Physiochemical characteristics and oxidative potential of ambient air particulate matter (PM₁₀) during dust and non-dust storm events: a case study in Tehran, Iran

In the present study, we investigated the characteristics of metal(loid)s, polycyclic aromatic hydrocarbons (PAHs) and oxidative potential (OP) in PM₁₀ during dust and non-dust days in a rural and an urban area in Tehran. Water-soluble ions, metal(loid)s, PAHs, and OP were measured using ion chromatography (IC), inductively coupled plasma optical emission spectrometer (ICP-OES) and gas chromatography/mass spectrometry (GC-MS), and dithiothreitol (DTT) assay respectively. The results showed that the average concentrations of ambient PM₁₀ were 284 ± 90.4 and 123 ± 31.4 μg m⁻³ on dusty and regular days in urban areas respectively, and were 258 ± 48.3 and 124 ± 41.4 μg m⁻³ on dusty and regular days in rural areas, respectively; these values were 95% above the World Health Organization (WHO) guideline level. The crustal elements Na⁺, Mg²⁺, Ca²⁺, Al, Si, Fe and Ti were the dominant for PM₁₀ on dusty days, and NO⁻₃ and SO₄²⁻ were dominant for PM₁₀ on regular days. The average ± SD concentrations of total PAHs were 34.3 ± 22.5 and 55.1 ± 28.3 ng m⁻³ on dusty and regular days, respectively, with the maximum value occurring on inversion days. The average OP was 8.90 ± 7.15 and 1.41 ± 0.35 and was 11.4 ± 3.97 and 19.9 ± 8.67 (nmol min⁻¹ μg PM₁₀⁻¹) for water and methanol extracts on dusty and regular days, respectively, with the lowest value occurring on dusty days. The OP was highly associated with Cu and Mn. Briefly; the results of this study demonstrate that OP is mass independent and consequence a promising proxy for PM mass.