Highlights
- Aerosols and their major sources are seasonally variable at Visakhapatnam.
- Total suspended matter was higher during winter than during summer.
- Biomass burning is a dominant source of aerosols during winter.
- Fossil fuel and coal combustion are the major sources during summer.
Abstract
The continuous rise in anthropogenic aerosol emissions degrades ambient air quality, and their deposition onto the surface ocean alters chemical and biological characteristics. Identifying the sources of aerosols is crucial for taking appropriate measures to minimize their impacts. Stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) are promising tools for identifying sources of carbonaceous aerosols. The objective of this study is to identify the dominant sources of carbonaceous aerosols over an urban region using stable carbon (δ13C) and nitrogen (δ15N) isotope ratios, and to evaluate their potential influence on surface ocean acidification in the coastal Bay of Bengal. Aerosol samples were collected between March 2016 and February 2017 at a fortnightly interval, over an urban region, to examine the sources of carbonaceous aerosols and to evaluate the possible impacts on surface ocean acidification. Significantly high concentrations of total suspended particulates (TSP) during winter (112 ± 26 μg m−3) compared to summer (58.8 ± 8 μg m−3), associated with an insignificant seasonality in δ13CTC (−26.9‰ to −22.9‰), indicating ageing of organic aerosol through oxidation. In contrast, higher δ15NTN during winter (2.2‰ to 12.1‰; 5.4 ± 2.9‰) than summer (−12.9‰ to −1.8‰; −4.7 ± 3.3‰) indicate different sources. Based on source characteristics of δ13CTC, δ15NTN and the isotope mixing model, biomass burning and coal combustion are the major sources of carbonaceous aerosols during winter, whereas coal and fossil fuel burning contributed during summer. Since biomass burning contains higher concentrations of acidic aerosols, such as sulfates, and its deposition over the surface ocean results in higher level of pH levels compared to coal ashes. A higher decline in pH of the coastal waters during winter than summer was reported in the coastal Bay of Bengal. This study confirms that the deposition of higher sulphate and nitrates due to biomass burning in the Indo-Gangetic Plain (IGP) region is responsible for a greater decline in pH of the surface ocean during winter than summer. Taking appropriate measures to reduce biomass burning in the IGP region would decrease ocean acidification and allow the atmospheric CO2 sink into the coastal Bay of Bengal to achieve net zero carbon emissions in the future.
Kumari V. R. & Sarma V. V. S. S., 2026. Identification of the source of carbonaceous aerosols using stable carbon and nitrogen isotopes and the implications of its deposition on the coastal ocean. Atmospheric Pollution Research 17(6): 102968. doi: 10.1016/j.apr.2026.102968. Article (subscription required).
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