Heavy metal accumulation in leaves of selected plant species in urban areas of Delhi

Heavy metals beyond their permissible limits are major contaminants and causes of concern due to their persistent nature and health hazards. Several studies validated the utilization of plants as biomonitors and bioaccumulators for heavy metal pollution. Therefore, this study was conducted to examine the proficiency for heavy metal monitoring and mitigation by commonly found plant species in urban areas of Delhi. For this objective, four sites (viz., control, residential, commercial, and industrial) and sixteen usually growing plant species were selected. Four heavy metals, i.e., lead (Pb), cadmium (Cd), copper (Cu), and zinc (Zn), were analysed for soil and dust from each site, and leaf samples from each plant, at all sites, and various other parameters were calculated. Among the four elements, Pb and Cd showed maximum geoaccumulation and contamination at all sites. Pollution load index (PLI) values for both soil and dust indicated that industrial sites (1.78, 2.15) were most contaminated followed by commercial (1.52, 1,87), residential (1.41, 1.67), and control (1.22, 1.37) sites. Concentrations of Pb, Cu, and Zn were found to be highest in Morus alba, while Cd concentrations were found to be highest in Millettia pinnata (L.) Panigrahi. From various analyses, we concluded that commonly found plant species such as Ficus religiosa L., Terminalia arjuna (Roxb. Ex DC.) Wight &Arn., Morus alba L., Prosopis juliflora (Sw.) DC., and M. pinnata proved to be exceptional biomonitors and bioaccumulators for heavy metals in urban areas. Therefore, these plant species are highly recommended for plantation in urban areas for decontamination of the air and soil by mitigating heavy metal pollution.