重庆典型岩溶槽谷区土壤氮素迁移过程分析

土壤-地下水系统中的硝氮污染和氮素的循环过程备受关注，但对岩溶区土壤氮素的迁移过程研究较少。选取重庆市典型岩溶槽谷区的灌丛和菜园地，分层取样分析土壤中各种形态的氮素，并用曲线拟合的方法分析氮素随土壤深度的变化，了解岩溶区土壤氮素的垂直分布情况。从分析结果看，硝态氮为土壤无机氮的主要存在和淋失形式；铵态氮垂直分布规律为表层多底层少，说明受土壤吸附作用的影响向下迁移较少；硝态氮的分布呈波峰波谷式变化，干燥时由于硝化作用产生积累，降雨时可能随雨水向下迁移而减少。研究结果可为指导岩溶区农业生产和氮素管理，以及科学治理石漠化提供理论依据。

Analysis on process of soil nitrogen transformation in typical karst valleys of Chongqing City

The nitrate-nitrogen pollution and the biogeochemical process of nitrogen cycling in soil and groundwater have drawn more and more attention,but there is less research on the process of soil nitrogen transformation in karst areas.The shrubs and vegetable gardens in a typical karst area of Chongqing City were selected,and all forms of nitrogen in soil were analyzed through stratified-sampling,so as to analyze the vertical distribution of nitrogen with soil depth in a karst area with curve fitting.The result shows that nitrate nitrogen is the main existing and leaching form of inorganic nitrogen in the soil;the law of vertical distribution of ammonium nitrogen is more in surface layers and less in bottom layers,indicating less downward transforming of ammonium nitrogen because of soil adsorption;and the distribution of nitrate nitrogen is characterized by peak and valley variations,namely,accumulation by nitrification in dry soil and reduction by transferring downward with rain in the rainfall.The research results provide a theoretical basis for agricultural production and nitrogen management in karst areas,as well as scientific control of rocky desertification.