Heavy metals in roadside dust, soil, and perennial plants of Dhaka mega south city corporation, Bangladesh: Accumulation characteristics, sources and risk factors
Tasrina Rabia Choudhury, Tasnim Ahshan, M. Nur E. Alam, Sheikh Fahim Faysal Sowrav, S M Mustafizur Rahman, M. Safiur Rahman, Md. Mostafizur Rahman
Abstract
Urbanization and industrialization have significantly increased heavy metal (HM) contamination in urban environments, posing ecological and health risks. This study evaluates the concentrations of nine HMs (As, Cd, Cr, Pb, Fe, Ni, Zn, Cu, and Mn) in roadside dust, surface soil, and perennial plant leaves (Banyan and Debdaru) within Dhaka South City Corporation (DSCC), Bangladesh. Samples from ten locations were analyzed using Atomic Absorption Spectroscopy (AAS). Pollution indices, including Enrichment Factor (EF), Contamination Factor (CF), Geo-Accumulation Index (Igeo), and Bioaccumulation Factor (BAF), were calculated to identify contamination levels, sources, and accumulation patterns. Ecological risk was quantified using the Potential Ecological Risk Index (PER), while human health risks were assessed via ingestion, inhalation, and dermal pathways. Results revealed varying levels of HM pollution, with cadmium (Cd) posing the highest ecological risk across all media. The concentration of heavy metals followed the descending order of Fe > Mn > Zn > Cu > Pb > Ni > Cr > Cd across all matrices. Specifically, concentrations in soil ranged from Fe (7128–10095 mg/kg), Mn (451–612 mg/kg), Zn (112–214 mg/kg), Cu (45–78 mg/kg), Pb (29–56 mg/kg), Ni (20–41 mg/kg), Cr (15–33 mg/kg), to Cd (0.78–2.10 mg/kg). Similar trends were observed in dust and plant leaves, with slightly varied concentrations reflecting differential accumulation capacities. Anthropogenic sources, including vehicular emissions and industrial activities, were identified as major contributors to contamination. Bioaccumulation was observed primarily for cadmium and zinc, highlighting the potential for biomagnification. Spatial distribution analysis identified hotspots with elevated HM concentrations, correlating with high traffic and industrial zones. Health risk assessments indicated low non-carcinogenic risks for local populations but emphasized arsenic's potential to impact vulnerable groups. This study provides a comprehensive baseline for understanding HM pollution in Dhaka's urban ecosystem. The findings underscore the necessity of implementing stricter environmental controls, enhancing urban planning strategies, and conducting regular monitoring to mitigate risks to both public health and the environment.