基于NMR技术的盐渍化冻融土壤未冻水及孔隙水含量试验研究  

NMR-based Research on Unfrozen Water and Pore Water Content in Saline Freezing-Thawing Soils

作　　者：卢星航 史海滨[1] 李瑞平[1] 梁建财[1] 徐昭[1] 步怀亮 

机构地区：[1]内蒙古农业大学水利与土木建筑工程学院,呼和浩特010018

出　　处：《水土保持学报》2017年第2期111-116,共6页Journal of Soil and Water Conservation

基　　金：国家自然科学基金项目(51369018);国家自然科学基金重点项目(51539005);教育部留学回国人员科研启动基金项目([2013]693);内蒙古自治区第五批"草原英才"工程项目([2015]56)

摘　　要：为探讨盐渍化土壤在冻融过程中孔隙水及未冻水含量的变化规律,运用核磁共振仪(NMR)测定了不同盐渍土与不同NaCl饱和试样的孔隙水及未冻水含量,同时研究了不同土质对冻结过程中未冻水含量的影响,分析了冻融过程中的滞后现象。试验设置8个处理,即轻度盐渍化粉砂壤土、中度盐渍化壤土2种土壤类型和蒸馏水、0.2%、0.6%、1.0%NaCl 4种溶液。结果表明:(1)在盐渍土冻结过程中,大孔隙降幅速率>小孔隙降幅速率,而盐渍土的融解先从小孔隙开始。(2)无论是轻度盐渍土还是中度盐渍土,1.0%NaCl饱和溶液的未冻水含量最大。饱和溶液为1.0%NaCl的中度盐渍土在冻融过程中出现二次突变,其二次突变温度点不一样,融解时二次突变温度高于冻结时二次突变温度。(3)比较不同土质对冻融过程中未冻水含量可知,壤土未冻水含量>粉砂壤土未冻水含量。在冻融过程中,结合T_2分布曲线可知,孔隙水的减少先从大孔隙开始,孔隙水的增多先从小孔隙开始;NaCl饱和溶液的浓度越高,其未冻水含量越大,冻结温度越低;不同土质对土壤未冻水含量有所影响,壤土的未冻水含量明显高于粉砂壤土的未冻水含量;盐渍土壤在冻结和融化过程中存在滞后现象,在冻融过程中的滞后现象明显区间,随浓度的增大,所处的温度范围有降低趋势。To explore the changes of pore and unfrozen water contents in saline soils during the freezing- thawing process, the pore and unfrozen water contents in different saline soils and NaC1 saturated soil samples were determined using nuelear magnetic resonance spectrometer （NMR） to detect, the effects of soil texture on unfrozen water content in the freezing process were studied, and the hysteresis during the freezing-thawing process was analyzed. Eight treatments were designed, i.e. two types of soil （mild saline silt loam and moderate saline loam） and four types of solution （distilled water, 0.2% NaC1, 0.6% NaCI and 1.0% NaC1 solutions）. The findings were as follows. （1） macropores showed a faster decrease in unfrozen water content than micropores during the process of salinized soil freezing, with the thawing dissolved first in micropores in salinized soil. （2） For both the slight and moderate salinized soils, unfrozen water content was the maximum when the soils were treated with 1.0% NaC1 solution. （3） As could be seen from the comparison of unfrozen water content between different soils during the freezing-thawing process, the loam had higher unfrozen water content than the silt loam. According to the experimental results, water content reduction started in macropores, while water content increase started in micropores during the freezing-thawing process. The higher the concentration of NaC1 solution was, the greater the unfrozen water content was, and the lower the freezing temperature was. Unfrozen water content changed to varying degree in different soils, and the unfrozen water content in the loam was obviously higher than that in the silt loam saline soil frozen and thawed relatively slowly, and in the areas where freezing and thawing lagged behind obviously, the temperature range tended to decrease with the rising concentration.

关 键 词：盐渍土 未冻水 T2分布 核磁共振 滞后作用 

分 类 号：S155.2[农业科学—土壤学]