Seasonal Dynamics of Stable Carbon and Nitrogen Isotope Ratio in PM10 Aerosols at a Coastal Urban Site in Mumbai, India

Particulate matter (PM) is a major air pollutant that poses significant risks to human health and the environment, particularly in urban areas with high concentrations of PM. In this study, stable isotopes of carbon (δ ¹³ C) and nitrogen (δ ¹⁵ N), the total carbon to total nitrogen ratio (TC/TN) were estimated in particulate patter (PM ₁₀ ) collected during the year 2022 from Trombay area, a coastal site in Mumbai, India. The results were analysed to identify the possible sources and fate of PM and understand the coastal effects on PM in the sampling area. The results showed that δ ¹³ C values ranged from − 26.2‰ to -22.4‰, while δ ¹⁵ N values ranged from − 2.3‰ to 21.4‰ during the study period. The average values of δ ¹³ C and δ ¹⁵ N was − 24.9 ± 0.9‰ and 9.1 ± 5.6‰, respectively. The TC/TN ratio ranged from 2.8 to 7.5, with an average of 4.8. The TN and TC concentrations varied from 0.1 µg.m ^− 3 to 2.3 µg.m ^− 3 and from 0.4 µg.m ^− 3 to 9.1 µg.m ^− 3 , respectively. The δ ¹³ C and δ ¹⁵ N values observed indicated fossil fuels and biomass burning, to be the dominant sources of the aerosol. The relative contribution of different sources (vehicular, biomass, coal, marine origin, and continental dust) showed seasonal variations. Systematic change in δ ¹³ C and δ ¹⁵ N values of aerosols from winter to pre-monsoon to monsoon period is noteworthy as it matches with systematically increasing influence of marine winds over the study area. The correlation between parameters reveals the formation of secondary organic and inorganic aerosols and long-range transport history of the aerosols.