THE ROLE OF PLANTS AND BACTERIA IN PHYTOREMEDIATION - KINETIC ASPECTS

Abstract

Phytoremediation is the common name for cleaning techniques for polluted soils, sediments, and wastewaters using plants. It has been shown repeatedly that several types of pollutants, e.g., petroleum products and solvents, are degraded faster in the presence of plants. A couple of processes are known to influence the elimination of pollutants, among them transpiration of water, oxygen transport, biological stimulation in the root zone and plant uptake of chemicals. However, it is frequently unclear whether the plants directly metabolise the pollutants, or whether they only play an indirect role by supporting microbial action. The metabolism kinetics of plant enzymes is mathematically described by the Michaelis-Menten kinetics. This means, that at low substrate concentrations, the degradation is first order, whereas it is linear and therefore limited at high substrate concentrations. Bacteria use the substrate for growth, and grow better at higher substrate availability. This is described by the Monod kinetics. Therefore, bacteria have a limited degradation capacity at low substrate concentrations. This often prohibits the biodegradation of polluted sites down to required levels. The combination of plants with bacteria might be a successful method to overcome these shortcomings .