Soil infiltration characteristics and pore distribution under
freezing-thawing conditions
Abstract
Frozen soil infiltration widely occurs in hydrological processes such as
seasonal soil freezing and thawing, snowmelt infiltration, and runoff.
Accurate measurement and simulation of parameters related to frozen soil
infiltration processes are highly important for agricultural water
management, environmental issues and engineering problems in cold
regions. Temperature changes cause soil pore size distribution
variations and consequently dynamic infiltration capacity changes during
different freeze-thaw periods. To better understand these complex
processes and to reveal the freeze-thaw action effects on soil pore
distribution and infiltration capacity, selected black and meadow soils
and chernozem, which account for the largest arable land area in
Heilongjiang Province, China. Laboratory tests of soils at different
temperatures were conducted using a tension infiltrometer and ethylene
glycol aqueous solution. The stable infiltration rate, hydraulic
conductivity were measured, and the soil pore distribution was
calculated. The results indicated that for the different soil types,
macropores, which constituted approximately 0.1% to 0.2% of the soil
volume under unfrozen conditions, contributed approximately 50% of the
saturated flow, and after soil freezing, the soil macropore proportion
decreased to 0.05% to 0.1%, while their saturated flow proportion
decreased to approximately 30%. Soil moisture froze into ice crystals
inside relatively large pores, resulting in numerous smaller-sized
pores, which reduced the number of macropores while increasing the
number of smaller-sized mesopores, so that the frozen soil infiltration
capacity was no longer solely dependent on the macropores. After the ice
crystals had melted, more pores were formed within the soil, enhancing
the soil permeability.