Atmospheric distribution of particulate- and gas-phase phthalic esters (PAEs) in a Metropolitan City, Nanjing, East China

Phthalic acid esters (PAEs) are used in many branches of industry and are produced in huge amounts throughout the world. An investigation on particulate- and gas-phase distribution of PAEs has been conducted in Nanjing (China). The 12-h daily sampling program (from 8:00 am to 8:00 pm) for ten consecutive days was conducted in April, July and October 2005, and in January 2006 at about 1.5 m above the ground level. For comparative purposes, sampling events were simultaneously conducted at two stations, one at the urban center and the other about 12 km from city center for suburban background monitoring. It was observed that the most abundant members of the PAE group were dimethyl phthalate (DMP) (10.1 ng m−3, average), diethyl phthalate (DEP) (3.4 ng m−3), dibutyl phthalate (DBP) (58.8 ng m−3), butylbenzyl phthalate (BBP) (3.2 ng m−3), di-2-ethylhexyl phthalate (DEHP) (20.3 ng m−3) and di-n-octyl phthalate (DOP) (1.2 ng m−3). The average contribution of PAEs in the gas phase to the total PAE concentration (Σ6PAE, sum of six PAE congeners) ranged from 75.0% to 89.2%. Both particulate- and gas-phase Σ6PAE concentrations decreased with increasing temperature. Experimentally determined gas-particle partitioning (Kp) of PAEs is well-correlated with their vapor pressure. The Σ6PAE levels in the urban area are ∼3.5 times as high as the levels found at the suburban station. The vertical profiles from 1.5 to 30.0 m above the ground display slight height dependence.