Decay Kinetics of Toluene Phytoremediation Stimulation

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  • 1 Urban Agriculture Research Division, National Institute of Horticultural and Herbal Science, Rural Development Administration, Suwon 441-440, Korea
  • 2 Department of Horticulture, 1111 Plant Sciences Building, University of Georgia, Athens, GA 30602-7273

Begonia maculata, Ardisia crenata, and Ardisia japonica plants exposed to 3.5 ppm toluene in air for 12 h displayed a pronounced stimulation (358%, 318%, and 252%, respectively) in subsequent toluene removal potential. The duration of the stimulation effect, monitored over 3 weeks, was short-lived decaying to prestimulation levels within 1 to 7 days depending on species. Elevated phytoremediation rate was dependent on the continued presence of toluene. The rapid rate of increase in phytoremediation and subsequent decay points toward a response mediated by changes in gene expression by the plant, microorganisms within the media, or both rather than an alteration in microbe population. A better understanding of the stimulation response may facilitate the use of plants for indoor air remediation in homes and offices.

Abstract

Begonia maculata, Ardisia crenata, and Ardisia japonica plants exposed to 3.5 ppm toluene in air for 12 h displayed a pronounced stimulation (358%, 318%, and 252%, respectively) in subsequent toluene removal potential. The duration of the stimulation effect, monitored over 3 weeks, was short-lived decaying to prestimulation levels within 1 to 7 days depending on species. Elevated phytoremediation rate was dependent on the continued presence of toluene. The rapid rate of increase in phytoremediation and subsequent decay points toward a response mediated by changes in gene expression by the plant, microorganisms within the media, or both rather than an alteration in microbe population. A better understanding of the stimulation response may facilitate the use of plants for indoor air remediation in homes and offices.

Indoor plants have the ability to remove various volatile organic compounds (VOCs) (Table 1) and may be useful for remediating the air in homes and offices, reducing the potential deleterious health effects on persons exposed. The phytoremediation effect is the result of both the plant and associated microorganisms in the media (Chun et al., 2010; Orwell et al., 2004; Son et al., 2000; Wolverton, 1986; Wolverton and Wolverton, 1993; Wood et al., 2002), the latter being the primary contributor to VOC removal during the night (Kim et al., 2008). Removal efficiency is known to vary widely among plant species, the VOC in question, and other factors (Kays, 2011).

Table 1.

Volatile organic compounds that have been shown to be removed from air by plants.

Table 1.

The U.S. Environmental Protection Agency (EPA) reported detection of more than 900 VOCs in the air of public buildings (EPA, 1989) and in a Finnish study (Kostiainen, 1995), over 200 VOCs were identified in each of 26 homes. Toluene is a highly toxic VOC commonly found as a component of indoor air, the presence of which can represent a serious health hazard. It is readily absorbed through the respiratory tract and to a lesser extent through the skin (EPA, 1990). Exposure to high levels is known to affect the kidneys, nervous system, liver, brain, and heart. Short-term exposure of humans to toluene (100 ppm v/v or greater) has elicited central nervous system effects such as fatigue, confusion, poor coordination, impairment of reaction time, perception, and motor control and function (NTP, 2000) in addition to poor performance on cognitive tests and eye and upper respiratory tract irritation (ATSDR, 1989).

We recently demonstrated that the removal efficiency of plants for toluene increased rapidly and markedly with their exposure to the gas (1.3 ppm for 18 h) (Kim et al., 2011). Of the 28 crops tested, 27 displayed an increase in toluene removal efficiency after the initial exposure with the greatest increase occurring after the first exposure. The increase in efficiency between the first and third exposure ranged from 378 μg·m−3·h−1·m−2 leaf area in Pinus densiflora Siebold & Zacc. to –16.6 in Salvia elegans Vahl (mean for all crops, 156 μg·m−3·h−1·m−2) with a maximum increase of over 600%.

Increasing the efficiency of toluene removal in particular and VOCs in general from indoor air is highly advantageous and could facilitate developing a horticultural solution to a serious health problem. Because a better understanding of the mechanism(s) involved may improve use of the response for practical applications, we determined the duration of the toluene stimulation effect on phytoremediation efficiency.

Materials and Methods

Plant materials.

Begonia maculata Raddi, a herbaceous foliage plant, and Ardisia crenata Sims. and Ardisia japonica (Thumb.) Blume, woody foliage plants, were obtained from a commercial market. The plants were transplanted into pots containing a uniform growing medium comprised of Mix #4 (Sun Gro Horticulture, Bellevue, WA), bark-humus (Biocom. Co., Seoul, Korea), and sand at 5:1:1, v/v/v. Mix #4 contained Canadian sphagnum peatmoss (55% to 65% by volume), perlite, dolomitic lime, gypsum, and a wetting agent. The plants were grown in a greenhouse for greater than 1 month after transplanting.

The plants were watered every 3 d with the excess water allowed to drain. All plants were watered the day before the gas treatments. Five pots (19-cm diameter with media volume of 2.2 L), each containing one or more plants (subsequently referred to as a plant), were placed in a chamber with a light intensity of 60 ± 2 μmol·m−2·s−1 using fluorescent lights and a 12-h photoperiod.

Three replicates (chambers) of each species were tested. Chambers without plants were used to determine toluene losses not resulting from the plants (e.g., leakage, adsorption, chemical reactions). Plant height was measured and leaf area determined using a LI-3100 leaf area meter (LI-COR Inc., Lincoln, NE) at the end of the experiment.

Treatment system.

The treatment system consisted of controlled-environment rooms containing the test chambers and a gas generator. The rooms controlled the temperature, light intensity, and relative humidity. The test chambers, as described by Kim et al. (2011), were 1.0 m3 (90 cm wide × 90 cm long × 123 cm high) and impervious to VOCs. Interior air was circulated (6 L·min−1) and tested for toluene concentration at three locations, 12, 70, and 98 cm above the bottom of the chamber.

Gas exposure and measurement.

Toluene gas (1.2 L) was introduced into each test chamber with the plants present, as previously described (Kim et al., 2011), and allowed to equilibrate within the chamber for 15 min. The internal concentration was determined and corrected to 3.5 ppm (13,181 μg·m−3) for the stimulation treatment. The plants remained in the stimulation treatment for 12 h and then were moved to fresh air for 12 h. After the stimulation treatment, the subsequent toluene removal rate by the plants was determined at 0, 1, 2, and 3 weeks after stimulation. Each test date included three replications of five individual plants for a total of 75 plants plus controls (i.e., plants that were not exposed to the toluene stimulation treatment) for each species. Time 0 was after 12 h in fresh air after the toluene stimulation treatment ended. The plants were exposed a 1.3 ppm (4896 μg·m−3) and the rate of toluene removal measured within the chambers after 6 and 12 h as previously described (Kim et al., 2011). Changes in toluene concentration within the chambers were expressed as cumulative removal (μg·m−3·m−2 leaf area) and as removal rate (μg·m−3·h−1·m−2 leaf area). B. maculata and A. japonica were also tested at 0, 1, 3, 5, and 7 d after exposure. Chambers devoid of plants were treated similarly to determine gas losses resulting from chamber effects.

Toluene quantification.

Air samples were collected at the appropriate time intervals using a quartz cold trap [120 mm long, 2.9 mm o.d., 1.0 mm i.d. (inlet), 2.0 mm i.d. (outlet); Markes International Ltd., Llantrisant, U.K.] connected to each chamber with the air collected for 5 min at 5 mL·min−1. An automated thermal desorption system with Air Server autosampler (UNITY; Markes International Ltd.) was connected to the injection port of the gas chromatograph–mass spectroscopy (TRACE DSQ; Thermo Electron Co., Waltham, MA). The desorbed sample was cryofocused at 5 °C for 5 min on the first few centimeters of the column, desorbed at 280 °C, and separated using a ZB-624 capillary column (30-m length × 0.25-mm i.d., 1.40-μm film thickness of 6% cyanopropylphenyl, 94% dimethylpolysiloxane; Phenomenex, Torrance, CA). The injection port temperature was 180 °C with a split ratio of 29:1. Helium was used as the carrier gas at a flow rate of 1.0 mL·min−1. The column temperature was held at 45 °C for 1 min and increased at a rate of 15 °C·min−1 to 100 °C and held for 1 min and then increased at a rate of 5 °C·min−1 to 135 °C.

Data analysis.

Gas concentrations were expressed as μg·m−3 with the data normalized to 24 ± 1 °C and 100 kPa (Hines et al., 1993). Data were expressed as the average of three replicates. The accumulated removal of toluene per unit leaf area [Eq. 1] and the removal efficiency per unit leaf area and time [Eq. 2] were calculated (Kim et al., 2008, 2011) as:

DE1
DE2
where P is the gas concentration measured in a chamber with plants (μL·L−1); Pi the initial gas concentration measured in a chamber with plants (μL·L−1); C the gas concentration measured in a chamber without plants (μL·L−1); Ci the initial gas concentration measured in a chamber without plants (μL·L−1); F the toluene conversion factor for volume (μL·L−1) to mass (mg·m−3); CV the volume of the chamber (m3); L the total leaf area per chamber (m2); and T the gas exposure time (h). The loss of toluene (Ci – C) not resulting from the plant and media was determined using empty chambers.

Results and Discussion

The actual toluene removal rate of B. maculata, A. crenata, and A. japonica increased 358%, 318%, and 252%, respectively, after the initial exposure to toluene. When expressed as accumulated removal on a mass per unit leaf area (μg·m−3·m−2) basis, B. maculata and A. japonica displayed substantially higher increases in phytoremediation as a result of the initial toluene exposure (stimulation treatment) than A. crenata, which had a modest although statistically significant effect (Fig. 1). Each species progressively removed subsequent toluene over the 12-h test period. With the exception of plants that were re-exposed immediately after the initial stimulation exposure (0 time), there were only small differences by 1, 2, or 3 weeks, indicating that the stimulation of toluene removal declines fairly rapidly, essentially reaching pre-exposure phytoremediation rates by 1 week. Assessing changes in the simulation of toluene removal efficiency, expressed as μg·m−3·h−1·m−2 leaf area, the decline in the initial increase in efficiency was striking, essentially reverting back to base levels (unstimulated control plants) within the first week (Fig. 2). The decline was most pronounced in A. japonica, which had the highest overall removal rate of the three species.

Fig. 1.
Fig. 1.

Accumulated removal of toluene (1.3 ppm in air) by potted plants as affected by the length of time after the initial toluene stimulation treatment. Unstimulated plants were not exposed to the stimulation treatment; 0 time indicates assessment of toluene removal rate 12 h after the simulation treatment.

Citation: HortScience horts 47, 8; 10.21273/HORTSCI.47.8.1195

Fig. 2.
Fig. 2.

Changes in the subsequent toluene (1.3 ppm in air) removal rate by potted plants as affected by the length of time (0 to 3 weeks) after the initial toluene stimulation treatment. Unstimulated plants were not exposed to the stimulation treatment; 0 time indicates assessment of toluene removal rate 12 h after the simulation treatment.

Citation: HortScience horts 47, 8; 10.21273/HORTSCI.47.8.1195

In subsequent tests in which the decline in the initial increase in toluene removal efficiency was assessed over a 7-d period, the timing of the decline was more precisely illustrated (Fig. 3). The decay in the stimulation response varied depending on the plant species tested. B. maculata declined essentially back to the initial prestimulation rate in a single day, whereas A. japonica declined progressively over the entire week. The cause of the difference in the rate of loss of the stimulation response between species is not clear. Based on the rapidity of the response, it is highly probable that the stimulation in phytoremediation efficiency with the initial exposure to toluene was the result of changes in gene expression, although whether it was the result of changes in the plant, microorganisms in the media, or both is not known.

Fig. 3.
Fig. 3.

Changes in toluene (1.3 ppm in air) removal rate by potted plants as affected by the length of time (0 to 7 d) after initial toluene stimulation pretreatment. Unstimulated plants were not exposed to the stimulation treatment; 0 time indicates assessment of toluene removal rate 12 h after the simulation treatment.

Citation: HortScience horts 47, 8; 10.21273/HORTSCI.47.8.1195

From a practical standpoint, the stimulation in phytoremediation requires continual exposure to toluene so preconditioning the plants before sale would at this time appear to be of no apparent value. It is significant, however, that the plants can very rapidly alter their metabolism in response to the chemistry of the surrounding air, greatly increasing their phytoremediation effectiveness. In addition to toluene, a stimulation in phytoremediation efficiency has been shown for benzene (Orwell et al., 2004) and formaldehyde (Kil et al., 2008), the latter being structurally very dissimilar from benzene and toluene.

It is evident that in closed systems, certain plant species can effectively remove a cross-section of VOCs; however, how effectively this translates to real-world situations in which there is a continual flux of VOCs being released into and escaping from the air in homes and offices remains to be seen. Maximizing the VOC removal efficiency of plants will help to expand the range of situations in which plants can be effectively used.

Literature Cited

  • ATSDR 1989 Toxicological profile for toluene. Agency for Toxic Substance and Disease Registry, Atlanta, GA

  • Aydongan, A. & Montoya, L.D. 2011 Formaldehyde removal by common indoor plant species and various growing media Atmos. Environ. 45 2675 2682

  • Chen, L., Yurimoto, H., Li, K., Orita, I., Akita, M., Kato, N., Sakai, Y. & Izui, K. 2010 Assimilation of formaldehyde in transgenic plants due to the introduction of the bacterial ribulose monophosphate pathway genes Biosci. Biotechnol. Biochem. 74 627 635

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    • Export Citation
  • Chun, S.-C., Yoo, M.H., Moon, Y.S., Shin, M.H., Son, K.-C., Chung, I.-M. & Kays, S.J. 2010 Effect of bacterial population from rhizosphere of various foliage plants on removal of indoor volatile organic compounds Kor. J. Hort. Sci. Technol. 28 476 483

    • Search Google Scholar
    • Export Citation
  • Cornejo, J.J., Munoz, F.G., Ma, C.Y. & Stewart, A.J. 1999 Studies on the decontamination of air by plants Ecotoxicology 8 311 320

  • EPA 1989 Report to Congress on indoor air quality. Vol. II: Assessment and control of indoor air pollution. EPA/400/1-89/001C

  • EPA 1990 Drinking water criteria document for toluene. Environmental Assessment Office, Office of Health and Environmental Assessment, U.S. Environmental Protection Agency, Cincinnati, OH

  • Hines, A.L., Ghosh, T.K., Loylka, S.K. & Warder, R.C. Jr 1993 Indoor air: Quality and control. Prentice Hall, Englewood Cliffs, NJ

  • Kays, S.J. 2011 Phytoremediation of indoor air—Current state of the art, p. 3–21. In: Kim, K.J. (ed.). The value creation of plants for future urban agriculture. Nat. Inst. Hort. Herbal Science, RDA, Suwon, Korea

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    • Search Google Scholar
    • Export Citation
  • Kim, K.J., Jeong, M.I., Lee, D.W., Song, J.S., Kim, H.D., Yoo, E.H., Jeong, S.J., Lee, S.Y., Kays, S.J., Lim, Y.W. & Kim, H.H. 2010 Variation in formaldehyde removal efficiency among indoor plant species HortScience 45 1489 1495

    • Search Google Scholar
    • Export Citation
  • Kim, K.J., Kil, M.J., Song, J.S., Yoo, E.H., Son, K.C. & Kays, S.J. 2008 Efficiency of volatile formaldehyde removal by indoor plants: Contribution of aerial plant parts versus the root-zone J. Amer. Soc. Hort. Sci. 133 1 6

    • Search Google Scholar
    • Export Citation
  • Kim, K.J., Yoo, E.H., Jeong, M.I., Song, J.S., Lee, S.Y. & Kays, S.J. 2011 Changes in the phytoremediation potential of indoor plants with exposure to toluene HortScience 46 1646 1649

    • Search Google Scholar
    • Export Citation
  • Kostiainen, R. 1995 Volatile organic compounds in the indoor air of normal and sick houses Atmos. Environ. 29 693 702

  • Liu, Y.J., Mu, Y.J., Zhu, Y.G., Ding, H. & Arens, N.C. 2007 Which ornamental plant species effectively remove benzene from indoor air? Atmos. Environ. 41 650 654

    • Search Google Scholar
    • Export Citation
  • NTP 2000 Toxicology and carcinogenesis studies of toluene in F344/N rats and B6C3F1 mice (inhalation studies). Technical Rept. Series No. 371, National Toxicology Program, National Institutes of Health, U.S. Department of Health and Human Service, Public Health Service, Research Triangle Park, NC

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    • Search Google Scholar
    • Export Citation
  • Orwell, R.L., Wood, R.L., Tarran, J., Torpy, F. & Burchett, M.D. 2004 Removal of benzene by the indoor plant/substrate microcosm and implications for air quality Water Air Soil Pollut. 157 193 207

    • Search Google Scholar
    • Export Citation
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    • Search Google Scholar
    • Export Citation
  • Sawada, A. & Oyabu, T. 2008 Purification characteristics of pothos for airborne chemicals in growing conditions and its evaluation Atmos. Environ. 42 594 602

    • Search Google Scholar
    • Export Citation
  • Son, K.C., Lee, S.H., Seo, S.G. & Song, J.E. 2000 Effects of foliage plants and potting soil on the absorption and adsorption of indoor air pollutants J. Korean Soc. Hort. Sci. 41 305 310

    • Search Google Scholar
    • Export Citation
  • Tani, A. & Hewitt, C.N. 2009 Uptake of aldehydes and ketones at typical indoor concentrations by houseplants Environ. Sci. Technol. 43 8338 8343

  • Tarran, J., Torpy, F. & Burchett, M. 2007 Use of living pot-plants to cleanse indoor air—Research review. Proc. Sixth Intern. Conf. on Indoor Air Quality, Ventilation & Energy Conservation in Buildings–Sustainable Built Environment, Sendai, Japan

  • Wolverton, B.C. 1986 Houseplants, indoor air pollutants, and allergic reactions. Rept., National Aeronautics Space Administration, Stennis Space Center, MS

  • Wolverton, B.C., McDonald, R.C. & Watkins, E.A. Jr 1984 Foliage plants for removing indoor air pollution from energy-efficient homes Econ. Bot. 38 224 228

    • Search Google Scholar
    • Export Citation
  • Wolverton, B.C. & Wolverton, J.D. 1993 Plants and soil microorganisms: Removal of formaldehyde, xylene, and ammonia from the indoor environment J. Miss. Acad. Sci. 38 11 15

    • Search Google Scholar
    • Export Citation
  • Wood, R.A., Orwell, R.L., Tarran, J., Torpy, F. & Burchett, M. 2002 Potted-plant/growth media interactions and capacities for removal of volatiles from indoor air J. Hort. Sci. Biotechnol. 77 120 129

    • Search Google Scholar
    • Export Citation
  • Xu, Z., Wang, L. & Hou, H. 2011 Formaldehyde removal by potted plant-soil systems J. Hazard. Materials 192 314 318

  • Yang, D.S., Pennisi, S.V., Son, K.C. & Kays, S.J. 2009 Screening indoor plants for volatile organic pollutant removal efficiency HortScience 44 1377 1381

    • Search Google Scholar
    • Export Citation
  • Yoo, M.H., Kwon, Y.J., Son, K.C. & Kays, S.J. 2006 Efficacy of indoor plants for the removal of single and mixed volatile organic pollutants and physiological effects of the volatiles on the plants J. Amer. Soc. Hort. Sci. 131 452 458

    • Search Google Scholar
    • Export Citation

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Contributor Notes

To whom reprint requests should be addressed; e-mail kaysstan@uga.edu.

  • View in gallery

    Accumulated removal of toluene (1.3 ppm in air) by potted plants as affected by the length of time after the initial toluene stimulation treatment. Unstimulated plants were not exposed to the stimulation treatment; 0 time indicates assessment of toluene removal rate 12 h after the simulation treatment.

  • View in gallery

    Changes in the subsequent toluene (1.3 ppm in air) removal rate by potted plants as affected by the length of time (0 to 3 weeks) after the initial toluene stimulation treatment. Unstimulated plants were not exposed to the stimulation treatment; 0 time indicates assessment of toluene removal rate 12 h after the simulation treatment.

  • View in gallery

    Changes in toluene (1.3 ppm in air) removal rate by potted plants as affected by the length of time (0 to 7 d) after initial toluene stimulation pretreatment. Unstimulated plants were not exposed to the stimulation treatment; 0 time indicates assessment of toluene removal rate 12 h after the simulation treatment.

  • ATSDR 1989 Toxicological profile for toluene. Agency for Toxic Substance and Disease Registry, Atlanta, GA

  • Aydongan, A. & Montoya, L.D. 2011 Formaldehyde removal by common indoor plant species and various growing media Atmos. Environ. 45 2675 2682

  • Chen, L., Yurimoto, H., Li, K., Orita, I., Akita, M., Kato, N., Sakai, Y. & Izui, K. 2010 Assimilation of formaldehyde in transgenic plants due to the introduction of the bacterial ribulose monophosphate pathway genes Biosci. Biotechnol. Biochem. 74 627 635

    • Search Google Scholar
    • Export Citation
  • Chun, S.-C., Yoo, M.H., Moon, Y.S., Shin, M.H., Son, K.-C., Chung, I.-M. & Kays, S.J. 2010 Effect of bacterial population from rhizosphere of various foliage plants on removal of indoor volatile organic compounds Kor. J. Hort. Sci. Technol. 28 476 483

    • Search Google Scholar
    • Export Citation
  • Cornejo, J.J., Munoz, F.G., Ma, C.Y. & Stewart, A.J. 1999 Studies on the decontamination of air by plants Ecotoxicology 8 311 320

  • EPA 1989 Report to Congress on indoor air quality. Vol. II: Assessment and control of indoor air pollution. EPA/400/1-89/001C

  • EPA 1990 Drinking water criteria document for toluene. Environmental Assessment Office, Office of Health and Environmental Assessment, U.S. Environmental Protection Agency, Cincinnati, OH

  • Hines, A.L., Ghosh, T.K., Loylka, S.K. & Warder, R.C. Jr 1993 Indoor air: Quality and control. Prentice Hall, Englewood Cliffs, NJ

  • Kays, S.J. 2011 Phytoremediation of indoor air—Current state of the art, p. 3–21. In: Kim, K.J. (ed.). The value creation of plants for future urban agriculture. Nat. Inst. Hort. Herbal Science, RDA, Suwon, Korea

  • Kil, M.J., Kim, K.J., Pak, C.H., Kim, H.H. & Lim, Y.W. 2008 Effects of growing media and exposure frequency on the volatile formaldehyde removal in potted Epipremnuma ureum Kor. J. Hort. Sci. Technol. 26 325 330

    • Search Google Scholar
    • Export Citation
  • Kim, K.J., Jeong, M.I., Lee, D.W., Song, J.S., Kim, H.D., Yoo, E.H., Jeong, S.J., Lee, S.Y., Kays, S.J., Lim, Y.W. & Kim, H.H. 2010 Variation in formaldehyde removal efficiency among indoor plant species HortScience 45 1489 1495

    • Search Google Scholar
    • Export Citation
  • Kim, K.J., Kil, M.J., Song, J.S., Yoo, E.H., Son, K.C. & Kays, S.J. 2008 Efficiency of volatile formaldehyde removal by indoor plants: Contribution of aerial plant parts versus the root-zone J. Amer. Soc. Hort. Sci. 133 1 6

    • Search Google Scholar
    • Export Citation
  • Kim, K.J., Yoo, E.H., Jeong, M.I., Song, J.S., Lee, S.Y. & Kays, S.J. 2011 Changes in the phytoremediation potential of indoor plants with exposure to toluene HortScience 46 1646 1649

    • Search Google Scholar
    • Export Citation
  • Kostiainen, R. 1995 Volatile organic compounds in the indoor air of normal and sick houses Atmos. Environ. 29 693 702

  • Liu, Y.J., Mu, Y.J., Zhu, Y.G., Ding, H. & Arens, N.C. 2007 Which ornamental plant species effectively remove benzene from indoor air? Atmos. Environ. 41 650 654

    • Search Google Scholar
    • Export Citation
  • NTP 2000 Toxicology and carcinogenesis studies of toluene in F344/N rats and B6C3F1 mice (inhalation studies). Technical Rept. Series No. 371, National Toxicology Program, National Institutes of Health, U.S. Department of Health and Human Service, Public Health Service, Research Triangle Park, NC

  • Orwell, R.L., Wood, R.L., Burchett, M.D., Tarran, J. & Torpy, F. 2006 The potted-plant microcosm substantially reduces indoor air VOC pollution: II. Laboratory study Water Air Soil Pollut. 177 59 80

    • Search Google Scholar
    • Export Citation
  • Orwell, R.L., Wood, R.L., Tarran, J., Torpy, F. & Burchett, M.D. 2004 Removal of benzene by the indoor plant/substrate microcosm and implications for air quality Water Air Soil Pollut. 157 193 207

    • Search Google Scholar
    • Export Citation
  • Oyabu, T., Sawada, A., Onodera, T., Takenaka, K. & Wolverton, B. 2003 Characteristics of potted plants for removal of offensive odors Sens. Actuators B Chem. 89 131 136

    • Search Google Scholar
    • Export Citation
  • Sawada, A. & Oyabu, T. 2008 Purification characteristics of pothos for airborne chemicals in growing conditions and its evaluation Atmos. Environ. 42 594 602

    • Search Google Scholar
    • Export Citation
  • Son, K.C., Lee, S.H., Seo, S.G. & Song, J.E. 2000 Effects of foliage plants and potting soil on the absorption and adsorption of indoor air pollutants J. Korean Soc. Hort. Sci. 41 305 310

    • Search Google Scholar
    • Export Citation
  • Tani, A. & Hewitt, C.N. 2009 Uptake of aldehydes and ketones at typical indoor concentrations by houseplants Environ. Sci. Technol. 43 8338 8343

  • Tarran, J., Torpy, F. & Burchett, M. 2007 Use of living pot-plants to cleanse indoor air—Research review. Proc. Sixth Intern. Conf. on Indoor Air Quality, Ventilation & Energy Conservation in Buildings–Sustainable Built Environment, Sendai, Japan

  • Wolverton, B.C. 1986 Houseplants, indoor air pollutants, and allergic reactions. Rept., National Aeronautics Space Administration, Stennis Space Center, MS

  • Wolverton, B.C., McDonald, R.C. & Watkins, E.A. Jr 1984 Foliage plants for removing indoor air pollution from energy-efficient homes Econ. Bot. 38 224 228

    • Search Google Scholar
    • Export Citation
  • Wolverton, B.C. & Wolverton, J.D. 1993 Plants and soil microorganisms: Removal of formaldehyde, xylene, and ammonia from the indoor environment J. Miss. Acad. Sci. 38 11 15

    • Search Google Scholar
    • Export Citation
  • Wood, R.A., Orwell, R.L., Tarran, J., Torpy, F. & Burchett, M. 2002 Potted-plant/growth media interactions and capacities for removal of volatiles from indoor air J. Hort. Sci. Biotechnol. 77 120 129

    • Search Google Scholar
    • Export Citation
  • Xu, Z., Wang, L. & Hou, H. 2011 Formaldehyde removal by potted plant-soil systems J. Hazard. Materials 192 314 318

  • Yang, D.S., Pennisi, S.V., Son, K.C. & Kays, S.J. 2009 Screening indoor plants for volatile organic pollutant removal efficiency HortScience 44 1377 1381

    • Search Google Scholar
    • Export Citation
  • Yoo, M.H., Kwon, Y.J., Son, K.C. & Kays, S.J. 2006 Efficacy of indoor plants for the removal of single and mixed volatile organic pollutants and physiological effects of the volatiles on the plants J. Amer. Soc. Hort. Sci. 131 452 458

    • Search Google Scholar
    • Export Citation
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