Black and white Episodes, chemical Evolution and eurasian Air Masses and long-range Transport of Carbon to the Arctic

Long-range transport of pollution aerosol from central Europe to southern Scandinavia has been recognized for a decade. Depending on the trajectory, high concentrations of sulfate in southern Sweden are accompanied by greater or lesser carbon, and have be come known as black or white episodes. It is now known that, when conditions are right, pollution aerosol (and elemental carbon) can be transported order-of-magnitude longer distances, from Eurasia to the Arctic. A simple model of long-range transport of S02, S04- and trace metals has been constructed to account for the large changes between Eurasia and the Arctic. This paper presents a broadened interpretation of black and white episodes which, in combination with atmospheric measurements at other locations in Eurasia and environs, allows this transport model to be checked empirically. It also allows the atmospheric lifetime of carbon to be compared with lifetimes of other primary aerosol pollutants. The results confirm most features of the model, and suggest that black and eastern white episodes are highly related, early stages of systematic atmospheric aging, later stages of which can be observed as far away as the Arctic. The lifetime of elemental carbon appears to be similar to that of other primary, submicron elements, but is still very uncertain