Oxidative potential of atmospheric PM10 at five different sites of Ahmedabad, a big city in Western India

Highlights: • Oxidative potential (OP) cannot be determined by PM₁₀ mass alone. • Volume-normalized OP shows a significant spatial variability over Ahmedabad. • Nitrogenous organics from the traffic-related sources have higher OP. The current study presents the oxidative potential (OP) along with a wide range of chemical speciation of particulate matter with an aerodynamic diameter less than 10 μm (PM₁₀) at five sites representing different environments in Ahmedabad, a big city in western India. On an average, PM₁₀ concentrations were 116 ± 36, 228 ± 43, 133 ± 29, 101 ± 21, and 70 ± 20 μg m⁻³; volume-normalized OP (OP_V) were 2.51 ± 0.71, 5.62 ± 0.68, 2.69 ± 0.76, 2.14 ± 0.41, and 1.55 ± 0.51 nmol DTT min⁻¹ m⁻³; and mass-normalized OP (OP_M) were 22 ± 3, 25 ± 5, 21 ± 6, 21 ± 2, and 22 ± 3 pmol DTT min⁻¹ μg⁻¹ over Bapunagar (backward residential area), Narol (industrial), Paldi (bus transport hub), Income Tax (huge running traffic) and Science City (posh residential area), respectively. Overall, OP_V showed a significant linear correlation with PM₁₀, whereas OP_M showed near uniformity with increasing PM₁₀. Although the OP_M values were similar, the site-to-site variability in PM₁₀ concentration reflects the corresponding health risks associated with PM₁₀ exposure for the people living in these areas. Further, a noticeable temporal variation in OP_M at Narol and Paldi suggests that species with diverse OP_M contributed to PM₁₀ on different days. A strong linear relationship between the ratio of OP_V to the mass concentration of organic carbon (OP_OC) and the ratio of m/z 43 signal to total water-soluble organic aerosols (WSOA) signals (f43) suggests that the fossil-fuel combustion derived WSOA have higher OP. Furthermore, the relationships of OP with water-soluble trace metals and brown carbon are also investigated and discussed in this paper. Nitrogenous organic compounds particularly emitted from the traffic-related sources in Paldi and Income Tax have higher OP_OC than those emitted from other sources over Bapunagar, Narol, and Science City.