Concentration, contamination level, source identification of selective trace elements in Shiraz atmospheric dust sediments (Fars Province, SW Iran)

Abstract

Geogenic dust is one of the most important environmental hazards in Iran. This study investigated the concentration, contamination level, potential sources, and ecological risk and human health assessment of Shiraz atmospheric dust, the largest city in southern Iran. Contents of atmospheric dust sediments geochemistry were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES). The mean concentrations of the elements in atmospheric dust are Zn (106.6 mg/kg), Cr (98.4 mg/kg), Ni (68.1 mg/kg), Cu (40.5 mg/kg), Pb (30.6 mg/kg), As (4.5 mg/kg), and Cd (0.28 mg/kg). Except As and Cd, levels of all other elements in dust sediments samples were higher than corresponding background world soils. In comparison with the concentrations of studied heavy metals in Shiraz urban street dust, the concentrations of heavy metals in Shiraz atmospheric dust were substantially at low levels. Based on Enrichment Factor (EF) and Geo-accumulation index (Igeo), Shiraz atmospheric dust is moderately to minimally polluted by selected heavy metals. The values of risk index (RI) for seven heavy metals in all dust samples were 146.2 and 130.8, which were lower than 150, indicating that ecological risks posed by studied elements in atmospheric dust were moderate. Human health risk assessment (non-carcinogenic) suggested that of the three exposure pathways, ingestion of atmospheric dust was the major pathway exposure to heavy metals in dust, followed by skin contact. The hazard index (HI) values for all studied heavy metals decreased in the following order: Cr > Pb > Ni > Cu > Zn > Cd for both children and adults. Cr and Ni contribute most to health risk posed by atmospheric dust exposure for both children and adults, and Cd, Zn, and Cu have smaller contributions. The result of cancer risk assessment suggested that Cr, Ni, and Cd were all below the safe level. Principal component analysis (PCA) indicated that grouped Cd, Ni, and Zn and grouped Cr, Cu, and Pb could be controlled by two different types of anthropogenic source. Whereas, As and Zn were controlled by both human and geogenic sources.

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