| 其他摘要 | 土壤侵蚀及其引起农业非点源污染是国际土壤侵蚀研究的前沿领域。本文借鉴国内外农业非点源污染研究的理论与方法，采用人工模拟降雨实验和室内分析测试的研究方法，通过理论推导和分析，研究了塿土和黄绵土近地表土壤水分条件对土壤侵蚀过程的影响，揭示了近地表土壤水分条件下土壤侵蚀过程对农业污染物运移的影响机理，分析了施肥水平对农业污染物运移过程的影响。论文取得的主要研究进展如下：1. 前期近地表土壤含水量对入渗、径流和侵蚀过程有重要影响。随着前期近地表土壤含水量的增加，入渗强度降低，径流强度和侵蚀产沙量增大。对于黄绵土，50 mm/h降雨强度下，当前期近地表土壤含水量为饱和含水量时，其地表径流量分别是占饱和含水量的75%、50%和25%时地表径流量的1.1倍，1.9倍和2.5倍，其侵蚀产沙量分别是2.0倍，38.0倍和50.0倍。在100 mm/h降雨强度条件下，当前期近地表土壤含水量为饱和含水量时，其径流量是土壤含水量占饱和土壤含水量25%时的2.5倍，其侵蚀产沙量为35.5倍。对于塿土，50 mm/h降雨强度下，当前期近地表土壤含水量为饱和含水量时，其地表径流量分别是占饱和含水量的50%和25%时地表径流量的1.0倍和1.1倍，其侵蚀产沙量分别是3.3倍和6.5倍。在100 mm/h降雨强度条件下，前期近地表土壤含水量分别为饱和土壤含水量和占饱和含水量的50%时，其径流量分别约是土壤含水量为占饱和土壤含水量的25%时径流量的1.0倍和1.1倍，其侵蚀产沙量分别为3.0倍和8.7倍。当前期土壤水分达到饱和时，黄绵土的入渗强度小于塿土，其径流强度和侵蚀产沙则大于塿土；而当前期土壤水分含量为非饱和时，黄绵土的入渗强度大于塿土，其径流强度和侵蚀产沙量小于塿土。2. 土壤剖面中，0-2 cm和2-5 cm土层深度是农业污染物发生反应最剧烈的深度，是降雨－径流－土壤相互作用的有效深度，特别是0-2 cm土层，是产生坡面农业污染物流失的主要来源区，2-5 cm土层则是表层与下层农业污染物的相互作用深度，是农业污染物发生淋溶与迁移的交汇区。由于受到径流和前期土壤水分的影响，土壤剖面的NO3--N发生了不同程度的淋溶，黄绵土中土壤剖面NO3--N的淋溶程度比塿土的剧烈。土壤剖面中，NH4+-N和可溶性P（dissovled phosphorus）基本上没有发生淋溶。3. 泥沙是土壤养分流失的主要途径，磷素流失相对平稳。在非饱含水量条件下，随前期土壤含水量的增加而增大，径流和泥沙中污染物浓度和流失量呈增加趋势；饱和含水量时径流和泥沙中污染物浓度及流失量大于非饱和含水量。饱和含水量时，径流和泥沙中污染物浓度及流失量均大于非饱和含水量，其中饱和含水量时径流和泥沙中NO3-N浓度分别是非饱和含水量时的1.2~5.0倍和1.3~62.9倍，饱和含水量时径流和泥沙中可溶性P浓度分别是非饱和含水量时的1.7~254.2倍和2.7~60.8倍。在非饱含水量条件下，随前期土壤含水量的增加，径流和泥沙中污染物浓度和流失量呈上升趋势。4. 降雨强度和施肥水平对污染物运移产生重要影响。在试验条件下，径流中养分流失量大于泥沙中养分流失量，硝态氮的流失量大于铵态氮与可溶性磷的流失量。; Agricultural non-point source pollution caused by soil erosion is the advanced field for international soil erosion research. The effects of soil erosion process, effects of soil erosion on agricultural non-point source pollutant (NPS) transport, and fertilizer application rates on agricultural NPS transport in different near-surface soil water conditions for Yangling Loutu and Ansai Loess, by using artifical simulating rainfall experiment, chemical analysis, and through theory deducting and analyzing. The main research progresses were showed as follows:1. Soil water distribution in soil profile, infiltration process, and runoff process were affected by different antecedent near-surface soil moisture, and different rainfall intensity had different affection on soil water distribution in soil profile subsequent rainfall. As antecedent soil moisture increased, infiltration rate decreased and runoff intensity increased. When rainfall intensity was 50 mm/h, for Ansai Loess, runoff discharge from soil moisture saturated condition, were 1.1, 1.9, and 2.5 times higher respectively, than that from 75% of the saturated condition of soil moisture, 50% of the saturated condition of soil moisture, and 25% of the saturated condition of soil moisture, soil loss were 2.0, 38.0, and 50.0 times greater, respectively. For Yangling Loutu, runoff discharges from soil moisture saturated condition were 1.0 and 1.1 times higher than that from 50% of the saturated condition of soil moisture, and 25% of the saturated condition of soil moisture, soil loss were 3.3 and 6.5 times greater, respectively. As rainfall intensity was 100mm/h, for Ansai Loess, runoff discharge from soil moisture saturated condition, was 2.5 times higher, than that from 25% of the saturated condition of soil moisture, soil loss was 35.5 times greater. For Yangling Loutu, runoff discharges from soil moisture saturated condition were 1.0 and 1.1 times higher than that from 50% of the saturated condition of soil moisture, and 25% of the saturated condition of soil moisture, soil loss were 3.0 and 8.7 times greater, respectively. As compared to Ansai Loess, the infiltration rates of Yangling Loutu were greater and its rainfall intensities were smaller when antecedent soil moisture was saturated; the infiltration rates of Yangling Loutu were smaller and its rainfall intensities were greater when antecedent soil moisture was unsaturated. With the increasing of antecedent soil water content, the time of runoff occurrence brought forward, and the time for Yangling Loutu was earlier than Ansai Loess, runoff discharge and soil loss increased, and the proportion of runoff discharge occupying rainfall also increased. As compared to Ansai Loess, runoff discharge from Yangling Loutu was grater except for antecedent soil moisture was saturated, and soil loss from Yangling Loutu was grater.2. In soil profile, the soil layers of 0-2cm and 2-5cm were the depth of agricultural NPS occurring reaction drastically, were available depth of rainfall, runoff and soil interaction, especially the layer of 0-2cm was the main source for agricultural NPS contamination losing, 2-5cm layer was the interwork depth of agricultural NPS contamination from surface and sub-surface soil layers, and was converge zone of agricultural NPS contamination leaching and transferring. Because of the effects of runoff and antecedent soil moisture at the same time, nitrate nitrogen (NO3--N) occurred different degree leaching on the soil profile, as compared to Yangling Loutu, NO3--N leaching of Ansai Loess was severe. Ammonium nitrogen (NH4+-N) and phosphorous didn’t leach.3. Eroded sediment was the dominant approach for soil nutrient loss, phosphorus loss was comparatively stable. During soil erosion processes, pollutant loss concentration and amount with runoff and sediment increased with antecedent soil moisture increased. Pollutant loss concentration and amount with runoff and sediment from soil moisture saturated condition was greater than that from unsaturated condition of soil moisture. When soil moisture was saturated condition, soil nutrient loss concentration and amount from runoff and sediment were greater than that unsaturated soil moisture condition. NO3-N loss concentration in runoff under saturated soil moisture condition was greater from 1.2 to 5.0 times than that under unsaturated condition of soil moisture, which loss concentration in sediment under saturated soil moisture condition was greater from 1.3 to 62.9 times than that under unsaturated condition of soil moisture. DP loss concentration in runoff under saturated soil moisture condition was greater from 1.7 to 254.2 times than that under unsaturated condition of soil moisture, which loss concentration in sediment under saturated soil moisture condition was greater from 2.7 to 60.8 times than that under unsaturated condition of soil moisture. When soil moisture was unsaturated sondition, pollutant loss concentration and amount in runoff and sediment increased with antecedent soil water content increased.4. Fertilizer application intensities had important effect on pollutants transport. Under experiment condition, nutrient loss in runoff was greater than that with soil loss, nitrate nitrogen loss was greater than ammonium nitrogen loss and dissolved phosphorus loss. |
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