• Journal of the Korean Society for Marine Environment & Energy
• /
• v.3 no.2
• /
• pp.3-10
• /
• 2000

The main purpose of this study were to estimate the benthic fluxes of dissolved inorganic nitrogen (DIN) from the sediment and denitrification rates in tidal flats of the Keum river estuary. Sediment specimens were collected by a core sampler from three stations along the Keum river estuary in April, August and December, 1999. The sediments were composed of 1.18 %, 29.34 % and 69.49 % of gravel and sand, sand and silt, respectively. The mean ignition loss of the sediment was found 6.7 % and its Oxidation Reduction Potential (ORP) was measured -12 mV. The total hydrogen sulfides was determined about 0.26 mg/gㆍdry. The estimated outflux of ammonium was found 11.2 m mole N/m²ㆍday from the sediment, whereas -1.09 m mole N/m²ㆍday of influx was obtained for nitrate and nitrite through the incubation experiment of sediment cores. Total DIN flux was 10.2 m mole N/m²ㆍday outflux from the sediment. From the incubation experiments executed with the flux studies, mean denitrification rate was found 30.6 m mole N₂/m²ㆍday measured by the direct assay of N₂ production technique. On the basis that DIN flux and denitrification rate in sediment of tidal flat of the Keum river estuary are may be effects to control the algal biomass in the coastal environment, it seems inevitable to pay more attention to investigate the flux of DIN and denitrification rate in tidal flat of the Keum river estuary.

• Journal of Korea Water Resources Association
• /
• v.48 no.1
• /
• pp.9-21
• /
• 2015

This study examined pollution level of sediment in Sookchun lake, and studied dredging validity by examining phosphorous release characteristics on surface polluted soil. Total phosphorous, the principal cause of algal blooms, exceeded dredging assessment standards regarding Daechung lake (1.5 mg/g) at all points. Also at all points, total nitrogen exceeded the dredging assessment standard regarding Paldang Lake (1.1 mg/g), but fell short of the standard regarding Daechung lake (3.0 mg/g). Dredging zone was suggested in this study is Chuso water body (WS-6~WS-12) in Sookchun lake. In relation to sediment pollution levels measured at different depths, LOI tended to decrease as it became deeper. The concentrations of T-N varied depending upon the depth as well as points, but no regular pattern was observed. The depth and site did not significantly influence T-P. From the results of phosphorous release tests, it was shown that total phosphorous release flux was calculated to be $7.2{\sim}15.4mg/m^2/d$ for anaerobic condition, $0.5{\sim}2.0mg/m^2/d$ for aerobic condition and $2.0{\sim}4.1mg/m^2/d$ for facultative condition. Release flux and T-P concentration of surface sediments had positive correlation ($R^2$ 0.7871). And The corelation between release flux and DO condition in reactor had strong negative correlation ($R^2$ 0.8824).

• Journal of Environmental Science International
• /
• v.13 no.12
• /
• pp.1089-1102
• /
• 2004

Seasonal variation of biogeochemical characteristics was determined in Lake Shihwa from October 2002 to August 2003. When the lake was artificially constructed for the freshwater reservoir in 1988, the development of the strong haline density stratification resulted in two-layered system in water column and hypoxic/anoxic environment prevailed in the bottom layer due to oxidation of accumulated organic matters in the lake. Recently, seawater flux to the lake through the sluice has been increased to improve water quality in the lake since 2000, but seasonal stratification and hypoxic bottom layer of the lake still developed in the summer due to the nature of artificially enclosed lake system. As the lake is still receiving tremendous amount of organic matters and other pollutants from neighboring streams during the rainy summer season, limited seawater flux sluicing into the lake may not be enough for the physical and biogeochemical mass balance especially in the summer. The excess of accumulated organic matters in the bottom layer apparently exhausted dissolved oxygen and affected biogeochemical distributions and processes of organic and inorganic compounds in the stratified two-layered environment in the summer. During the summer, ammonia and dissolved organic carbon remarkably increased in the bottom layer due to the hypoxic/anoxic condition in the bottom layer. Phosphate also increased as the result of benthic flux from the bottom sediment. Meanwhile, dissolved organic carbon showed the highest value at the upstream area and decreased along the salinity gradient in the lake. In addition to the sources from the upstream, autochthonous origin of particulate organic carbon from algal bloom in the lake might be more important for sustaining aggravated water quality and development of deteriorated bottom environment in the summer. The removal of trace metals could be attributed to scavenging by strong insoluble metal-sulfide compounds in the hypoxic/anoxic bottom layer in the summer.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.4 no.1
• /
• pp.71-79
• /
• 1999

As part of an on-going project investigating flux of materials in the Keum River Estuary, we have monitored seasonal variations of nutrients, suspended particulate matter (SPM), chlorophyll, and salinity since 1997. Meteorological data and freshwater discharge from the Keum River Dike were also used, Our goal was to answers for (1) what is the main factor for the seasonal fluctuation of nutrients in the Keum River Estuary? and (2) are there any differences in nutrient distributions before and after the Keum River Dike construction? Nitrate concentrations in the Keum River water were kept constant through the year. Whereas other nutrients varied with evident seasonality: high phosphate and ammonium concentrations during the dry season and enhanced silicate contents during the rainy season. SPM was found similar trend with silicate. During the rainy season, the freshwater discharged from the Keum River Dike seemed to dilute the phosphate and ammonium, but to elevate SPM concentration in the Keum Estuary. In addition, the corresponding variations of SPM contents in the estuarine water affected the seasonal fluctuations of nutrients in the Estuary. The most important source of the nutrients in the estuarine water is the fluvial water. Therefore, the distribution patterns of nutrients in the Estuary are conservative against salinity. Nitrate, nitrite and silicate are conservative through the year. The distribution of phosphate and ammonium on the other hand, display two distinct seasonal patterns: conservative behavior during the dry season and some additive processes during the rainy days. Mass destruction of freshwater phytoplankton in the riverine water is believed to be a major additive source of phosphate in the upper Estuary. Desorption processes of phosphate and ammonium from SPM and organic matter probably contribute extra source of addition. Benthic flux of phosphate and ammonium from the sediment into overlying estuarine water can not be excluded as another source. After the Keum River Dike construction, the concentrations of SPM decreased markedly and their role in controlling of nutrient concentrations in the Estuary has probably diminished. We found low salinity (5~15 psu) within 1 km away from the Dike during the dry season. Therefore we conclude that the only limited area of inner estuary function as a real estuary and the rest part rather be like a bay during the dry season. However, during the rainy season, the entire estuary as the mixing place of freshwater and seawater. Compared to the environmental conditions of the Estuary before the Dike construction, tidal current velocity and turbidity are decreased, but nutrient concentrations and chance of massive algal bloom such as red tide outbreak markedly increased.

• Ocean and Polar Research
• /
• v.36 no.4
• /
• pp.423-435
• /
• 2014

Verifying the similarity of environmental characteristics between an artificial impact site and a preserved or reference site is necessary to quantitatively and qualitatively evaluate the environmental impact of mining activity. Although an impact site (BIS station) and a preserved site (called KOMO station) that have been selected in the Korea manganese nodule contract area may share similar environmental characteristics, similarities in terms of the water column environment between both sites has not been investigated. In this study, we compared the chemical properties of the water columns and sinking particle fluxes between BIS and KOMO stations through two observations (August 2011 and September 2012). Additionally, we observed particle fluxes at the KOMO station for five years (July 2003~July 2008) to understand long-term natural variability. Vertical distributions of water column properties such as dissolved oxygen, inorganic nutrients (N, P, Si), total organic carbon below surface layer (within the depth range of 200 m) were not considerably different between the two sites. Especially, values of water column parameters in the abyssopelagic zone from 4000 m to bottom layer (~5000 m) were very similar between the BIS and KOMO sites. Sinking particle fluxes from the two sites also showed similar seasonality. However, natural variation of particle flux at the KOMO site varied from 3.5 to $129.9mg\;m^{-2}day^{-1}$, with a distinct temporal variation originating from ENSO events (almost forty times higher than a minimum value). These results could provide valuable information to more exactly evaluate the environmental impact of mining activity on water columns.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.15 no.3
• /
• pp.186-197
• /
• 2012

In order to understand hydrodynamic and water quality changes on the Saemangeum reservoir in accordance to inner development plan, intensive numerical simulations using EFDC have been done. Due to inner dike construction and proposed dredging plans, stratification might occur and yield flow field change. It should be noticed that very conditional gate operation schedule adjusting target water elevation of -1.5 meter causes severe stratification and hence plays an important role in poor water qualities. By using random walk particle tracking residence simulations, it is found that hydrodynamic characteristics depends greatly on riverine inflow conditions. It is also inferred that the northern part of the Mangyeong reservoir behaves as a dead zone and acts as major reasoning of water quality deterioration owing to benthic flux from long-term residing settled sediment.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.21 no.2
• /
• pp.58-66
• /
• 2016

We have evaluated the ammonium data in seawater as a potential short-term index for marine environment through the following steps. 1. reviewing of chemical characteristics of ammonium in seawater, 2. comparative relationships of ammonium data with other water quality indices such as DO, COD, and nutrients from Typical Marine Environment(TME) and Special Marine Environment(SME). Ammonium data generally represent negative correlation with DO, while positive correlation with COD. In particular, under frequent cases of seawater conditions showing similar concentration of COD or DO, we have limited choice of explanation for such situation. However ODIN(ODIN/RDIN) or RDIN(RDIN/TDIN) ratio could provide advanced information to understand these seawater conditions. Based on these results, we suggest ammonium data as a potential short-period index for transilient marine environment, such as benthic flux of bottom sediment, hypoxia, and algal bloom. Under overcoming several handicaps, ammonium data could be an useful tool for better understand short transformation of marine environment.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.14 no.4
• /
• pp.205-212
• /
• 2009

To suggest possible to bioremediation by benthic microalgae Nitzschia sp. isolated from the Jinhae Bay, the studies investigated the effects o flight quality and quantity on the growth of Nitzschia sp. and its growth kinetics for phosphate investigated. The Nitzschia sp. was cultured under blue (450 nm), yellow (590 nm) and red wavelength (650 nm) using light emitting diode (LED) and mixed wavelengths using a fluorescent lamp. The maximum specific growth rate showed the Nitzschia sp. under blue wavelength, although photoinhibition was observed above $100\;{\mu}mol\;m^{-2}\;s^{-1}$. Mixed wavelengths were also observed by decreasing the maximum cell density from high irradiances (>$100\;{\mu}mol$ photons $m^{-2}\;s^{-1}$). The compensation photon flux density ($I_0$) calculated from the mixed wavelengths equated to a depth of 4-10 m in Jinhae Bay, and was lower in the summer season than the depth due to suspended matter (ca. 4 m). Thus, the suitable depth for maximum growth of Nitzschia sp. might be extremely limited. In the growth kinetics for phosphate, half-saturation constant ($K_s$) was similar among different wavelengths, although the maximum growth rate was varied among different wavelengths. Because the $K_s$ was high than that of the phytoplankton, Nitzschia sp. might have adapted to the high nutrient concentrations, and have effective nutrient storage in the cell quota. Thus, Nitzschia sp. may be a useful species for bioremediation of the benthic layer in polluted inner bays by means of irradiated specific wavelength as blue.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.7 no.1
• /
• pp.13-21
• /
• 2004

Temporal changes of Chl-α, physical and chemical factors were investigated by diurnal observation at 2-hour interval at three fixed stations in the western Chinhae Bay from 12 Aug. to 13 Aug. 1999. Difference of dissolved oxygen between surface and bottom layer was maximum when the thermocline were strong. Organic distribution such as COD was affected by the growth of phytoplankton. Limitting factor was nitrogen, that is, inorganic nitrogen plays a significant role on regulating the algal growth. Surface distribution of dissolved inorganic nitrogen was very low compared to bottom layer by uptake of organisms. Maximum value of Chl-α at station C2 and C11 were observed from subsurface layer, ranges of which exceeded possibility concentration of red tide outbreak, 10 mg/㎥. On the other hand, that of C15 exist at surface layer. In this area, DIN and DIP concentrations increased by input sources such as rainfall and benthic flux before the bloom of phytoplankton. Accumulation of phytoplankton occurred at subsurface layer by the rapid uptake of DIN, especially nitrate ion, when strong thermocline existed as approach to the afternoon, which led to the increase of organics in water column and oxygen deficiency water mass at bottom layer until late at evening. Since then, DIN increases gradually as water temperature decrease to minimum. The quantitative understanding of nitrogen of fluxed to and from the various sources is necessary for environmental management.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.10 no.1
• /
• pp.47-55
• /
• 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.