Passive Sampling of Gaseous Persistent Organic Pollutants in the Atmosphere

The polyurethane foam (PUF) disk-based passive air samplers (PAS), mounted inside two aluminium bowls to buffer the air flow to the disk and to shield it from precipitation and sunlight, were used for the collection of atmospheric POPs in Singapore during April 2008eJune 2008. Data obtained from PAS measurements are compared to those from active high-volume air sampling (AAS). Single factor ANOVA tests show that there were no significant differences in chemical distribution profiles between actively and passively collected samples(PAHs, F=3.38×10-8) < Fcritica l= 4.17 with p>0.05; OCPs, F=2.71×10-8< Fcritical = 4.75 with p > 0.05). The average air-side mass transfer coefficient (kA) for PAS, determined from the loss of depuration compounds such as 13C6-HCB (1000 ng), 13C12 - 4,4' DDT (1000 ng) and 13C12-PCB 101 (1000 ng)spiked on the disks prior to deployment, was 0.12 ± 0.04 m s-1. These values are comparable to those reported previously in the literature. The average sampling rate was 3.78 ± 1.83 m3 d- 1 for the 365 cm2 PUF disk. Throughout the entire sampling period (∼68 d), most of the PAHs and all OCPs exhibited a linear uptake trend on PAS, while naphthalene, acenaphthylene, acenaphthene and fluorene reached the curvilinear phase after the first ∼30 d exposure. Theoretically estimated times to equilibrium (teq) ranged from around one month for Acy to hundreds of years for DB(ah)A. Sampling rates, based on the time integrated active sampling-derived concentrations and masses collected by PUF disks during the linear uptake phase, were determined for all target compounds with the average values of 2.50 m3 d-1 and 3.43m3 d-1 for PAHs and OCPs, respectively. More variations were observed as compared to those from th depuration study. These variations were most likely due to the difference of physicochemical properties of individual species. The validation and calibration work conducted for PAS in this study clearly indicates that it would be feasible to use such an economic PAS for routine measurements of POPs in the tropical atmosphere at a large network of sampling locations.