Concentrations, seasonal variations, and outflow of atmospheric polycyclic aromatic hydrocarbons (PAHs) at Ningbo site, Eastern China

Thirty six pairs of gas and particle (PM2.5) atmospheric samples were collected by high-volume samplers from July 2009 to March 2010 at an eastern background site in Ningbo and analyzed for polycyclic aromatic hydrocarbons (PAHs). The total (gas+particle) air concentrations of 16 PAHs ranged from 11.0 to 103 ng m(-3), with an average of 46.0 +/- 23.4 ng m(-3). Seasonal trends of PAH concentrations were observed with high concentrations in winter and low in summer, mainly due to regional sources and meteorological conditions. The association with other airborne pollutants and diagnostic ratio analysis indicated that PAHs in Eastern China background were predominantly from coal/biomass combustion. Coal combustion controlled atmospheric PAHs in winter, whilst biomass burning became important in summer and autumn. Located at eastern coastal areas, Ningbo site was chosen to estimate the atmospheric outflow of PAHs. Transport fluxes were characterized by elevated values in spring and winter. Southward transport fluxes dominated during the sampling period, presenting the transport from northern to southern China.