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This paper investigates the chemical composition of Particulate Matter, Organic Carbon (OC), and Elemental Carbon (EC) in residential and traffic sites in Mumbai. The average PM2.5 and PM10 concentrations at the traffic site (Sakinaka) were 240 µg/m3 and 424 µg/m3, respectively. The observed levels of OC were 35 µg/m3, 22 µg/m3, and 15.5 µg/m3 at Sakinaka junction (high-density traffic), YP-Gate (low-density traffic), and Hostel Premise (Residential), respectively. The average OC/EC ratio value was high (4.5) at the residential site, indicating contributions from stationary combustion sources and secondary production of carbonaceous species to OC. The residential site has a higher percentage of low volatile OC fraction (57%) in total OC than the traffic sites. On the other hand, Sakinaka has a higher percentage of highly volatile OC fractions (36%) in total OC. The crustal-originated metals were dominating in all areas, but the concentration of metals from anthropogenic sources was highest at Sakinaka, i.e., As (381 ng/m3), Pb (352 ng/m3), Zn (679 ng/m3). The K/Al, Ca/Al, Mg/Al, and Fe/Al ratios were high in all the samples compared to the crustal ratio indicating biomass burning and traffic emission sources of these metals. PM originating from traffic was more enriched with heavy metals that are toxic to human health, increasing cancer risks (CR) through inhalation. The hazard quotient was above 1 at all the locations, and CR was above 1 × 10− 4, causing health risks. According to the dosimetry model, more PM was deposited in the lungs of traffic location occupants through inhalation, increasing the cancerous risk. [ABSTRACT FROM AUTHOR]

In this study, we investigated the temporal variation of organic and inorganic aerosol with its optical properties in Mumbai (India), an urban coastal region. Mean PM 2.5  concentrations during the sampling period were 175 μg/m 3 (winter) and 90 μg/m 3 (summer). During winter, the average concentrations of organic (OC), elemental (EC), and water-soluble organic carbon (WSOC) were three times higher than in summer. Secondary organic carbon (SOC) contribution in OC was higher in summer (78%) than in winter (53%), and strong solar radiation in summer likely caused this outcome. Aerosols were slightly acidic in both seasons, with an average pH of 5.7 (winter) and 6.0 (summer). A correlation was observed between SOC and the acidity of particles in summer (R 2  = 0.6), indicating some amount of acid-catalysed SOC formation. In both seasons, the sulphate oxidation ratio (SOR) was higher than the nitrate oxidation ratio (NOR), which may reflect a preference for SO 2 oxidation over NO 2 or the difference in partitioning ammonium nitrate into ammonium sulphate under high RH. The dominant mechanism of SOC formation (gas vs aqueous phase oxidation) also showed seasonal variation. In winter, a relatively steep reduced major axis (RMA) slope of O 3 /CO suggests gas phase oxidation was the dominant mechanism of SOC production. Winter has more BrC fraction than summer, indicating higher absorbing aerosols, though the efficiency of absorbing the light was higher in summer. To assess the radiative forcing of PM 2.5 on a local scale, an effective carbon ratio (ECR) was computed. The findings pointed to a local radiative heating impact caused by PM 2.5 . The spectral slope ratio and MAE at 250 to 300 nm ratio (E 2 /E 3 ) revealed a higher abundance of high molecular weight species in WSOC during summer than in winter., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)