# Fire-Induced Changes in Soil and Implications on Soil Sorption Capacity and Remediation Methods
## 3 Fire-Induced Changes in Soil Properties and the Implications on Soil Sorption Capacity
### Fire-Induced Changes in Soil Textural Properties and Implications on Soil Sorption
Increase in coarseness of soils post fire events would therefore result in a decrease in the fraction of the soil sorption capacity contributed by the clay fraction, and consequently on the soil's overall ability to sorb cationic and organic compounds. Fire-Induced Changes in Soil Mineralogical Properties and the Implications on Soil Sorption Capacity  
Changes in soil mineralogy caused by fire are correlated with the moisture condition of the soil according to [PERSON] [31], and vary with type of soil. Laboratory experiments by [PERSON] [44] revealed significant changes in the mineralogy of uncontaminated soils at about 300 \({}^{\circ}\)C whereas in mine tailings contaminated soil, similar changes were only observed at 500 \({}^{\circ}\)C (Table 2). Changes in the mineralogy of both contaminated and uncontaminated soils occur after 4 h of heating at temperatures of 300 \({}^{\circ}\)C and after 2 h of heating at 500 \({}^{\circ}\)C [44]. These changes could be attributed to the conversion of secondary mineral to primary minerals as a result of dihydroxylation. Although [PERSON] et al. [97] have shown that the mineralogical assemblage of soil is not affected by fires below 500 \({}^{\circ}\)C, [PERSON] et al. [50] and [PERSON] and [PERSON] [98] have also shown that soil mineralogical composition could be affected by fire events with temperatures as modest as 200-600 \({}^{\circ}\)C.  
Results from research on the effect of soil temperature changes on soil mineralogy show that both primary and secondary soil minerals are affected by fire events. Quartz, for example, is unaffected when exposed to temperatures of 600 \({}^{\circ}\)C or greater, but diminished intensities of quartz peaks have been reported at this temperature as well. [PERSON] et al. [67] reported unchanged quartz peak  
\begin{table}
\begin{tabular}{|c|c|c|c|c|c|c|c|c|c|c|c|c|c|c|c|c|c|c|c|c|} \hline \multirow{2}{*}{**Sillumination**} & \multirow{2}{*}{**CEC**} & \multicolumn{10}{c|}{**Minerals Composition (\%)**} \\ \cline{3-14}  & & & **TCO1** & & **TCO2** &  
intensities at 300 \({}^{\circ}\)C, but lower peaks after exposure of subsoil to temperatures of 600 \({}^{\circ}\)C. The content of K-feldspars in soil has also been shown to decrease with increasing soil temperatures, whereas quartz content increases as indicated in Table 2[44]. No changes in hematite content of soils were reported at temperatures of 750 \({}^{\circ}\)C by [PERSON] [44], and calcareous soils have also been shown to resist changes up to temperatures of about 1000 \({}^{\circ}\)C. [PERSON] and [PERSON] [99], however, observed that gibbsite alters to amorphous phase at temperatures as low as 200 \({}^{\circ}\)C, whereas goethite is transformed to hematite at temperatures of approximately 300 \({}^{\circ}\)C. The contribution of soil primary minerals to its sorption capacity is, however, lower than that of secondary minerals (Table 3), so fire-induced changes in primary minerals may have a negligible effect on the soil's overall sorption capacity. The situation with secondary minerals is, however, different. The effects of fire on secondary minerals occur at much lower temperatures compared to the primary minerals possibly because of their lower thermal conductivity, and vary with type of clay mineral. Dehydroxylation of most minerals occurs when soil temperatures are raised to about 500 \({}^{\circ}\)C, but [PERSON] et al. [31] have shown that though phyllosilicates like micas and vermiculite are affected by fire events of high intensity, they are not completely decomposed. [PERSON] et al. [51] and [PERSON] et al. [100] reported the disappearance of kaolinite at 500 \({}^{\circ}\)C and attributed this to loss of hydroxyl ions from the lattice structure of kaolinite and formation of metakaolinite thereof. [PERSON] et al.