四川紫色土吸附气态水特征及其热力学函数的研究

STUDIES ON THE PROPERTIES OF WATER VAPOR ADSORBED ON PURPLE SOILS IN SICHUAN PROVINCE AND THEIR THERMODYNAMIC FUNCTIONS

本文用平衡水汽压法研究了紫色土对气态水的吸附特征以及被吸附气态水的热力学函数.结果表明,紫色土对气态水的吸附属多分子吸附,在一定温定、湿度条件下,土壤具有一定吸附限量。最大平衡吸附量为中性紫色土>钙质紫色土>酸性紫色土,并与土壤物理性粘粒、粘粒、有机质、粘粒团聚度、阳离子代换量(CEC)密切相关.其中,以物理性粘粒含量及其团聚度和阳离子代换量影响最大.土壤吸附气态水是一个放热过程,被吸附气态水的相对偏摩尔焓(△(?))、自由能(△(?))和熵(△(?))比纯水低。当土壤含水量为6.00%时,相对偏摩尔焓、自由能和熵的大小顺序为中性紫色土<钙质紫色土<酸性紫色土。偏摩尔熵和焓受有机质的影响最大,物理性粘粒和CEC 对相对偏摩尔自由能(△(?))的作用较大。

The method of equilibrium water vapor pressure was adopted in this study.Theadsorption of water vapor on the soils has been proved to be a case of multilayersorption.There exists an equilibrium sorption capacity of soil in the temperature and the relativemoisture(P/P_o).The maximum equilibrium sorption capacity of the soils used in this ex-periment is in the sequence of neutral purplc soil>calcarcous purple soil>acid purple soil,and is closely related to the contents of physical clay,clay,organic matter,CEC anddegrecs of aggregation of<0.01mm physical clay and<0.001mm clay in the soil.Theadsorption of water vapor on the soil is an exothermic reaction.The relative partial molarenthalpy(△(?)),free energy(△(?))and entropy(△(?)),of water vapor absorbed on the soilare lower than those of pure water.At 0.06 of soil moisture content,the sequences for thethree thermodynamic functions are similar:neutral purple soil<calearcous purplesoil<acid purple soil.A significant negative correlation is present between △(?) or △(?)and the content of organic matter in the soil and between △(?) and the contents of physi-cal clay and CEC in the soil.