Changes in Soil Properties During Smoldering Fire Caused by Wildfire

This study experimentally investigates the changes in soil internal temperature, color, pH, and EC caused by smoldering fire arising from forest fire. The soil surface temperature reaches approximately 300 ℃, and the soil temperature in the lower section increases continuously owing to heat transfer from the upper section, thus confirming that smoldering fire can occur in the lower section of the soil. The soil internal temperature differs depending on the composition ratio of sand and clay, which is attributed to the difference in the thermal conductivity of sand and clay and the pore size between the soil particles. The soil pH decreases as heating progresses. Meanwhile, the soil electrical conductivity is higher than that before the experiment, although no change is observed as heating progresses. The lethal time of the soil increases with the soil depth; furthermore, under the same depth, the lethal time is longer for higher clay contents.