Distribution, source, and risk analysis of PAHs and trace elements in roadside soils of Dhaka-Bhanga expressway: a case study.

With rapidly increasing traffic flow across the Padma Bridge, concerns have emerged regarding potential pollutant accumulation in adjacent roadside soils. This study investigates the distribution of priority polycyclic aromatic hydrocarbons (PAHs) and trace elements at multiple sites along the Dhaka-Bhanga highway on both sides of the bridge. Soil samples were analyzed using gas chromatography-mass spectrometry and atomic absorption spectroscopy to determine PAHs and trace metals profile, respectively. Bhanga and Pacchor were identified as the most impacted areas for trace elements. PAHs compositions were dominated by 3- and 4-ring compounds, indicating mixed origins from petroleum and combustion sources, particularly at Hasnabad and Abdullahpur. Phenanthrene exceeded guidelines at all sites, with few other PAHs showing localized exceedances. Diagnostic ratio analysis confirmed vehicular petroleum combustion as the major contributor. Health risk assessments did not indicate immediate hazards; however, chromium emerged as the most significant metal in terms of carcinogenic risk, while zinc posed the greatest non-carcinogenic concern for children through dermal exposure. Overall, this study establishes an essential baseline for environmental quality along one of Bangladesh's busiest transport corridors and highlights the need for continuous monitoring and pollution-control measures as traffic density continues to rise.