• Korean Journal of Ecology and Environment
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• v.40 no.1
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• pp.61-71
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• 2007

The photosynthetic characteristics and primary production by phytoplankton in open waters of two wetlands (the Banwol and the Donghwa wetland) of Sihwa Constructed Wetland with different water chemistry were investigated to provide the information for the wetland management considering the water treatment efficiency. During the study period (from March to October, 2005) the primary productivity in open waters ranged from 481 to 11,275 mgC $m^{-2}$ $day^{-1}$, which is very high compared with the eutrophic level of 600mgC $m^{-2}$ $day^{-1}$. From the analysis of the photosynthesis-irradiance (P-I) model parameters, the photosynthetic characteristics may be affected by different concentration and ratio of nutrient (N and P) between two wetlands. Assimilation number (AN) was higher in the Donghwa wetland (average AN: 8.5gC $gChl^{-1}$ $hr^{-1}$) with high P and low N/P ratio than the Banwol wetland (average AN: 5.8gC $gChl^{-1}$ $hr^{-1}$) with high N and high N/P ratio. This result indicates that AN may be concerned with phosphorus than nitrogen and low NIP ratio. Positive correlation (R=0.81) was observed between the initial slope and AN, implying that AN was high in case of phytoplankton having more active photosynthesis ability under low light. On the other hand, maximum photosynthesis (Pmax) was related positively with chlorophyll a concentration showing correlation coefficient of 0.47. In this study, considering the high primary production through phytoplankton photosynthesis in open waters of Sihwa Constructed Wetland, the produced organic matter by phytoplankton may affect the water quality within wetland and its efficiency of water treatment. Also, the photosynthetic characteristics may be affected by different nutrient enrichment (especially phosphorus) of wetlands. This study suggests that the production by phytoplankton and its characteristics in open water of constructed wetland for water treatment should be considered to improve the removal efficiency of organic matter.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.26 no.1
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• pp.76-90
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• 1993

To clarify the relations between photoperiodism and x-organ of eyestalks to the control of gonadal maturation in a freshwater prawn, Macrobrachium nipponense, the present investigation was performed with following examinations: 1) the influence of water temperature and daylength on the control of gonadal maturation, 2) the effect of eyestalk ablation on the gonadal maturation, 3) the seasonal variation of histology of MEX-organ (medulla externa X-organ) in the eyestalk. In previtellogenesis period (December${\sim}$March) and vitellogenesis period (April${\sim}$May), gonadal maturation was considerablely influnced by water temperature. In these periods, GSI increased and gonads were matured with water temperature rising without regard to photoperiod conditions (12L/12D and 15L/9D). In spawning period (June${\sim}$August), however, gonadal maturation was influenced by photoperiod condition. While high value of GSI was kept at long photoperiod regime (15L/9D), GSI was decreased at short photoperiod regime (12L/12D). In resting period (September${\sim}$November), no rematuration was occurred at all the experimental regimes combinated with water temperatures ($16^{\circ}C,\;22^{\circ}C,\;28^{\circ}C$) and photoperiod (12L/12D, 15L/9D). Effect of X-organ which inhibite the gonadal maturation was stronger in resting period than that in previtellogenesis and ealy spawning periods by observations on the effectiveness of eyestalk ablation on the gonadal maturation. In MEX-organ of eyestalk, the number of neurosecretory cells of which size was over $20{\mu}m$ in diameter varied according to the reproductive cycle. The number of cells increased $77{\pm}12$ in resting period, and decreased $55{\pm}7$ in vitellogenesis period. Volume of Bellonci's organ, however, increased in vitellogenesis period in comparison with that in resting period.

• Journal of Aquaculture
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• v.5 no.1
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• pp.93-108
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• 1992

This study was conducted to understand the variation of suspended matters in coastal waters of Cheju Island. Water sampling was carried out at 22 stations along the coast of this island from March 1988 to November 1989. Analyzed and/or observed items were water temperature, salinity, total solids (TS), total dissolved solids (TDS), volatile suspended solids (VSS), and fixed suspended solids (FSS). Inter-relationships between wind velocity, precipitation and total suspended solids (TSS) were also investigated. More windy days prevail in winter season (December, January and February) in Cheju Island. Thirty-six points seven percent of total windy days of a year appeared in this season. The rate of windy days in spring was $27.3\%$ and those in summer and fall were $17.9{\%}$ each. From February to July, the heaviest precipitation was observed in the southeastern area and that from August to January was observed in the eastern part of this island. TS and TDS were firmly related with the fluctuation of salinity. Therefore, there were higher in spring and lower in summer. The highest TSS (7.73 $mg/{\ell}$) was observed in February and was the lowest (4.73 $mg/{\ell}$) in September. Annual mean value of TSS was 6.3$mg/{\ell}$. The highest VSS (2.03 $mg/{\ell}$) was observed in July and lowest (1.42 $mg/{\ell}$) in September. The percentage of VSS per 755 was $30.6{\%}$ in average that was not much higher level compared to the other polluted areas. This value became higher in summer (av. $34.17{\%}$) and lower in winter (av. $24.2{\%}$). Fluctuation of TSS was mainly related with the freshwate. discharge, tidal action, and re-suspension of bottom sediments by the wind waves. Therefore, TSS concentration was low in summer and hish in winter.

• Korean Journal of Ecology and Environment
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• v.41 no.3
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• pp.382-394
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• 2008

The objective of this study was to analyze temporal trends of water chemistry and spatial heterogeneity between the dam site (Daecheong Reservoir, S1) and the downstream (S2$\sim$S4) using water quality dataset (obtained from the Ministry of Environment, Korea) during 2000$\sim$2007. Water quality, based on eight physical and chemical parameters, varied largely depending on the years, sampling sites, and the discharge volume. Conductivity and nutrients (TN and TP) showed a decreasing trend in the downstream (S4) rather than the dam site during the monsoon. Spatial variation increased toward downstream (S4) from Daecheong Reservoir (S1). Also, BOD and COD increased toward downstream. Because of input of nutrient and pollutant nearby S1, lentic ecosystem in monsoon, BOD and COD were slightly increased. whereas relatively decreased in S4, lotic ecosystem in monsoon, by dilution effect of nutrient and pollutant by discharge from upper dam, S1. Spatial variation of SS increased toward downstream (S4) by the side of Daecheong Reservoir (S1). Based on the dataset, efficient water quality management in the point source tributary streams is required for better water quality of downstream. Monthly characteristics of DO showed the lowest value in the monsoon that tend to increase water temperature. DO was lowest in October at S1 because turbid water, input to the Daecheong Reservoir in the monsoon affect to the postmonsoon period. In contrast, water temperature increased toward summer monsoon, in spite of some differences showed between S1 and S4 environment. Overall, the characteristics of water quality in downstream region have close correlation with discharge amount of Daecheong Reservoir. Thus, those characteristics can explain that discharge control of upper dam mainly affect to the water quality variation in downstream reach.

• Journal of Korea Water Resources Association
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• v.40 no.12
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• pp.921-930
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• 2007

The objective of this study is to present temporal-spatial variation of water resources on climate change impacts using the IPCC SRES A2 scenario and dynamical downscaling of the results (using the MM5 model with a resolution of 27km by 27km) at 139 sub-basins in Korea. The variation of runoff shows differences in the change of rate according to the each sub-basins and analysis durations. It has increased in the sub-basins located in Han river basin and east part of it, the other basins have decreased. In seasonal analysis, runoff in autumn and winter have increased, while in spring and summer have decreased. The results of frequency analyzing classified runoff(Low flow(Q$\leq$5mm), Normal flow(5$\geq$100mm)) show that low flow increase in most of the sub-basins for 2031-2060 and 2061-2090. In the case of high flow, it have higher frequency ranging from -100% to 500% than low flow. Regardless of the variation of mean runoff, maximum discharge appeared to be increase in process of time. The regression method is used to figure out the relationship between the rate of runoff change and mean temperature, mean precipitation under A2 scenario. The mean actual evapotranspirations from the regression equations increased by 3.4$\sim$5.3% for the change of $1^{\circ}C$. Also, for the precipitation change of $\pm$10%, runoff variety range is -18.2$\sim$+12.4% in Han River, -21.6$\sim$+14.6% in Nakdong River, -17.5$\sim$+11.5% in Gum River, -18.4$\sim$+10.6% in Sumjin River, -19.9$\sim$+12.7% Youngsan River basin.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.8 no.1
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• pp.47-68
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• 1970

Experiments were conducted by moderate season culture of each of 7 early, medium and late maturing varieties which were considered to be of strong salt tolerance in non-salty, low- and high-salty reclaimed areas (salt content: 0.5% and 1% at the end of April). The results of the experiments revealed that the early maturing varieties were suffered greatly from salt damage in such reclaimed salty area which is the "fall better type" in the year-round changes of soil salt concentration in Korea. Better yielding varieties in the salty area showed generally a high yield ratio in the salty area compared with the non-salty area. This indicates that they are strong salt tolerant varieties. It seemed that the salt tolerance could be measured by the number of delaying days in heading, the growth rate of culm length, number of panicles and number of grains per panicle in the salty area to compare with the non-salty area. The effects or salt damage on the yields of each variety at maturing stage and agronomic characteristics in the salty area were compared and discussed with the non-salty area.alty area.

• Korean Journal of Agricultural and Forest Meteorology
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• v.11 no.2
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• pp.61-71
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• 2009

Most deciduous trees in temperate zone are dormant during the winter to overcome cold and dry environment. Dormancy of deciduous fruit trees is usually separated into a period of rest by physiological conditions and a period of quiescence by unfavorable environmental conditions. Inconsistent and fewer budburst in pear orchards has been reported recently in South Korea and Japan and the insufficient chilling due to warmer winters is suspected to play a role. An accurate prediction of the flowering time under the climate change scenarios may be critical to the planning of adaptation strategy for the pear industry in the future. However, existing methods for the prediction of budburst depend on the spring temperature, neglecting potential effects of warmer winters on the rest release and subsequent budburst. We adapted a dormancy clock model which uses daily temperature data to calculate the thermal time for simulating winter phenology of deciduous trees and tested the feasibility of this model in predicting budburst and flowering of Niitaka pear, one of the favorite cultivars in Korea. In order to derive the model parameter values suitable for Niitaka, the mean time for the rest release was estimated by observing budburst of field collected twigs in a controlled environment. The thermal time (in chill-days) was calculated and accumulated by a predefined temperature range from fall harvest until the chilling requirement (maximum accumulated chill-days in a negative number) is met. The chilling requirement is then offset by anti-chill days (in positive numbers) until the accumulated chill-days become null, which is assumed to be the budburst date. Calculations were repeated with arbitrary threshold temperatures from $4^{\circ}C$ to $10^{\circ}C$ (at an interval of 0.1), and a set of threshold temperature and chilling requirement was selected when the estimated budburst date coincides with the field observation. A heating requirement (in accumulation of anti-chill days since budburst) for flowering was also determined from an experiment based on historical observations. The dormancy clock model optimized with the selected parameter values was used to predict flowering of Niitaka pear grown in Suwon for the recent 9 years. The predicted dates for full bloom were within the range of the observed dates with 1.9 days of root mean square error.

• Korean Journal of Agricultural and Forest Meteorology
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• v.16 no.3
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• pp.233-245
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• 2014

Nighttime correction of $CO_2$ flux is one of the most important and challenging tasks in eddy covariance measurements over a complex mountainous terrain. In this study, we have scrutinized the quality and the credibility of the $CO_2$ flux datasets which were produced by employing three different methods of nighttime correction, i.e., (1) friction velocity ($u^*$) correction, (2) light response curve (LRC) correction, and (3) advection-based van Gorsel (VG) correction. The whole year datasets used in our analysis were collected at the two KoFlux tower sites (i.e., GDK deciduous forest site at the upper hill and GCK coniferous forest site at the lower hill) located in the valley of Gwangneung National Arboretum in central Korea. The resultant magnitudes and patterns of ecosystem respiration ($R_E$), gross primary productivity (GPP), and net ecosystem exchange (NEE) of $CO_2$ showed marked differences among the datasets produced with three different correction methods, which were also site-specific. The examination from micrometeorological and ecological perspectives suggests that the major cause of some inconsistency seems to be associated with the advection of $CO_2$ along the sloping terrain and the inappropriate selection of the correction data that might have been already affected by advective flows. The comparison with the results from other studies indicated that the overall characteristics of the corrected $CO_2$ fluxes at GDK and GCK (except those with LRC correction) were well within the ranges reported in the literature for various ecosystems in East Asia in similar latitudes. However, our study also implies that there will be always a room for further improvement in the present datasets. Therefore, caution must be exercised for the data users in order to properly use the updated version of datasets through transparent, open and participatory communication with data producers.

• Journal of Climate Change Research
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• v.4 no.4
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• pp.397-407
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• 2013

Seasons in Korea have very distinguishable features. Due to continental high pressure, spring in Korea is dry and has low precipitation. Due to climate change derived from the increase of greenhouse gases, climate variability had increased and it became harder to predict. This caused the spring drought harsher than usual. Since 1990s, numbers of chronic drought from winter to spring increased in southern regions of Korea. Such drought in the spring damages the growth and development of the crops sown in the spring and decreases its quantity. For stable agricultural production in the future, it is necessary to assess vulnerability of the relationship between spring drought and agricultural production as well as to establish appropriate measures accordingly. This research used CCGIS program to perform vulnerability assessment on spring drought based on climate change scenario SRES A1B, A1FI, A1T, A2, B1, B2 and RCP 8.5 in 232 regions in Korea. As a result, Every scenario showed that vulnerability of spring drought decreased from 2000s to 2050s. Ratio of decrease was 37% under SRES scenario but, 3% under RCP 8.5 scenario. Also, for 2050 prediction, every scenario predicted the highest vulnerability in Chungcheongnam-do. However, RCP-8.5 predicted higher vulnerability in Gyeonggi-do than SRES scenario. The reason for overall decrease in vulnerability of agriculture for future spring drought is because the increase of precipitation was predicted. The assessment of vulnerability by different regions showed that choosing suitable scenario is very important factor.

• Journal of Preventive Medicine and Public Health
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• v.15 no.1
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• pp.187-196
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• 1982

The followings are the results of the study on industrial accidents occurred at 12 factories manufacturing metal products during the period of 2 years from January 1980 to December 1981 in the area of Yong-Dung-Po in Seoul. The results of the study are as follows: 1. The incidence rate of industrial injuries was 45.7 per 1,000 workers of the sample group and the rate of male (54.0) was three times higher than that of female (17.5). 2. In age groups, the highest rate was observed in the group of under 19 years old with 83.5, while the lowest in the group of 40s. 3. It was found that those who had short term of work experience produced a higher rate of injuries, particularly, the group of workers with less than 1 year of experience showed the highest rate of it as 48.1%. 4. In working time, the highest incidence rate occurred 3 and 7 hours after the beginning of their working showing the rate of 6.0 and 6.1 per 1,000 workers, respectively. 5. The highest incidence rate was observed on Monday as 8.4 per 1,000 workers, and it was 18.3% in aspect of the days of a week. 6. In aspect of the months of a year, the highest incidence was observed on July 1,000 workers and the next was on March as 4.8. These figures account for 11.8% of total occurrence in respective month. as 5. 4 per and 10.5% 7. In causes of injuries, the accident caused by power driven machinery showed the highest rate with 37.5%, the second was due to handling without machinery with 17.2%, and the third was due to falling objects with 14.2%, and striking against objects with 10.2%, and so on. 8. By parts of the body affected, the most injuries 84.3% of them occurred on both upper and lower extremities with the rate of 58.8% for the former and 25.5% for the latter. Fingers were most frequently injured with a rate of 40.3%. Comparing the sites of extremities affected, rate of injuries on the right side was 55.0% and 45.0% on the left side. 9. In the nature of injury, laceration and open wound were the highest with 34. 0%, the next was fracture and dislocation with 31. 9%, and sprain was the third with 8.1%. 10. On the duration of treatment, it lasted less than one month in 68.9% of the injured cases, of which 14.5% of the cases were recovered within 2 weeks, and 54.4% of them were treated more than 2 weeks. And the duration of the treatment tended to be prolonged in larger industries. 11. The ratio of insured accidents to uninsured accidents was 1 to 4.7.