Assessment of air pollution tolerance and heavy metal bioaccumulation in plants from areas surrounding Raniganj, India: implications for environmental monitoring

Abstract

Green vegetation plays a crucial role in monitoring air pollution in a sustainable and cost-effective manner. The present study evaluated the tolerance of ten plant species to air pollution in the Raniganj coalfield area by calculating their Air Pollution Tolerance Index (APTI). Four adjoining sites, including polluted and reference areas, were selected for comparison. Calotropis procera, with a higher APTI, was reported as a resistant species in all the study areas and considered an excellent performer. In contrast, Cassia tora had the lowest APTI, marking it as sensitive and a potential bio-indicator. Physiological parameters such as pH, relative water content (RWC), and ascorbic acid were higher in tolerant species, whereas total chlorophyll was stable under pollution stress. The concentration of heavy metals in plant leaves followed the trend Manganese (Mn) > Iron (Fe) > Lead (Pb) > Cadmium (Cd) and was higher in polluted sites than in the reference area. The Metal Accumulation Index (MAI) also varied significantly among species. Plants like Calotropis procera and Ficus religiosa, with high APTI and MAI, showed minimal leaf area reduction, indicating greater resilience. Elevated ascorbic acid levels at polluted sites suggest an adaptive antioxidant response to oxidative stress. The findings of the present study highlight the utility of APTI and MAI as effective tools in identifying plant species suitable for monitoring environmental pollution. The results support the integration of tolerant species in greenbelt design and warrant further exploration of their genetic and molecular responses for long-term environmental sustainability. Future research should emphasize on detailed investigations into defense mechanisms, large-scale field validation, seasonal monitoring and the exploration of plant-based phytoremediation strategies to strengthen their role in urban and industrial landscape planning.