PARTICIPATE MATTER,GAS-PHASE AND PARTICLE-BOUND POLYCYCLIC AROMATIC HYDROCARBONS IN AN URBAN ENVIRONMENT HEAVILY IMPACTED BY VEHICULAR TRAFFIC (BOLOGNA,ITALY).

摘要

A set of 8 polycyclic aromatic hydrocarbons (PAHs) has been analysed in a traffic-limited area in Bologna downtown,both in the gas-phase and in the particulate phase (PM_(10)),and gas-to-particle partitioning has been investigated.From Sep 2002 to May 2003,28 high volume PM_(10) samplings were carried out,and in 50 % of the samplings,PM_(10) concentrations exceeded the limit of 50 mug/m~3 established by a 1999 EU directive.A precisely defined sampling strategy was adopted to limit artifacts (8 h sampling in the same time interval) in the 28 samplings carried out in different meteorological conditions.A linear log-log correlation was found between gas-particle partitioning coefficients KB_p and the subcooled liquid vapour pressures pB~0_L~B ,with rP~(2P) = 0.82 and slope = -0.59.This empirical correlation may be used to anticipate the total (gas + particle-bound) concentration of each PAHs in this urban site,once PM_(10) and the particle-bound concentration is measured.Parallel samplings of PM_(10) and of PM_(2.5) allowed us to ascertain that PM_(2.5) represents the gross contribution to PM_(10) and that most of the particle-bound PAHs reside on the finest fraction of particulate matter.