Experimental Study on the Effect of Foliage Plants on Removing ...

Proceedings of Clima 2007 WellBeing Indoors

Experimental Study on the Effect of Foliage Plants on Removing Indoor Air Contaminants Hiroshi Matsumoto and Masashi Yamaguchi Toyohashi University of Technology, Japan Corresponding email: [email protected] SUMMARY The objective of this paper is to demonstrate an ability of foliage plants quantitatively to remove chemical contaminants by experiments using a small desiccator for the different kinds of plant under the different luminescence and light sources, fluorescent, incandescent and light-emitting-diode (LED) lamps. The foliage plants, Benjamin, Spathiphyllum, Areca palm and Concinna, cultivated in hydroponics were used. As a result of the experiments, the effective performance of contaminant removal was obtained under lighting conditions with the different intensity distribution by wavelength for the case of pulse injection of toluene into the chamber without ventilation. The removal efficiency of toluene under an incandescent light was larger than that under a fluorescent lamp. The different removal efficiency was obtained according to the kind of LED with different intensity distribution and foliage plants. The blue LED lamp showed the highest removal efficiency among the LED lamps evaluated in this study. INTRODUCTION An ability of foliage plants to absorb chemical compounds from the indoor air has been demonstrated in many studies. In the report of the National Aeronautics and Space Administration (NASA) Wolverton et al. [1] showed that low-light-requiring houseplants such as Bamboo palm, English ivy and so on have demonstrated the potential for improving indoor air quality by removing trace organic pollutants from the air in energy-efficient buildings. In this study they revealed that the root-soil zone appeared to be the most effective area for removing volatile organic chemicals, and proposed an indoor air purification system combining houseplants with an activated carbon filter. Wood et al. [2] carried out an investigation of the biological decontamination capabilities of indoor plants. The work showed that Kentia palms (Howea forsteriana Becc.) had capacity to remove several times the maximum occupational levels of n-hexane and benzene in indoor air, and their capacity to do so was increased by exposure. Also they suggested that the intimate association between VOC metabolizing bacteria and the roots system was highlighted by hydroponic conditions. The removal of airborne toluene by means of the phyllosphere of Azalea indica augmented with a toluene-degrading enrichment culture of Pseudomonas putida TVA8 was studied by Kempeneer et al [3]. The results presented were promising and could be practical importance in the field of indoor air pollution control.


Sawada et al. [4] measured TVOC and odors to examine purification effect of plants by using Golden pothos and Peace lily. The results showed that the removal rate for TVOC was 74% and the one for odor was 68%. It was confirmed that plants had high purification capability in the real environment. Wood et al. [5] obtained the results by the office field-study that the presence of potted-plants brought about highly significant reduction in TVOC levels, of up to 75% when indoor average concentrations rose above 100ppb. The findings also indicated that the potted-plant microcosm represented an adaptive, self-regulating, low-cost, sustainable system for bioremediation of VOC pollution in indoor air. The authors has been investigated the VOC removal performance of foliage plants under the different lighting conditions, kinds of plant and light, and the illuminance [6]. It was found that the VOC removal efficiency was strongly affected by the illuminance and the intensity distribution by wavelength of light. The processes of diffusive exchange between air and leaves through stomata and cuticle, metabolism and dilution by growth may be involved with the effect. Nevertheless the valid mechanism of biological decontamination and the quantitative performance to remove indoor air contaminants have not been established. Therefore further studies concerning the effect need to be done; especially the effects of light source on the removal efficiency of indoor plants should be investigated. The objective of this paper is to investigate an ability of foliage plants quantitatively to remove chemical contaminants by the experiments using a desiccator for the different kinds of foliage plant under the different luminescence and light sources, fluorescent, incandescent and LED. METHODS An overview of the measurement system used here is shown in Figure 1. The experiments were carried out for each plant put in a transparent desiccator made of acrylic resin with dimension L560 × W 483 × H986 mm. Toluene gas was used as a chemical contaminant to be removed from the test chamber. The concentrations of toluene and carbon dioxide were analyzed by B&K Multi Gas Monitor. Sampling points were fixed in the lower part of the desiccator and the outside air. Artificial light was set at the above the desiccator. The illuminance was measured by the illumination photometer (Tokyo Koden). Spectrometer (SOLAR Laser Systems) with the operational spectral range, 190 to 1,100 nm, was used to investigate the intensity distribution by wavelength of lightings used here. The test plants were set in the desiccator after exposing fresh air for 24 hours and more, and then a small quantity of VOC gas adjusted the initial concentration was injected by a syringe three hours after the measurement start. The measurement data of the VOC and carbon dioxide was obtained every 75 seconds for 24 hours. To avoid the air exchange between the desiccator and the outside, the exhaust air from the desiccator used for detecting the concentration of sampling air was returned to the desiccator. Air temperature and relative humidity in the desiccator and the outside air were also measured every 10 minutes during the experiment.


Experimental items evaluated are shown in Table 1. Toluene, one of VOCs, was used as a chemical contaminant evaluated. Fluorescent light, incandescence light and LED lights such as blue, red and blue mixed with red LED were evaluated. Each LED light was composed of 1,200 LEDs with the maximum rating 100mA per a LED set on a flat board of dimension L50 × W45 cm. The desiccator was set in a laboratory where the room air temperature was controlled at 20-30 degree C. The illuminance of lighting was set at 350, 700, and 1,050 lx. The foliage plants, Benjamin (scientific name: Ficus benjamina L.), Spathiphyllum (Spathiphyllum clevelandii), Areca palm (Chrysalidocarpus lutescens ) and Concinna (Dracaena concinna), which are considered to remove VOC effectively, cultivated in hydroponics were used. Lighting

Sampling point Return air

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Figure1. Measurement system. Table 1. Experimental items. Items

Contents

Chemical contaminant Light sources

Toluene Fluorescent light

Foliage plants

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RESULTS Effect of light sources

Incandescence light Light-emitting diode (LED) Benjamin Spathiphyllum Areca palm Concinna 350 lx 700 lx 1050 lx Red LED Blue LED Red and blue (B/R ratio 0.25)


To investigate the effect of light sources on VOC removal of foliage plants, fluorescent and incandescent lights with the relative intensity distribution by wavelength as shown in Figure 2 were used. The incandescent light has relatively continuous intensity distribution through the wide range of wavelength, but the fluorescent light has discrete intensity distribution and some peaks for the specific wavelength. Figure 3 shows the cumulative removal of toluene for a pot of Concinna at 10 and 20 hours after a small amount of toluene injection using a syringe under the different lights, incandescent and fluorescent lights, in comparison with no lighting. The illuminance on the middle plane of the desiccator was controlled at 356 lx. The removal of toluene was strongly affected by the lighting. In this experiment the removal efficiency of toluene under an incandescent light was larger than that under a fluorescent lamp. 4000 Fluorescent Incandescent

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Figure 3. Cumulative removal of toluene under the different lights.


Kinds of plant and illuminance of lights The foliage plants, Benjamin, Spathiphyllum, Areca palm and Concinna, which are considered to have high removal performance of VOC, cultivated in hydroponics were used. Figure 4 shows an example of the measurement results of toluene and CO2 concentrations for Concinna under the fluorescent illuminance 700 and 1,050 lx, to identify the removal of VOC under the different illuminance. In this case the air temperature inside the desiccator was about 23 degree C and the relative humidity was changed from 30 to 80 %. Under the illuminance 700 lx, toluene concentration was decreased from 0.32 to 0.2 mg/m3 at 15 hours after toluene injection. CO2 concentration was slightly increased as the elapsed time. For the illuminance 1,050 lx, toluene concentration was decreased from 0.31 to 0.25 mg/m3 at 15 hours after toluene injection. CO2 concentration was decreased after 9 hours from the measurement start. This data shows that the photosynthesis of the plant was not active in spite of remarkable VOC removal under the illuminance 700 lx, while photosynthesis was active under the illuminance 1,050 lx. 500

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Figure 4. Toluene and CO2 concentrations vs. elapsed time.

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Figure 5 shows the VOC removal efficiency, defined by the ratio of the concentration difference between the initial concentration and the concentration at the evaluated time to the initial value, for the different foliage plant under the different fluorescent illuminance. For Spathiphyllum and Concinna, the removal efficiency under low illuminance was over 80% and larger than that under high illuminance. Benjamin and Areca palm showed the highest efficiency above 80% for the illuminance 700 and 1,050 lx, respectively. On the other hand the efficiency for Spathiphyllum under the illuminance 1,050 lx was very low. These results can be considered that each plant has the particular illuminance to remove VOC efficiently. 100 350lx

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Figure 5. Removal efficiency of toluene under different illuminance. Wavelength of the lights Relative intensity distribution by wavelength of LED lights, blue, red and the mixed light (B/R ratio 0.25), used here is shown in Figure 6. The most part of intensity including the peak of the blue LED was covered within the wavelength range 420 to 470 nm, which range is considered to be wavelength range required for normal growth of plants [7, 8]. On the other hand, the most part of intensity distribution of the red LED is close to the wavelength range 640 to 690 nm, which is considered to be wavelength range for effective photosynthesis. Figure 7 shows the removal efficiency of toluene under the different LED light. The illuminance of the lights on the middle of the plane in the desiccator was controlled at 350 lx. All the cases showed the removal efficiency of 60% and more. Especially the highest removal efficiency was the case under the blue LED, and the efficiency over 100 % means that the plant reduced VOC concentration in the desiccator less than the initial value before setting the plant. For the red LED and the mixing of red with blue, both of the cases were almost similar.


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CONCLUSIONS As a result of the experiments, the effective performance of contaminant removal was obtained under lighting conditions with the different intensity distribution by wavelength for the case of pulse injection of toluene into the chamber without ventilation. The removal efficiency of toluene under a fluorescent light, illuminance 356 lx on the upper part of the desiccator, was larger than that under incandescent lamps. For Spathiphyllum and Concinna, the removal efficiency under low illuminance was over 80% and larger than that under high illuminance. Benjamin and Areca palm showed the highest efficiency above 80% for the illuminance 700 and 1,050 lx, respectively. This result suggests that each plant has the particular illuminance to remove VOC efficiently. Also it was found that the highest removal efficiency was obtained under the lighting condition with the blue LED out of the LEDs evaluated in this study. In the next stage, experiments using a full scale room model to investigate VOC removal performance of foliage plants and further experiments using a desiccator to identify the fundamental characteristic of plants for removing VOC as well are required. ACKNOWLEDGEMENT This study was supported in part by the Hibi Science Foundation in the 2006 fiscal year. We wish to thank Miss Takahashi, who was a graduate student of Toyohashi University of Technology (TUT), and Mr. Nakao, a student of TUT, for their help with this study. REFERENCES 1. Wolverton, B C, Johnson, A, and Bounds, K. 1989. Interior Landscape Plants for Indoor Air Pollution Abatement. Final Report for NASA. 2. Wood, R A, Orwell, R L and Burchett, M D. 1997. Rates of Absorption of VOCs by Commonly Used Indoor Plants, Proc. of ISIAQ 5th International Conference on Healthy Buildings. Vol. 2, pp 59-64. 3. Kempeneer, L D, Sercu, B, Vanbrabant, W, Van Langenhove et al. 2004. Bioaugmentation of the Phyllosphere for the Removal of Toluene from Indoor Air. Appl Microbiol Biotechnol. 64, pp 284-288. 4. Sawada, A, Yoshida, T, Kuroda, H, Oyabu, T and Takenaka, K. 2005. Purification EEfects of Golden Pothos and Peace Lily for Indoor Air-Pollutants and its Application to a Real Environment. IEEJ Trans. SM. Vol. 125, No.3, pp 118-123 (in Japanese). 5. Wood, R A, Burchett, M D, Alquezar, R, Orwell, R, Tarran, J and Torry, F. 2006. The Potted-plant Microcosm Substantially Reduces Indoor Air VOC Pollution: I. Office-field Study. Water, Air and Soil Pollution. 175, pp 163-180. 6. Yamaguchi, M, Matsumoto, H, Okura, T, and Sato, H. 2005. Experimental Study on VOC Removal of Foliage Plants in Rooms Part 1 Outline of Experiments and VOC Removal of different Plants. Summaries of Technical Papers of Annual Meeting AIJ. pp957-958. (in Japanese) 7. Takatsuji, M. 1996. The Basic and Practices of Plant Factories. Shokabo Tokyo. 8. Eiji Goto. 2005. Application of LEDs to Plant Production. J. Illum. Engang. Inst. Jpn. Vol.89, No.3. pp142-145. (in Japanese)