丹江口库区土壤氮磷养分流失特征

目的]研究丹江口库区土壤的水土流失和非点源污染物氮磷流失的特点,为农业非点源污染模型的建立提供理论依据。方法]通过室内人工模拟降雨试验,研究了坡度和施肥等处理对产流产沙、氮磷养分(硝态氮、铵态氮、总氮、有效磷和总磷)流失特点的影响。结果](1)随着坡度的增加,平均入渗率和初始产流时间呈减小趋势,而径流总量和泥沙总量呈增加趋势。(2)相同施肥处理下,随着坡度的增加,泥沙中硝态氮、总氮、有效磷和总磷的流失浓度呈减小趋势,铵态氮流失浓度在不施氮肥条件下呈减小趋势,而在施氮肥处理下呈增加趋势。(3)在相同坡度条件下,随降雨时间推移,总氮浓度呈先减小后趋于稳定的趋势;铵态氮浓度随施肥处理的变化均呈现出波浪形变化;在施氮肥时,径流中硝态氮的浓度随着时间的推移,呈逐渐减小并趋于平缓的趋势,而在不施氮肥时几乎无变化。结论]在不同施肥措施和坡度条件下,硝态氮主要随径流而流失,为随泥沙流失的8~11倍;铵态氮主要是随径流泥沙而流失,为随径流流失的1~17倍;总氮则是随径流和径流泥沙共同流失;有效磷和总磷都是以泥沙结合态流失为主,分别为随径流流失的1 000~6 200和1~3倍。

Characteristic of Soil Nitrogen and Phosphorus Loss in Danjiangkou Reservoir Area

Objective] We aimed to study the characteristics of soil erosion and non-point pollutants-nitrogen and phosphorus in Danjiangkou reservoir area, and to provide theoretical basis for the establishment of agricultural non point source pollution model. Methods] Through rainfall simulation experiments, we analyzed factors affecting soil and water loss and soil nutrients, including total nitrogen(TN), NH₄-N, NO₃-N, total phosphorus(TP), available phosphorus(AP), from purple soil, such as slope gradient and fertilizer measures. Results] (1) The average infiltration rate and the initial runoff time decreased, however the total amount of runoff and sediment increased with the creasing slope. (2) The concentration of TN, NO₃-N, TP and AP in sediments decreased with the increasing slope when they were under the same treatment. The concentration of NH₄-N in runoff decreased under the condition of no nitrogen, and increased under nitrogen treatment. (3) The loss of TN was stable after the first reducing trend, the loss of NH₄-N under various fertilizer treatments showed a wave-like change, the loss of NO₃-N gradually decreased and flatten out at last under nitrogen treatment, but had almost no change under the condition of no nitrogen along with the rainfall time under the condition of the same grade. Conclusion] The NO₃-N was mainly lost with runoff, which was 8 to 11 times of the loss with sediment. NH₄-N loss was mainly caused by the sediment erosion, which was 1 to 17 of times the loss caused by runoff erosion. The total loss of nitrogen was summary of the loss in runoff and sediment. The main way of the loss of AP and TP were lost by sediment, which were 1 000 to 6 200 times and 1 to 3 times of that by runoff erosion, respectively.