Table 3.
A summary of passive pot plant studies (2012–2022) that detail the removal of various VOCs from static chambers, for studies before this time period see (Pettit et al. 2018b)
| Study | Year | Pollutants | Starting concentrations | Plant species | Substrate information | Chamber volume | Removal rate/efficiency | Removal mechanism |
|---|---|---|---|---|---|---|---|---|
| (Treesubsuntorn and Thiravetyan) | 2012 | Benzene | 20 ppm |
C. seifrizii, S. aureus, S. trifasciata, P. domesticum, I. craib, M. acuminate E. aureum, and D. sanderiana |
Pot covered with aluminium foil | N/A | Removal at 72 h range from 43–77% depending on species |
Benzene can be removed through both stomatal uptake and through crude wax, during dark conditions cuticle wax uptake was more prevalent However, light conditions still revealed optimum pollutant uptake |
| (Irga et al.) | 2013 | Benzene | 25 ppmv | S. podophyllum |
Planted Hydroculture Substrate only |
15.86 L 15 L 500 ml |
50% removal at 1444 µg/m3/h1/pot 50% removal at 739 µg/m3/h1/pot 50% removal at 519 µg/m3/h1/pot |
Benzene removal within hydroculture substrate was slower than traditional potted plants. Concluded that the more diverse bacterial community within the potting substrate increased VOC removal |
| (Sriprapat and Thiravetyan) | 2013 | Benzene, Toluene, Ethylbenzene, Xylene | 20 ppm of each BTEX | Z. zamiifolia | 1:1 soil to coconut coir | 15.6 L |
0.96 ± 0.01 (B), 0.92 ± 0.02 (T), 0.92 ± 0.02 (E), 0.86 ± 0.07 (X), mmolm−2 at 72 h |
Benzene may be taken up faster than other BTEX due being a smaller molecule. BTEX toxicity was not found during 3-day fumigation The ratio of stomata and cuticles showed that 80% of benzene, 76% of toluene, 75% of ethylbenzene, and 73% of xylene were removed by stomatal pathways, while 20, 23, 25, and 26% were removed by non-stomatal pathways or cuticles |
| (Torpy et al.) | 2013 | Benzene | 25 ppmv (80 mg/m3) | S. wallisi | Standard potting | 216 L | Bio stimulation increased removal rates by ~ 27% | Provided evidence of the importance of microorganisms in pollutant removal, bio stimulated plants demonstrated higher benzene removal rates |
| (Treesubsuntorn et al.) | 2013 | Benzene | 20 ppm | 21 ornamental plants from commercial Thai shop | No pot just leaf | 6 L | 1.10 – 23.46 µmol/g of plant material over 3 days | High quantities of wax in the cuticle produced higher removal rates for benzene across the plant species |
| (Kim et al.) | 2014 | Toluene, Xylene | 1 µ/L | F. japonica and D. fragrans |
5:1:1 (Bark, humus, sand) |
996.3 L | N/A |
F. japonica exhibited a more rapid rate of removal for toluene and xylene than D. fragrans Efficiency of VOC removal increased as the root zone volume increased |
| (Sriprapat, Suksabye, et al.) | 2014 | Toluene, Ethylbenzene | 20 ppm or 12 µm | 12 ornamental plant species from Thailand florest | 1:1 soil to coconut coir | 15.6 L |
~ 77% removal at 72 h (Toluene) across 12 plants ~ 70% removal at 72 h (Ethylbenzene) across 12 plant |
Highest toluene and ethylbenzene removal were observed in S. trifasciata and C. comosum respectively Cuticle wax composition showed higher removal. Hexadecenoic acid was present |
| (Mosaddegh et al.) | 2014 | Benzene, Toluene, Ethylbenzene, Xylene, Methanol, Acetone, Acetonitrile | 2 ppm | D. deremensis and O. microdasy | Soil | 50 L |
3.2 mg/m3 per day (O.microdasy) 1.46 mg/m3 per day (D.deremensis) |
Benzene removal pathways by plant or substrate media was not explored |
| (Su and Liang) | 2015 | Formaldehyde | 30, 60 or 120 mg/L | C. comosum |
Hydroponically with Hoagland’s solution |
52.5 L |
135 µg/h/plant (maximum) |
Majority of formaldehyde was taken up into the plant’s roots Plant leaves showed an ability to dissipate formaldehyde which increased over time |
| (Kim et al.) | 2016 | Toluene, xylene | 0.5 µL/L of toluene with 0.3 µL/L of xylene | S. actinophylla and F. benghalensis |
5:1:1 (Bark, humus, sand) |
996.3 L |
Removal efficiency of toluene and xylene was 13.3 and 7.0 µg/m3/m2 leaf area over a 24 h period in S. actinophylla, and was 13.0 and 7.3 µg/m3/m2 leaf area for F. benghalensis |
Concluded that root zone is the main contributor for toluene and xylene removal with transport to the plant stem also playing a role, with 47% of toluene and 60% of xylene transported via plant stem for both species |
| (Sriprapat and Thiravetyan) | 2016 | Benzene | 170 µg |
S. podophyllum, S.trifasciata, E.milii, C.comosum, E.aureum, D.sanderiana, H.helix, and C. ternatea |
Murashige and Skoog (MS) medium supplemented with Gamborg vitamin | undisclosed | 25.3 – 34 µmol m−2 h−1 |
Most efficient plant for benzene removal was C. comosum Cronobacter sp., Pseudomonas sp. and Enterobacter sp. Highlighted importance of endophytic and epiphytic bacteria in benzene removal |
| (Hörmann et al.) | 2017 | Toluene, 2 – ethylhexanol | 20.0 mg/m3 (Toluene) and 14.6 mg/m3 (2-ethylhexanol) | D. maculata and S. wallisii | Potting soil | 240 L |
~ 70% (Toluene) 48 h ~ 90% (2-ethylhexanol) |
No significant difference between empty chambers and planted chambers for 2-ethylhexanol removal Significant VOC adsorption by both chamber surfaces and aerial plant parts and potting soil was evident for toluene |
| (Chen et al.) | 2017 | Formaldehyde | ≥ 5 ppm | H. helix | Sterilized media | 225 L | ~ 4 ppm over 17.1 h | Showed that potted H. helix reduced 70% of the required time to reach 0.5 ppm of gaseous formaldehyde when compared with natural dissipation. Potted H. helix also removed residual formaldehyde |
| (Setsungnern et al.) | 2017 | Benzene | 500 ppm | C.comosum | Roots wrapped in tissue paper and aluminium foil | 15.6 L |
31.37% removal under 1:1 LED light 24.75% removal under fluorescent light |
Benzene removal by plants was best under LED light, helping plants produce more brassinosteroids to degrade benzene and utilize it as a carbon source |
| (Hörmann et al.) | 2018 | Toluene, 2-ethylhexanol | 20.0 mg/m3 (Toluene) and 14.6 mg/m3 (2-ethylhexanol) | D. maculata, S. wallisii and A. densiflorus | Undisclosed | 240 L | 1.4 – 1.5 L h−1 m−2 | Specifically looked at aerial plant part removal rather than the whole system. Concluded aerial plant parts have no major impact on chamber air quality |
| (Teiri et al.) | 2018 | Formaldehyde | 0.66 – 16.4 mg/m3 | C. elegans | Loamy soil | 375 L | 1.47 mg/m2/h | Substantial contribution of soil and roots for formaldehyde removal, attributed to microorganisms |
| (Budaniya and Rai) | 2022 | Particulate matter | 350 – 750 µg/m3 |
H.splendens, C.macrocarpa, A.heterophylla, P.orientalis, P.roebelenii, E.purpureum, D.reflexa, S.trifasciata, E.aureum, F.retusa, C. variegatum |
Undisclosed | 210 L |
CADRs; 0.002 ± 0.004 m3/h (needle leave plants) 0.084 ± 0.009 m3/h (broad-leaved plants |
Significantly lower CADRs for passive plant systems compared to filter-based purifiers (170–800 m3/h). Concluded that passive plant systems cannot compete with conventional air purifiers, large quantities of plants would be required to achieve modest indoor PM concentrations |
| (Liu et al.) | 2022 | CO2, HCHO, TVOC, PM10, PM2.5 |
795 ppm (CO2) 120 µg m−3 (HCHO) 2,786 µg m−3 (TVOC) 87 |
E.aureum | Potting soil | 216 L |
Removal efficiency over 12 h; 26.87% (CO2) 61.73% (HCHO) 30.04% (TVOC) 81.97% (PM10) 79.2% (PM2.5) |
Removal pathways were not explored |
Table includes pollutant type, starting concentration, plant species, substrate information, chamber volume and efficiency. Removal mechanisms as described by the authors of each study are also presented