Simulating Atmospheric Organic Aerosol in the Boreal Forest Using Its Volatility-Oxygen Content Distribution

Various parameterizations of organic aerosol (OA) formation and its subsequent evolution in the two-dimensional Volatility Basis Set (2D-VBS) framework are evaluated using ground measurements collected in the 2013 PEGASOS field campaign in the boreal forest station of Hyytiala in southern Finland. A number of chemical aging schemes that performed well in the polluted environment of the Po Valley in Italy during the PEGASOS 2012 campaign are examined, taking into account various functionalization and fragmentation pathways for biogenic and anthropogenic OA components. All seven aging schemes considered have satisfactory results, consistent with the ground measurements. Despite their differences, these schemes predict similar contributions of the various OA sources and formation pathways for the periods examined. The highest contribution comes from biogenic secondary OA (bSOA), as expected, contributing 40-63% depending on the modeling scheme. Anthropogenic secondary OA (aSOA) is predicted to contribute 11-18% of the total OA, while SOA from intermediate-volatility compounds (SOA-iv) oxidation contributes another 18-27%. The fresh primary OA (POA) contributes 4%, while the SOA resulting from the oxidation of the evaporated semivolatile POA (SOA-sv) varies between 4 and 6%. Finally, 5-6% is predicted to be due to long-range transport from outside the modeling domain.