Source, enrichment and risk assessment of atmospheric aerosols (PM10) at urban/industrial city, Hyderabad, India

A long-term study (2019-2021) to understand the chemical characteristics of atmospheric aerosols (PM₁₀), collected fortnightly on quartz fibre filters in an urban/industrial location of Hyderabad, India was carried out by measuring the trace, rare earth and heavy elements, water-soluble inorganic ions and carbon isotopes. High K⁺_nss/OC was observed during post-monsoon and winter, suggesting contribution from local and biomass/crop residue burning from surrounding regions. Cr, Mo, Cs, Ce and Pb were observed to be 22%, 88%, 92%, 20% and 18% higher than WHO's daily and annual limit. The role of transition elements, mainly Fe and Mn, in catalysing HO₂^- or O₂^- and converting them to H₂O₂ and H₂O, respectively was explored, where Cu/Fe (annual average: 0.02 ± 0.01) and Cu/Mn (0.24 ± 0.15) ratios suggested the dominance of H₂O regime compared to H₂O₂ regime. The enrichment factor (EF) of trace and heavy metals were mostly in the range of 10 < EF < 100 (Fe ref ) and 1 < EF < 10 (Ti ref). Enrichment of Ba and Se during post-monsoon, Sb and Cr during post-monsoon 2019 and winter 2020 and Co during summer were observed. The stable carbon isotopes of TC (δ¹³C_TC) and EC (δ¹³C_EC) varied from - 28.1 to - 24.7 ‰ (avg. - 26.5 ± 0.7) and - 32.5 to - 24.6 ‰ (avg. - 27.4 ± 1.1), indicating contribution from C₃ plant burning and liquid fuel combustion (vehicular exhausts). Positive value of δ¹³C_OC - δ¹³C_EC and heavier δ¹³C_TC, along with gradual enrichment in δ¹³C_TC and δ¹³C_EC from December 2020 to March 2021, implied the photochemical aging of CA. Lighter δ¹³C_TOC and OC/EC > 4 for all seasons suggest the dominance of biomass burning (wood and crop residue burning), photochemical oxidation and SOA formation.

Further, the inhalation risk on human health during exposure to harmful metals was investigated for entire sampling duration, and the dominance of sources for carcinogenic Cd at the sampling location were inferred compared to electronic-plastic waste-burning sources (eg Sn). La, Ce, V, Mo, Cs and Rb were observed to be from continental crust sources, considering their common sources. Carcinogenic inhalation risk for Cr(VI) was only observed during post-monsoon 2019, and non-carcinogenic inhalation risk (hazard index >1) was observed throughout the sampling duration for all considered metals was observed.