Substances Contributing to Fire‐Induced Water Repellency in Soils

A soil susceptible to heat‐induced water repellency was heated at several temperatures and oxygen concentrations. The materials emanating from the heated soil were captured and their mass determined. The greatest quantity of products was captured at temperatures above 300C. Increasing amounts of material were produced with increasing oxygen concentrations up to 20%. From 0.3% to 1.75% of the total soil was captured as products. Fractionation of these captured products by adsorption chromatography resulted in the isolation of several different components. Three of these components were capable of causing extreme water repellency in sand if the treated sand were heated. Some evidence suggested that the heating of these substances on the sand surfaces altered their structure. These three effective components represented from 25–50% of the total materials collected from the soil. Elemental and spectroscopic analyses of the effective components indicated them to be basically aliphatic hydrocarbons. The undecomposed and partially decomposed plant materials present in the soil were determined to be the primary source of the products coming from the heated soils.