不同土壤冻融特征曲线的试验研究

土壤冻融特征曲线是反映冻土强度、冻土的热性质和土壤冻融过程中的水分和盐分迁移规律的重要参数.为了研究不同植物养分对不同土壤冻融过程的影响,采用NMR法对加入5种不同溶质的4种土壤的冻融特征曲线进行了测定与分析.结果表明:混合Ⅱ5%溶液均对这4种土壤的冻融特征曲线影响最明显,Ca(NO₃)₂ 5%溶液次之,再次为加入K₂S0₄和混合Ⅰ5%溶液的,P₂O₅ 5%溶液最小.这主要是由于在负温下不同溶质的溶解度和土壤对不同溶质的固持作用等不同所致.在加入相同溶液的情况下,康平下层土壤的冻融特征曲线明显低于其它3种土壤,而这3种土壤之间未冻水含量高低次序随所加入的溶质不同而不同.各试样的冻融特征曲线均出现了滞后现象.

Experimental Study of the Freezing and Thawing Characteristic Curves of Different Soils

The freezing and thawing characteristic curves of soil are the most important ones,which reflect the strength,thermal properties and water and solute transport regularities.In order to study the effect of different nutrients during soil freezing and thawing,four kinds of soil mixed with five kinds of different solutions were measured by nuclear magnetic resonance.It was found that the influence of the solution of mixⅡ5% on the freezing and thawing curves is the maximum,the next is Ca(NO₃)₂ of 5%,the third is K₂S0₄ of 5% and mixⅠof 5%,and P₂O₅ of 5% is the minimum.This is mainly caused by different solubility of different solutes,and the different fixing abilities of soil for different solutes etc..When soil was mixed with the same solution,freezing and thawing characteristic curves of the next layer of soil from Kangping are lower than that of the other soils obviously.The magnitude of unfrozen water content of those three soils changes with solutes.This is mainly caused by the differences in the texture and physical-chemical properties between different soils.Hysteresis exists in the freezing and thawing characteristic curves of each sample.