or seasons.