苏打盐渍土的微域特征及土壤表层积盐机理探讨——以吉林省大安地区嫩江古河道碱滩地为例

通过野外定位观测和室内分析,探讨了苏打盐渍土微域尺度(32 m长的横截面)的土壤结构以及冻融期土壤表层积盐的机理。结果表明:高平地的地层剖面为粉砂质亚粘土-粘土-粉砂-砂砾质地结构;洼地以粉砂质为主,缺少粘土层。盐化草甸土表层的水分以毛管水为主,粗毛管孔隙占总孔隙度的70%以上;苏打碱土的水分主要为束缚水,含水率低且变化微弱。苏打碱土和盐化草甸土镶嵌的微域格局对土壤水分和盐分的迁移规律有明显的影响。冻融季节,盐化草甸土成为水分迁移的汇集区,其表层含水率达50%以上(达到过饱和状态);苏打碱土冻层的水分变化十分微弱,但是盐分含量显著增加并在消融期表聚,导致土壤的盐渍化程度不断加重。

Micro Scale Feature of Sodic Saline Soil and Salt Accumulation Mechanism in Surface Layer Taking alkaline floodplain in Da'an County of Jilin province as an example

By in-situ observation and analysis in laboratory, structure and salt-accumulation mechanism infrozen-thawing season in micro scale (a 32 m long transect) of sodic saline soil region were discussed.Results show that texture along soil profile on micro plat was silty sub slay-slay-silt-gravel structure; themain component in micro basin was silt and gravel, lacking of slay layer. Moisture in saline meadow soilsurface layer was mainly in the form of capillary water, porosity of macro capillary can exceed 70% of totalporosity; moisture in sodic alkaline soil was mainly in the form of confined water, the water content was lowand variation range was very weak. The water and salinity transportation in frozen-thawing period werecontrolled by mosaic structure composed by alkaline soil and saline meadow soil. The surface layer of salinemeadow soil became accumulation sink groundwater in frozen-thawing season, in which the water contentcould reach up to 50%; the vast salinity accumulated in surface layer resulted in the saline degree graduallyaggravated in thawing season.