Variations in particulate matter chemical composition in the urban coastal city of India

Particulate matter (PM) is collected in the urban coastal city of Mumbai. The PM_2.5 concentrations averaged from 200 μg m⁻³ to 90 μg m⁻³ throughout the year during sampling. These values were substantially higher than national ambient air quality standards (60 μg m⁻³). The Organic carbon (OC) concentration in PM ranged from 6 μg m⁻³ to 17 μg m⁻³ from summer to winter, whereas elemental carbon (EC) has varied from 1.2 μg m⁻³ to 4.8 μg m⁻³. The OC/EC ratio was lower in winter than summer because of high EC emissions during winter and low photochemical activities. The summer samples have a high percentage of low volatile OC fraction (53%) than the winter samples. The calculated secondary organic carbon (SOC) also varies seasonally. The fraction of SOC in overall OC was highest in summer (65.7%), whereas the concentration of SOC was higher in winter, i.e., 9 μg m⁻³. High temperatures and strong solar radiation favor SOC formation during the summer, resulting in a high percentage of low volatile OC in total OC. The overall chemical composition of PM_2.5 reveals that almost 68% of the total mass was elemental composition (SO₄²⁻, NO₃⁻, NH₄⁺, Na⁺, Ca²⁺and K⁺) in winter and 16% in summer. Seasalt contribution to PM_2.5 was 32% and 5% in winter and summer, respectively. Chlorine to sodium molar ratios was below the seawater ratio line in both seasons (0.69 winters and 0.30 summers), but the drop in the summer season might indicate more loss of chlorine. In summer, aerosols are slightly less acidic than in winter and pH value ranged from 3.2 to 7.1. Therefore, we can say that Mumbai suffers from air pollution problems during the winter, despite being a coastal city. These high concentrations of PM have an adverse effect on the health of the urban population.