# Fire-Induced Changes in Soil and Implications on Soil Sorption Capacity and Remediation Methods
## 4 Fire-Induced Changes in Soil and Choice of Soil Remediation Technologies
### Chemical Remediation Methods
#### Chemical Fixation  
Soil remediation using chemical fixation involves immobilizing contaminants in the soil using a variety of reagents or materials, which may include but not limited to clays, metallic oxides, biosolids, animal manures, biochar and lime [135]. Most immobilization technologies can be performed ex situ or in situ. Chemical processes involved in this technique of remediation include adsorption, chelation, precipitation, and complexation, which cause contaminants to be redistributed from solution to solid phase thereby immobilizing them in the environment. These processes are influenced by soil pH, texture, CEC, organic matter content, mineralogical composition and types of oxides contained in the soil. Precipitation, for example, is favored under alkaline pH conditions. Remediation methods which are based on precipitation of the contaminants could be effective on fire-affected soils because of the prevailing alkaline pH conditions. Methods which exploit soil sorption capacity may be enhanced in fire-affected soils where biochar is produced. The sorption capacity of biochar has been widely published and is attributed to complexation of contaminants, especially heavy metalswith alkylated and anomeric carbons, aromatic structures and aromatic C-O groups it contains. When added to soils, biochar interacts with plant roots, soil organic matter and microorganisms to form an organo-mineral-biochar complex because of its reducing nature and electrochemical properties [143]. The efficiency of biochar in the immobilization of contaminants in fire-affected soils may be negatively affected by the low organic matter content and microbial population commonly found in fire-affected soils, especially if remediation occurs soon after the fire event.  
The use of organic amendments as chemical fixers in contaminated soil also relies on the interaction between these amendments and soil mineral contents to form organo-mineral complexes which increase the soil's binding capacity for various contaminants [144]. Organic amendments, especially at their initial stage of application, can immobilize heavy metal(loid)s in soil through adsorption reactions or formation of stable complexes. They contain cellulose, lignin hemicellulose, proteins, lipids, starches, simple sugars, hydrocarbons, and many other compounds with functional groups such as carbonyl, phenolic, acetamide groups, amide, amino, structural polysaccharides and esters, which have high affinity for metal complexation. Formation of organo-mineral complexes may not be possible in soils where the soil mineral assemblage has been shifted towards more inert primary minerals that are not likely to form any complexes with the added organic material. Whereas, increase in pH and formation of biochar in fire-affected soils may favor immobilization of contaminants in the soil, changes in soil mineralogy and texture may mobilize them. Considering that fire-affected soils have low organic matter content, use of organic amendment as contaminant immobilizers in fire-affected soil would increase organic matter content. Contaminant immobilization using organic amendment may therefore be a suitable method of remediating fire-affected soils, because it will also improve soil organic matter content, tilth, water retention capacity, and microbial population and its overall functionality in the ecosystem.