【作者】 邓建才；

【导师】 陈效民；

【作者基本信息】 南京农业大学 ， 土壤学， 2003， 硕士

【摘要】 采用马氏瓶、恒流泵控制饱和、非饱和土壤中水的流速，通过室内土柱模拟实验，研究了饱和、非饱和土壤中硝态氮的垂直运移规律与非饱和土壤中硝态氮的水平运移特性以及影响因素，并应用CXTFIT模型描述饱和土壤中硝态氮垂直运移特征，可以得到以下结论： 黄淮海平原3种主要土壤类型各土层的饱和导水率在5.95×10^-6～1.08×10^-2cm．s^-1之间变化，并随着土壤剖面深度的增加呈现出表土层高、中间土层低、底土层又升高的趋势；扰动土与原状土的饱和导水率差异较大，经统计分析达到极显著水平；土壤容重、孔隙度、有机质含量和粘粒含量对饱和导水率均有影响。应用RETC（Retension Curve Model）估算的3种土壤各土层非饱和导水率，均随土壤水吸力的增加而减少；当土壤水吸力较低时，表土层土壤非饱和导水率大于底层土和中间土层的土壤非饱和导水率；当土壤水吸力增大到一定值时，中间土层的土壤非饱和导水率反而大于底土层和表土层。各土层的水分特征曲线总的趋势是一致的，即随土壤水吸力的增加土壤体积含水量逐渐下降；应用RETC拟合的水分特征曲线与测定曲线的符合程度达到极显著水平。3种土壤水分扩散率在1.0×10^-3～15 cm²．min^-1之间变化；土壤水分扩散率与土壤体积含水量之间的关系符合经验公式D（θ）=a e^bθ，皆呈指数函数变化，经统计均达到极显著水平。 在硝态氮水平运移过程中，各土层硝态氮水平运移速率与运移距离间符合幂函数关系，经统计分析，均达到了极显著水平；其水平运移速率随土壤体积含水量的变化趋势基本一致，即随着土壤体积含水量的增加而增加；其水平运移速率还随土壤水分扩散率呈指数曲线变化，经统计分析达到极显著水平。硝态氮水平运移浓度随硝态氮源距离的增加而逐渐增加，并且在土壤干湿交界处（湿润锋面）达到最大值；其浓度随着土壤体积含水量的增加而成比例减少，符合幂函数曲线变化趋势，经统计分析均达到极显著水平；其浓度还受土壤水分扩散率的影响，即随土壤水分扩散率升高而下降。黄淮海平原主要土壤中硝态氮运移规律及模型应用研究 在土壤饱和条件下，用稍态氮作垂直运移试验，不同浓度（100mg’L一‘、200mg’L一，）的硝态氮示踪后得到的稍态氮穿透曲线基本重合，表明稍态氮的浓度对穿透曲线影响不大;伴随阴离子（SO了一）和不同价态的陪伴阳离子（K十和Ca2+）示踪处理后3种土壤的表土层穿透曲线的形状、峰值以及完成一个的出流周期所经历的时间变化不明显，并且对各土层峰值的影响较小;但经伴随so了一离子示踪后的中间土层、底土层的硝态氮出流时间提前;经过Ca“+示踪后的中间土层、底土层中稍态氮出流时间具有滞后效应，这些现象在中间土层中表现较为突出。 在土壤非饱和条件下，经不同流速处理后稍态氮垂直运移获得的曲线是一种前缘陡峭、后缘拖尾的“拖尾”型穿透曲线，输入峭态氮溶液的速率越小，拖尾现象愈明显、穿透曲线就越不对称。 在稳定流和土壤饱和条件下，运用C犷刀刁T对稍态氮在垂直运移过程中的轨迹进行拟合具有较高精度，决定系数均达到极显著水平，表明模拟穿透曲线与测定的穿透曲线之间无差别，因此可以用此模型对试验区土壤中硝态氮的运移规律进行预测、预报。更多还原

【Abstract】 Vertical and horizontal transports of nitrate-N and influential factors in saturated-unsaturated soils were studied and characteristics of vertical transport of nitrate-N were described with CXTFIT model. Results were as follows:(1)The saturated hydraulic conductivities of all soil layers in the main three kinds of soil in the Huang-Huai-Hai Plain were changeable from 5.95 X 10-6 to 1.08 X 10-2 cm. s-1 and changed with increase of the depth. The highest saturated hydraulic conductivities occurred in topsoil layer and the lowest in middle soil layer. The saturated hydraulic conductivities were very different between undisturbed and disturbed soil and were affected by bulk density, porosity, organic matter content, and clay content.(2)Simulating the unsaturated hydraulic conductivities of the three kind of soils reduced with increase of soil water suctions by RETC model. When the soil water suctions were low, the unsaturated hydraulic conductivities in topsoil layers were higher than those in middle soil layers. While the soil water suctions increased to some values, the unsaturated hydraulic conductivities in middle soil layers were higher than those in topsoil layers.(3)Tendencies of the soil water retention curves of all soil layers in three kinds of soil were similar, the soil volumetric water content decreased with the soil water suctions. Simulated by RETC model and tested soil water characteristic curves fitted quite well and these relationships were sharply significant by statistic analysis.(4)The soil moisture diffusivity of all soil layers in the three kind of soils was changeable from 1.0 X 10-3 to 15 cm2, min-1 and changed with increase of the depth. When soil volumetric water content was constant, the high soil moisture diffusivity occurred in topsoil layers and the low in middle soil layers. Relationship between soil moisture diffusivities and soil volumetric water content in every soil layer was sharply positive exponential function, which was fitted by the empirical equation ( D( ) = aeb ), and this relationshipwas significant by statistical analysis.(5)In the process of the nitrate-N horizontal transport, the horizontal transport velocity of nitrate-N decreased with rise of the distance of the tracer source in power function, and this relationship was sharply significant by statistic analysis. Trends of the horizontal transport velocity of nitrate-N of all soil layers in three kinds of soil were correspondent, namely, the horizontal transport velocity of nitrate-N increased with the soil volumetric water content increase in each soil layer in three kinds of soil. The horizontal transport velocity of nitrate-N was affected by the soil moisture diffusivity, and these changes can be described by exponential function. This relationship was sharply significant by statistic analysis.(6)In the process of the nitrate-N horizontal transport, the concentration of nitrate-N slowly increased with increasing the distance of the tracer source in power function, the maximum of the concentration of nitrate-N occurred where there were wet and arid soil. The concentration of nitrate-N reduced with increase of the soil volumetric water content and the soil moisture diffusivity, and the former can be described in power function. This relationship was sharply significant by statistic analysis, too.(7)Under saturated soil condition and in the process of the vertical transport of the nitrate-N, a large part of the Breakthrough Curves (BTCs) of different concentration of nitrate-N (100mg L-1 200mg L-1 NO3- - N) overlapped, that is, vertical transport of nitrate-N wasn’t influenced by different concentration of nitrate-N (100mg L-1 200mg L-1 NO3- -N) in soil column. Accompanying anion (SO42-) and co-existing cations (K+ andCa2+) weren’t affected the form and peak value of BTC of vertical transport of nitrate-N in all topsoil layers of soil column, but the former made time of outflow of nitrate-N in all middle and low soil layers short, and the latter long. These phenomena were quite outstand更多还原