• Journal of Environmental Impact Assessment
• /
• v.32 no.6
• /
• pp.389-406
• /
• 2023

The research area, located in the northern coastal region of South Korea's West Sea, involves three bird habitats. Among these are two newly established habitats in Songdo International Business District, created by filling and developing tidal flats that were previously utilized as stopover sites for migratory birds. One of these areas showed decrease (Residual tidal flats, site.1) while the other showed increase (Artificial lake, site.2) in bird influx. The third habitat (Namdong reservoir, site.3) is a pre-existing stable habitat which has been maintained as a stable habitat. This study conducts an assessment of habitats based on avian population clusters and environmental surveys and proposes habitat management measures. A survey of bird populations and habitat environments was conducted for a total of 39 occasions from January to December 2022. The observed bird species totaled 14 families and 48 species with 20,760 individuals. Compared to the existing habitats, the newly established habitats showed relatively lower influx of bird species and individuals. During the habitat assessment, the newly established habitats were rated as I to II grade, while the existing habitat was rated as relatively high III grade on the grading assessment of the tidal flat. An analysis of habitat types revealed that the existing habitat, in which diverse strategies for habitat type diversity and mitigating anthropogenic interference were demonstrated, attracted a diverse range of bird species. Through this research, it was deduced that the diversity of habitat types plays a significant role in attracting various bird species. Upon evaluation of habitat types concerning the habitat characteristics of the bird species selected for habitat management, as habitat management measures, it is deemed that the creation of shielded green areas (referred to as 'buffer green') to minimize interference from the surroundings, the establishment of reed fields (site.1, 2) positively correlated with reservoirs, and the improvement of sandbanks (site.1) positively associated with tidal flats, the two relations which we drew from correlation analysis between occurrence species and habitat types, would contribute to the future restoration and maintenance of stable habitats. The results of this study can be applied not only to the study area but also to other development zones, such as coastal reclamation sites, which share similar geographical and environmental characteristics, including arrival sites for migratory birds.

• Korean Journal of Ichthyology
• /
• v.36 no.1
• /
• pp.48-57
• /
• 2024

Distribution status and extinction threat evaluation of an endangered species, Cobitis choii, were investigated from 2015 to 2019. In 2015 and 2018, we investigated past appearance sites of C. choii. In 2015, 163 individuals from nine sites were collected by surveying 19 stations. In 2018, 19 individuals from five sites were collected by surveying 22 sites. In 2019, 156 individuals from 12 sites were collected as a result of a survey of 79 sites of past appearance and potential appearance of C. choii. Appearance regions were Mihocheon (Baekgokcheon (2 sites), Chopyeongcheon (1 sites)), Gapcheon (3 sites), Yugucheon (2 sites), Jicheon (4 sites), and Geumgang mainstream (2 sites). Among these appearing regions, Baekgokcheon, Yugucheon, and Mihocheon mainstreams showed a sharp decline in population. Baekgokcheon was estimated to have a habitat change due to a project to raise the bank of Baekgok Reservoir. Yugucheon was estimated to have a habitat disturbance due to flood-induced collapse and reconstruction of weir. Mihocheon mainstream was estimated to have water pollution and habitat disturbance. On the other hand, Chopyeongcheon and Geumgang mainstream were newly habitat identified and Gapcheon was noted to show an increase in the number of individuals. After performing extinction threat evaluation, C. choii was evaluated as Endangered (EN A2ac) due to its rapid population decline (more than 50%) in its habitats of Baekgokcheon, Yugucheon, and Mihocheon based on criteria A, while it was evaluated as Vulnerable (VU B1ab (iii,v) +B2ab +B2ab (iii,v)) due to its narrow extent of occurrence (EOO, 1,735 km²) and area of occupancy (AOO, 36 km²) in 6 locations with a continuous population decline based on criteria B. Therefore, the final threat of extinction grade was evaluated as Endangered (EN A2ac). In Baekgokcheon, Yugucheon, and Mihocheon mainstream where the population has declined rapidly recently, conservation measures are urgently required to increase its population.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.26 no.2
• /
• pp.377-398
• /
• 1999

Calcium fluoride, created by topical fluoride application, is the reservoir for fluoride ion regulated by pH in the oral environment. Therefore, the amount and the maintenance of calcium fluoride have an important role in preventing dental caries. The aim of this study is to evaluate the effect of Nd:YAG laser irradiation on the generation of calcium fluoride and the acid resistance of tooth enamel. The bovine anterior permanent teeth were prepared (n=276), and divided into following groups : no treatment (control) fluoride application alone, laser irradiation alone, laser irradiation after fluoride application, and fluoride application after laser irradiation. And each group was subdivided based on the application time of 1.23% acidulated phosphate fluoride (APF) (5 min and 30 min) and the irradiation energy of Nd:YAG laser ($20J/cm^2\;and\;40J/cm^2$). In case of fluoride application, each group was divided according to KOH treatment. Twenty three treatment conditions were made for this experiment and twelve specimens were assigned to each treatment condition. In each treatment condition, ten specimens were used for chemical analysis and two specimens were observed under SEM. In groups without treating KOH, fluoride content and the depth of enamel dissolved were measured using enamel biopsy technique. In groups with treating KOH, the amount of calcium fluoride was measured by the treatment with 1 M KOH for 24 hours and enamel biopsy was performed after KOH treatment. The results were analyzed by the fluoride content and the depth of enamel dissolved by enamel biopsy, amount and thickness of calcium fluoride, and the surface structures of enamel. The results are as follows: 1. In groups without treating KOH, the fluoride content of removed enamel showed a positive relationship with the energy density of laser when the laser irradiated before fluoride application 2. In groups without treating KOH, the depth of enamel dissolved decreased more with the combined laser and fluoride treatment than with laser or fluoride treatment, except for the case of $20J/cm^2$ laser irradiation after 5 minute fluoride application (p<0.05). 3. The amount of calcium fluoride did not increased by laser treatment with no statistical significance(p>0.05). 4. The particle size of calcium fluoride increased in case of fluoride treatment after laser irradiation, compared with fluoride application alone. In case of laser treatment after fluoride application, the particle size of calcium fluoride increased and some of the particles fused as well. 5. There were no significant differences in the fluoride content of dissolved enamel between groups without treating KOH and control group, except for the case of laser irradiation after treatment of APF for 30 minutes (p>0.05). 6. In groups with treating KOH, depth of removed enamel in the groups of combined treatment with laser and fluoride was shallower than that in fluoride application groups (p<0.05). 7. In groups without treating KOH, the relationship between fluoride content and the depth of enamel dissolved showed more negative (Spearman correlation coefficient: -0.6281) than in groups with treating KOH (Spearman correlation coefficient: -0.3792). The greater amount of calcium fluoride could be found in case where there was a significant differences of the depth of enamel dissolved between groups with and without treating KOH. From these results, it can be concluded that laser seems to be a little effects on the amount of calcium fluoride formation, but has some effect on the lowering the solubility of calcium fluoride. As the combined treatment of laser and fluoride application showed more effective acid-resistant property, more extended recall period for fluoride application can be achieved with this combined treatment in the clinic.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.38 no.5
• /
• pp.80-92
• /
• 2010

The purpose of this study was to analyze drainage facilities in mountainous urban neigbborhood parks--Baebongsan Park and Ogeum Park--in Seoul. Based on an analysis of existing drainage facilities, the volume of storm water runoff (VSW), the runoff rate of open channels(ROC), and the detention capacity of open charmels(DCOC) by each drainage watershed, the coefficient of runoff rate(CROC) as evaluated to be relevant between VSW and ROC and the coefficient of the detention capacity of open channe1s(CDCOC) as evaluated with DCOC compared to VSW were estimated and analyzed by parks and by watersheds. The results are as follows: 1. The total drainage area of Baebongsan Park was 34.13ha including surface runoff area(15.05ha; 44.09%), open channel area(l4.60ha; 42.78%), and natural waterway area(4.48ha; 13.13%). The total drainage area of Ogeum Park was 20.39ha including open channel area (10.14ha; 49.73%), ridge-side gutter area(7.17ha; 35.16%), surface runoff area (2.52ha; 12.36%), and natural waterway area (0.56ha; 2.75%). In Baebongsan Park, the portion of surface runoff was comparatively higher while the portion of artificial drainage area was higber in Ogeum Park. 2. In Baebongsan Park drainage districts were largely divided: VSW was $7.28m^3/s$ in total(average $0.23m^3/s$). Comparatively, tbe VSW in Ogeum Park, including smaller drainage districts, was $4.37m^3/s$ in total(average $0.12m^3/s$). 3. The ROC of Baebmgsan Park was $11.58m^3/s$ in total(average $0.77m^3/s$) and the CROC was 5.26, while in Ogeum Park, the ROC was $15.40m^3/s$(average $0.34m^3/s$) and tbe CROC was 8.87 higher than that of Baebongsan Because the size and slope of the open channel in Baebongsan Park was higher, the average ROC was larger, while tbe CROC of Ogeum Park was higher than that of Baebongsan Park, for the VSW in Ogeum Park was comparatively lower. 4. The DCOC in Baebongsan Park was $554.54m^3$ and the average of CDCOC was 179.83. That of Ogeum Park was $717.74m^3$ and the average of the CDCOC was 339.69, meaning that the DCOC of Ogeum Park was so much higber that drainage facilities in Ogeum Park were built intensively. This study was focused m the capacity of the drainage facilities in mountainous urban neighborhood parks by using the CROC to evaluate relevance between VSW and ROC and the CDCOC to evaluate the DCOC as compared with VSW. The devised methodology and coefficient for evaluating drainage facilities in mountainous urban neighborhood parks may he universally applicable through additional study. Further study m sustainable urban drainage systems for retaining rainwater in a reservoir and for enhancing ecological value is required in the near future.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.13 no.4
• /
• pp.2456-2470
• /
• 1971

Compaction of soil is very important for construction of soil structures such as highway fills, embankment of reservoir and seadike. With increasing compaction effort, the strength of soil, interor friction and Cohesion increas greatly while the reduction of permerbilityis evident. Factors which may influence compaction effort are moisture content, grain size, grain distribution and other physical properties as well as the variable method of compaction. The moisture content among these parameter is the most important thing. For making the maximum density to a given soil, the comparable optimum water content is required. If there is a slight change in water content when compared with optimum water content, the compaction ratio will decrease and the corresponding mechanical properties will change evidently. The results in this study of soil compaction with different water content are summarized as follows. 1) The maximum dry density increased and corresponding optimum moisture content decreased with increasing of coarse grain size and the compaction curve is steeper than increasing of fine grain size. 2) The maximum dry density is decreased with increasing of the optimum water content and a relationship both parameter becomes rdam-max=2.232-0.02785 $W_0$ But this relstionship will be change to $r_d=ae^{-bw}$ when comparable water content changes. 3) In case of most soils, a dry condition is better than wet condition to give a compactive effort, but the latter condition is only preferable when the liquid limit of soil exceeds 50 percent. 4) The compaction ratio of cohesive soil is greeter than cohesionless soil even the amount of coarse grain sizes are same. 5) The relationship between the maximum dry density and porosity is as rdmax=2,186-0.872e, but it changes to $r_d=ae^{be}$ when water content vary from optimum water content. 6) The void ratio is increased with increasing of optimum water content as n=15.85+1.075 w, but therelation becames $n=ae^{bw}$ if there is a variation in water content. 7) The increament of permeabilty is high when the soil is a high plasticity or coarse. 8) The coefficient of permeability of soil compacted in wet condition is lower than the soil compacted in dry condition. 9) Cohesive soil has higher permeability than cohesionless soil even the amount of coarse particles are same. 10) In generall, the soil which has high optimum water content has lower coefficient of permeability than low optimum water content. 11) The coefficient of permeability has a certain relations with density, gradation and void ratio and it increase with increasing of saturation degree.

• Tuberculosis and Respiratory Diseases
• /
• v.55 no.5
• /
• pp.449-458
• /
• 2003

Background : The poor prognostic factors of far-advanced pulmonary tuberculosis(FAPTB) are lymphocytopenia in the peripheral blood(PB)(< $1,000/mm^3$) and $T_4$-cell count ${\leq}500/mm^3$. However, the cause of PB lymphocytopenia in FAPTB is unclear. The aim of this study was to analyze the lymphocyte proportion and cytokines of the bone marrow(BM) in FAPTB patients with peripheral lymphocytopenia in order to clarify whether the limiting step of the lymphocytopenia occurs in production, differentiation, or circulation. Methods : This study included patients with FAPTB between August 1999 and August 2002 who visited Gachon Medical School Gil Medical Center. The exclusion criteria were old age(${\geq}65years$), cachexia or a low body weight, shock, hematologic diseases, or BM involvement of tuberculosis. The distributions of cells in PB and BM were analyzed and compared to the control group. The interleukin(IL)-2, IL-7, IL-10, TNF-${\alpha}$, Interferon-${\gamma}$, and TGF-${\beta}$ levels in the BM were measured by ELISA. Result : Thirteen patients(male : female=9:4) were included and the mean age was $42{\pm}12$years. The proportion and count of the lymphocytes in the PB were significantly lower in the FAPTB group ($7.4{\pm}3.0%$, $694{\pm}255/mm^3$ vs. $17.5{\pm}5.8%$, $1,377{\pm}436/mm^3$, each p=0.0001 and 0.002). The proportion of immature lymphocyte in the BM showed a decreasing trend in the FAPTB group($9{\pm}4%$ vs. $12{\pm}3%$, p=0.138). The IL-2($26.0{\pm}29.1$ vs. $112.2{\pm}42.4pg/mL$, p=0.001) and IL-10($3.4{\pm}4.7$ vs. $12.0{\pm}8.0pg/mL$, p=0.031) levels in the BM were significantly lower in the FAPTB group than those in control. The levels of the other cytokines in FAPTB group and control were similar. Conclusion : These results suggest that the cause of lymphocytopenia in PB is associated with a abnormality IL-2 and IL-10 production in the BM. More study will be needed to define the mechanism of a decreased reservoir in BM.

• Tuberculosis and Respiratory Diseases
• /
• v.54 no.1
• /
• pp.71-79
• /
• 2003

Background : A bronchoalveolar lavage(BAL) is useful in diagnosing the etiology of bilateral pulmonary infiltrations, but may worsen the oxygenation and clinical status in severely hypoxemic patients. This study assessed the safety and efficacy of the continuous positive airway pressure(CPAP) using a conventional mechanical ventilator via a face mask as a tool for maintaining the oxygenation level during BAL. Methods : Seven consecutive patients with the bilateral pulmonary infiltrates and severe hypoxemia ($PaO_2/FIO_2$ ratio ${\leq}200$ on oxygen 10 L/min via mask with reservoir bag) were enrolled. The CPAP 5-6 $cmH_2O(F_IO_2\;1.0)$ was delivered through an inflatable face mask using a conventional mechanical ventilator. The CPAP began 10 min before starting the BAL and continued for 30 min after the procedure was completed. A bronchoscope was passed through a T-adapter and advanced through the mouth. BAL was performed using the conventional method. The vital signs, pulse oxymetry values, and arterial blood gases were monitored during the study. Results : (1) Median age was 56 years(male:female=4:3). (2) The baseline $PaO_2$ was $78{\pm}16mmHg$, which increased significantly to $269{\pm}116mmHg$(p=0.018) with CPAP. After the BAL, the $PaO_2$ did not decrease significantly but returned to the baseline level after the CPAP was discontinued. The $SpO_2$ showed a similar trend with the $PaO_2$ and did not decrease to below 90 % during the duration of the study. (3) The $PaCO_2$ increased and the pH decreased significantly after the BAL but returned to the baseline level within 30 min after the BAL. (5) No complications directly related to the BAL procedure were encountered. However, intubation was necessary in 3 patients(43 %) due to the progression of the underlying diseases. Conclusion : In severe hypoxemic patients, CPAP using a face mask and conventional mechanical ventilator during a BAL might allow minimal alterations in oxygenation and prevent subsequent respiratory failure.

• Journal of the Korean association of regional geographers
• /
• v.3 no.2
• /
• pp.37-87
• /
• 1997

As a results of researches on the cultivation processes and settlement developments on the Mangyoung river valley as a whole could be have four 'Space-Time Continuity' through a [Origin-Destination] theory model. On a initial phases of cultivation, the cultivation process has been begun at mountain slopes and tributory plains in upper part of river-basin from Koryo Dynasty to early Chosun Dynasty. At first, indigenous peasants burned forests on the mountain slopes for making 'dryfield' for a cereal crops. Following population increase more stable food supply is necessary facets of life inducing a change production method into a 'wetfield' in tributory plains matching the population increase. First sedentary agriculture maybe initiated at this mountain slopes and tributory plains on upper part of river basin through a burning cultivation methods. Mountain slopes and tributory plains are become a Origin area in cultivation processes. It expanded from up to down through the valleys with 'a bits of land' fashion in a steady pace like a terraced fields expanded with bit by bit of land to downward. They expanded their land to the middle part of river basin in mid period of Chosun Dynasty with dike construction techniques on the river bank. Lower part of river cultivated with embankment building techniques in 1920s and then naturally expanded to the tidal marshes on the estuaries and river inlets of coastal areas. 'Pioneer fringes' are consolidated at there in modern times. Changes in landscapes are appeared it's own characters with each periods of time. Followings are results of study through the Mangyoung river valley as a whole. (1) Mountain slopes and tributory plains on the upper part of river are cultivated 'dryfields' by indigenous peasants with Burning cultivation methods at first and developed sedentary settlements at the edges of mountain slopes and on the river terrace near the fields. They formed a kind of 'periphery-located cluster type' of settlement. This type of settlement are become a prominant type in upper part of river basin. 'Dryfields' has been changed into a 'wetfields' at the narrow tributory plains by increasing population pressure in later time. These wetfields are supplied water by Weir and Ponds Irrigation System(제언수리방법). Streams on the tributory plains has been attracted wetfields besides of it and formed a [water+land] complex on it. 'Wetfields' are expanded from up to downward with a terraced land pattern(adder like pattern, 붕전) according to the gradient of valley. These periphery located settlements are formed a intimate ecological linkage with several sets of surroundings. Inner villages are expanded to Outer villages according to the expansion of arable lands into downward. (2) Mountain slopes and tributory plains expanded its territory to the alluvial deposited plains on the middle part of river valley with a urgent need of new land by population increase. This part of alluvial plains are cultivated mainly in mid period of Chosun Dynasty. Irrigation methods are changed into a Dike Construction Irrigation method(천방수리방법) for the control of floods. It has a trend to change the subjectives of cultivation from community-oriented one who constructed Bochang along tributories making rice paddies to local government authorities who could be gather large sums of capitals, techniques and labours for the big dike construction affairs. Settlements are advanced in the midst of plains avoiding friction of distances and formed a 'Centrallocated cluster type' of settlements. There occured a hierarchical structures of settlements in ranks and sizes according merits of water supply and transportation convenience at the broad plains. Big towns are developed at there. It strengthened a more prominant [water+land] complex along the canals. Ecological linkages between settlements and surroundings are shaded out into a tiny one in this area. (3) It is very necessary to get a modern technology of flood control at the rivers that have a large volume of water and broad width. The alluvial plains are remained in a wilderness phase until a technical level reached a large artificial levee construction ability that could protect the arable land from flood. Until that time on most of alluvial land at the lower part of river are remained a wilderness of overgrown with reeds in lacks of techniques to build a large-scale artificial levee along the riverbank. Cultivation processes are progressed in a large scale one by Japanese agricultural companies with [River Rennovation Project] of central government in 1920s. Large scale artificial levees are constructed along the riverbank. Subjectives of cultivation are changed from Korean peasants to Japanese agricultural companies and Korean peasants fell down as a tenant in a colonial situation of that time in Korea. They could not have any voices in planning of spatial structure and decreased their role in planning. Newly cultivated lands are reflected company's intensions, objectives and perspectives for achieving their goals for the sake of colonial power. Newly cultivated lands are planned into a regular Rectangular Block settings of rice paddies and implanted a large scale Bureaucratic-oriented Irrigation System on the cultivated plains. Every settlements are located in the midst of rice paddies with a Central located Cluster type of settlements. [water+land] complex along the canal system are more strengthened. Cultivated space has a characters of [I-IT] landscapes. (4) Artificial levees are connected into a coastal emnankment for a reclamation of broad tidal marshes on the estuaries and inlets of rivers in the colonial times. Subjectives of reclamation are enlarged into a big agricultural companies that could be acted a role as a big cultivator. After that time on most of reclamation project of tidal marshes are controlled by these agricultural companies formed by mostly Japanese capitalists. Reclaimed lands on the estuaries and river inlets are under hands of agricultural companies and all the spatial structures are formed by their intensions, objectives and perspectives. They constructed a Unit Farming Area for the sake of companies. Spatial structures are planned in a regular one with broad arable land for the rice production of rectangular blocks, regular canal systems and tank reservoir for the irrigation water supply into reclaimed lands. There developed a 'Central-located linear type' of settlements in midst of reclaimed land. These settlements are settled in a detail program upon this newly reclaimed land at once with a master plan and they have planned patterns in their distribution, building materials, location, and form. Ecological linkage between Newly settled settlemrnts and its surroundings are lost its colours and became a more artificial one by human-centred environment. [I-IT] landscapes are become more prominant. This region is a destination area of [Origin-Destination] theory model and formed a 'Pioneer Fringe'. It is a kind of pioneer front that could advance or retreat discontinously by physical conditions and socio-cultural conditions of that region.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.16 no.1
• /
• pp.3225-3262
• /
• 1974

The purposes of this thesis are to clarify experimentally the variation of ground water temperature in tube wells during the irrigation period of paddy rice, and the effect of ground water irrigation on the growth, grain yield and yield components of the rice plant, and, furthermore, when and why the plant is most liable to be damaged by ground water, and also to find out the effective ground water irrigation methods. The results obtained in this experiment are as follows; 1. The temperature of ground water in tube wells varies according to the location, year, and the depth of the well. The average temperatures of ground water in a tubewells, 6.3m, 8.0m deep are $14.5^{\circ}C$ and $13.1^{\circ}C$, respercively, during the irrigation period of paddy rice (From the middle of June to the end of September). In the former the temperature rises continuously from $12.3^{\circ}C$ to 16.4$^{\circ}C$ and in the latter from $12.4^{\circ}C$ to $13.8^{\circ}C$ during the same period. These temperatures are approximately the same value as the estimated temperatures. The temperature difference between the ground water and the surface water is approximately $11^{\circ}C$. 2. The results obtained from the analysis of the water quality of the "Seoho" reservoir and that of water from the tube well show that the pH values of the ground water and the surface water are 6.35 and 6.00, respectively, and inorganic components such as N, PO4, Na, Cl, SiO2 and Ca are contained more in the ground water than in the surface water while K, SO4, Fe and Mg are contained less in the ground water. 3. The response of growth, yield and yield components of paddy rice to ground water irrigation are as follows; (l) Using ground water irrigation during the watered rice nursery period(seeding date: 30 April, 1970), the chracteristics of a young rice plant, such as plant height, number of leaves, and number of tillers are inferior to those of young rice plants irrigated with surface water during the same period. (2) In cases where ground water and surface water are supplied separately by the gravity flow method, it is found that ground water irrigation to the rice plant delays the stage at which there is a maximum increase in the number of tillers by 6 days. (3) At the tillering stage of rice plant just after transplanting, the effect of ground water irrigation on the increase in the number of tillers is better, compared with the method of supplying surface water throughout the whole irrigation period. Conversely, the number of tillers is decreased by ground water irrigation at the reproductive stage. Plant height is extremely restrained by ground water irrigation. (4) Heading date is clearly delayed by the ground water irrigation when it is practised during the growth stages or at the reproductive stage only. (5) The heading date of rice plants is slightly delayed by irrigation with the gravity flow method as compared with the standing water method. (6) The response of yield and of yield components of rice to ground water irrigation are as follows: \circled1 When ground water irrigation is practised during the growth stages and the reproductive stage, the culm length of the rice plant is reduced by 11 percent and 8 percent, respectively, when compared with the surface water irrigation used throughout all the growth stages. \circled2 Panicle length is found to be the longest on the test plot in which ground water irrigation is practised at the tillering stage. A similar tendency as that seen in the culm length is observed on other test plots. \circled3 The number of panicles is found to be the least on the plot in which ground water irrigation is practised by the gravity flow method throughout all the growth stages of the rice plant. No significant difference is found between the other plots. \circled4 The number of spikelets per panicle at the various stages of rice growth at which_ surface or ground water is supplied by gravity flow method are as follows; surface water at all growth stages‥‥‥‥‥ 98.5. Ground water at all growth stages‥‥‥‥‥‥62.2 Ground water at the tillering stage‥‥‥‥‥ 82.6. Ground water at the reproductive stage ‥‥‥‥‥ 74.1. \circled5 Ripening percentage is about 70 percent on the test plot in which ground water irrigation is practised during all the growth stages and at the tillering stage only. However, when ground water irrigation is practised, at the reproductive stage, the ripening percentage is reduced to 50 percent. This means that 20 percent reduction in the ripening percentage by using ground water irrigation at the reproductive stage. \circled6 The weight of 1,000 kernels is found to show a similar tendency as in the case of ripening percentage i. e. the ground water irrigation during all the growth stages and at the reproductive stage results in a decreased weight of the 1,000 kernels. \circled7 The yield of brown rice from the various treatments are as follows; Gravity flow; Surface water at all growth stages‥‥‥‥‥‥514kg/10a. Ground water at all growth stages‥‥‥‥‥‥428kg/10a. Ground water at the reproductive stage‥‥‥‥‥‥430kg/10a. Standing water; Surface water at all growh stages‥‥‥‥‥‥556kg/10a. Ground water at all growth stages‥‥‥‥‥‥441kg/10a. Ground water at the reproductive stage‥‥‥‥‥‥450kg/10a. The above figures show that ground water irrigation by the gravity flow and by the standing water method during all the growth stages resulted in an 18 percent and a 21 percent decrease in the yield of brown rice, respectively, when compared with surface water irrigation. Also ground water irrigation by gravity flow and by standing water resulted in respective decreases in yield of 16 percent and 19 percent, compared with the surface irrigation method. 4. Results obtained from the experiments on the improvement of ground water irrigation efficiency to paddy rice are as follows; (1) When the standing water irrigation with surface water is practised, the daily average water temperature in a paddy field is 25.2$^{\circ}C$, but, when the gravity flow method is practised with the same irrigation water, the daily average water temperature is 24.5$^{\circ}C$. This means that the former is 0.7$^{\circ}C$ higher than the latter. On the other hand, when ground water is used, the daily water temperatures in a paddy field are respectively 21.$0^{\circ}C$ and 19.3$^{\circ}C$ by practising standing water and the gravity flow method. It can be seen that the former is approximately 1.$0^{\circ}C$ higher than the latter. (2) When the non-water-logged cultivation is practised, the yield of brown rice is 516.3kg/10a, while the yield of brown rice from ground water irrigation plot throughout the whole irrigation period and surface water irrigation plot are 446.3kg/10a and 556.4kg/10a, respectivelely. This means that there is no significant difference in yields between surface water irrigation practice and non-water-logged cultivation, and also means that non-water-logged cultivation results in a 12.6 percent increase in yield compared with the yield from the ground water irrigation plot. (3) The black and white coloring on the inside surface of the water warming ponds has no substantial effect on the temperature of the water. The average daily water temperatures of the various water warming ponds, having different depths, are expressed as Y=aX+b, while the daily average water temperatures at various depths in a water warming pond are expressed as Y=a(b)x (where Y: the daily average water temperature, a,b: constants depending on the type of water warming pond, X; water depth). As the depth of water warning pond is increased, the diurnal difference of the highest and the lowest water temperature is decreased, and also, the time at which the highest water temperature occurs, is delayed. (4) The degree of warming by using a polyethylene tube, 100m in length and 10cm in diameter, is 4~9$^{\circ}C$. Heat exchange rate of a polyethylene tube is 1.5 times higher than that or a water warming channel. The following equation expresses the water warming mechanism of a polyethylene tube where distance from the tube inlet, time in day and several climatic factors are given: {{{{ theta omega (dwt)= { a}_{0 } (1-e- { x} over { PHI v })+ { 2} atop { SUM from { { n}=1} { { a}_{n } } over { SQRT { 1+ {( n omega PHI) }^{2 } } } } LEFT { sin(n omega t+ { b}_{n }+ { tan}^{-1 }n omega PHI )-e- { x} over { PHI v }sin(n omega LEFT ( t- { x} over {v } RIGHT ) + { b}_{n }+ { tan}^{-1 }n omega PHI ) RIGHT } +e- { x} over { PHI v } theta i}}}}{{{{ { theta }_{$\infty$ }(t)= { { alpha theta }_{a }+ { theta }_{ w'} +(S- { B}_{s } ) { U}_{w } } over { beta } , PHI = { { cpDU}_{ omega } } over {4 beta } }}}} where $\theta$$\omega$; discharged water temperature($^{\circ}C$) $\theta$a; air temperature ($^{\circ}C$) $\theta$$\omega$';ponded water temperature($^{\circ}C$) s ; net solar radiation(ly/min) t ; time(tadian) x; tube length(cm) D; diameter(cm) ao,an,bn;constants determined from $\theta$$\omega$(t) varitation. cp; heat capacity of water(cal/$^{\circ}C$ ㎥) U,Ua; overall heat transfer coefficient(cal/$^{\circ}C$ $\textrm{cm}^2$ min-1) $\omega$;1 velocity of water in a polyethylene tube(cm/min) Bs ; heat exchange rate between water and soil(ly/min)

• Journal of agricultural medicine and community health
• /
• v.8 no.1
• /
• pp.44-65
• /
• 1983

As a part of the epidemiological studies of clonorchiasis, this study was conducted to evaluate the current endemicity and the natural transition of the Clonorchis infection in Gimhae Gun and delta area a high endemic area in Korea in recent years, prior to the introduction of praziquantel which will eventually influence the status of the prevalence. The data obtained in this study in 1983 were evaluated for natural transition of the infection in comparison with those obtained 16 years ago in 1967 by the author(Kim, 1974). The areas of investigation, villages and schools surveyed, methods and techniques used in this study were the same as in 1967, except for the contents of the questionnaire for raw freshwater fish consumption by the local inhabitants. 1) The prevalence rate of clonorchiasis in the general population of the villages was 48.1% on the average out of a total of 484 persons examined. The average of those of the riverside-delta area was 65.2% and 43.0% in the inland area. Among the schoolchildren, the prevalence rate was 8.2% on the average out of a total of 1,423 examined. By area, the prevalence rate was 10.8% in the riverside delta area and 2.8% in the inland area. By sex, difference in the prevalence was seen only in the inhabitants of the inland area showing 52.4% in the male and 33.5% in the female. 2) In the natural transition of the infection, the prevalence rate among the inhabitants has decreased from 68.8% in 1967 to 48.1% in 1983, and in the schoolchildren from 56.4% in 1967 to 8.2% in 1983. The reduction rate was higher in the riverside-delta area than in the inland area. 3) In the prevalence rate by age, 11.9% was first seen in the 5-9 age group and the rate gradually increased up to 75.0% in the 50-59 age group. By sex, the rate was higher in the male than in the female in the 20-29 age group and over. 4) In the natural transition of the prevalence rate by age, the reduction rate of the infection during the past 16 years was greater in the younger age groups up to the 40-49 age group and reached the same level in the age group 50-59. Reduction was seen again in the age group over 60s. By sex, the reduction rate was greater in the female than in the male in the 20-29 age group and over. By area, the reduction rate was greater in the riverside delta area than in the inland area, particularly in the young age groups. 5) In the intensity of the infection among the cases, the mean egg out-put per mg feces per infected cases(EPmg) in the inhabitants was 6.3. EPmg of those of the river-side-delta area was 15.4 and that of the in-land was 2.8. On the other hand, in the schoolchildren, EPmg was 3.2, and no difference was seen between the two areas, the river-side-delta area and the inland area. 6) In the transition of the intensity of the infection by area, EPmg among the inhabitants inexplically increased from 7.8 in 1967 to 15.4 in 1983. This was probably caused by uneven specimen collection in the process of sampling the population. EPmg of the inhabitants in the inland area and those of the schoolchildren of both riverside delta and inland areas showed a similar decrease in the past 16 years. 7) The intensity of the infection by age showed a relatively low level in the 20-29 age group and below, and EPmg 5.1-9.5 was seen in the 30-39 age group and over. Sex, Epmg was 5.8 in the male and 4.7 the female. By in 8) In the transition of the intensity of the infection, EPmg decreased from 6.2 in 1967 to 5.4 in 1983. By age, in contrast to the figures of 1967 in which EPmg gradually increased with some fluctuation from 1.1 in the 0-4 age group to peak 10.5 in the 50-59 age group, in 1983 lower intensity of the infection was seen in the age group from 10-14 to 20-29 with the EPmg range of 0.6-2.7. 9) In the distribution of the clonorchiasis cases by the range of EPmg value, 43.2% of the cases were in 0.1 0.9 and 34.6% in 1.0-4.9. As a whole by cumulative percent, 44.6% of them were under 0.9 as light infection and 86.1% of them under 9.9 up to moderate infection. By sex, no difference was seen in Epmg. 10) In the transition of the distribution by the range of Epmg, the cases were distributed up to the range 80.0-99.9 in 1967 and to 60.0-79.9 in 1983. By cumulative percent, in the range of 0.1-0.9 and less, light infection, 34.3% of them were distributed in 1967 and 44.6% in 1983 with about 10% increase. In the range of 5.0-9.9 and less, up to moderate infection, 83.2% in 1967 and 86.1% in 1983 of the cases were seen, respectively. 11) The practice of raw freshwater fish consumption among the inhabitants seems to have decreased in recent years. Those who admitted to raw freshwater fish consumption in the last two years among the infected inhabitants were 59.3%, although 86.8% of them professed to have experience with raw freshwater fish consumption. 31.7% of those who have had experience of the raw freshwater fish consumption denied any further consumption in recent years. From an interview of 543 school-children, 24.1% of them admitted to an experience of raw freshwater fish consumption. However, those who have practised in the past two years comprized 17.9%. Those who denied raw freshwater fish consumption in recent years among those who had such experience were 26.0% out of 131 interviewed. The rate of raw freshwater fish consumption in both inhabitants and schoolchildren were higher in the male than in the female. On the contrary, the rate of those who did not practise in recent years among those who had experience of raw freshwater fish consumption was higher in the female than in the male. 12) The major reason for the reduction of raw freshwater fish consumption among the local inhabitants was the risk of the fluke infection. However, it has become apparent that such change of taste has resulted from water pollution impact which has affected throughout the areas of the freshwater systems in this locality since last several years. 13) In animal survey, Clonorchis infection was seen in 14.8% of 88 dogs examined and 3.7% of 27 house rats examined. It was noted that populations of dogs and cats have increased in the villages surveyed. Although the prevalence rate was lower in the present survey than those of 1967, the significance of the animals as the reservoir host has not changed. 14) Prevalence rate of Clonorchis infection by cercariae in the first intermediate host, Parafossarulus manchouricus, was 0.6% out of 517 snails examined. The infection rate was lower in comparison with 2.3% out of 2,124 examined in 1967. Moreover, sharp decreases in number and distribution of the intermediate host snails in many watershed areas of the huge freshwater systems in this locality seemed to reduce transmission of Clonorchis in connection with the intermediate host stage of its life cycle. 15) Clonorchis infection in the second intermediate fish hosts was relatively low. The mean number of Clonorchis metacercaria per fish in Pseudorasbora parva was 517 in 1983, whereas it was 1943 in 1968 through 1969. Environmental water pollution has also caused the decreased fish population density in these areas, and this has also apparently affected to the practice of raw freshwater fish consumption among the local inhabitants. 16) In conclusion, endemicity of Clonorchis infection in Gimhae Gum and delta area of the Nagdong River has sharply decreased during the past 16 years. The major cause of the regressive transition of the infection was the water pollution of the land water systems of this locality. The pollution has upset the ecosystems comprizing of the intermediate hosts of Clonorchis in many areas, and also affected to a significant extent to the discontinuance of the local inhabitants for raw freshwater fish consumption.