Uncovering the sources of major air pollutants, such as black carbon (BC), is important for understanding their impact on climate. A new study by researchers at the Department of Environmental Science published in Proceedings of the National Academy of Sciences (PNAS) shows that the sources of BC found over the Indian Ocean differ between winter and summer. This finding may have implications for the monsoon buildup as well as ecosystems and agriculture.
Black carbon (BC), otherwise known as soot, is released via the incomplete combustion of biomass or fossil fuels.
Prof Örjan Gustafsson and his colleague Krishnakant Budhavant at the MCOH Observatory, Maldives. Photo: Joakim Romson
“The Indian Monsoon rains are hugely important for South Asian societies. Improved knowledge of the sources of aerosols affecting cloud formation over the Indian Ocean is important for understanding the changing monsoon dynamics,” says Örjan Gustafsson, Professor at the Department of Environmental Science and co-author of the study.
The researchers carried out carbon-14 and carbon -13 isotope fingerprinting over five years at a remote observatory in the Indian Ocean. Based on the carbon isotope signatures of BC particles, the researchers were able to pinpoint their sources. They found that African savanna burning fires accounted for up to half of all BC particles over the Indian Ocean.
“The isotope fingerprints revealed a more variable and different source distribution during the summer than what has been determined earlier for the winter, which helps to guide efforts to mitigate BC aerosol emissions,” says Örjan Gustafsson.
