Non-point Source Pollution Model In The Purple Hilly Region Of The Upper Yangtze River

As the purple hilly area of Yangtze River for many years accumulation of agricultural fertilizer, soil shorter soil characteristics, agricultural practices and unreasonable people on the land obtained from the increasing intensity of the area led to chemical fertilizers and pesticides as the main body of the Agricultural Pollution more serious. In the nature and under human activity's disturbance and the superimposed effect, this area has become the Yangtze River upstream soil erosion most serious region, is three canyon storehouse district most main surface source pollution origin. However, studies so far more concerned about the single farm model of agriculture in a single time-point source pollution characteristics, ignoring the different mode of farming season farming activities on agricultural production caused by agricultural nonpoint source pollution, and little attention to the comprehensive application of model effect. Therefore, this article take the purple rolling country model small basin as the object of study, uses method which the open country investigation, the indoor analysis and the AGNPS model dispersion parameter simulation unifies, has studied the Yangtze River upstream purple ochre rolling country surface source pollution main pollution factor as well as the model simulation effect, the small basin surface source contaminating material's predominant type and the year change rule, promulgates the non-vegetative season and under the vegetative season model planter pattern between the nitrogen outflow characteristic and the rule as well as the pattern nitrogen outflow contrast, provides the scientific basis take the time as the area pollution control and the reasonable cultivation management.(1) AGNPS model of a typical purple hills of the Yangtze River runoff and sediment in areas more accurate simulation, the simulation of water quality and the basic right, model test evaluation index less than 30%, the model parameters that determine the basic right, and display the model through the bridge area in five agricultural watershed point source pollution load estimation and evaluation of potential applications, for the river basin planning of pollution control the main factor and the determination of critical watershed pollution and point source pollution, provides a dynamic monitoring quantitative tools. (2) AGNPS model sensitivity analysis covering the topography, soil erodibility, surface roughness, and many other factors, in the simulation, the parameters F, H, I and J the value of such increase and decrease of 25%, respectively and 10%, through the model output, while in the above parameters do not change, clearly the sensitivity of each parameter. To identify the impact of point source pollution process, the main factor. Most of the sensitivity analysis on sediment yield impact, primarily E, F, H, I, J, K, L, M and N and other parameters; on the parameters of the sensitivity of runoff showed that only E and I; E on N, P and have shown sensitivity of the total COD, and other sediment yield model showed sensitivity of parameters on the adsorption states of nitrogen and phosphorus showed sensitivity to K values in addition to the increase of the total adsorbed reduce nitrogen and phosphorus, the increase in value as the other parameters, total nitrogen and total phosphorus adsorbed increased. These parameters runoff curve E is particularly important, as it happens changes, model output are all Jiang change; and thus to determine the priority of the value of any direct model(3)In order to characterize the N and P looses in the purple hilly region of the upper Yangtze River in non-cropping period, the N and P loss characteristics of 4 representative cropping modes in purple hilly region, and the application of their modeling simulation were studied just after cropping season from November 1 to December 31,2008. Losses of N and P were relative serious in non-cropping season in the studied cropland, whose maximum values were (0.491±0.079 kg·hm-2) and (12.604±13.173×10-3 kg·hm-2), respectively. N losses were significantly higher than P losses in these studied croplands. Compared to infiltration flow, runoff flow was the main pathway during N and P losses. Obvious differences of N and P losses were found in different cropping modes. Ginger cropping modes had the maximum N and P losses via both runoff and infiltration, whereas soybean cropping modes exhibited the minimum values. Additionally, the semi-mixture model could be efficiently applied in forecasting N and P losses of these cropping lands in this region. The simulated effected coefficients were higher than 0.6, which reached to 0.958 for simulating N losses. The results demonstrated that the losses of N and P in non-cropping season could also be the important resources in agricultural non-point pollution in this region, and the incompletion mixture model could be the regional efficient model in loss forecasting of N and P, which provided the potential effective way in controlling agricultural non-point pollution in this purple hilly region.(4)In the purpose of realizing the characters of annual N and P loses in the YangZi River upriver purple upland region, our paper respectively analyses the effects of different cropping patterns on surface runoff, infiltration of water and the accumulation of N losses. Our research uses four typical cropping patterns as research objects, which include paddy-astragali(M1),soybean(M2),ginger(M3) and corn-sweet potato(M4),also is based on the survey data of annual precipitation and runoff. The results show that during one year, under different cropping patterns, the losses of dissoluble nitrogen and phosphor have a close relationship with accumulating soil losses.Cumulative dissolved nitrogen losses in runoff were closely related to cumulative runoff, while cumulative particular nitrogen losses in runoff were closely related to cunmulative erosion,64.61% and 85.67% dissolved nitrogen in runoff and infiltration, so cumulative dissolved nitrogen losses more than cumulative particular nitrogen losses in infiltration. The cumulative runoff and infiltration have M4>M3>M2>Mland nitrogen losses have M3>M4>M2>M1.Through a serial of periods, involve the non-cropping season then follow by crop seedling phase, growing metaphase and anaphase, the changes of surface runoff, infiltration of water, accumulating soil losses and the accumulation of N losses mainly depend on the effects of the coverage of crop canopy and the distance between canopy and surface. This can improve, a significant source of agricultural superficial pollution is coming from the annual N loses in arable land. At last, we point out that if the field plant more proportions of soybean and paddy-astragali, the surface runoff and N losses would be substantially decreased.