Assessment of anthropogenic activities impact based on metals in soil and tree leaves along roadside in Bangladesh

The assessment of heavy metal pollution in leaves and soils is essential in environmental health monitoring. We assessed the effect of anthropogenic activities along an industrial-urban-rural gradient in the roadside soil and tree leaves of Bangladesh based on their metal concentration. The concentrations of Pb, Cr, Ni, and Cd were analysed in leaves of Ficus benghalensis, Swietenia macrophylla, and Polyalthia longifolia and topsoil samples using ICP-OES. We used pollution indices to quantify the impact of contaminants on ecosystems. Our findings indicated that there were higher metal concentrations, especially Cd and Pb, in soil and leaves in close proximity to locations with substantial traffic and industrial activities. Igeo index indicated moderately to strongly polluted areas by Cd. The contamination factor (CF) for Cd indicated a severe contamination, while moderately contamination show by Cr, Pb, and Ni. The value of the ecological risk factor was below 40 for Cr, Ni, and Pb; thus, negligible ecological risks were considered for these elements. But, the ecological risk assessment indices showed that Cd poses high ecological risks in soil and leaves across all study areas. Bioaccumulation analysis indicated substantial heavy metal absorption in tree foliage, with F. benghalensis and P. longifolia exhibiting elevated Pb accumulation in urban environments. The PCA indicated that Cd, Cr, Ni, and Pb mostly derived from anthropogenic sources in leaves and soil samples, too. Our results demonstrated that F. benghalensis, S. macrophylla, and P. longifolia are good indicator to assess the effect of anthropogenic activities on the terrestrial ecosystem. Our results also indicated the critical need for environmental monitoring and mitigation techniques in urban and industrial zones to reduce heavy metal pollution in roadside ecosystems.