It is needed to manage agricultural runoff effectively and scientifically in long term monitoring. Because an Agricultural runoff is one of the leading non-point sources of water quality impacts to rivers and lakes. This thesis aimed to document the characteristics of agricultural runoff from farms(sweet potato farm and cherry tree farm), which is one of non-point sources pollutions in agricultural areas, and also the properties of refractory dissolved organic matters. This thesis consists of 6 chapters including background and the scope in chapter 1, general characteristics of non-point source pollution and management trend on domestic and foreign in chapter 2, results of long term monitoring to determine runoff characteristics in chapter 3, results of river investigation, analysis of runoff and model test to determine refractory dissolved organic matter characteristics in chapter 4 and results of the coagulation treatment of runoff in chapter 5. Finally the main results of the thesis are briefly evaluated and the future research is presented in chapter 6. I also provided an effective and an scientific way for managing non-point source pollutions via this thesis. The following results were obtained from chapter 3 to chapter 5.
Non-point source pollution in the agricultural areas showed great uncertainty whether runoff would occur in the two levels of rainfall: between 10mm and 30mm and between 30mm and 50mm. The current non-point source pollution unit considers only the rainfall events in which a runoff occurred, so it is likely to overestimate the level of pollution in certain rainfall ranges. Thus it is necessary to examine the method of estimating non-point source pollution in the agricultural areas based on the pollution sources. The suspended solid(SS) concentration of runoff that took place in farm could show behaviors similar to those of SS concentration of various source pollutants. It is necessary to construct the database of suspended solid matters by monitoring them steadily, which can be used as indexes to predict and manage any pollution in farm.
This thesis also investigated the compositions of organic matters in several branches of the Nakdong River. As a result, as the influent runoff increased, the compositions of algae became similar to those of organic matters from agricultural areas like rice pads and farms. It means that the composition of organic matters in rivers affected by land use changes according to land use characteristic. Therefore it is necessary to investigate the land use in each small watershed and to prepare technical and systematic plans. According to results of the model test that volume of surface flow was affected by rainfall intensity and moisture contents, respectively. It showed that physical characteristics of soil had a much greater impact than rainfall intensity and antecedent dry day on runoff volume. Runoff volume was directly linked to total pollutant mass(TPM). Therefore it is needed to construct the relationship between runoff volume and many types of soil characteristics such as particle size, rainfall intensity and moisture content.
The results of the coagulation treatment showed that this process of coagulation could not remove dissolved pollutants including refractory dissolved organic matters. On the other hand, the relationship among DOC removal and other pollutant removal showed highly more than 0.77 as coefficient of correlation. Thus, refractory dissolved organic matters were treated during the treatment process for suspended solids.
Long term monitoring is essential to manage for non-point source pollution from farms. We could establish reasonable management and water environment policy formulation for non-point source pollutions from farms based on construction of database. Further study is necessary for ①physical soil quality standard by type of crop, ②runoff characteristics of standard soil, ③agricultural technology development for sediment yield reduction, ④crop imporvement for Suspended solids reduction.