6533b7d3fe1ef96bd1260a37

RESEARCH PRODUCT

PM2.5-bound oxygenated PAHs, nitro-PAHs and parent-PAHs from the atmosphere of a Chinese megacity: Seasonal variation, sources and cancer risk assessment

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Polycyclic aromatic compounds (PACs) in air particulate matter contribute considerably to the health risk of air pollution. The objectives of this study were to assess the occurrence and variation in concentrations and sources of PM2.5 bound PACs [Oxygenated PAHs (OPAHs) nitro PAHs and parent PAHs] sampled from the atmosphere of a typical Chinese megacity (Xi'an) to study the influence of meteorological conditions on PACs and to estimate the lifetime excess cancer risk to the residents of Xi'an (from inhalation of PM2.5 bound PACs). To achieve these objectives we sampled 24 h PM2.5 aerosols (once in every 6days from 5 July 2008 to 8 August 2009) from the atmosphere of Xi'an and measured the concentrations of PACs in them. The PM2.5 bound concentrations of scarbonyl OPAHs ?hydroxyl+carboxyl OPAHs snitro PAHs and salkyl+parent PAHs ranged between 5 22 0.2 13 0.3 7 and 7 387ng m 3 respectively being markedly higher than in most western cities. This represented a range of 0.01 0.4 and 0.002 0.06 of the mass of organic C in PM2.5 and the total mass of PM2.5 respectively. The sums of the concentrations of each compound group had winter to summer ratios ranging from 3 to 8 and most individual OPAHs and nitro PAHs had higher concentrations in winter than in summer suggesting a dominant influence of emissions from household heating and winter meteorological conditions. Ambient temperature air pressure and wind speed explained a large part of the temporal variation in PACs concentrations. The lifetime excess cancer risk from inhalation (attributable to selected PAHs and nitro PAHs) was six fold higher in winter (averaging 1450 persons per million residents of Xi'an) than in summer. Our results call for the development of emission control measures. © 2013 Elsevier B.V.