ORT Screening Indoor Plants For Volatile Organic Pollutant .
POSTHARVEST BIOLOGY AND TECHNOLOGYHORTSCIENCE 44(5):1377–1381. 2009.Screening Indoor Plants for VolatileOrganic Pollutant Removal EfficiencyDong Sik YangDepartment of Horticulture, University of Georgia, Athens, GA 30602-7273Svoboda V. PennisiDepartment of Horticulture, University of Georgia, Griffin, GA 30223Ki-Cheol SonDepartment of Environmental Science, Konkuk University, Seoul 143-701,KoreaStanley J. Kays1The Plant Center, Department of Horticulture, University of Georgia, 1111Plant Science Building, Athens, GA 30602-7273Additional index words. volatile organic compounds, benzene, toluene, octane, trichloroethylene, a-pinene, phytoremediation, indoor air qualityAbstract. Twenty-eight ornamental species commonly used for interior plantscapes werescreened for their ability to remove five volatile indoor pollutants: aromatic hydrocarbons (benzene and toluene), aliphatic hydrocarbon (octane), halogenated hydrocarbon [trichloroethylene (TCE)], and terpene (a-pinene). Individual plants were placedin 10.5-L gas-tight glass jars and exposed to ’10 ppm (31.9, 53.7, 37.7, 46.7, and55.7 mg m–3) of benzene, TCE, toluene, octane, and a-pinene, respectively. Air samples(1.0 mL) within the glass containers were analyzed by gas chromatography–massspectroscopy 3 and 6 h after exposure to the test pollutants to determine removalefficiency by monitoring the decline in concentration over 6 h within sealed glasscontainers. To determine removal by the plant, removal by other means (glass, plant pot,media) was subtracted. The removal efficiency, expressed on a leaf area basis for eachvolatile organic compound (VOC), varied with plant species. Of the 28 species tested,Hemigraphis alternata, Hedera helix, Hoya carnosa, and Asparagus densiflorus had thehighest removal efficiencies for all pollutants; Tradescantia pallida displayed superiorremoval efficiency for four of the five VOCs (i.e., benzene, toluene, TCE, and a-pinene).The five species ranged in their removal efficiency from 26.08 to 44.04 mg m–3 m–2 h–1 ofthe total VOCs. Fittonia argyroneura effectively removed benzene, toluene, and TCE.Ficus benjamina effectively removed octane and a-pinene, whereas Polyscias fruticosaeffectively removed octane. The variation in removal efficiency among species indicatesthat for maximum improvement of indoor air quality, multiple species are needed. Thenumber and type of plants should be tailored to the type of VOCs present and their ratesof emanation at each specific indoor location.The importance of indoor air quality tohuman health has become of increasinginterest in developed countries where inhabitants often spend over 90% of their timeindoors (Jenkins et al., 1992; Snyder, 1990).Indoor air has been reported to be as much as12 times more polluted than that outdoors(Ingrosso, 2002; Orwell et al., 2004; Zabiega1a,2006). Indoor air pollutants primarily originate from building product emissions, humanactivities inside the building, and infiltrationof outdoor air (Wolkoff and Nielsen, 2001;Zabiega1a, 2006) and have increased as aresult of the lower gas exchange rates ofnewer, more energy-efficient buildings (Cohen,1996). Indoor air pollutants include volatileorganic compounds (VOCs), particulate mat-Received for publication 14 Nov. 2008. Acceptedfor publication 7 Jan. 2009.1To whom reprint requests should be addressed;e-mail kaysstan@uga.edu.HORTSCIENCE VOL. 44(5) AUGUST 2009ter, ozone, radon, lead, and biological contaminants (Destaillats et al., 2008). Exposurecan cause acute illnesses (e.g., asthma,nausea) and chronic diseases (e.g., cancer,immunologic, neurologic, reproductive, developmental, and respiratory disorders) (Suhet al., 2000).VOCs emanating from paints, varnishes,adhesives, furnishings, clothing, solvents,building materials, combustion appliances,and potable water (Jones, 1999; Maroni et al.,1995; Zabiega1a, 2006) have a negative effect on indoor air quality (Darlington et al.,2000). VOCs are generally classified asaromatic hydrocarbons (e.g., benzene, toluene, ethylbenzene, xylene), aliphatic hydrocarbons (e.g., hexane, heptane, octane,decane), halogenated hydrocarbons [e.g., trichloroethylene (TCE), methylene chloride],and terpenes (e.g., a-pinene, d-limonene)(Jones, 1999; Suh et al., 2000; Wolkoff andNielsen, 2001; Won et al., 2005; Zabiega1a,2006). Benzene and toluene, octane, TCE, anda-pinene are representative VOCs from eachclass (i.e., aromatic hydrocarbons, aliphatichydrocarbons, halogenated hydrocarbons, andterpenes, respectively) and are considered tobe important indoor air pollutants as a resultof their toxicity (Liu et al., 2007; Newmanet al., 1997; Orwell et al., 2006).Plants remove VOCs from indoor airthrough stomatal uptake, absorption, andadsorption to plant surfaces (Beattie andSeibel, 2007; Korte et al., 2000; Sandhuet al., 2007). Several indoor species havebeen screened for their ability to removebenzene (Liu et al., 2007), some of whichcould remove 40 to 88 mg m–3 d–1 (Orwellet al., 2004), in addition to other VOCs (e.g.,toluene, TCE, m-xylene, hexane) (Cornejoet al., 1999; Orwell et al., 2006; Wood et al.,2002; Yoo et al., 2006). The efficiency ofVOC removal varies substantially amongspecies (Yoo et al., 2006) and with themolecular characteristics of each compound.To date, only a limited number of indoorspecies have been tested for their phytoremediation potential and the range of pollutantsassessed is even more limited (Cornejo et al.,1999; Ugrekhelidze et al., 1997; Wolvertonet al., 1989; Wood et al., 2002). It is evidentthat a better understanding of the phytoremediation potential of a diverse range of indoorplants is needed. In this study, a cross-sectionof indoor plants (28 species) was screened fortheir ability to remove five important VOCswith differing chemistries (benzene, toluene,octane, TCE, and a-pinene).Materials and MethodsPlant material. Twenty-eight species ofpopular indoor ornamental plants available inthe southeastern United States, which represented 26 genera and 15 botanical families(Table 1), were obtained from commercialsources. After the media was washed fromthe roots, the plants were repotted in 10-cm(500-cc) pots using a growing media comprised of peatmoss, pine bark, and perlite/vermiculite (2:1:1, v/v) (Fafard 3B; Fafard,Anderson, SC) and grown in a shade housefor 8 weeks before acclimatization for 12weeks under indoor conditions, 22 1 C,50% relative humidity, and 5.45 mmol m–2 s–1photosynthetically active radiation (PAR)(LI-COR LI-189 light meter with a linequantum sensor; LI-COR, Lincoln, NE).The plants were watered as needed duringgrowth and acclimatization periods. At theend of the experiment, the leaf areas weredetermined using a LI-3100c leaf area meter(LI-COR) to allow expressing the removalefficiency on a leaf area basis.Introduction of volatile organic compounds. Plants were placed in 10.5-L gas-tightglass jars (one plant/jar) with the lid fitted withwelded stainless steel tubing inlet and outletports. To facilitate a uniform distribution ofthe gases in the jar, the inlet tubing extendeddownward within the jar following the contourof the side of the jar, three-fourths of thedistance to the base. The lids were sealed usingspecially constructed 11.8 cm o.d. · 9.8 cm i.d.1377
Table 1. Family, Latin binomial, common name, and leaf area of test plants exposed to five representative volatile organic compounds (benzene, toluene, octane,trichloroethylene, and a-pinene) over 6 h during the day.No.FamilyLatin binomial1AcanthaceaeFittonia argyroneura Coem.2AcanthaceaeHemigraphis alternata (Burm.f.) T. Anders ‘Exotica’3AgavaceaeDracaena fragrans (L.) Ker-Gawl.4AgavaceaeSansevieria trifasciata Prain5AnthericaceaeChlorophytum comosum (Thunb.) Jacq. ‘Fire Flash’6AraceaeAnthurium andreanum Linden7AraceaeDieffenbachia seguine (Jacq.) Schottz8AraceaePhilodendron scandens ssp. oxycardium9AraceaeEpipremnum aureumy10AraceaeSpathiphyllum wallisii Regal11AraceaeSyngonium podophyllum Schott12AraliaceaeSchefflera arboricola (Hayata) Merr. ‘Variegata’13AraliaceaeSchefflera elegantissima (Hort. Veitch ex Mast.) Lowry & Frodinx14AraliaceaeHedera helix L.15AraliaceaePolyscias fruticosa (L.) Harms16AsclepiadaceaeHoya carnosa (L.f.) ‘Variegata’17BromeliaceaeGuzmania sp.18CommelinaceaeTradescantia pallida (Rose) D.R. Hunt ‘Purpurea’19EuphorbiaceaeCodiaeum variegatum (L.) Blume20GeraniaceaePelargonium graveolens L’Her. ex Ait.21LiliaceaeAsparagus densiflorus (Kunth) Jessop ‘Sprengeri’22LiliaceaeAspidistra elatior Blume ‘Milky Way’23MarantaceaeCalathea roseopicta (Linden) Regal24MarantaceaeMaranta leuconeura E. Morren25MoraceaeFicus benjamina L.26MoraceaeFicus elastica Roxb. Rubra27PalmaeHowea belmoreana (C. Moore & F. Muell.) Becc.28PiperaceaePeperomia clusiifolia (Jacq.) Hook. ‘Variegata’Data are means SEM (n 3).zSyn. Diffenbachia amoena Hort. and Bull.ySyn. Scindapsus aureus Engl.xSyn. Dizygotheca elegantissima (Veitch) R.Vig. and Guillaumin.gaskets in which a 4.2-mm-thick EPDM rubber gasket was sealed within a Teflon envelope(Phelps Industrial Products, Elkridge, MD).The inlet port was connected to a charcoalfilter [Pyrex glass tube (10 cm · 1 cm i.d.) with2.5 g of charcoal (Alltech Assoc. Inc., Deerfield, IL)] such that purified air was introducedinto the jar at 150 ml min–1. The plants wereplaced in the jars 24 h before treatment andwere maintained at 5.45 mmol m–2 s–1 PARduring a light period (12 h). Just before theintroduction of the VOCs, the inlet and outletports were closed using gas-tight Swagelokfittings (Georgia Valve & Fitting, Co., Alpharetta, GA). The exit port was configured withSwagelok fittings holding a gas-tight gaschromatography septum that was capped toprevent leakage. The cap was briefly removedwhen a gas sample was drawn for analysis.The individual plants were exposed to 10ppm (31.9, 53.7, 37.7, 46.7, and 55.7 mg m–3)of high-purity analytical-grade benzene, TCE,toluene, octane, and a-pinene (Table 2),respectively, in the gas-tight glass jars.Through preliminary tests, concentrations of9.66 (30.9), 11.00 (59.1), 9.66 (36.4), 9.49(44.3), and 9.82 (54.7) ppm (mg m–3) of eachcompound were created by introducing 2.0,2.7, 2.4, 4.0, and 4.0 mL of benzene, TCE,toluene, octane, and a-pinene, respectively,into the jar using a microsyringe (AgilentTechnologies, Wilmington, DE) and calibrating the amount of each compound adsorbedonto the inner surface of the jar. A small 4 cmdiameter 6-V DC brushless fan (RadioShack,Fort Worth, TX) was placed near the top ofeach jar to ensure adequate mixing of the1378Common nameSilver-net leafPurple waffleCorn plantSnake plantSpider plantFlamingo flowerDumb caneHeart leaf philodendronPothosPeace lilyArrowhead vineVariegated scheffleraFalse araliaEnglish ivyMing araliaVariegated wax plantGuzmani bormeliadPurple heart plantCrotonRose geraniumAsparagus fernCast iron plantPeacock plantPrayer plantWeeping figRed rubber treeSentry palmVariegated red-edged peperomiavolatiles. The gas concentration within the jarwas determined after 3 and 6 h during the day.Three replications of each species were testedat a setting with a fourth jar used as a controlwithout the potted plant to measure the concentration of airborne VOCs within the emptyjar. Leak tests were carried out on the emptyjar before every fourth experiment; no leakagewas found during the 6-h test period.Analysis of volatile organic compounds.Air samples (1.0 mL) within the glass containers were removed during the light periodfrom the outlet port using a gas-tight syringe(Agilent Technologies) 3 and 6 h after exposure to the test VOCs and analyzed bycapillary gas chromatography–mass spectroscopy (GC-MS) (6890N/5973; Agilent,Palo Alto, CA) equipped with a 30 m length(0.25 mm i.d., 0.25 mm film thickness of 5%phenyl methyl siloxane) capillary column(HP-5MS; Agilent). The injection port temperature was 225 C and was operated in thesplitless mode. Helium was used as thecarrier gas at a flow rate of 1.8 mL min–1.The column temperature was held at 36 Cfor 0.5 min and then programmed at 10 C/min to 90 C and held for 1 min. Massspectroscopy conditions were: ion source230 C; electron energy 70 eV; multipliervoltage 1247 V; GC-MS interface zone 280 C; and a scan range of 35 to 350 mass units.For quantifying absolute concentrations ofeach compound, standard curves for eachcompound were determined using analyticalstandards. Solutions of 0.5, 1, 2, 5, 10, 20, 50,and 100 mL L–1 in hexane of each compoundwere prepared. Each standard solution (1.0Leaf area (cm2/plant)660 45352 37712 39346 51574 76616 76670 521085 281201 136598 58718 54587 56372 68319 20477 26452 51535 78253 33926 48501 79337 91079 192650 78574 13482 36562 34769 108935 22mL, three replications) was injected directlyinto the GC-MS using a microsyringe. Theconcentration of VOCs removed by a plantwas calculated as (Yoo et al., 2006):ðAÞ VOC removal efficiency ½C ðS MÞ ðL 3 TÞ½1 ðBÞ Accumulated removal concentration ofVOC ½C ðS MÞ L½2 where:C the concentration of VOC in thecontrol jar (mg m–3)S the concentration of VOC in thesample jar (mg m–3)Table 2. Accumulated removal concentrationof volatile organic compounds (VOCs) byplastic pot (10 cm, 500 cc) containing soillessmedia without plant 3 h and 6 h afterintroduction of five representative VOCs[benzene, toluene, octane, trichloroethylene(TCE), and a-pinene].Accumulated removal concn by plasticpot containing media (mg m–3)3h6hVOCBenzene0.34 0.060.38 0.05Toluene1.13 0.061.21 0.04Octane0.35 0.080.47 0.07TCE1.00 0.171.10 0.08a-Pinene1.03 0.171.13 0.07Data are means SEM (n 3).HORTSCIENCE VOL. 44(5) AUGUST 2009
M the concentration of VOC in the jarcontaining only the plastic pot andmedia (mg m–3) (Table 2)L total leaf area (m2)T VOC exposure time (h)Statistical analysis. Analysis of varianceand Duncan’s multiple range test were carried out by using the SAS system for Windows v8 (SAS Institute, Cary, NC).Results and DiscussionThe initial concentrations of benzene,toluene, octane, TCE, and a-pinene withinthe container were 9.66 0.03 (30.9), 9.66 0.07 (59.1), 9.49 0.06 (36.4), 11.00 0.07(44.3), and 9.82 0.20 (54.7) ppm (mg m–3),respectively. The concentration of eachVOC, after subtraction of the concentrationof VOC in jars containing the pot and mediawithout a plant (Table 2) from that in thesample jar with plant, decreased with exposure duration, indicating VOC removal by theplants (Fig. 1). Because the test plants variedin size and foliar surface area, the removalefficiency for each VOC was expressed on aleaf area basis to allow identification ofspecies with superior removal efficiency.VOC removal represents the effect of theplant and subterranean micro-organismsassociated with the plant in the potting media,the latter of which is known to be animportant contributor (Wood et al., 2002).The removal efficiency varied substantially among the species tested: benzene(0.03 to 5.54 mg m–3 m–2 h–1), toluene (1.54to 9.63), octane (0 to 5.58), TCE (1.48 to11.08), a-pinene (2.33 to 12.21), and totalVOC (5.55 to 44.04) (Table 3). The resultsdemonstrate the rate of removal variesdepending on the VOC in question and theplant species present.Benzene. Six species with superior benzene removal efficiency were identified:Hemigraphis alternata (5.54 mg m–3 m–2 h–1),Tradescantia pallida (3.86), Hedera helix(3.63), Fittonia argyroneura (2.74), Asparagus densiflorus (2.65), and Hoya carnosa(2.21) (Table 3; Fig. 1A). H. alternata hadthe highest removal efficiency and the highest accumulated removal of benzene at 3 hand 6 h. At 3 h, five species classified ashaving high removal efficiency were notstatistically significant in their accumulatedremoval concentrations; however, by 6 h,there were significant differences (Fig. 1A).Sansevieria trifasciata (1.76), Ficus benjamina (1.66), Polyscias fruticosa (1.53), Guzmania sp. (1.46), Anthurium andreanum(1.31), and Peperomia clusiifolia (1.20) wereclassified as having an intermediate benzeneremoval efficiency; the remainder had verylow benzene removal efficiencies (Table 3).Toluene. H. alternata had the highest toluene removal efficiency (9.63 mg m–3 m–2 h–1)followed by T. pallida (9.10), H. helix (8.25),A. densiflorus (7.44), H. carnosa (5.81), F.argyroneura (5.09), and F. benjamina (5.06)(Table 3; Fig. 1B). The plants were muchHORTSCIENCE VOL. 44(5) AUGUST 2009Fig. 1. Accumulated removal of (A) benzene, (B) toluene, (C) octane, (D) trichloroethylene, and (E)a-pinene by plants with superior volatile organic compound removal efficiency over 6 h during theday. Plots with different letters at the same time are significantly different by Duncan’s multiple rangetest (P 0.05). The solid squares, solid triangles, solid circles, open squares, open triangles, and opencircles represent the following species in sequence: (A) Hemigraphis alternata, Tradescantia pallida,Hedera helix, Fittonia argyroneura, Asparagus densiflorus, and Hoya carnosa; (B) H. alternata, T.pallida, H. helix, A. densiflorus, H. carnosa, and F. argyroneura; (C) H. alternata, H. helix, Ficusbenjamina, H. carnosa, A. densiflorus, and Polyscias fruticosa; (D) H. alternata, H. helix, T. pallida, A.densiflorus, F. argyroneura, and H. carnosa; and (E) H. helix, H. alternata, A. densiflorus, T. pallida,F. benjamina, and H. carnosa.more effective in removing toluene thanbenzene, a finding corroborated by Yoo et al.(2006). The rate of toluene removal during theinitial 3-h exposure was more rapid comparedwith the second 3 h of exposure. Tolueneremoval occurs through adsorption to the plant1379
Table 3. Removal efficiency based on leaf area of five representative volatile organic compounds (VOCs) [benzene, toluene, octane, trichloroethylene (TCE), anda-pinene] of 28 indoor plants over 6 h during the day.BenzenePlantSuperior removal efficiencyHemigraphis alternata5.54 0.29Hedera helix3.63 0.33Tradescantia pallida3.86 0.58Asparagus densiflorus2.65 0.24Hoya carnosa2.21 0.21Intermediate removal efficiencyFicus benjamina1.66 0.07Polyscias fruticosa1.53 0.08Fittonia argyroneura2.74 0.28Sansevieria trifasciata1.76 0.48Guzmania sp.1.46 0.25Anthurium andreanum1.31 0.120.66 0.19Schefflera elegantissimazPoor removal efficiencyPeperomia clusiifolia1.20 0.10Chlorophytum comosum0.75 0.11Howea belmoreana0.80 0.10Spathiphyllum wallisii0.75 0.11Schefflera arboricola0.44 0.07Codiaeum variegatum0.89 0.04Calathea roseopicta0.94 0.18Aspidistra elatior0.53 0.08Maranta leuconeura0.74 0.19Dracaena fragrans0.55 0.01Ficus elastica0.38 0.070.18 0.04Dieffenbachia seguineyPhilodendron scandens ssp. oxycardium0.49 0.08Syngonium podophyllum0.03 0.020.44 0.05Epipremnum aureumxPelargonium graveolens0.03 0.02Data are means SEM (n 3).zSyn. Dizygotheca elegantissima (Veitch) R.Vig. and Guillaumin.ySyn. Diffenbachia amoena Hort. and Bull.xSyn. Scindapsus aureus Engl. f.surface and absorption through stomataluptake; the removal rate depends on thenumber of stomata and the cuticular structure(Jen et al., 1995; Ugrekhelidze et al., 1997).Octane. H. alternata had the highest octaneremoval efficiency (5.58 mg m–3 m–2 h–1) followed by H. helix (5.10), F. benjamina (3.98),H. carnosa (3.80), A. densiflorus (3.76), andP. fruticosa (3.43) (Table 3; Fig. 1C). Pelargonium graveolens had no effect on octaneconcentration, whereas Maranta leuconeura(0.51 mg m–3 m–2 h–1), Schefflera elegantissima (0.65), Syngonium podophyllum (0.76),Calathea roseopicta (0.83), and Epipremnumaureum (0.86) had very low octane removalefficiencies. The removal of octane, an aliphatic hydrocarbon, by indoor plants has notbeen reported; however, hexane, also analiphatic hydrocarbon, was removed by Dracaena deremensis and Spathiphyllum wallisii(Wood et al., 2002).Trichloroethylene. The six species thateffectively removed toluene also had superior TCE removal efficiencies: H. alternata(11.08 mg m–3 m–2 h–1), H. helix (8.07), T.pallida (7.95), A. densiflorus (6.69), F. argyroneura (6.15), and H. carnosa (5.79) (Table3; Fig. 1D). Similar to toluene, the highestrate of TCE removal was during the initial 3h, declining subsequently with the exceptionof T. pallida in which the rate remained fairlyconsistent. Chlorophytum comosum, whichwas previously reported to remove TCE1380TolueneVOC removal efficiency (mg m–3 m–2 h–1)OctaneTCEa-PineneTotal9.63 0.948.25 0.649.10 1.177.44 0.285.81 0.675.58 0.685.10 0.492.76 1.083.76 0.643.80 0.6211.08 0.998.07 0.777.95 1.206.69 0.495.79 0.7512.21 1.6113.28 0.9510.45 1.7811.40 0.788.48 1.1744.04 2.9838.33 3.1734.12 5.5231.94 2.4026.08 3.405.06 0.194.29 0.045.09 0.234.97 0.704.04 0.563.60 0.374.94 0.373.98 0.193.43 0.081.77 0.252.73 0.502.07 0.242.45 0.240.65 0.464.74 0.153.98 0.166.15 0.364.61 0.814.01 0.493.58 0.353.87 0.108.68 0.408.30 0.124.30 0.395.49 1.316.43 0.555.85 0.547.33 0.3624.13 0.8621.53 0.4220.05 1.4619.56 3.6818.01 1.7716.78 1.5917.46 0.812.75 0.113.18 0.142.95 0.322.52 0.132.25 0.232.28 0.082.70 0.382.22 0.242.67 0.282.01 0.082.29 0.112.03 0.101.80 0.111.84 0.151.54 0.151.67 0.292.03 0.011.70 0.081.81 0.281.55 0.211.75 0.131.21 0.030.83 0.141.22 0.170.51 0.191.18 0.081.20 0.131.01 0.100.98 0.060.76 0.160.86 0.090.00 0.002.40 0.132.86 0.132.71 0.282.25 0.191.78 0.172.34 0.102.32 0.402.00 0.202.35 0.401.90 0.091.75 0.191.83 0.071.66 0.161.67 0.221.52 0.161.48 0.444.61 0.144.17 0.214.25 0.674.09 0.214.18 0.343.61 0.093.25 0.583.17 0.402.76 0.673.31 0.192.66 0.122.99 0.202.33 0.122.75 0.172.34 0.212.37 0.2612.98 0.3912.66 0.5412.52 1.6411.15 0.8310.40 0.8410.33 0.3110.04 1.629.14 1.069.03 1.688.95 0.448.28 0.568.05 0.397.26 0.527.04 0.706.71 0.645.55 0.99(Cornejo et al., 1999), had an intermediate TCEremoval efficiency (2.86 mg m–3 m–2 h–1).a-Pinene. H. helix had the highest a-pineneremoval efficiency (13.28 mg m–3 m–2 h–1) ofthe 28 species tested followed by H. alternata(12.21), A. densiflorus (11.40), T. pallida(10.45), F. benjamina (8.68), H. carnosa(8.48), and P. fruticosa (8.30) (Table 3; Fig.1E).Based on the total VOC removal efficiency, the plants were classified into superior, intermediate, and poor categories (Table3). Five species (i.e., H. alternata, H. helix, T.pallida, A. densiflorus, and H. carnosa) withsuperior phytoremediation potential wereidentified. Their total VOC removal rangedfrom 26.08 to 44.04 mg m–3 m–2 h–1 and theyeffectively removed each of the test compounds. In contrast, the total VOC removalefficiency of the six plants classified as havingan intermediate phytoremediation potentialranged from 17.46 to 24.13 mg m–3 m–2 h–1,whereas those with poor efficiencies rangedfrom 5.55 to 12.98 mg m–3 m–2 h–1.There were no discernible trends in VOCremoval potential based on taxonomicalrelatedness. However, the Araceae family[e.g., E. aureum (6.71 mg m–3 m–2 h–1), S.podophyllum (7.04), P. scandens ssp. oxycardium (7.26), Dieffencachia seguine(8.05), S. wallisii (11.15)] generally had poorphytoremediation potential, whereas representatives of the Araliaceae family had, ingeneral, a far better removal potential [e.g.,H. helix (38.33 mg m–3 m–2 h–1), P. fruticosa(21.53), and S. elegantissima (17.46)].The volatiles tested in this study arecommonly found in buildings. They canadversely affect indoor air quality and havea potential to seriously compromise thehealth of exposed individuals (Mitchellet al., 2007; Suh et al., 2000; Zabiega1a,2006). Benzene and toluene are known tooriginate from petroleum-based indoor coatings, cleaning solutions, plastics, environmental tobacco smoke, and exterior exhaustfumes emanating into the building; octanefrom paint, adhesives, and building materials; TCE from tap water, cleaning agents,insecticides, and plastic products; anda-pinene from synthetic paints and odorants.Some of the common indoor VOCs areknown carcinogens (Jones, 1999; Newmanet al., 1997) and at sufficiently high concentrations, a number of VOCs are harmful toplants (Cape, 2003). Visible injury to plantsin this study was not observed.Although a diverse cross-section of plantswas capable of removing the VOCs tested(Table 3), removal efficiency varied within asingle species as a result of differences inthe chemical properties of the individualcompounds (e.g., polarity, vapor pressure,molecular weight, solubility, dissociation),an effect previously noted by Yoo et al.(2006). The fate of VOCs (e.g., accumulation,HORTSCIENCE VOL. 44(5) AUGUST 2009
adsorption, absorption, penetration, transportation, metabolism), therefore, dependson the chemical characteristics of each volatile(Cape, 2003; Deinum et al., 1995; Korteet al., 2000) and the physical and chemicalcharacteristics of the plants. Lipophilic compounds more readily penetrate the cuticularsurface of plants, expediting uptake in contrastto compounds that are largely restricted tostomatal penetration (Deinum et al., 1995;Schmitz et al., 2000). In addition, the abilityto metabolize VOCs varies widely amongspecies and volatiles (Beattie and Seibel,2007; Cape, 2003; Deinum et al., 1995; Jenet al., 1995). Therefore, a better understandingof the basic physical and chemical factorsmodulating the phytoremediation processes inthe most efficient species is needed.Conclusions and SummaryOf the 28 species tested, H. alternata, H.helix, H. carnosa, and A. densiflorus hadsuperior removal efficiencies for each ofthe test compounds (i.e., benzene, toluene,octane, TCE, and a-pinene). Likewise, T.pallida had superior removal efficiencies forfour of the compounds (i.e., benzene, toluene,TCE, and a-pinene). H. alternata, in particular, had the highest removal efficiencyfor four of the compounds (benzene, toluene,octane, and TCE). Indoor plants are knownto confer significant psychological and physical benefits to individuals living/working inenvironments where they are present[e.g., reduced stress, increased task performance, and decreased symptoms of ill health(Bringslimark et al., 2007; Son, 2004)]. Basedon this and other studies, plants also have thepotential to significantly improve the quality ofindoor air. Their increased use in both ‘‘green’’and traditional buildings could have a tremendous positive impact on the ornamental industry by increasing customer demand and volumeof sales. Further studies focusing on screeningadditional plant species for superior VOCremoval efficiencies are warranted.Literature CitedBeattie, G.A. and J.R. Seibel. 2007. Uptake andlocalization of gaseous phenol and p-cresol inplant leaves. Chemosphere 68:528–536.Bringslimark, T., T. Hartig, and G.G. Patil. 2007.Psychological benefits of indoor plants inHORTSCIENCE VOL. 44(5) AUGUST 2009workplaces: Putting experimental results intocontext. HortScience 42:581–587.Cape, J.N. 2003. Effects of airborne volatileorganic compounds on plants. Environ. Pollut.122:145–157.Cohen, Y. 1996. Volatile organic compounds in theenvironment: A multimedia perspective, p. 7–32. In: Wang, W., J. Schnoor, and J. Doi (eds.).Volatile organic compounds in the environment. ASTM STP 1261. American Society forTesting and Materials, West Conshohocken, PA.Cornejo, J.J., F.G. Munoz, C.Y. Ma, and A.J.Stewart. 1999. Studies on the decontaminationof air by plants. Ecotoxicol. 8:311–320.Darlington, A., M. Chan, D. Malloch, C. Pilger,and M.A. Dixon. 2000. The biofiltration ofindoor air: Implications for air quality. IndoorAir 10:39–46.Deinum, G., A.C. Baart, D.J. Bakker, J.H. Duyzer,and K. Dick Van Den Hout. 1995. The influence of uptake by leaves on atmosphericdeposition of vapor-phase organics. Atmos.Environ. 29:997–1005.Destaillats, H., R.L. Maddalena, B.C. Singer, A.T.Hodgson, and T.E. McKone. 2008. Indoorpollutants emitted by office equipment: Areview of reported data and information needs.Atmos. Environ. 42:1371–1388.Ingrosso, G. 2002. Free radical chemistry and itsconcern with indoor air quality: An openproblem. Microchem. J. 73:221–236.Jen, M.S., A.M. Hoylman, N.T. Edwards, and B.T.Walton. 1995. Experimental method to measure gaseous uptake of 14C-toluene by foliage.Environ. Exp. Bot. 35:389–398.Jenkins, P.L., T.J. Phillips, E.J. Mulberg, and S.P.Hui. 1992. Activity patterns of Californians—Use of and proximity to indoor pollutant sources. Atmos. Environ. 26:2141–2148.Jones, A.P. 1999. Indoor air quality and health.Atmos. Environ. 33:4535–4564.Korte, F., G. Kvesitadze, D. Ugrekhelidze, M.Gordeziani, G. Khatisashvili, O. Buadze, G.Zaalishvili, and F. Coulston. 2000. Organictoxicants and plants. Ecotoxicol. Environ. Saf.47:1–26.Liu, Y.J., Y.J. Mu, Y.G. Zhu, H. Ding, and N.C.Arens. 2007. Which ornamental plant specieseffectively remove benzene from indoor air?Atmos. Environ. 41:650–654.Maroni, M., B. Seifert, and T. Lindvall. 1995.Indoor air quality: A comprehensive referencebook. Elsevier, Amsterdam, The Netherlands.Mitchell, C.S., J.F.J. Zhang, T. Sigsgaard, M.Jantunen, P.J. Lioy, R. Samson, and M.H.Karol. 2007. Current state of the science:Health effects and indoor environmental quality. Environ. Health Perspect. 115:958–964.Newman, L.A., S.E. Strand, N. Choe, J. Duffy, G.Ekuan, M. Ruszaj, B.B. Shurtleff, J. Wilmoth,P. Heilman, and M.P. Gordon. 1997. Uptakeand biotransformation of trichloroethylene byhybrid poplars. Environ. Sci. Technol. 31:1062–1067.Orwell, R.L., R.A. Wood, M.D. Burchett, J. Tarran,and F. Torpy. 2006. The potted-plant microcosm substantially reduces indoor air VOCpollution: II. Laboratory study. Water Air SoilPollut. 177:59–80.Orwell, R.L., R.L. Wood, J. Tarran, F. Torpy,and M.D. Burchett. 2004. Removal of benzene by the indoor plant/substrate microcosmand implications for air quality. Water AirSoil Pollut. 157:193–207.Sandhu, A., L.J. Halverson, and G.A. Beattie.2007. Bacterial degradation of airborne
Additional index words. volatile organic compounds, benzene, toluene, octane, trichloroeth-ylene, a-pinene, phytoremediation, indoor air quality Abstract. Twenty-eight ornamental species commonly used for interior plantscapes were screened for their ability to remove five
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