Concentration, likely sources, and ecological risk assessment of potentially toxic elements in urban soils of Shiraz City, SW Iran: a preliminary assessment

Potentially toxic elements (PTE) are considered as hazardous pollutants that could have adverse effects on the environment. In recent decades, Shiraz, one of the largest cities of Iran, has been faced with extensive development and its environmental consequences. In this paper, urban soils of Shiraz were collected for preliminary evaluation of potential ecological risk as well as likely source identification of PTE (As, Pb, Cu, Co, Cr, Ni, Sr, and Zn). The concentrations of PTE were analyzed by inductively coupled plasma-optical emission spectrometry (ICP-OES). Geochemical indices (geo-accumulation index (Igeo) and enrichment factor (EF)) and potential ecological risk (PER) index were used to measure the contamination level. Correlation coefficient (CA) and principal component analyses (PCA) as statistical models were applied to recognize the probable sources of PTE. The study shows that the average levels of As, Pb, Cu, Co, Cr, Ni, Sr, and Zn in urban topsoil are 3.96, 11.5, 50.0, 11.5, 334.5, 102.0, 339.4, and 49.0 mg/kg, respectively. For both Igeo and EF, the values are Cu > Sr > Pb > Cr > Zn > Ni > Co > Cd > As. Geochemical indices indicate that the studied soils are mostly un-polluted to moderately polluted. Also, potential ecological risk assessment values of PTE are < 150, illustrating a low ecological risk level. Correlation coefficient and PCA suggest likely anthropogenic origins for Zn, Pb, Co, Ni, Cu, and As and geogenic source for Sr, while Cr appears to have a mixed anthropogenic origins.