Formaldehyde removal in the air by six plant systems with or without rhizosphere microorganisms

Uptake and in-plant transport of formaldehyde by six plants with or without soil microorganisms were investigated. The capabilities of fresh and boiled leaf extracts to dissipate added formaldehyde were also measured to evaluate formaldehyde metabolism in plant tissues. Results show that when the initial formaldehyde level in air was 0.56 ± 0.04 mg·m^-3, the removal rate in the plant-only systems varied from 1.91 to 31.8 μg·h^-1·g^-1 FW (fresh weight). The removal rate of plants in the plant-only systems were ordered as Helianthus annuus Linn > Lycopersicon esculentum Miller > Oryza sativa > Sansevieria trifasciata Prain > Bryophyllum pinnatum > Mesembryanthemum cordifolium L. f. Most reduction of formaldehyde in the air was due to degradation by active components in the plant tissues, of which 4-64% of these were through to be enzymatic reactions. In the microbe-plant systems, formaldehyde removal rates increased by 0.24-9.53 fold compared to the plant-only systems, with approximately 19.6-90.5% of the formaldehyde reduction resulting from microbial degradation. Microorganisms added to the rhizosphere solution enhanced phytoremediation by increasing the downward transport of formaldehyde and its release by roots. Results suggest a new means to screen for efficient plant species that can be used for phytoremediation of indoor air.