Accumulation of airborne microplastics and its impact on pollution tolerance ability of plants in an urban setup in India

Airborne microplastics (MP) are a recently hyped but unexplored area of research leading to some unanswered questions concerning its impact on vegetation. Work was conducted to evaluate the MP accumulating potential and its impact on the biochemical parameters of plants in an urban area (Sambalpur) in India. Four forms of MPs (viz. fiber, fragment, film, and bead) deposited on the leaf surface were analyzed through fluorescence microscopy using the Nile red dye method. Biochemical parameters (ascorbic acid (AA), leaf extract pH (P), total chlorophyll (TC), and relative water content (RWC)) and air pollution tolerance index (APTI) were also determined through standard protocol. The result found the dominance of beads with other MPs in the order: bead (44.7%) > film (27.7%) > fragment (20.7%) > fiber (6.9%) displaying significant spatial and species variation (p < 0.05). Spatially, the MP accumulation on leaf surface followed an order: residence (4.8 count/cm²) > sensitive (4.6 count/cm²) > urban biotope (4.3 count/cm²) > industry (3.3 count/cm²) > traffic (2.2 count/cm²). Species-wise Ficus benghalensis, Polyalthia longifolia, and Mangifera indica performed reasonably well concerning the MP accumulation while exhibiting good APTI scores. The RWC and leaf extract pH were the most influential factors regulating the MP accumulation. The former was chiefly responsible for dictating the tolerance ability of plants which is corroborated by the principal component and cluster analyses. Thus, it can be ascertained that the plant species offer distinct specificity in MP accumulation which is largely influenced by spatial variations, relative water content, and APTI value of plants.