# Fire-Induced Changes in Soil and Implications on Soil Sorption Capacity and Remediation Methods
## 1 Introduction  
Fire events are becoming more frequent in occurrence, and larger in terms of areal coverage [1]. Analyses of charcoal records in sediments and isotopic records in ice cores have indicated lower biomass burning in present times than any time in the previous 2000 years [2; 3], but [PERSON] et al. [1] and [PERSON] et al. [4] reported an increase in the occurrence of wildfires. Data from Europe, Australia, and New Zealand also show a decline in the occurrence of fire events but similar data sets from South East Asia, the Middle East and North America show an increase [5]. Results from studies carried out around the globe indicate that spatially, fire incidents occur in every continent except Antarctica whereas temporal occurrence is related to climatic changes [6]. According to [PERSON] et al. [1], lightning, climate change and precipitation will account for 3.6%, 19%, and 36.7% increase in the occurrence of wildfires respectively by the year 2050. Lightning, volcanic eruptions, and sparks from rock falls are natural occurrences which have been cited as being responsible for wildfires. Increased occurrences of fire events in recent years have been associated mainly with anthropogenic activities aimed at promoting habitat diversity, stopping bush encroachment, controlling and/or eliminating pathogens (thermosanitation), and preparing land for planting [7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19]. Fires have also been used for training firefighting personnel [20]. Improper waste disposal practices, slash and burn agriculture, and clearing of rangelands are some human activities which have caused accidental fires in recent times. Ecological factors including vegetation cover have also been identified to play a role in the occurrence of wildfires [21; 22]. Whereas human influences ignite fires, ecological factors are said to determine whether a fire will spread once it has been ignited. The cause of fire incidents and their occurrence and spread are therefore influenced by several factors most of which are related to human activities.  
Whether natural or human induced, fires have been classified as ground fires (which burn near the ground surface), surface fires (which burn shrubs, larger plants and lower branches of trees), and crown fires which mainly burn trees. Fires have also been described as flaming fires which burn at higher temperatures and spread faster or smoldering fires which burn more slowly, have lower temperatures, and are usually flameless [23]. Smoldering fires destroy large amounts of biomass and cause severe damage to the soil ecosystems [24; 25]. Ground fires typically burn by smoldering and can last for days to months with relatively low temperatures (500 \({}^{\circ}\)C to 700 \({}^{\circ}\)C) compared to flaming fires (1500 \({}^{\circ}\)C to 1800 \({}^{\circ}\)C) [25]. Fires likely to affect soils are ground fires and crawling or surface fires because of their proximity to the soil surface.  
Irrespective of whether they are natural or manmade, fire events affect the ecosystems in which they occur in several ways. According to [PERSON] [26], soil properties could experience short-term, long-term and permanent fire-induced changes which may trigger ecosystem wide impacts with consequences on ecosystem resilience and stability. In contaminated soils where natural attenuation processes are hindered by the presence of high concentrations of contaminants, fire-induced changes in soil properties could have serious consequences. These changes could influence soil sorption and attenuation capacities and dictate the choice of remediation method to use on fire-affected contaminated sites. This paper reviews soil- and fire-related factors that dictate changes in selected soil properties during fire events and the extent to which these properties are affected. It also discusses how these changes may affect soil sorption capacity and the choice of remediation methods used on contaminated fire-affected soils.