Analysis of the TSP, PM10 concentrations and water-soluble ionic species in airborne samples over Sistan, Iran during the summer dusty period

The present study analyzes the total suspended particulates (TSP) and particulate matter less than 10 μm (PM10) concentrations along with the water-soluble ionic species (WSIS) in airborne dust samples collected in Zabol, located in the Sistan basin of southeast Iran. Rather extreme TSP and PM10 mean concentrations of 1867.0 μg m−3 and 433.4 μg m−3 are found, while the WSIS contribute only 8.9% and 19.3% to the TSP and PM10 mass, respectively indicating large fraction of water-insoluble crustal elements, carbonaceous aerosols and heavy metals that remained unexplored. Ca2+ is the most abundant ionic species contributing ∼25-26% to the total WSIS mass, followed by NH4+, K+, and SO42−. Important fractions of Cl− and Na+ (7-9% of the total WSIS mass) indicate the presence of saline dust storms over Sistan due to desiccation of the Hamoun lakes and uplift of evaporated minerals by the strong Levar (120-days) wind. High correlations between the WSIS suggest large possibility for formation of NaCl, (NH4)2SO4, MgSO4, K2SO4, CaSO4 and NH4NO3. The dusty days (visibility < 2 km) are associated with intense winds (11.7 ms−1 on average) and large increase (∼80-100%) in the concentrations of the crustal elements (e.g., Ca2+, Mg2+ and Cl−) compared to the normal days, while the TSP and PM10 concentrations reach to 4496 μgm−3 and 1010.6 μgm−3, respectively.