Sources and distribution of potentially toxic elements in urban road dust: A comparative insights and risk assessment of two polluted cities

This study provides a comprehensive comparative analysis of seven potentially toxic elements (PTEs) from thirty samples using instrumental neutron activation analysis on the roadside dust samples collected from a southwestern city (Khulna) and a highly urban megacity (Dhaka), Bangladesh. The mean concentrations (mu g.g(-1)) of Cr, Mn, Fe, Co, Zn, As, and Sb in the analyzed dust samples were 67.5+33.2, 386+136, 25648+5334, 6.86+1.79, 98+63, 3.02+1.08, and 1.37+1.10, respectively in Khulna city and 66.7+6.9, 547+110, 25150+1723, 8.39 +0.65, 125+17, 3.63+0.56, and 0.75+0.28, respectively, in Dhaka city, showing uneven distribution in both cities. PMF modelling and multivariate statistical approaches demonstrated that 65.68% anthropogenic and 34.32% geogenic sources for Khulna city, whereas 64.93% mixed (anthropogenic and geogenic) and 35.07% anthropogenic sources were the main contributors of measured elements in Dhaka city. In both cities, anthropogenic contributions were primarily linked to traffic emissions and industrial activity. Various geoenvironmental indicators, including element-specific (I-geo, EF, CF), site-specific (Cd, mC(d), PLI, NIPI), and ecological indices (Er-i, RI), were used to assess the contamination characteristics of PTEs and contamination levels in both cities were in the following decreasing order: Sb >Zn >Cr >Fe >As >Mn >Co, whereas individual ecological risks were in the following decreasing order: Sb(34.28) >As(6.28) >Co(1.98) >Cr(1.47) >Zn(1.46) >Mn(0.50) in Khulna, and Sb(18.64) >As(7.56) >Co(2.43) >Zn(1.86) >Cr(1.45) >Mn(0.71) in Dhaka. The study site demonstrated lower potential ecological risks, even though non-carcinogenic and carcinogenic risks from various exposure pathways appeared minimal. Notably, children in both urban cities exhibited heightened vulnerability compared to adults.