不同降雨强度下三种典型农田土壤非点源氮输出研究

Non-point Source Nitrogen Outputs of Three Typical Farmland Soils Under Different Rainfall Intensities

以河南淮河流域典型土壤砂姜黑土、褐土、潮土为对象,人工模拟0.5、1.0、1.5、2.0、2.5、3.0 mm/min降雨强度下径流产出、泥沙流失、氮元素输出状况,研究降雨强度与土壤类型对非点源氮元素输出的影响,为量化淮河流域农田非点源输出负荷、建立本地化非点源污染模型、制定区域非点源污染防治策略等提供依据.结果表明:降雨强度越大,径流量、泥沙流失量、氮元素输出负荷及其平均产出速率均较大;土壤类型对径流产出影响较小,对泥沙流失量与氮元素输出负荷有一定影响;径流中氮元素平均浓度以2.0 mm/min降雨强度时最大;三种土壤的累积氮元素输出负荷均随降雨强度的增大而增大,增加幅度较明显的降雨强度,砂姜黑土为1.0、2.5 mm/min,潮土为1.0、3.0 mm/min,褐土为1.5、3.0 mm/min;氮元素通过泥沙输出的量占总输出量的81.57%以上.降雨强度、土壤类型均对径流产出、泥沙流失、氮元素输出等产生影响,氮元素输出负荷具初期冲刷效应.控制产流初期氮流失与泥沙流失是减少农田非点源氮输出负荷的重要途径.

Taking typical soils(mortar black soil,cinnamon soil and fluvo-aquic soil)in the Huaihe River Basin of Henan Province as the research objects,the runoff output,sediment loss and nitrogen output were simulated artificially under the rainfall intensity of 0.5,1.0,1.5,2.0,2.5 and 3.0 mm/min.The effects of rainfall intensity and soil type on non-point source nitrogen output were studied to provide a basis for quantifying the non-point source output load of farmland in the Huaihe River Basin,establishing a localized non-point source pollution model and formulating regional non-point source pollution prevention and control strategy.The results show that the larger the rainfall intensity,the larger the surface runoff,sediment loss,nitrogen output load and the average output rate.Soil type has little effect on runoff output,but has a certain effect on sediment loss and nitrogen output load.The average nitrogen concentration in runoff is the highest at 2.0 mm/min rainfall intensity.The cumulative nitrogen output loads of the three soils increase with the increase of rainfall intensity.The rainfall intensities that cause the significant change of nitrogen output load for the mortar black soil are 1.0 and 2.5 mm/min,while that of the fluvo-aquic soil are 1.0 and 3.0 mm/min,and that of the cinnamon soil are 1.5 and 3.0 mm/min.The amount of nitrogen output through sediment accounts for more than 81.57%of the total output.Rainfall intensity and soil type all have effects on runoff output,sediment loss and nitrogen output,and nitrogen output load has initial scour effect.The important mean for controlling non-point source nitrogen output load of farmland is controlling nitrogen loss and sediment loss in the early stage of runoff production.