Assessment of filtration efficiency and physiological responses of selected plant species to indoor air pollutants (toluene and 2-ethylhexanol) under chamber conditions

Pettit

et al. 2019

Environ Sci Pollut Res

Volatile organic compounds (VOCs) are of public concern due to their adverse health effects. Botanical air filtration is a promising technology for reducing indoor air contaminants, but the underlying mechanisms are not fully understood. This study assessed active botanical biofilters for their single-pass removal efficiency (SPRE) for benzene, ethyl acetate and ambient total volatile organic compounds (TVOC)s, at concentrations of in situ relevance. Biofilters containing four plant species (Chlorophytum orchidastrum, Nematanthus glabra, Nephrolepis cordifolia 'duffii' and Schefflera arboricola) were compared to discern whether plant selection influenced VOC SPRE. Amongst all tested plant species, benzene SPREs were between 45.54-59.50%, with N. glabra the most efficient. The botanical biofilters removed 32.36-91.19% of ethyl acetate, with C. orchidastrum and S. arboricola recording significantly higher ethyl acetate SPREs than N. glabra and N. cordifolia. These findings thus indicate that plant type influences botanical biofilter VOC removal. It is proposed that ethyl acetate SPREs were dependent on hydrophilic adsorbent sites, with increasing root surface area, root diameter and root mass all associated with increasing ethyl acetate SPRE. The high benzene SPRE of N. glabra is likely due to the high wax content in its leaf cuticles. The SPREs for the relatively low levels of ambient TVOCs were consistent amongst plant species, providing no evidence to suggest that in situ TVOC removal is influenced by plant choice. Nonetheless, as inter-species differences do exist for some VOCs, botanical biofilters using a mixture of plants is proposed. Keywords Air pollution; botanical biofilters; phytoremediation; green walls; VOCs 'active green walls', which utilise mechanical assistance to funnel air into the biofilter substrate, improves their bioremediation efficiency to the extent that functional air remediation is probable (Torpy et al. 2015). These systems may also be practical for large infrastructure use, given that they are accessible, robust, cost-effective and have a low-energy footprint. Although the available types of botanical biofiltration systems differ in design, they all use active airflow facilitated with devices such as impellers that increase the airflow across or through the systems and therefore allow larger volumes of air to be processed by the biofilter. Whilst there is a growing body of literature that demonstrates the air pollutant remediation capabilities of this technology (Pettit et al. 2019), to date, the potential for plant selection to enhance botanical biofilters ability to filter some of the more dangerous air pollutants is required. Plant selection is known to have an influence on VOC removal efficiency for static, potted-plant systems (e.g. Kim et al. 2010). Whilst the nature of the plant characteristics that determine these effects have yet to be resolved, there may be phylogenetic associations where certain groups of plants are more effective for the removal of certain forms of VOC (Ki...

Section: Discussionmentioning

confidence: 99%

Does plant species selection in functional active green walls influence VOC phytoremediation efficiency?

Pettit

et al. 2019

Environ Sci Pollut Res

“…This is comparable to quantities of bioactive VOCs reported by others ( Ryu et al, 2003 ; Zou et al, 2010 ; Blom et al, 2011 ; Park et al, 2015 ). Additionally, one of the bioactive VOC tested here (2-ethyl-1-hexanol) is phytotoxic to ornamental plants ( Hörmann et al, 2018 ). Demonstrating whether similar effects occur under field conditions will be a challenge that will require to carefully take soil parameters as well as source and sink mechanisms under consideration.…”

Section: Discussionmentioning

confidence: 99%

Fungi Indirectly Affect Plant Root Architecture by Modulating Soil Volatile Organic Compounds

et al. 2018

The plant-growth modulating effect of microbial volatile organic compounds (VOCs) has been demonstrated repeatedly. This has most often been performed by exposing plants to VOC released by microbes grown on nutrient rich media. Here, we used soil instead to grow fungi of the Fusarium genus and investigate how VOCs emitted by this system influenced the development of Arabidopsis plants. The volatile profiles of Fusarium strains grown in soil and malt extract were also compared. Our results demonstrate that distinct volatile signatures can be attributed to different Fusarium genetic clades but also highlight a major influence of the growth medium on volatile emission. Furthermore, all soil-grown Fusarium isolates increased primary root length in Arabidopsis by decreasing VOC concentrations in soil. This result represents a major paradigm shift in plant-microbe interactions since growth modulating effects have been attributed so far to the emission and not the consumption of volatile signals.

“…These species were Spathiphyllum wallisii (peace lily) and Syngonium podophyllum (arrowhead vine). These species are both common indoor houseplants and green wall species, and both have been tested for their capacity to phytoremediate a range of VOCs [33,[45][46][47][48][49][50]. All tested plants were grown in their biofilters in a glasshouse (Sydney, Australia) for~8 weeks prior to testing.…”

Section: Biofilter Design and Plant Selectionmentioning

confidence: 99%

An Assessment of the Suitability of Active Green Walls for NO2 Reduction in Green Buildings Using a Closed-Loop Flow Reactor

et al. 2019

Nitrogen dioxide (NO 2 ) is a common urban air pollutant that is associated with several adverse human health effects from both short and long term exposure. Additionally, NO 2 is highly reactive and can influence the mixing ratios of nitrogen oxide (NO) and ozone (O 3 ). Active green walls can filter numerous air pollutants whilst using little energy, and are thus a candidate for inclusion in green buildings, however, the remediation of NO 2 by active green walls remains untested. This work assessed the capacity of replicate active green walls to filter NO 2 at both ambient and elevated concentrations within a closed-loop flow reactor, while the concentrations of NO and O 3 were simultaneously monitored. Comparisons of each pollutant's decay rate were made for green walls containing two plant species (Spathiphyllum wallisii and Syngonium podophyllum) and two lighting conditions (indoor and ultraviolet). Biofilter treatments for both plant species exhibited exponential decay for the biofiltration of all three pollutants at ambient concentrations. Furthermore, both treatments removed elevated concentrations of NO and NO 2 , (average NO 2 clean air delivery rate of 661.32 and 550.8 m 3 ·h −1 ·m −3 of biofilter substrate for the respective plant species), although plant species and lighting conditions influenced the degree of NO x removal. Elevated concentrations of NO x compromised the removal efficiency of O 3 . Whilst the current work provided evidence that effective filtration of NO x is possible with green wall technology, long-term experiments under in situ conditions are needed to establish practical removal rates and plant health effects from prolonged exposure to air pollution.