Comparative study of PAHs in PM1 and PM2.5 at a background site in the north China plain

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic and mutagenic. They bounded in atmospheric fine (PM2.5) and submicron (PM1) particles severely affect human health. To characterize 18 PAHs at a background site (Mount Tai) in the heavily polluted North China Plain (NCP), PM1 and PM2.5 samples were collected in the autumn of 2014. The sampling periods were classified into clean conditions and polluted conditions according to PM2.5 concentration. Biomass burning condition was selected from polluted conditions to clarify the impact of biomass burning to PAHs concentrations. The concentrations of ∑18 PAHs were 14.5 and 24.5 ng m–3 and the contents were 515 and 607 µg g–1 in PM1 and PM2.5, respectively. Three-ring PAHs were the primary contributors to the total PAHs. The major PAHs sources at Mount Tai were pyrogenic and traffic emission. Diesel combustion played more significant role to the emission of PM1-bound PAHs, while wood burning source was more obvious for PM2.5-bound PAHs. PAHs concentrations and cancer risks were the highest during biomass burning condition compared with those during polluted and clean conditions. The lifetime accumulated cancer risk of PM1-bound PAHs was considered to be acceptable, whereas it elevated to “potential risk” (10−6) for adults (30–70 years old) exposed to PM2.5-bound PAHs. The Concentration-weighted trajectory (CWT) model indicated long-distance transport from Northwest China was the major source of PM1-bound PAHs under the clean conditions. Compare with clean conditions, PAHs were more strongly influenced by short-distance transported air masses from the South of Shandong Province under the polluted conditions.