一维非饱和水平土柱中多离子运移和交换反应的研究

Multi-ion Transport and Exchange During Unsteady,Unsaturated Water Flow in Horizontal Soil Columns

进行的非饱和土壤中多离子运移和交换反应的研究表明,在非饱和非稳态流下,土壤中非反应性溶质Cl^-运移时的锋面趋向滞后于水的湿润锋面。由于交换反应,交换性离子锋面和峰出现的位置则滞后的更多,并与离子的交换能力、浓度和供水强度有关。交换反应主要表现在含水量较为稳定和溶液总浓度较为恒定的区域。在一定浓度范围内,用恒定的2离子 Gapon 交换参数,能够较好地模拟以 Ca^(2+)为主的土壤中 Ca-Mg-Na-K 交换体系中 Ca^(2+)的运移;当某1离子与土壤溶液中总的阳离子的活度比发生较大的变化时,模拟时应考虑 Gapon 交换参数的改变。由本研究确定的供试土壤的 Gapon 交换参数 K_(Mg-Ca),K_(Na-Ca)和 K_(K-Ca)分别为0.9～0.6,2和0.3。本研究利用非水溶的重有机试剂和高速离心技术提取土壤溶液样品,可用小量土样同时获得离子的液相和交换相组成的分布等信息,因而更贴切地反映了土壤溶液和交换反应的实际情况。

From the results of this experiment,the sharp position of the Cl^-front was lagged behind the water front.Due to exchange reaction,the sharp position of the cation front was lagged more behind the water and Cl^-front.The shape and position of the cation fronts in the solution and exchangeable phase depended on the cation selectivity coefficient, the concentration of inflow solution and the water flux.The moving zone of ion exchange oc- cured in the zones with relatively constant both water content and total concentration of solu- tion.The experiments and numerical simulation permitted an examination of the cation selec- tivity coefficient in a large variation of concentration.In general,it was essentially adequate for simulating 4-cation transport using constant Gapon selectivity coefficient in a certain range of concentration.If the activity ratio of a cation with the total cations in soil solution varied significantly,Gapon selectivity coefficient should be changed accordingly.After hori- zontal infiltration,adopting dense water-immiscible liquid(TFE)as the extractant and cen- trifuge technique,the horizontal distribution of concentration of ions in solution and in ex- changeable phase could be simultaneously obtained from small quantity of soil sample.