Phytoremediation and necrophytoremediation of petrogenic hydrocarbon- contaminated soils

While many human activities rely heavily on the use of petrogenic hydrocarbons, contamination of the environment by petrogenic hydrocarbons during extraction, refining, and transport of petroleum remains a global issue. The aim of this chapter is to assess the potential for phytoremediation (plant-assisted bioremediation) and necrophytoremediation (dead plant biomass-assisted bioremediation) for the remediation of hydrocarbon-contaminated soils. Phytoremediation is defined as the use of plants and their associated microorganisms to remove or degrade organic or inorganic contaminants. In terms of hydrocarbon degradation, microorganisms present in the plant rhizosphere (root zone) have been shown to be effective at remediating the contaminants; this is called rhizoremediation (rhizodegradation). Plant roots increase microbial activities (including hydrocarbon degrading activities) through the release of root exudates such as nutrients, oxygen, and hydrocarbon analogues, which may contribute to the acceleration of the degradation of petrogenic hydrocarbons. However, toxicity associated with many hydrocarbon products towards the plants coupled with undesirable soil conditions such as salinity may limit the effectiveness of phytoremediation (rhizoremediation). In this case, necrophytoremediation can be used as an alternative method; this is defined as the use of dead plant biomass (e.g. straw) and its associated microflora to degrade the contaminant. Necrophytoremediation is a toxic-independent process, one which is less affected by soil conditions unlike phytoremediation. In summary, both these technologies are promising tools which can be used to remediate hydrocarbon-contaminated soils as they are cost-effective, sustainable, and environmental friendly.