Removal of pentachlorophenol in a rhizotron system with ryegrass (Lolium multiflorum)

Abstract

Degradation of pentachlorophenol (PCP) in the rhizosphere of Lolium multiflorum (ryegrass) was studied in an Andisol of southern Chile. A rhizotron system was designed to evaluate the effect of different PCP concentrations (50, 100 and 250 mg kg-1) on plant biomass, organic acid exudation, dehydrogenase and the β-glucosidase activity of L. multiflorum. Moreover, the microbial biomass was estimated using a molecular technique in different sections of rhizotrons. More than 96% of PCP was removed in the rhizotron system by adsorption in the soil and degradation by the rhizosphere of L. multiflorum. The plant biomass decreased when the PCP concentration was increased in the soil, the biomass for the treatment with 250 mg kg-1 being significantly lower. The estimation of the microbial biomass and β-glucosidase activity in the soil was not affected when the PCP concentration was increased, indicating a low toxicity of the contaminant due to its lesser availability. However, the dehydrogenase activity decreased when increasing the PCP concentration, showing negative effects on microorganisms. The organic acid exudates varied during the incubation time, influenced by the stress of the different treatments and the distribution of roots. Therefore, Lolium multiflorum is a promising candidate for designing field scale phytoremediation processes.