Temporal and spatial variations of deposition and elemental composition of dust fall and its source identification around Tabriz, Iran.

Coarse particles are primarily deposited via sedimentation, commonly referred as dust fall (DF). This study presented the monthly and spatial variations of atmospheric DF and their elemental components (Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Se, Sr, Ti, V, Si, and Hg). Dust samples were collected from four urban and suburban sampling sites around Tabriz, Iran, by using the ASTM method D-1739 during April to September 2017. Moreover, the ICP-OES was used to determine metal components of the DF. The obtained results showed that the DF amount ranged between 1.8-27.6 (7.4 ± 5.6) g/m2.month. The elements of Fe (11863-13,906 mg/Kg and 85%-89%), Al (858-1205 mg/Kg and 4%-8%), and Si (274-386 mg/Kg) were the dominant elemental concentrations of the DF. The average value of enrichment factor (EF) for Hg, Pb, Cu, Sr, Co, Ni, Mn, and V was greater than 10 in all the samples, showing that anthropogenic sources emit a considerable amount of elements in DF rather than the soil or Urmia lake bed. The result of correlations between the concentration of dust fall with humidity, temperature, wind speed, and precipitation showed that there was a direct relationship between the amount of dust fall and wind speed while humidity, precipitation, and temperature were inversely proportional to the amount of dust fall. This study revealed that earth crust and anthropogenic activities such as vehicle traffic, combustion of fossil fuel, and different industrial activities were the main sources of the DF in the studied areas.