Mechanism of freeze–thaw action in the process of soil salinization in northeast China

Abstract

As a particular mechanism of soil salinization, freeze–thaw action has an obvious control on soil salinization in northeast China; it essentially differs from the present-day salinization process by involving violent evaporation. A special rule of water/salt movement is formed during the process of freezing and thawing, and the resultant soil profile is divided into three layers: frozen layer, semi-frozen layer, and unfrozen layer. It is evident that the salinity in the frozen layer increases, along with soil water and salt mass moves towards the frozen layer from the underlying beds, through the process of soil freezing. The salinity of the frozen layer assembles in the upper soil layer and violent vaporizing occurs. The salinization vaporization intensity resembles an "eruption" in springtime. Because the unthawed soil layer serves as a waterproof stratum and insulates unconfined water, soil salinization in the spring has no direct relation with the groundwater table, and is only affected by the thawed perched groundwater above the frozen layer. Therefore, it is not true that "the critical depth of groundwater" controls the springtime "eruption" salification in northeast China.