Chemical characterization and source apportionment of PM10 in the Sistan basin under high dust conditions

This study analyzes the chemical composition of airborne PM 10 samples collected in the Sistan Basin, eastern Iran, during the summer dust period of 2021. The chemical speciation emphasized carbonaceous aerosols (organic, elemental and carbonate carbon) examined for the first time in Sistan, water-soluble inorganic species (WSIS) and trace elements. A high mean PM 10 concentration of 308.9 μg m −3 (range: 62.5–1791 μg m −3 ) was observed, while the OC and EC concentrations were 6.95 μg m −3 and 0.56 μg m −3 , respectively, with even higher levels of carbonate carbon (7.45 μg m −3 ). WSIS were dominated by Ca 2+ (20.03 μg m −3 ), followed by SO 4 2− (5.32 μg m −3 ), Cl − , NO 3 − and Na + . The anion deficit in the ion chromatography analysis was highly correlated to Ca 2+ (R 2 = 0.99), revealing the presence of carbonates, while the high concentrations of Na + indicated halite presence in the dust from the desiccated Hamoun lakes. Major and trace elements mainly comprised crustal particle markers (Ca > Al > Fe > Mg). In contrast, the sum of anthropogenic trace elements averaged lower than 200 ng m −3 (with contributions mainly by Mn and Zn). The strong correlations between most ionic species and trace elements suggest common area sources, mostly related to mineral emissions and secondarily to urban activities in Zabol City. The mass closure analysis revealed a dust contribution of 73 % to PM 10 , followed by carbonaceous aerosols (17 %). In addition, the first-time Positive Matrix Factorization (PMF) analysis in Sistan highlighted dust as the major source (63.5 %), followed by regional/secondary aerosols (29.2 %) and fossil-fuel combustion (7.4 %). • Severe period-average (>300 μg m −3 ) and daily maximum (>1500 μg m −3 ) PM 10 concentrations. • High levels of carbonate carbon from lake-bed erosion and of NaCl from halite dissolution. • Organic aerosols are mostly from secondary formation. • Three sources identified via PMF analysis with dust to be the dominant contributor (>60 %). • Low EC concentrations linked to limited contribution of fossil fuel combustion to PM 10 (<10 %).