潮土中阿特拉津解吸滞后特征

采用批量动态实验方法,研究了阿特拉津初始浓度与解吸时间对潮土中阿特拉津解吸滞后特征的影响.结果表明:土壤溶液中阿特拉津的浓度随其解吸时间的增加而逐渐下降,二者间可用经验指数公式表达.阿特拉津连续解吸5d后,阿特拉津的初始浓度从50μg·L^-1增加到2 000μg·L^-1时,对应解吸率分别为23.1%、30.4%、33.0%、36.4%和38.5%.土壤吸附阿特拉津与对应土壤溶液中阿特拉津浓度关系可用传统和依时解吸等温线2种方式描述.无论传统还是依时解吸等温线都与吸附进行到168h的吸附等温线之间存在着解吸的滞后现象.传统和依时Freundlich解吸等温线参数能对吸附解吸等温线的滞后作用进行量化,滞后系数ω只适合传统解吸等温线的滞后量化,而滞后系数H和λ对2类解吸等温线都适用.

Hysteretic Characteristics of Atrazine Desorption from Fluvo-Aquic Soil

Kinetic batch experiments are carried out in order to investigate the effects of a wide range of atrazine initial concentrations and consecutive desorption time on the desorption characteristics of atrazine from fluvo-aquic soil. The results reveal that, atrazine concentrations in soil solution gradually decreased with desorption time increasing, whose relationship can be expressed with empirically exponential functions. After consecutive five steps (or 5 days), when atrazine initial concentrations increased from 50 microg x L(-1) to 2000 microg x L(-1), the average desorption percentages were 23.1%, 30.4%, 33.0%, 36.4% and 38.5%, respectively. The relationships between the amount of atrazine adsorbed by soil colloids and corresponding atrazine concentrations in soil solutions may be described through the traditional and time-dependent desorption isotherms. The obvious discrepancies in two families of both traditional and time-dependent desorption isotherms from adsorption isotherm, which retention time last for 168 hours before commencement of desorption, were indicative of hysteresis. Two sets of Freundlich parameters derived from both desorption isotherms can quantify the hysteresis between desorption and adsorption isotherms. However, hysteresis coefficient, omega, was applicable only for the traditional desorption isotherms, H and lamda applicable for both.