Biomedical subjects

C G Yoon

Publications and source records attributed to C G Yoon.

5 recordsLinked to original sources

PubMed2006

Evaluation of BASINS/WinHSPF applicability for pollutant loading estimation for a Korean watershed.

Applicability of a widely accepted watershed-based water quality assessment tool (BASINS) and its associated watershed model (WinHSPF) was evaluated on the Seamangeum watershed in Korea. The study site is the largest polder project area in Korea and its environmental quality has been debated for the last five years. BASINS was found to be a convenient and powerful tool for assessment of watershed characteristics, and provided various tools to delineate the watershed into land segments and river reaches, reclassify land use, and parameterize for WinHSPF simulation. Calibration results were satisfactory showing model efficiency over 0.80 for stream flow, temperature, and dissolved oxygen simulation, and model output for water quality constituents also reasonably matched the observed data. It was demonstrated that calibration with dry-day data for a relatively long period might be adequate to simulate hydrologic characteristics and water quality of the watershed with WinHSPF, and using parameters generated with BASINS for nonpoint source pollution simulation is suggested when enough wet-day monitoring data are not available. The unit-area load of biochemical oxygen demand, total nitrogen, and total phosphorus was 27.8, 48.2, and 4.3 kg/ha/yr, respectively. These values are within the expected range but on the high side of the reported values, which implies that effective control measures are required to protect water quality of the downstream reservoir. Overall, BASINS/WinHSPF was applicable and found to be a powerful tool in pollutant loading estimation from the watershed, and its use in Korea is recommended.

Calibration↗

PubMed2006

Water quality modeling to evaluate BMPs in rice paddies.

A water quality model applicable to rice paddies was developed using field data from 1999-2002. Use of the Dirac delta function efficiently explained the nutrient-concentration characteristics of ponded water. The model results agreed reasonably well with the observed data. The ponded-water quality was influenced primarily by fertilization; nutrient concentration was especially high during early cultivation periods. Reducing surface drainage during the fertilization period may substantially reduce nonpoint source loading from paddies. Increased weir heights and shallow irrigation methods were evaluated by the model as practical methods for reducing nutrient loading from paddies. These methods were effective in reducing surface drainage and are suggested as "best management practices" (BMPs) if applied based on site-specific paddy conditions.

Agriculture↗

PubMed2005

Mass balance analysis and water quality model development for loading estimates from paddy fields.

Mass balance analysis and water quality model development for paddy field were performed using field experimental data during 2001-2002. About half (47-62%) of the total outflow was lost by surface drainage, with the remainder (490-530 mm) occurring by evapotranspiration. Most of nutrient inflow and outflow were mediated by fertilization and plant uptake, respectively. Nutrient outflow by surface drainage runoff was substantial about 15%-29% for T-N and 6%-13% for T-P. However, the responses of yield and drainage outflow to fertilization were not significant in this study. A water quality model applicable to paddy fields was developed and it demonstrates good agreement with observed data. The nutrient concentration of ponded water was high by fertilization at early culture periods, so reducing surface drainage during fertilization period can reduce nutrient loading from paddy fields. Shallow irrigation, raising the weir height in diked rice fields, and minimizing forced surface drainage are suggested to reduce surface drainage outflow.

Fertilizers↗

PubMed2001

Feasibility study of treated sewage irrigation on paddy rice culture.

A feasibility study was performed to examine the agronomic application of the treated sewage on paddy rice culture through field experiment. The domestic sewage was treated using a constructed wetland system, a subsurface flow type consisting of sand and macrophyte. The effluent of the wetland system was diluted to maintain the total nitrogen concentration below 25 mg/L and was used as irrigation water. Addition of the treated sewage to the irrigation water showed no adverse effect on the paddy rice culture; in fact some enhancement was noticed in both growth and yield. Irrigation with the treated sewage after the concentration was adjusted accompanied by conventional fertilization showed a better result, with the yield exceeding that of the control where clean water was used, thus suggesting that reuse of the treated sewage as supplemental irrigation water could be a feasible and practical alternative. For a full-scale application, however, further study is recommended on the specific guideline for controlling the major water quality components in the treated sewage.

Agriculture↗

PubMed2001

Feasibility study of a constructed wetland for sewage treatment in a Korean rural community.

A pilot study was performed to examine the feasibility of using a constructed wetland system for treatment of sewage in a Korean rural community. The treatment system was a subsurface flow wetland with a loading rate and hydraulic residence time of 6.3 cm/day and 3.5 days, respectively. The wetland system was highly effective in treating the sewage; median removal efficiencies of BOD5 (biological oxygen demand) and TSS (total suspended solids) were about 70.0%, with median effluent concentrations of 24 and 13 mg/L, respectively, for these constituents. However, BOD5 and TSS did often exceed the effluent water quality standards of 20 mg/L. Removal of TN (total nitrogen) and TP (total phosphorus) was relatively less effective and median effluent concentrations were approximately 81 and 8 mg/L, respectively. The treatment system did not experience any clogging or accumulation of organic and inorganic solids during the study, and during winter a substantial amount of removal of BOD5 and TSS continued to occur. Overall, the constructed wetland was judged to be an effective sewage treatment system, but not sufficient by itself to attain regional water quality standards. Therefore, treatment of rural sewage by a wetland system should be followed by another process such as use of the effluent for irrigation of agricultural crops (e.g., rice).

Agriculture↗