Study On COD Pollutant Load In Surface Runoff Of Different Soil Types

With controlling the point source pollution gradually,the pollution caused by the non-point source becomes more serious at present. It becomes a significant issue to control the non-point source pollution effectively. Farmland surface runoff pollution is a major part of it.So it is great meaning to study the law of farmland surface rainfall-runoff quality and calculate pollutant load.Based on the developed research at home and outside,this paper researches the transportation law of surface rainfall-runoff pollution by laboratory testing. Four typical agricultural runoff plots in Sichuan basin were selected and experiments were conducted.There have been 6 artificial rains in the time of more than one month. The content are summarized as follows:(1) The variation law of surface runoff load is analyzed. SCS (Soil Conservation Service) model is used in this study to estimate the runoff load.(2) The transportation law of silt load is analyzed. The relationship between silt load and rainfall intensity is analyzed,also with the characters of soils.(3) The transportation characteristics of COD drived by natural rainfall-runoff were studied.It is proved that there is great relevance between the load of COD transportation with rainfall and runoff and silt load. On the basis of the results,the variation of COD transportation under the rainfall condition is analyzed. Furthermore,different kinds of land in the basin were investigated on frequency distribution.Regression relationships between COD transportation variation with rainfall and runoff fluxes and silt load were set up. The researches are useful in setting up the watershed water quality models.The researches are useful in the study of agricultural nonpoint pollution and offer scientific help to control agricultural nonpoint pollution.