The Chemical Regulation Of Soil Erosion Processon Loess Hillslope

Loess Plateau is the most serious soil erosion area in China, even in the world. The intense soil erosion has seriously damaged the local ecological environment and affected the security of the downstream areas of Yellow River. Soil erosion chemical regulation is a kind of the new technical measures of soil and water conservation, which is different from the traditional soil and water conservation measures, and is easy to use and effective control soil erosion.Researches of the chemical regulation of soil erosion processes on loess hillslope can help understand the lasting effect of chemical materials on soil erosion, revealing the regulation mechanism of loess slopes soil erosion.The study can provide scientific basis for controlling the soil erosion and promote the further development of the theory of soil erosion.The chemical regulation of soil erosion processes on loess hillslope are studied under simulated rainfall experiments for two consecutive sessions rainfall of interval 12 hours with the rainfall intensities of 2.0 mm/min and slopes of 20°, spraying chemical materials of Jag C162, HP-120 and PAM and dosage of 1 g/m2, 3 g/m2, 5 g/m2. The study focuses on the continuous effect of chemical materials on the runoff processes, the soil erosion processes, hydrodynamic parameters characteristics and top soil characteristics. The main results are as follows:1.To analyse the lasting regulation effect of Jag C162, PAM and HP-120 on the slopes runoff processes:(1) For the treatments of spraying Jag C162, PAM and HP-120, the variations of runoff rates with the first rainfall time and the second rainfall time were similar to the bare slope, in the trends of a rise in the beginning and then going to a stability or a low-slope rise;(2) Compared with bare soil, the runoff depth of dosage of 1g/m2, 3g/m2 and 5g/m2 of spraying Jag C162 respectively reduced by 17.21%, 24.79% and 20.11% in the first runoff processes, and respectively decreased by 1.79%, 10.08% and 9.52% in the second runoff processes. Spraying PAM corresponding values were respective-12.18%, 9.39% and 11.20%, and 1.91%,-0.92% and 10.65%, while Spraying HP-120 corresponding values were respective 3.51%,-7.97% and-11.33%, and 3.58%,-5.98% and-4.99%.(3) In the first runoff processes and the second runoff processes, the water-reducing effect of Jag C162 was the best, PAM followed, and HP-120 worst; The best dosages of water-reducing effect were respective 3 g/m2 of Jag C162, 5 g/m2 of PAM and 1g/m2 of HP-120; The lasting water-reducing effect of PAM was the best, Jag C162 followed, and HP-120 worst; The best dosages of lasting water-reducing effect were respective 5 g/m2 of Jag C162, 5 g/m2 of PAM and 1g/m2 of HP-120.2.To research the lasting regulation effect of Jag C162, PAM and HP-120 on the slopes soil erosion processes:(1) For the treatments of spraying Jag C162 and HP-120, the variations of erosion rates with the first rainfall time were similar to the bare slope, showing rapid rise after a sharp decline and then tend to be relatively stable state, while the variations of erosion rates of spraying PAM were the trends of a rise in the beginning and then going to a stability; For the treatments of spraying Jag C162, PAM and HP-120, the variations of erosion rates with the second rainfall time were similar to the bare slope, in the trends of a rise in the beginning and then going to a stability.(2) Compared with bare soil, the erosion modulus of dosage of 1g/m2, 3g/m2 and 5g/m2 of spraying Jag C162 respectively reduced by 80.08%, 90.95% and 93.43% in the first rainfall processes, and 66.13%, 80.31% and 85.37% in the second rainfall processes. Spraying PAM corresponding values were respective 43.51%, 74.83% and 85.02%, and 53.28%, 70.83% and 85.34%, while Spraying HP-120 corresponding values were respective 68.28%, 13.42% and 13.62%,and 65.69%, 0.59% and-22.99%.(3) In the first rainfall processes and the second rainfall processes, the sediment-reducing effect of Jag C162 was the best, PAM followed, and HP-120 worst; The best dosages of sediment-reducing effect were respectively 5 g/m2 of Jag C162, 5 g/m2 of PAM and 1g/m2 of HP-120; The lasting sediment-reducing effect of PAM was the best, Jag C162 followed, and HP-120 worst; The best dosages of lasting sediment-reducing effect were respective 5 g/m2 of Jag C162, 5 g/m2 of PAM and 1g/m2 of HP-120.3.To explore the lasting regulation effect of Jag C162, PAM and HP-120 on the flow hydrodynamic parameters:(1) For all treatments, the variations of hydrodynamic parameters(stream shear stress, stream power and unit stream power) with the first rainfall time and the second rainfall time were similar to the bare slope, in the trends of a rise in the beginning and then going to a stability or a low-slope rise, in which the change trends of stream power were consistent with the change trends of runoff rates.(2) Compared with bare soil, the mean stream power of dosage of 1g/m2, 3g/m2 and 5g/m2 of spraying Jag C162 respectively reduced by 12.02%, 17.37% and 11.95% in the first rainfall processes, and 2.31%, 10.22% and 9.21% in the second rainfall processes. Spraying PAM corresponding values were respective-11.45%, 9.34% and 10.74%, and 1.85%,-0.88% and 6.75%, while Spraying HP-120 corresponding values were respective 2.29%,-9.06% and-12.08%, and 3.31%,-6.04% and-5.04%.(3) In the first rainfall and the second rainfall, Jag C162 was the best chemical material to decrease the stream shear stress, stream power and unit stream power; In the first rainfall, the maximum reducing effect of Jag C162 and PAM on the three flow hydrodynamic parameters were stream power, while for HP-120, it was stream shear stress; In the second rainfall, the maximum reducing effect of Jag C162, PAM and HP-120 on the three flow hydrodynamic parameters were stream shear stress.4.To reveal the lasting regulation effect of spraying Jag C162, PAM and HP-120 on the top soil characteristics(closely associated with the anti-erosion):(1) Compared with bare soil, three dosages of mean >0.25 mm water stable aggregate contents of spraying Jag C162, PAM and HP-120 respectively increased by 23.09%, 11.52% and 52.37% before the first rainfall, respectively increasing by 44.59%,18.42% and 54.41% after the first rainfall, respectively increasing by 28.78%, 13.85% and 39.07% after the second rainfall, and the differences value between the first rainfall and the second rainfall were respective 15.81%, 4.57% and 15.34%, which showed treatments of spraying Jag C162, PAM and HP-120 effectively can improve >0.25 mm water stable aggregate content, and the best lasting improving effect of >0.25 mm water stable aggregate content was PAM, HP-120 followed, and Jag C162 worst in two sessions rainfall.(2) Compared with bare soil, three dosages of mean soil shear strength of spraying Jag C162, PAM and HP-120 respectively increased by 34.72%, 30.90% and 18.75% before the first rainfall, respectively increasing by 10.53%, 17.25% and 15.50% after the first rainfall, respectively increasing by-9.58%,1.43%、4.05% after the second rainfall, and the differences value between the first rainfall and the second rainfall were respective 20.11%, 15.82% and 11.45%, which showed the treatments of spraying Jag C162, PAM and HP-120 can improve soil shear strength(after the second rainfall soil shear strength of spraying Jag C162 decreased), and the best lasting improving effect of soil shear strength was HP-120, PAM followed, and Jag C162 worst in two sessions rainfall.5. To clarify the lasting regulation mechanism of spraying Jag C162, PAM and HP-120 on soil erosion: soil erosion depends on erosion forces and soil resistance to erosion. For all treatments of spraying Jag C162, PAM and HP-120, top soil characteristics(closely associated with the anti-erosion), including >0.25 mm soil waterstable aggregates and soil shear strength, have been effectively improved, and most of runoff depths and hydrodynamic parameter closely associated with the anti-erosion have been effectively reduced, so the slope soil erosion has been effectively reduced. With the increase rainfall sessions, however, for all treatments of spraying Jag C162, PAM and HP-120, when the top soil of gradually lossed, the improving effects of soil properties and soil resistance to erosion gradually decreased, so that the lasting regulation effects of Jag C162, PAM and HP-120 gradually reduced.