Air pollution tolerance index of plants growing near an industrial site

Highlights

• Air pollution tolerance index of 25 plant species has been estimated.

• Highest APTI was observed in Ficus bengalensis.

• APTI has been used to categorized plant species into sensitive and tolerant.

• Ascorbic acid showed significant positive correlation with APTI.

Abstract

Green vegetation around industrial premises can provide a cost-effective and eco-friendly technique to mitigate air pollution. Sensitive and tolerant plant species can be identified by evaluating their air pollution tolerance index (APTI). APTI is deduced by evaluating the pH, ascorbic acid, total chlorophyll, and relative water content (RWC) of plant leaves. An APTI score of ≤ 11, 12–16, and ≥ 17 classifies the tree species as sensitive, intermediate, and tolerant towards air pollution respectively. The present study was designed to estimate the air pollution tolerance index (APTI) of 25 plant species growing at Talkatora Industrial Area, Lucknow Uttar Pradesh, India. The biochemical properties of plant species ranged from; ascorbic acid: 0.6–19.6 mg/g, RWC 41.34%–98.62%, pH 4.5–8.2 and chlorophyll content 0.59–1.49 mg/g. Findings revealed that among 25 plant species, Ficus bengalensis > Ficus religiosa > Eucalyptus globus > Azadirachta indica juss > Heveabra brasiliensis are tolerant towards air pollution; whereas, Polythalia longifolia was found to be most sensitive. In addition, the dust capturing potential of the plant leaves has also been evaluated. Moringa oleifera leaves were found to have the highest dust capturing potential (5.7 mg/cm²), whereas, the lowest was noticed in Acacia nilotica (0.10 mg/cm²). Pearson correlation of biochemical parameters revealed that ascorbic acid showed significant correlation (R² = 0.897) with APTI. The species having < 11 APTI values may be used as a bio-indicator of air quality, while those having APTI ≥ 17 can be used for green belt designing.

Introduction

In recent decades, air quality in major cities of developing countries has deteriorated sharply due to rapid increase in traffic, vehicular and industrial emission, and the reduction of urban vegetation cover (Kim et al., 2015, Santos et al., 2015). Vehicular emission is considered to be a major source of air pollutants viz. particulates, CO, SO_x, NO_x, heavy metals, and polyaromatic hydrocarbons (PAHs) (Kulshreshtha and Sharma, 2015, Kisku et al., 2013). Release of such pollutants into the atmosphere not only deteriorates the ambient air quality, but also poses health risk to the people particularly those suffering from respiratory and cardiovascular illness (Jahan et al., 2016, Adrees et al., 2016). To reduce the impact of toxic airborne pollutants, environmentalists and policy makers have emphasized the need of perennial green belt in and around urban areas as well as along roads (Klumpp et al., 2004, Chaulya et al., 2001). Green belts provide the natural ways to reduce the atmospheric pollution by capturing particulate matter, and absorbing gaseous pollutants (Hamraz et al. 2014). Leaves of the plants in particular provide a large surface area for the deposition of atmospheric pollutants and subsequently act as a sink (Kim et al. 2015). Plants have the capacity to remove air pollutants by three means: absorption by the leaves, deposition of particulates over leaf surfaces, and the fallout of particulates on the leeward side of the vegetation (Rawat and Banerjee 1996). Plants can remove air pollutants like HF, SO₂, PAN, and heavy metals such as mercury (Hg) and lead (Pb) from the air (Shannigrahi et al. 2003). However, certain air pollutants can adversely affect the plant growth by altering the biochemical composition, rate of photosynthesis, seed germination, number of flower on florescence, length of pedicle, and stomata (Chakraborty et al. 2009). Some plants can adapt to the changed environment by virtue of biochemical adjustments particularly in chlorophyll, ascorbic acid, pH of leaf, and relative water content (Kuddus et al., 2011, Flowers et al., 2007). These adjustments in biochemical characteristics can be combined to determine the air pollution tolerance index (APTI) of a particular plant species. Broadly, APTI can be used for identifying the sensitive, intermediate, and tolerant plants species towards air pollutants (Nayak et al., 2015, Leghari et al., 2011, Das and Prasad, 2010, Liu and Ding, 2008).

Plant species, those are more sensitive acts as bioindicator of air pollution, while tolerant one act as sink for airborne pollutants and can be used for the development of green belt (Rai and Panda, 2014, Kousar et al., 2014, Kuddus et al., 2011, Agbaire and Esiefarienrhe, 2009, Singh et al., 1991). Lucknow being the most populated state of India i.e. U.P. is facing twin challenge of high population and uncontrolled vehicular growth, which has adversely affected the ambient air quality particularly in urban areas (Bharti et al., 2017, Barman et al., 2008). Poor air quality problem can be addressed by planting tolerant plant species having high APTI. The present study was conducted to determine the sensitivity/ tolerance of common plants species towards air pollution growing near Talkatora Industrial Area by calculating their APTI. The APTI of various plant species shall be helpful in selection of suitable plants for the purpose of development of green belt in the vicinity of urban/industrial areas.