THE EFFICACY OF PLANTS TO REMEDIATE INDOOR VOLATILE ORGANIC COMPOUNDS AND THE ROLE OF THE PLANT RHIZOSPHERE DURING PHYTOREMEDIATION

A wide range of volatile organic compounds (VOC) are released from building materials, household products and human activities. These have the potential to reduce indoor air quality (IAQ), poor IAQ remains a serious threat to human health. Whilst the ability of the single plant species to remove VOC from the air through a process called phytoremediation is widely recognised, little evidence is available for the value of mixed plant species (i.e. plant communities) in this respect. The work reported herein explored the potential of plant communities to remove the three most dominant VOCs: benzene, toluene and m-xylene (BTX) from indoor air. During phytoremediation, bacteria in the root zone (rhizosphere) of plants are considered the principal site contributing to the VOC reduction. This project explored BTX degrading bacteria in the rhizosphere through culture-dependent and independent approaches. This research revealed that mixed plant culture could remove low and high concentrations of BTX from the air. Interestingly, 100 ppm BTX removal rates by single plant species were higher than the removal rate observed for mixed plant species in all cases. At the low concentration (10 ppm), all plants showed higher removal rates of benzene and toluene than m-xylene. Some bacteria in the rhizosphere utilised gaseous BTX as their sole carbon and energy sources were isolated on minimal salt agar. The majority of isolated bacteria were Gram-positive and belonged to the phylum Actinobacteria. Most of the identified bacteria belonged to the genera Microbacterium, Rhodococcus, Arthrobacter and Pseudomonas. In considering the impact of BTX upon the rhizosphere microbiome, it was shown that overall there were little compositional and functional changes following exposure to 10 ppm gaseous benzene. Findings from this work enhanced our understanding of the benefit of indoor plants in relation to VOC remediation and the consequent improvement of phytoremediation systems for the protection of public health