塿土水分入渗、再分布过程反应性溶质(NH_4~ )运移特征研究

利用土柱切割法研究（土娄）土水分入渗、再分布过程反应性溶质（NH4 ）运移特征。在水分入渗初期,土壤剖面溶质分布曲线为斜线,随入渗时间延长,土壤剖面溶质分布曲线上部逐渐出现垂直于横坐标的垂直线段。与水分入渗、再分布相比,溶质（NH4 ）入渗、再分布明显滞后;水分入渗深度增加,水溶质入渗距离比增加,溶质入渗滞后程度增大。入渗液浓度增大,溶质入渗滞后程度及溶质入渗阻滞因子减小,相应的土壤吸持溶质的反应速率常数增大,表观活化自由能减小。不同再分布时间的土壤剖面溶质分布曲线具有交点（溶质再分布等浓度点）,且该交点随入渗液浓度增大而加深。水分再分布过程中,溶质再分布等浓度点的土壤溶质吸持量基本不变,而其上部的土壤吸持量减小,下部的土壤吸持量增大。

CHARACTERISTICS OF REACTIVE SOLUTE TRANSPORT DURING WATER INFILTRATION AND REDISTRIBUTION IN MUM-ORTHIC ANTHROSOL

Characteristics of NH4 transport during water infiltration and redistribution have been studied with the soil column destruction method. The solute distribution curve in the soil profile (depth vs. amount of solute retained in per gram dry soil) was of slope at the beginning of infiltration, and its upper part gradually became vertical to the abscissa while infiltration continued. Compared with water in infiltration and redistribution, solute was significantly delayed. The ratio of water wetting front depth to solute front depth, indicating the delay of solute infiltration, increased with the process of infiltration . With increasing concentration of displacement solution, the solute retardation factor during infiltration decreased and the velocity constant of soil NH4 retention reaction increased, accord-ingly, the apparent Gibbs free energy decreased. Solute redistributed while water was redistrbuting. The solute amount retained in per gram dry soil at the iso-concentration point of solute redistribution , which was the cross point of solute distribution curves of different times, was not changed during solute redistribution. In the upper part of the soil column above the iso-concentration point, the solute amount retained in per gram dry soil decreased, contrarily that in the lower column part increased due to solute redistribution. The depth of the iso-concentration point increased with increasing concentration of the displacement solution.