Contribution of volatile precursor substances to the flux of perfluorooctanoate to the Arctic.

Perfluorooctanoate (PFO) has recently been found in remote ocean water and Arctic samples, despite not having been used in significant quantities in remote areas. Two main scenarios for the contamination of the Arctic by PFO have been suggested: (i) direct emissions of PFO and oceanic transport to the Arctic and (ii) emissions of volatile precursor substances that are transported and oxidized in the atmosphere to form PFO, which is subsequently deposited to the Arctic. Focusing on the atmospheric transport pathway, we compare the importance of fluorotelomer alcohols (FTOHs) and perfluorooctyl sulfonamidoethanols (FOSEs) for PFO deposition to the Arctic. Using a global scale multispecies mass balance model, we simultaneously calculate the transport, degradation, partitioning, and deposition of precursor substances, intermediate degradation products, and PFO and compare model results to field measurements. Prior to 2002, the modeled deposition fluxes of PFO to the Arctic originating from FOSEs and FTOHs are of a similar magnitude, and total estimated deposition compares well with deposition measurements for Arctic ice cores. However, the model underpredicts recent measurements of FOSEs in Arctic air, indicating that there may be additional emissions not taken into account. Using Monte Carlo calculations we quantify the uncertainties in our model results and identify that emission estimates, degradation yields, and degradation rate constants are the most influential input parameters controlling the estimated deposition of PFO to the Arctic.