How can plants manage polycyclic aromatic hydrocarbons? May these effects represent a useful tool for an effective soil remediation? A review

Abstract

Plants are autotrophic organisms which are able to use sunlight and carbon dioxide as the sources of energy and carbon. Plants' roots absorb a range of natural and anthropogenic toxic compounds for which they have developed some extraordinary detoxification mechanisms. From this point of view, plants can be seen as natural, solar-powered pump-and-treat systems for cleaning up contaminated soils, leading further to the concept of phytoremediation. The phytoremediation of polycyclic aromatic hydrocarbons (PAHs) refers to the use of plants and associated soil microorganisms in terms of reducing the concentrations or toxic effects of these contaminants in the environment. Although there is little evidence to prove that PAHs from soils are accumulated considerably in plants' parts, there is a lot of evidence that in soils vegetated with grasses and legumes, a significant dissipation of PAHs occurs. Namely, the primary mechanism controlling this process is the rhizospheric microbial degradation, where soil microbial populations use organic compounds as carbon substrates for its growth. This is usually stimulated by roots exudates. The final result of this process is the breakdown and eventual total mineralization of the contaminants. The main challenge in PAH phytoremediation is to improve the performances of plants and rhizospheric microorganisms requiring thus more basic research and knowledge on natural detoxification mechanisms.