The Potted-Plant Microcosm Substantially Reduces Indoor Air VOC Pollution: I. Office Field-Study

Volatile organic compounds (VOCs) are major contaminants of indoor air, with concentrations often several times higher than outdoors. They are recognized as causative agents of “building-related illness” or “sick-building syndrome”. Our previous laboratory test-chamber studies have shown that the potted-plant/root-zone microorganism microcosm can eliminate high concentrations of air-borne VOCs within 24 hours, once the removal response has been induced by an initial dose. However, the effectiveness of the potted-plant microcosm in ‘real-world’ indoor spaces has never previously been tested experimentally. This paper reports the results of a field-study on the effects of potted-plant presence on total VOC (TVOC) levels, measured in 60 offices (12 per treatment), over two 5–9 week periods, using three planting regimes, with two ‘international indoor-plant’ species. Fourteen VOCs were identified in the office air. When TVOC loads in reference offices rose above 100 ppb, large reductions, of from 50 to 75% (to <100 ppb), were found in planted offices, under all planting regimes The results indicate that air-borne TVOC levels above a threshold of about 100 ppb stimulate the graded induction of an efficient metabolic VOC-removal mechanism in the microcosm. Follow-up laboratory dose-response experiments, reported in the following paper, confirm the graded induction response, over a wide range of VOC concentrations. The findings together demonstrate that potted-plants can provide an efficient, self-regulating, low-cost, sustainable, bioremediation system for indoor air pollution, which can effectively complement engineering measures to reduce indoor air pollution, and hence improve human wellbeing and productivity.     

Removal of Benzene by the Indoor Plant/Substrate Microcosm and Implications for Air Quality

Water, Air, &; Soil Pollution - The quality of the indoor environment has become a major health consideration, since urban-dwellers spend 80-90% of their time indoors, where air pollution can be...     

Profiling indoor plants for the amelioration of high CO2 concentrations

Research over the last three decades has shown that indoor plants can reduce most types of urban air pollutants, however there has been limited investigation of their capacity to mitigate elevated levels of CO₂. This study profiled the CO₂ removal potential of eight common indoor plant species, acclimatised to both indoor and glasshouse lighting levels, to develop baseline data to facilitate the development of indoor plant installations to improve indoor air quality by reducing excess CO₂ concentrations. The results indicate that, with the appropriate choice of indoor plant species and a targeted increase in plant specific lighting, plantscape installations could be developed to remove a proportion of indoor CO₂. Further horticultural research and development will be required to develop optimum systems for such installations, which could potentially reduce the load on ventilation systems.     

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

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 air-borne 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.     

In vitro propagation of Blandfordia grandiflora (Liliaceae)

Multiple shoots were obtained when single shoot tips of Blandfordia grandiflora were exposed to different concentrations of kinetin, N6~ benzylaminopurine (BAP) and N6- isopentenylaminopurine (2iP). The best multiplication results were obtained when explants were subjected to kinetin at 8 (iM BAP at 0.5,2 and 8 (iM and 2iP at 2,8,32 and 128 |iM. Preliminary rooting trials were performed with three different auxins: indo- lebutyric acid (IB A), naphthalene acetic acid (NAA) and indole acetic acid (I A A). IB A at a concentration of 8 |iM and IAA at a concentration of 32 |xM gave highest root number, but when transplanted to the glasshouse, the best surviving plantlets were those treated with 2 |xM of IBA or 0.5 μM of IAA.     

Short-term responses of two contrasting species of earthworms in an agricultural soil amended with coal fly-ash

With the renewed interest in the use of coal fly-ash for amendment of agricultural soils in Australia, we assessed how earthworms, as indicators of soil health, responded to this ameliorant. We assessed survival, weight, burrowing and elemental concentrations for earthworms of a native unnamed Megascolecid species and of exotic Aporrectodea trapezoides in intact soil cores treated with an alkaline fly-ash at rates equivalent to 0, 5 and 25 t/ha over 6 weeks. Fly-ash did not affect survival, growth, number of burrows created or phosphorus solubilisation. Transfer of the earthworms to the new environment having vastly different pH from where they were collected, and possibly overcrowding, caused mortality in the soil cores for all treatments. A. trapezoides that had smaller individuals suffered mortality of 12% compared with 23% for the larger earthworms of Megascolecids. Earthworms of Megascolecids each increased their weight by 0.24g (25% of their original weight) while those of A. trapezoides lost 0.18g each (21% of their original weight). The difference in growth between the two earthworms was associated with grazing habit and probably with the large difference in the pH between source soil and that of the core soil. Megascolecids appeared to minimize grazing on ash-tainted soil and so ingested less Zn, which was more abundant in the fly-ash than in the soil, compared with A. trapezoides that had elevated concentration of this metal. Extractable P in the soil was increased with both species of earthworms, more so with the exotic species that solubilized 11% more P than the native Megascolecids. The benign influence of fly-ash on survival and growth of worms was associated with the pH of soil remaining unchanged during the six weeks of incubation.