The Potted-Plant Microcosm Substantially Reduces Indoor Air VOC Pollution: II. Laboratory Study

Abstract

Indoor air-borne loads of volatile organic compounds (VOCs) are usually significantly higher than those outdoors, and chronic exposures can cause health problems. Our previous laboratory studies have shown that the potted-plant microcosm, induced by an initial dose, can eliminate high airborne VOC concentrations, the primary removal agents being potting-mix microorganisms, selected and maintained in the plant/root-zone microcosm. Our office field-study, reported in the preceding paper, showed that, when total VOC (TVOC) loads in reference offices (0 plants) rose above about 100 ppb, levels were generally reduced by up to 75% (to <100 ppb) in offices with any one of three planting regimes. The results indicate the induction of the VOC removal mechanism at TVOC levels above a threshold of about 100 ppb. The aims of this laboratory dose-response study were to explore and analyse this response. Over from 5 to 9 days, doses of 0.2, 1.0, 10 and 100 ppm toluene and m-xylene were applied and replenished, singly and as mixtures, to potted-plants of the same two species used in the office study. The results confirmed the induction of the VOC removal response at the lowest test dosage, i.e in the middle of the TVOC range found in the offices, and showed that, with subsequent dosage increments, further stepwise induction occurred, with rate increases of several orders of magnitude. At each dosage, with induction, VOC concentrations could be reduced to below GC detection limits (<20 ppb) within 24 h. A synergistic interaction was found with the binary mixtures, toluene accelerating m-xylene removal, at least at lower dosages. The results of these two studies together demonstrate that the potted-plant microcosm can provide an effective, self-regulating, sustainable bioremediation or phytoremediation system for VOC pollution in indoor air.

Improvement of Indoor Air Quality by Houseplants in New-built Apartment Buildings

“…Moreover, previous studies found three major channels of air-pollutant decomposition by houseplants: most air-pollutant decomposition was a result of photosynthesis by houseplants after absorbing air pollutants through the stomata (Kondo and Saji, 1992), and the remainder was adsorption by media (Orwell et al, 2006;Wood et al, 2002) or with the help of microbes in the rhizosphere (Godish and Guindon, 1989). In a 1-m 3 airtight chamber, a pot without plants caused about a 100-μg decrease in formaldehyde for 5 h but a pot of fatsia plants resulted in an approximately 700-μg decrease during the same period.…”

Nature and Health

“…Indoor plants, especially such species as English ivy and spider plant, have been shown to reduce levels of many VOCs (81,140). Bacteria in the soil may account for some VOC scavenging attributed to the plants (102).…”

Phytoremediation on Air Pollution

“…Furthurmore, hydroxylation is considered to be the first step of the aromatic ring cleavage of benzene and toluene in higher plants (Ugrekhelidze, 1997). Besides, a substantial role of microorganisms in the growth medium in removing benzene and toluene was also reported by previous researches (Orwell et al, 2004;Orwell et al, 2006;Wood et al, 2002;Wood et al, 2006).…”