Seasonal variations and source apportionment of atmospheric PM2.5-bound polycyclic aromatic hydrocarbons in a mixed multi-function area of Hangzhou, China.

To reveal the seasonal variations and sources of PM2.5-bound polycyclic aromatic hydrocarbons (PAHs) during haze and non-haze episodes, daily PM2.5 samples were collected from March 2015 to February 2016 in a mixed multi-function area in Hangzhou, China. Ambient concentrations of 16 priority-controlled PAHs were determined. The sums of PM2.5-bound PAH concentrations during the haze episodes were 4.52 ± 3.32 and 13.6 ± 6.29 ng m-3 in warm and cold seasons, respectively, which were 1.99 and 1.49 times those during the non-haze episodes. Four PAH sources were identified using the positive matrix factorization model and conditional probability function, which were vehicular emissions (45%), heavy oil combustion (23%), coal and natural gas combustion (22%), and biomass combustion (10%). The four source concentrations of PAHs consistently showed higher levels in the cold season, compared with those in the warm season. Vehicular emissions were the most considerable sources that result in the increase of PM2.5-bound PAH levels during the haze episodes, and heavy oil combustion played an important role in the aggravation of haze pollution. The analysis of air mass back trajectories indicated that air mass transport had an influence on the PM2.5-bound PAH pollution, especially on the increased contributions from coal combustion and vehicular emissions in the cold season.