Item talk:Q147579

Volatilization of polycyclic aromatic hydrocarbons from coal-tar-sealed pavement

Coal-tar-based pavement sealants, a major source of PAHs to urban water bodies, are a potential source of volatile PAHs to the atmosphere. An initial assessment of volatilization of PAHs from coal-tar-sealed pavement is presented here in which we measured summertime gas-phase PAH concentrations 0.03 m and 1.28 m above the pavement surface of seven sealed (six with coal-tar-based sealant and one with asphalt-based sealant) and three unsealed (two asphalt and one concrete) parking lots in central Texas. PAHs also were measured in parking lot dust. The geometric mean concentration of the sum of eight frequently detected PAHs (ΣPAH₈) in the 0.03-m samples above sealed lots (1320 ng m^-3) during the hottest part of the day was 20 times greater than that above unsealed lots (66.5 ng m^-3). The geometric mean concentration in the 1.28-m samples above sealed lots (138 ng m^-3) was five times greater than above unsealed lots (26.0 ng m^-3). Estimated PAH flux from the sealed lots was 60 times greater than that from unsealed lots (geometric means of 88 and 1.4 μg m^-2 h^-1, respectively). Although the data set presented here is small, the much higher estimated fluxes from sealed pavement than from unsealed pavement indicate that coal-tar-based sealants are emitting PAHs to urban air at high rates compared to other paved surfaces.