Investigation of bioaccessibility and sources of elements in road dust: Implications for ecological and human health risks

This manuscript describes a study that investigated the concentration of selected elements in Bolu city center, Turkey. The research objectives included determining bioaccessibility, identifying potential sources, and assessing contamination and exposure level. A total of 50 road dust samples were collected from various locations in the area, and elemental concentrations were measured. The results revealed that the average concentration of total metal ranged from 0.2 mg kg(-1) (Cd) to 2.4 x 10(5) mg kg(-1) (Ca). Notably, Mercury (53) and Sb (86) exhibited enrichment factors exceeding 20 which means very high enrichment, while the EF of As, Co, Sn, Cr, Zn, Pb, Ca, and S varied from 5 to 20 indicating significant enrichment. These elements were primarily attributed to traffic and combustion-related activities, which released them into the atmosphere and led to their deposition on road surfaces. The ecological risk index indicated that the TEM (E-80 highway) route posed the highest risk. Moreover, the Simple Bioaccessibility Extraction Test (SBET) revealed that Pb, and Zn had the highest bioaccessibility at 50 %, and 45 %, respectively. Positive Matrix Factorization (PMF) analysis identified four primary sources: brake/tire wear, industrial emissions, exhaust emissions, and contaminated soil. Finally, the average daily dose intakes (ADD) for all elements were calculated as ADD(ing) > ADD(derm) > ADD(inh) and did not differ significantly between adults and children. These findings provide valuable insights into the sources and concentrations of heavy metals in Bolu city center, which can inform efforts to mitigate potential health risks associated with heavy metal exposure in this area.