Research On Transport Models Of Main Non-point Sources Pollutant In The Sloping Orchards On Weibei Plateau

One important reason of the degradation of soil quality and the expansion of non-point source pollutions is caused by the agriculatural management of'higher input, and higher yield'. So it is of great significance to investigate the transport mechanism and model of nonpoint source pollutant at intensively-eroded Weibei Plateau for reasonable fertilize and effectively predicting pollutant on loss sloping orchards.Selecting total nitrogen, total phosphorus, total cadmium and total chromium as materials of study, the paper has discussed the output proceeding of pollutant by the methods of simulated rainfall in both the indoor soil boxes and the field plots, and developed prediction models in order to serve valuable scientific data for reasonable fertilize and evaluating the status of non-point source pollution in the loess region. Aresults showed:(1) The results of experiments in simulating rainfall showed that the time runoff was generated from the soil boxes is about 5 minutes after rain. After 12 minutes the radial flow modulus maximize, the peak value is higher than 2000m3/km2. And the peak of transport sediment modulus value is about 65t/km2. Besides, the transport sediment character is independent of soil fertilizer level. The transport model of radial flow modulus and transport sediment modulus can be fitted by formulas Mw=f(t) and Ms=f(t). Contrasting the test results and model forecast, we can find the model are rational.(2) According to the fertilizer level of low yield apple orchard, mid yield apple orchard and high yield apple orchard, setting four fertilizer levels, which include no fertilizer level. In different fertilizer level the values of radial flow N consistency vary among 0.74-1.02mg/L, 0.76-1.01mg/L, 0.87-1.26mg/L and 0.98-1.67mg/L. The values of radial flow P consistency vary among 1.05-1.71mg/L, 1.63-2.3mg/L, 2.18-2.74mg/L和2.42-3.39mg/L. The values of radial flow Cd consistency vary among 12.7-18.8ug/L, 15.9-19.3ug/L, 17.4-21.8ug/L和 21.0-28.3ug/L. The values of radial flow Cr consistency vary among 61.4-68.2ug/L, 65.8-68.6ug/L, 72.2-83.9ug/L和83.0-94.6ug/L. The changing process of N consistency in water sample was similar to the process of runoff modulus during the rainfull, which both with the change of peak value. The changing processes of other pollutant concentration were wavilness.(3) In this four different fertilizer level the values of N consistency in sediment sample vary among 85.47-114.16mg/kg, 93.31-126.18mg/kg, 108.16-135.27mg/kg and 110.36-146.38mg/kg. The values of P consistency in sediment sample vary among 76.47-80.33mg/kg, 78.51-83.29mg/kg, 82.63-89.39mg/kg and 80.06-114.28mg/kg. The values of Cd consistency in sediment sample vary among 77.4-98.7ug/kg, 79.2-98.5ug/kg, 86.4-114.3ug/kg and 93.3-120.7ug/kg. The values of Cr consistency in sediment sample vary among 163.75-564.49mg/kg, 221.04-807.9mg/kg, 369.96-1003.41 mg/kg and 225.96-124.59mg/kg.The changing processes of values in N and P consistency in sediment sample increased at first and then gradually decreased. The changing processes of values in Cd and Cr consistency in sediment sample showed increasing tend in wavilness.(4) There is a close relationship between the amount of pollutant loss and fertilize. The amount of fertilize is higher, the loss amount of pollutant is larger. The loss of N in sediment sample is 100 multiples of it in radial flow. The loss of P in sediment sample is 30 multiples of it in radial flow. The loss of Cd in sediment sample is 4-6 multiples of it in radial flow. The loss of Cr in sediment sample have ascendency. So the loss of pollutant in soil occupies a predominent proportion in the total loss of pollutant.(5) By the analysis of experiment results, the connection curve between runoff modulus and pollutant concentration is similar to sinusoidal function. Through fitting formula, the pollutant transport model in radial flow and in sediment sample (Cw= Mw/fw(t), Cs= Ms/fs(t)) and the pollutant loss transport model (Cz=f(t)) and be found. After proof the model formula is rational and can be used to forecast the pollutant concentration of nonpoint source pollutant in the sloping orchards around the Weibei Plateau. While the model formulas need to be modified.