Yong Hun Choi

Application of Surface Cover Materials and Soil Amendments for Reduction of Non-Point Source Pollution from Upland Fields

The objective of the study was to investigate the effect of rice straw mat, rice straw mat with PAM (Polyacrylamide) and gypsum addition on surface runoff and sediment discharge in field. Six experimental plots of in size and 3 % in slope prepared on gravelly sandy loam soil were treated with control, rice straw mat cover with gypsum and rice straw mat cover with gypsum and PAM. Radish in Spring and Chinese cabbage in autumn growing seasons were cultivated. Non point source (NPS) pollution discharge was monitored and compared among the treatments. Rainfall of the 10 monitored events ranged from 17.0 mm to 93.5 mm. Runoff coefficient of the events was 0.005~0.239 in control plot, 0~0.176 in rice straw plot with gypsum and 0~0.046 in rice straw mat plot with gypsum and PAM. When compared to the control plot, the runoff amount was reduced by 10.4~100 % (Ave. 60.8) in rice straw plot with gypsum and 80.7~100 % (Ave. 96.7 %) in rice straw mat plot with gypsum and PAM. The reduction of NPS pollution load was 54.6 % for BOD5, 71.5 % for SS, 41.6 % for TN and 61.4 % for T-P in rice straw with gypsum plot and 91.9 % for BOD5, 92.0 % for SS, 88.0 % for TN and 88.5 % for T-P in rice straw mat with gypsum and PAM plot. This research revealed that rice straw mat cover with soil amendments on the soil surface could not only increase the crop yield but also reduce the NPS pollution loads substantially.

Quantification of NPS Pollution to Meet the TMDL in Korea

Concept of TMDL system of Korea is briefly introduced. Objectives and target pollutant in the first and second stage TMDL, classification of pollution source groups, and concept of unit load were explained. Advantages and disadvantages of current unit load were compared and a new normalized method to estimate the unit load was suggested. Government land cover classification method was introduced to explain the efforts to expand unit load for more detailed land uses than current ones. Characteristics and current status of NPS monitoring studies in Korea also were briefly explained. And future challenges in the quantification of NPS pollution load were described where a proposal for the change of unit load system to BMPs based method for agricultural area in the computation of pollution load was made.

Effect of Surface Cover Materials and Soil Amendments on Sediment Discharge from Upland Fields

The effect of surface cover with rice straw mats, polyacrylamide (PAM) and gypsum on runoff and sediment discharge was investigated in a laboratory under rainfall simulation (Figure 1). Four treatments of control, straw mat covers, straw mats with a PAM cover, and straw mats with a PAM and gypsum cover were applied to small soil box plots. Rainfall simulations of 30 and 60 mm/h on 10% and 20% sloped boxes were made for 60 minutes. The runoff coefficient from the mat-covered plots decreased significantly, regardless of rainfall intensity or the slope gradient. The effect of the mat covers on the reduction of sediment discharge was greater than on runoff reduction. Under 60 mm/h rainfall intensity and 20% slope, which was the worst case, the covered plots with the mats and the soil amendments could reduce 98.8% of the sediment. It was concluded that the function of the mat was significantly improved by adding PAM and gypsum. The combined use of the mats, PAM, and gypsum could be an effective best management practice, and a series of field experiments was recommended to verify the effect of the combined use of the mats, PAM and gypsum on runoff and sediment reduction.

Evaluation of Rice Straw Mat Surface Cover Materials under a Laboratory Rainfall Simulation Condition

Soil erosion and muddy runoff from sloping agricultural fields during monsoon season has been a major cause of water quality and aquatic ecosystem degradation in Korea. The objective of this research was to experimentally test the effect of rice straw mats on the reduction of runoff, sediment and discharge under a laboratory scale with different rainfall intensity and slopes. Experimental treatments were three types of rice straw mat, rainfall intensity (30 and 60 mm/h), and slope (10 and 20%). The time of initial runoff from control plots was significantly faster than that from covered plots regardless the cover material, rainfall intensity and slope (Figure 1). Runoff volume and coefficients from covered plots were significantly lower than those from control plots. Under the 30 mm/h and 10% simulations, average runoff coefficient of covered plots decreased more than 92%. Under 60 mm/h and 20% simulations, the ratios were between 39.8~58.1%. Under the condition of 30 mm/h rainfall and 10% slope, sediment discharge from covered plots was practically zero. And at 20% plots, sediment reduction ratio was more than 95%. Under the condition of 60 mm/h rainfall, sediment reduction ratio of 10 and 20 % plots ranged between 86.3~95.3% and between 79.8~ 86.5%, respectively. The differences in initial runoff time, runoff and sediment discharge among different cover materials were not significant. Rainfall intensity showed higher impact on initial runoff time, runoff, and sediment discharge than slope. It was also shown that even if runoff reduction by surface cover were low, sediment discharge reduction could be very significant and contribute to improve the water quality of streams in sloping agricultural regions. It was concluded that the use of straw mat and PAM on sloping agricultural fields could reduce soil erosion and muddy runoff significantly and help improve the water quality and aquatic ecosystem in receiving waters.

A study on Compare Characteristics of Nonpoint Source in Storm-water versus Steepness of Field Slope

This study was focused on analysis Nonpoint source characteristics from Flat slope field and Steep slope field. We performed Storm-water monitoring for obtain flow data and concentration data. Totally, eleven times Event was occurred. We calculated EMC(Event Mean Concentration) and Pollutants Loads using data we obtained. As a result, steep sloping field has more discharge than flat field. SS value, one of the water quality contents, has largest variation and T-N has least variation. There is runoff differences even though events has same rainfall. We assume that not only amount of Rainfall, but also Rainfall Duration Times, Intensity, Number of Previous Non-precipitation days can affect to Run-off.

Effect of Surface Cover and Slope on Runoff and Soil Erosion

Agricultural activities on sloping fields cause soil erosion due to incomplete cover of soil surface during rainfall events, agricultural productivity is lowered, and muddy runoff in streams and lakes causes water quality deterioration and eutrophication. In this study, effect of straw cover and slope of plot(5%, 10%, 20%) and rainfall intensity(30mm/h, 60mm/h) on surface runoff and sediment discharge were discussed. The surface runoff showed increasing tendency in both straw covered and bare boxes as the slope(5%, 10%, and 20%) increased. Also the surface runoff volume from straw covered surface boxes were much lower than bare surface boxes. Under the same rainfall intensity and slope condition, 2.4~8.2 times of sediment yield were occurred from bare surface boxes compared to straw covered surface boxes. The volume of infiltrated water increased due to straw cover, the direct runoff decreased with the increase of infiltration and of tractive force in surface.

Characteristics of NPS pollution discharge from a coal mining area

This study was conducted to know characteristics of Runoff Non-point Source(NPS) Pollution discharge from a coal mining area in korea. Study Area is location at Jeonduri, Dogyeup, Samchuck, Gangwon province where there is a coal mining workplace. Monitoring system was installed at a drainage channel and flow rate and water samples were collected from Sep. 2007 to Sep. 2008. Two and Five rainfall events were monitored in 2007 and 2008, respectively. collected water samples sere analyzed with respect to SS, BOD, CODCr, CODMn, T-N, T-P, and TOC. It was obesrved that the runoff and water quality were largely influenced by mine drainage. As the study progresses in the future, runoff and pollution loads will be updated.

Sediment Control with Rice Straw Mat Covers from Sloping Sandy Fields – a Rainfall Simulation Study

The Han River has been suffered from muddy runoff from sloping sandy fields in the alpine area in Korea. One of the utmost priorities of the government was to reduce the muddy runoff and sediment discharges and restore the water quality. The objective was to experimentally investigate the effect of rice straw mat cover on runoff, SS and sediment discharge from small laboratory plots that simulate the alpine area. The size of runoff plots was 1x1x0.5 m. Experimental treatments were rice straw mat cover of 0 (control), 3,000, 6,000 and 10,000 kg/ha, slope of 10 and 20%, and rainfall intensity of 30 and 60 mm/h, respectively. Runoff coefficient from the control runoff plots (0 kg/ha) was 55.0% and 70.4% (30 mm/h simulation) and were 66.1% and 85.3% (60 mm/h simulation) from 10% and 20% sloped-plots, respectively. Under 30 mm/h simulation, straw mat cover of 3,000 kg/ha reduced runoff by 98% and 82% from 10% and 20% plots, respectively. Under 60 mm/h simulation, when the soil was tightly covered, runoff coefficient decreased from 66.1% (control) to 1.3% (10% plot) and from 85.3% (control) to 16.6% (20% plot), respectively. Under 30 mm/h simulation, 3,000 kg/ha cover reduced sediment discharge 100% and 95.7% from 10% and 20% plots, respectively. Under 60 mm/h simulation, 6,000 kg/ha cover reduced sediment 91.2% and 94.3% from 10% and 20% plots, respectively. Suspended solids concentration from 0 kg/L (control plot) ranged from 1,450 to 2,930 mg/L. SS concentration from 3,000 kg/L plots were between 160 and 1,470 mg/L which meant the reduction of 89.0% and 49.8%, respectively. When the soil was tightly covered, the concentration further decreased to between 500 and 710 mg/L. It was concluded from a laboratory experiment that rice straw mat could be one of the agricultural BMPs that could control muddy runoff and sediment from sloping fields in alpine area in Korea. However, extensive field application tests were suggested to validate the laboratory test results before practical application.