Background levels of black carbon over remote marine locations
While the Northern Hemisphere (NH) hosts 85% of the world’s population, the Southern Hemisphere (SH) is mostly oceanic surface, meaning the "background" marine air should be notably cleaner over SH oceans than over oceans in the NH. As black carbon (BC) is a product of incomplete combustion that is ubiquitous and unique to air pollution, it is often used as a tracer for polluted or continentally influenced air. In a paper in Atmospheric Research, the authors use the refractory BC data from a single particle soot photometer (SP2) to statistically investigate the degrees of pollution in "background" marine air in the NH and SH. The measurements show that while both NH and SH oceans have similarly low background concentrations of refractory BC, and likely air pollution, the SH marine air was cleaner much more frequently.
Reference: Fossum, K. N., Ovadnevaite, J., Liu, D., et al., (2022). Background levels of black carbon over remote marine locations. Atmospheric Research, 271, 106119. https://doi.org/10.1016/j.atmosres.2022.106119.