Seasonal variation of biochemical parameters and air pollution tolerance index (APTI) of selected plant species in Delhi city, and detailed meta-analysis from Indian metropolitan cities

Abstract

Plants act as the primary barrier to atmospheric pollution. Thus, while considering the role of plants in restricting air pollutants, one of the environmental tools used to assess tolerant plant species is the Air Pollution Tolerance Index (APTI). We conducted a study in Delhi during the pre-and post-monsoon seasons at polluted (Nehru Nagar) and non-polluted (Pusa Road) sites to assess the site-specific and seasonal variation of biochemical parameters (ascorbic, pH, relative water content, and chlorophyll) and APTI. Two-way ANOVA, Pearson's test, and Principal Component Analysis (PCA) were performed for the statistical analysis. Also, a detailed meta-analysis of biochemical parameter and their influence on APTI based on published literature in metropolitan cities of India has been performed. The study conducted in Delhi at a non-polluted site found higher APTI in the pre-monsoon than post-monsoon season. In addition, the maximum ascorbic acid content of 2.47 mg/g (Azadirachta indica A.Juss) and 1.37 mg/g (Ficus benjamina L) was reported at polluted and non-polluted sites, respectively, during pre-monsoon. The detailed meta-analysis of published literature revealed that plants' chlorophyll and ascorbic acid content were more at polluted sites than at non-polluted sites and substantially impacted APTI calculation. Linear regression showed a significant correlation of ascorbic acid (Mangifera indica L, R2 = 0.9670) and chlorophyll content (Polyalthia longifolia (Sonn.), R2 = 0.958) with APTI. Also, in the PCA test, measured characteristics of different species were strongly correlated, with 72.55% of overall variability. Furthermore, the meta-analysis revealed the average APTI of the plants in the following order Ficus benghalensis L > Polyalthia longifolia > M.indica > A. indica > Delonix regia (Boj. ex Hook) > Ficus religiosa L. A substantial seasonal, site-specific variation and statistically significant differences in the biochemical parameters of plants were observed. These results could be used to classify plant species as air pollution sinks and bioindicators.