• Korean Journal of Soil Science and Fertilizer
• /
• v.48 no.4
• /
• pp.271-277
• /
• 2015

Anaerobic decomposition of organic material in flooded rice fields produces methane, which escapes to the atmosphere primarily by transport through the rice plants. The annual amount of $CH_4$ emitted from a given area of rice is a function of the number and duration of crops grown, water regimes before and during cultivation period, and organic and inorganic soil amendments. Soil type, temperature, and rice cultivar also affect $CH_4$ emissions. The field experiment was conducted for three years to develop methane emission factor for water regime before the cultivation period from the rice fields. It was treated with three different water regimes prior to rice cultivation, namely: non-flooded pre-season < 180 days, non-flooded pre-season > 180 days, flooded per-season in which the minimum flooding interval is set to 30 days. Methane emission increased with days after transplanting and soil redox potential (Eh) decreased rapidly after flooding during the rice cultivation. The average methane emission fluxes were $5.47kg\;CH_4\;ha^{-1}day^{-1}$in flooded pre-season > 30 days, 5.04 in non-flooded pre-season < 180 days and 4.62 in non-flooded pre-season > 180. Methane emission flux was highly correlated with soil temperature and soil Eh. Rice yields showed no difference among treatments with water regime before the cultivation period.

• 한국해양학회지
• /
• v.26 no.3
• /
• pp.204-222
• /
• 1991

The annual cycles of plant major nutrients and dissolved oxygen in a nutrients-rich semi-enclosed coastal inlet, chinhae Bay, of the southern coast of the Korean Peninsula are first presented. The water column of the bay is stratified during summer (April-late September) and well0mixed during winter (October-March). During the summer stratification period, dissolved oxygen contents exceed 400uM in the surface but diminish to less than 50uM in the near bottom waters, which often results in an anoxic environment in the inner part of Chinhae Bay. After the breakdown of the stratification in October, dissolved oxygen concentration remains undersaturated until February. The evidence of allochthonous input of N-nutrients throughout the year is readily seen in the water column: however. crude budget calculations show that the nutrients are efficiently utilized within the bay ecosystem, and that export of the nutrients from the bay to the shelf must be negligible. There is no sign of the enrichment of the nutrients in the water column. The eutrophication phenomenon sensu stricto is not observed in chinhae Bay. Using the standing stock of dissolved oxygen and estimation of the oxygen fluxes across the air-sea boundary, a benthic oxygen respiration rate during winter is estimated conservatively at 21-24 mmol Cm/SUP -2/d/SUP -1/. this oxygen respiration rate accounts for about 20% of the total phytoplankton production in winter.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.29 no.1
• /
• pp.84-91
• /
• 1996

Heat flux of the East China Sea was estimated with the bulk method, the East China mount based on the marine meteorological data and cloud amount data observed by a satellite. Solar radiation is maximum in May and minimum in December. Its amount decreases gradually southward during the winter half year (from October to March), and increases northward during the summer half year (from April to September) due to the influence of Changma (Baiu) front. The spatial difference of long-wave radiation is relatively small, but its temporal difference is quite large, i.e., the value in February is about two times greater than that in July. The spatial patterns of sensible and latent heat fluxes reflect well the effect of current distribution in this region. The heat loss from the ocean surface is more than $830Wm^{-2}$ in winter, which is five times greater than the net radiation amount during the same period, The annual net heat flux is negative, which means heat loss from the sea surface, in the whole region over the East China Sea. The region with the largest loss of more than $400Wm^{-2}$ in January is observed over the southwestern Kyushu. The annual mean value of solar radiation, long-wave radiation, sensible and latent heat fluxes are estimated $187Wm^{-2},\;-52Wm^{-2},\;-30Wm^{-2}\;and\;-137Wm^{-2}$, respectively, consequently the East China Sea losses the energy of $32Wm^{-2}(2.48\times10^{13}W)$. Through the heat exchange between the air and the sea, the heat energy of $0.4\times10^{13}W$ is supplied from the air to the sea in A region (the Yellow Sea), $2.1\times10^{13}W$ in B region (the East China Sea) and $1.7\times10^{13}W$ in C region (the Kuroshio part), respectively.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.5 no.3
• /
• pp.208-215
• /
• 2000

The estimated total material transports through the Cheju Strait using all data which investigated in 1997 and 1999 are as follows; A large amount of suspended sediments and dissovted inorganic nutrients are carried tothe South Sea through the Cheju Strait by a persistent eastward flow (Cheju Current) from the Y311ow Sea andthe East China Sea. The annual material Oanspous by the Cheju Current are as follows; 22.9${\times}$10$^6$ ton yr$^{-1}$(SS), 0.52${\times}$10$^{10}$ mol yr$^{-1}$ (NH$_4\;^+$), 6.05${\times}$10$^{10}$ mol yr$^{-1}$ (NO$_3\;^-$), 0.36${\times}$10$^{10}$ mol yr$^{-1}$ (PO$_4\;^{3-}$), 10.27${\times}$10$^{10}$ mol yr$^{-1}$ (Si(OH)$_4$). The annual suspended sediment flux per water transport in the Cheju Strait (44.48${\times}$10$^6$ ton yr$^{-1}$ Sv$^{-1}$) is about 1.7 larger than that in the Korean Strait (26.08${\times}$10$^6$ ton yr$^{-1}$ Sv$^{-1}$). The annual nitrate flux per water transport (11.60${\times}$10$^{10}$ mol yr$^{-1}$ Sv$^{-1}$) is about 1.2 larger than that in the Korean Strait (9.72${\times}$10$^{10}$ mol yr$^{-1}$ Sv$^{-1}$) and 2/3 of that by Kuroshio in the East China Sea (18.55${\times}$10$^{10}$ ton yr$^{-1}$ Sv$^{-1}$). It suggests that chemical rich Cheju Current will play a significant role in the biogeochemical processes in the South Sea where the huge land-based waste are introduced.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.18 no.4
• /
• pp.366-377
• /
• 2016

Water use efficiency (WUE) is considered as an important ecological indicator which may provide information on the process-structure relationships associated with energy-matter-information flows in ecosystem. The WUE at ecosystem-level can be defined as the ratio of gross primary productivity (GPP) to evapotranspiration (ET). In this study, KoFlux's long-term (2007-2015) eddy covariance measurements of $CO_2$ and water vapor fluxes were used to examine the WUE of needle fir plantation in Korea National Arboretum. Our objective is to ascertain the seasonality and inter-annual variability in WUE of this needle fir plantation so that the results may be assimilated into the development of a holistic ecological indicator for resilience assessment. Our results show that the WUE of needle fir plantation is characterized by a concave seasonal pattern with a minimum ($1.8-3.3g\;C{\cdot}(kg\;H_2O)^{-1}$) in August and a maximum ($5.1-11.4g\;C{\cdot}(kg\;H_2O)^{-1}$) in February. During the growing season (April to October), WUE was on average $3.5{\pm}0.3g\;C\;(kg\;H_2O)^{-1}$. During the dormant seasons (November to March), WUE showed more variations with a mean of $7.4{\pm}1.0g\;C{\cdot}(kg\;H_2O)^{-1}$. These values are in the upper ranges of WUE reported in the literature for coniferous forests in temperate zone. Although the growing season was defined as the period from April to October, the actual length of the growing season (GSL) varied each year and its variation explained 62% of the inter-annual variability of the growing season WUE. This is the first study to quantify long-term changes in ecosystem-level WUE in Korea and the results can be used to test models, remote-sensing algorithms and resilience of forest ecosystem.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.22 no.4
• /
• pp.187-198
• /
• 2017

Dissolved and particulate organic carbon concentrations and fluxes were measured and estimated for the Yeongsan River during 2006~2015. The dissolved organic carbon (DOC) concentrations ranged from 2.49 to $4.39mg{\cdot}C/L$ with a variance of 30.1% (${\sigma}_x/\bar{x}$), and showed a simple correlation to algal bloom and precipitation. The particulate organic carbon (POC) concentrations had gradually decreased from 6.68 to $0.19mg{\cdot}C/L$ for 10 years, and changed definitely with weir construction in 2011. Based on the relationships between POC and suspended particulate matters and between POC and chlorophyll-a, we found out that the distinct variation of the origin and composition of POC was caused by stagnation and screening effect of the dammed river. The total organic carbon (TOC) concentrations dropped to 52.3% (from 8.26 to $3.94mg{\cdot}C/L$) as the POC concentrations diminished to more than 94.8% after weir construction, in which the DOC forms up to 90.9%. The fluxes of TOC, based on the relationship between the annual TOC concentration and the discharge of Yeongsan dike sluice, were $2.56{\sim}19.41{\times}10^9g{\cdot}C/yr$, and showed a great deal of variability in 2011. Since then the TOC flux dropped to $5.40{\times}10^9$ (2011~2015) from $14.54{\times}10^9g{\cdot}C/yr$ (2006~2010). These results suggest that the weirs trapped annually $1.83{\times}10^9g{\cdot}C$ on a river bed, but released in great levels of dissolved organic form at their exits.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.11 no.2
• /
• pp.70-77
• /
• 2008

In this study, to establish countermeasure from marine casualties as a basic study fur long-term prediction of topographical change around Jinudo in the Nakdong river estuary, spatio-temporal topographical change monitoring was carried out. Also, in order to estimate the deposition variations concerning SS (Suspended Solid) flux which moved at St.S1 during neap and spring tide, respectively. From the topographical monitoring, it was found that the annual mean ground level and deposition rate were 141 mm and 0.36 mm/day and all parts except the northern part of Jinudo had the active topographical changes and a tendency to annually deposit. From vertical distribution of SS net fluxes, $SS_{LH}$ (latitudinal SS net flux) during spring tide overall flows average 28 $kg/m^2/hr$ (eastward), and $SS_{LV}$ (longitudinal SS net flux) flows average 11.1 $kg/m^2/hr$ (northward). And, $SS_{LH}$ overall flows average 4.8 $kg/m^2/hr$ (eastward), and $SS_{LV}$ flows average 1.5 $kg/m^2/hr$ (northward) during neap tide similar with spring tide. The depth averaged values of the latitudinal and longitudinal SS net fluxes during spring tide were approximately 6 times higher than those during neap tide. As result of, it was considered that topographical change of southern part of Jinudo was affected by resuspension of bottom sediments due to strong current in bottom layer during flood flow.

• Journal of the Korean earth science society
• /
• v.21 no.5
• /
• pp.611-622
• /
• 2000

To investigate the exchange rates of mercury(Hg) across soil-air boundary, we undertook the measurements of Hg flux using gradient technique from a major waste reclamation site, Nan-Ji-Do. Based on these measurement data, we attempted to provide insights into various aspects of Hg exchange in a strongly polluted soil environment. According to our analysis, the study site turned out to be not only a major emission source area but also a major sink area. When these data were compared on hourly basis over a full day scale, large fluxes of emission and deposition centered on daytime periods relative to nighttime periods. However, when comparison of frequency with which emission or deposition occurs was made, there emerged a very contrasting pattern. While emission was dominant during nighttime periods, deposition was most favored during daytime periods. When similar comparison was made as a function of wind direction, it was noticed that there may be a major Hg source at easterly direction to bring out significant deposition of Hg in the study area. To account for the environmental conditions controlling the vertical direction of Hg exchange, we compared environmental conditions for both the whole data group and those observed from the wind direction of strong deposition events. Results of this analysis indicated that the concentrations of pollutant species varied sensitively enough to reflect the environmental conditions for each direction of exchange. When correlation analysis was applied to our data, results indicated that windspeed and ozone concentrations best reflected changes in the magnitudes of emission/deposition fluxes. The results of factor analysis also indicated the possibility that Hg emission of study area is temperature-driven process, while that of deposition is affected by a mixed effects of various factors including temperature, ozone, and non-methane HCs. If the computed emission rate is extrapolated to the whole study area we estimate that annual emission of Hg from the study area can amount to approximately 6kg.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.27 no.4
• /
• pp.194-210
• /
• 2022

The monthly inventory of dissolved inorganic carbon (C_T) and its fluxes were simulated using a box-model for the southeastern Yellow Sea, bordering the northern East China Sea. The monthly C_T data was constructed by combining the observed data representing four seasons with the data adopted from the recent publications. A 2-box-model of the surface and deep layers was used, assuming that the annual C_T inventory was at the steady state and its fluctuations due to the advection in the surface box were negligible. Results of the simulation point out that the monthly C_T inventory variation between the surface and deep box was driven primarily by the mixing flux due to the variation of the mixed layer depth, on the scale of -40~35 mol C m^-2 month^-1. The air to sea CO₂ flux was about 2 mol C m^-2 yr^-1 and was lower than 1/100 of the mixing flux. The biological pump flux estimated magnitude, in the range of 4-5 mol C m^-2 yr^-1, is about half the in situ measurement value reported. The C_T inventory of the water column was maximum in April, when mixing by cooling ceases, and decreases slightly throughout the stratified period. Therefore, the total C_T inventory is larger in the stratified period than that of the mixing period. In order to maintain a steady state, 18 mol C m^-2 yr^-1 (= 216 g C m^-2 yr^-1), the difference between the maximum and minimum monthly CT inventory, should be transported out to the East China Sea. Extrapolating this flux over the entire southern Yellow Sea boundary yields 4 × 10⁹ g C yr^-1. Conceptually this flux is equivalent to the proposed continental shelf pump. Since this flux must go through the vast shelf area of the East China Sea before it joins the open Pacific waters the actual contribution as a continental shelf pump would be significantly lower than reported value. Although errors accompanied the simple box model simulation imposed by the paucity of data and assumptions are considerably large, nevertheless it was possible to constrain the relative contribution among the major fluxes and their range that caused the C_T inventory variations, and was able to suggest recommendations for the future studies.

• Journal of the Korean earth science society
• /
• v.22 no.5
• /
• pp.415-422
• /
• 2001

Studies of atmospheric general circulation in the troposphere and stratosphere are very important to understand the influence of human activities on the global climate and its change. Recently, the existence of an annual cycle in the circulation has been reported by a number of studies. In this study, the residual mean meridional circulation is calculated by the TEM momentum and continuity equations for the period from December 1985 to November 1995 (10 years), and the long-term variations of the circulation and mass fluxes across the 100hPa surface are examined. The multiple regression statistical model is used to obtain quantitatively the long-term variations. This study is focused especially on mean meridional circulation in the troposphere and stratosphere associated with ENSO (El Ni${\tilde{n}}$o-Southern Oscillation) which is known as a cause of the unusual weather, global climate, and its change. The results show that the global scale troposphere-stratosphere mean meridional circulation is intensified during El Ni${\tilde{n}}$o event and QBO (quasi-biennal oscillation) easterly phase and weakened during La Ni${\tilde{n}}$o event and QBO westerly phase. The signal of Mount Pinatubo volcanic eruption in June 1991 is obtained. Due to the volcanic eruption the global scale troposphere-stratosphere mean meridional circulation is abruptly intensified.