Source apportionment and deposition of dustfall-bound trace elements around Tabriz, Iran.

The monthly and spatial variations of atmospheric dustfall (DF) and their elemental components were determined. The DF sampling was performed using the ASTM method D-1739 from April 2017 to March 2018 in four urban and suburb sampling sites around Tabriz, Iran. The ICP-OES was utilized for the determination of the elemental components of DF. The results showed that the level of DF varied from 1.3 to 27.6 (8.0 ± 3.4) g/m2.month during the sampling period, and the level of DF was higher in warm seasons than cold seasons. Also, it was revealed that the mean DF has a direct and significant relationship with temperature, wind speed, and relative humidity. The elements of Fe (11,997–17,093 mg/Kg and 71–81%) and Al (2903–6852 mg/Kg and 14–25%), which are the main elements of the Earth crust, were the dominant metals of DF among the analyzed elements. The lowest average value of the enrichment factor (EF) was for Al and was 10 in all the sites, indicating that anthropogenic emission sources spread a considerable amount of trace elements in DF compared to the Lake Urmia bed or soil. The EF values for various elements (except than Cu and Hg) in cold seasons considerably increased compared to warm seasons. In all the study sites, Fe (540–1307 mg/m2.yr) had the highest deposition rates among the metals. This study revealed that the Earth crust is the main source of DF in the region.