Seasonality and sources of tiny light-absorbing atmospheric particles over Northwestern-Siberia

What is it about?

We observed the concentrations and isotopic sources of tiny particles in airborne black carbon (BC) for over a year, in the Russian Arctic (Tiksi, Siberia), and eventually compared these observations to model results, using the freely available atmospheric transport model FLEXPART and emission inventories for natural and man-made BC emissions. We saw a clear seasonality of the BC concentrations, like it has been reported in the literature before, and the model was able to reproduce this relatively well, but less so than in our study of the Swedish Arctic. Elevated concentrations were found in the winter, which is sometimes referred to as Arctic haze. The combustion sources showed a strong seasonality as well. The radiocarbon data showed, that fossil fuel combustion dominated in the winter and (wood) biomass burning during the low BC-burden periods in the summer. With a combination of the stable isotope fingerprints and Bayesian statistics we further created a best-fit scenario for the model results. This best-fit was achieved by changing all emissions at the same time, so that observations were matched as good as possible. This way we could tell which emissions the model did not get right for our specific case. It showed that power plant emissions (i.e. coal) , transport emissions (e.g., diesel) and house hold heating emissions (a mix of wood, diesel, and coal) had to be increased by roughly 100%. While gas flaring emissions (previously believed to be responsible for up to 40% of BC) had to be reduced by ~80%.

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Why is it important?

Black Carbon (BC) originates from incomplete combustion caused by either natural (e.g., wild fires) or human (e.g., diesel car emissions) activities. As the name suggests, BC is a dark particle which absorbs sunlight very efficiently. In scientific terms we call this a strong and positive radiative forcing (there are also air particles with negative forcing, i.e. cooling). Which means that the presence of BC in the atmosphere is helping to heat the planet. Some estimates put its radiative forcing in second place, only after CO2. The significant thing about BC is that it has a short atmospheric lifetime (days to weeks), meaning we could quickly avoid some climate warming by getting rid of its emissions. Currently global emissions are increasing year by year and on snow and ice, the dark particles have a longer lasting effect due to the freeze and thaw cycle, where BC can re-surface, before it is washed away. It is important however to note, that our main focus on emission reduction should target (fossil-fuel) CO2 emissions, because they will affect the climate long after (several centuries) they have been emitted.

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