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Schematic of botanical indoor air biofilter design, taken from http://livebuilding.queensu.ca/green_features/biowall.

Schematic of botanical indoor air biofilter design, taken from http://livebuilding.queensu.ca/green_features/biowall.

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The deployment of complex biological systems in urban settings has evolved as a technology to mitigate what has come to be known as the sick building syndrome. Indoor air quality (IAQ) is a rising concern as people are spending more time indoors and buildings are increasingly sealed to reduce energy consumption. Accumulation of gaseous contaminants...

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... technology effectively hybridizes the positive attributes of PPM and biofiltration approaches to con­ taminant removal, resulting in a botanical indoor air biofilter (BIAB). The basic design (Figure 1) consists of plants rooted into a thin (~5 cm), stable, and very porous medium that is oriented in the vertical plane. Water flows gravimetrically from the top of the biofilter and is recirculated. ...

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Citations

... Research indicates that static systems like pot plants may be ineffective for the purification of high-capacity pollutants. Therefore, technological advances such as using active biofiltration systems or green walls have been developed that can actively impact airflow to a high surface area of plants and their root zone resulting in a huge amount of pollutants contact with plants and their growth substrates (Llewellyn and Dixon 2011;Teiri et al. 2018b;Zhang et al. 2020). ...
... Thus, hydrophilic contaminants such as formaldehyde can hardly enter the plant through the cuticle that is the adipose tissue, while lipophilic contaminants such as benzene can be easily absorbed through the cuticle, in addition to the stomata (Kim et al. 2008;Hörmann et al. 2018;Teiri et al. 2018a). However, some studies have concluded that the contribution of the aerial parts of plants on the removal of VOCs from indoor air is not significant (Girman et al. 2009;Llewellyn and Dixon 2011;Hanoune et al. 2013;Hörmann et al. 2018). ...
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... Apart from that, several other gasses are also responsible for degrading IAQ. CO 2 is one of the most predominant gasses in indoor environments that is primarily generated from respiratory emissions (Llewellyn and Dixon, 2011). A vicinity with excessive amounts of CO 2 is reported to cause the wellknown sick building syndrome (Jafari et al., 2015); along with that, it is shown to decline workplace productivity and students' school attendance (Seppänen et al., 2006;Gaihre et al., 2014). ...
... The nature/characteristics of VOCs readily influence plants' absorption capacity as benzene may freely pass through the cuticle; however, the hydrophilic VOC formaldehyde can pass through stomatal openings (Dela Cruz et al., 2014a, b). Several early botanical air purifying research mostly reinforced the basic methodology of NASA through the passive use of potted plants in order to increase the quality of indoor air (Wolverton et al., 1984;Godish and Guindon, 1989;Wolverton and Wolverton, 1993;Wood et al., 2002Wood et al., , 2006Orwell et al., 2004Orwell et al., , 2006Cruz et al., 2014;Teiri et al., 2018) and the experiments were carried out under high VOC concentrations within a small closed chamber (Llewellyn and Dixon, 2011). ...
... ppm per 1 h from a 100 cm 2 leaf area, but these are mainly laboratory results [28,29]. The air quality improvement effect of indoor plants is constantly changing because pollutants in actual space do not maintain a constant concentration [30,31]. On the other hand, because there is a difference between the minimum detected concentration of the human body and the exposure reference concentration of indoor air pollutants, occupants are not properly aware of this, even though they are exposed to dangerous levels of indoor air quality [32][33][34]. ...
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... Green walls have low temperature and high humidity, resulting in creating a microclimate and reducing the heat island effect (Chew & Conejos, 2016). Not only they affect indoor and outdoor air quality by supplying oxygen and removing toxic gases, plants also reduce the electronic haze in the air and also increase the humidity of the air and lower the temperature as a result of the leaves sweating (Llewellyn, 2011;Saki, 2020;Kalay, 2019;Hazel, 2012). ...
... Green walls have low temperature and high humidity, resulting in creating a microclimate and reducing the heat island effect (Chew & Conejos, 2016). Not only they affect indoor and outdoor air quality by supplying oxygen and removing toxic gases, plants also reduce the electronic haze in the air and also increase the humidity of the air and lower the temperature as a result of the leaves sweating (Llewellyn, 2011;Saki, 2020;Kalay, 2019;Hazel, 2012). ...
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... The idea of removing VOCs from indoor air by plants was introduced by Wolverton and his colleagues in 1989; this field of study led to the National Aeronautics and Space Administration's (NASA) research on biological life support systems for space travel [117]. These research studies have positively shown that potted plants could delete significant or large amounts of gaseous VOCs in sealed chambers, reducing VOCs from 10% to 90% in 24 h [135]. Wolverton et al. investigated 12 plants to remove VOCs and proved the possibility of enhancing indoor air quality by abolishing trace organic pollutants from the air in energy-efficient houses. ...
... The use of this system reduce the concentration of VOCs (VOCs: ketones, acetone, methyl ethyl ketone, and methyl isobutyl ketone), alcohols (ethanol, butanol), BTEX (benzene, toluene, ethylbenzene, o-xylene and p-xylene), halogens (trichloroethylene, dichloromethane, and tetrachloroethylene), limonene and pinene). Depending on the experimental condition, the concentration of VOCs controlled between 20 and 300 ppb [135]. Caron studied the types of indoor air VOC pollutants by a green wall. ...
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... Emissions from materials such as chairs, electronic equipment (Cruz et al. 2014), solvents, plastics and cleaning products , degradation of lignin and cellulose from older books, insulating materials, and furniture (Fenech et al. 2010) were possibly the main sources responsible for the high concentration of TVOCs. While inadequate combustion, black carbon charting on lightened burners (Bhattacharya and Salam 2002;Bruce et al. 2004;Dasgupta et al. 2006;Baumgartner et al. 2011;Yamamoto et al. 2014) and occupancy respiratory pollution coupled with poor ventilation (Llewellyn and Dixon 2011) could have resulted in an accumulation of CO 2 and CO in the indoor setting. Many foundational researches have documented that cooking LPG (Liquid Petroleum Gas) raises CO 2 and CO levels in closed or partly closed conditions (Berkley 2012;WHO 2014;IEA 2016;Obeng et al. 2017). ...
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... Various researchers have identified the possibility of epiphytic and endophytic microbiota, which reside on the leaves and shoots (and it is known as the phyllosphere) to remove VOCs (Khaksar et al. 2016;Sandhu et al. 2007). In addition to leaves of the plant, rhizospheric microbes also contribute to the depletion of VOCs from the internal environment (Llewellyn and Dixon 2011). Popek et al. (2015) demonstrated that trees and shrubs, forming a biofilter on the path of PM flow, have reduced the amount of PM about 50% that accumulates on the foliage of distant trees in the park. ...
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The recent expansion of human industrial activity, including mining, smelting and synthetic compounds, has increased the amount of toxic harmful gases released in the atmosphere, water and soil which contaminated the environment directly and indirectly. There has been a significant rise in the levels of heavy metals (Pb, As, Hg and Cd) due to their increased industrial usage causing a severe concern to public health. The accumulation of these heavy metals generates oxidative stress in the body causing fatal effects to important biological processes leading to cell death. The ability to prevent and manage this problem is still a subject of much debate, with many technologies ineffective and others too expensive for practical large-scale use, especially for developing nations where major pollution occurs. Currently, green technologies require pressure to develop the management of contaminated sites which benefit the society directly and indirectly. Bioremediation is another biological mechanism of waste recycling in another form which can be used and reused by other organisms. Therefore, to reduce the potential toxicity of any pollutant in the environment by degradation, change, bioremediation in the form of bio-systems by the microbes and plants, stabilizing these undesirable substances for less harmful forms.