Source identification, pollution status, and ecological risk assessment of heavy metals contamination in a highly populated unplanned industrial area (Wadi El-Qamar), Alexandria, Egypt

ased on the contents of heavy metals (Co, Cr, Cu, Fe, Mo, Mn, Pb, and Zn) in 22 road dust samples, the urban environmental quality of Wadi El-Qamar area was evaluated. It is a residential area suffering from unplanned industrial activities, overpopulation, and uncontrolled urbanization. Heavy metal sources and geochemical associations were deciphered using a multivariate statistical approach, while the contamination degree and ecological risks were identified using various pollution indices. Moreover, the human health risks (carcinogenic and non-carcinogenic) for residents were estimated via different exposure pathways. The mean abundances of elements were as follows: Fe > Mn > Zn > Cr > Cu > Pb > Mo > Co, while the individual contamination grades decreased in the following order: Mo > Cu > Zn > Pb > Cr > Fe > Mn > Co, according to the geoaccumulation index (I geo ) and the contamination factor (CF) average values. The high correlation between Zn and Cu ( r = 0.92) reflected their common origin (traffic-related emissions). Notably, only Cu showed individual ecological risk; meanwhile, the overall ecological risk index (RI) classified the study area as having low ecological risk (RI < 150), with an average of 75.20. The health risk assessment indicated the absence of adverse non-carcinogenic risks and the presence of unacceptable carcinogenic risks posed by Cr and Pb. Ultimately, heavy-duty vehicular emissions (e.g., tire and brake wear) and industrial emissions from cement and refining companies are likely the main contributors to heavy metal loadings in the study area. The results of this research will be useful in developing strategies for pollution control and management and can be utilized for comparison in future studies.