Characterizing the origin and long-range transport behavior of persistent organic pollutants in the North American atmospheric environment using passive samplers.

Description

Monitoring is recognized as an essential tool for identifying status and spatial and temporal trends of persistent organic pollutant (POPs) in the atmosphere. To investigate the origin and long-range transport behavior of POPs in air, a novel passive air sampler (PAS) was developed based on the polystyrene/divinylbenzene co-polymeric resin XAD. The PAS was characterized by sorption measurements of chlorobenzenes onto XAD at various temperatures, wind tunnel experiments and computer simulations of the uptake kinetics, and field calibration experiments under Arctic and temperate conditions. The performance of this PAS was evaluated by comparing PAS-derived concentrations with those measured by conventional HiVol samplers. These studies demonstrated the usefulness of XAD-based PAS for atmospheric POP monitoring. A PAS network was established across North America, consisting of 40 stations covering 72 degrees of latitude (10° to 82°N) from the Arctic to Costa Rica and 72 degrees of longitude (53° to 125°W) from Newfoundland to Vancouver Island. Four of these stations constituted an altitudinal transect in the southern Canadian Rocky Mountains, covering an elevational range of more than 1500m. Annually averaged air concentrations of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) were determined in 2000/2001 at these stations, as was the enantiomeric composition of chiral OCPs. The distribution patterns of the POPs were found to depend on their physical-chemical properties, their emission history, and the environmental conditions. Evidence for global fractionation along latitude and altitude was observed. Multivariate statistical analysis allowed for a better understanding of the observed composition patterns of PCBs and PBDEs. Estimation of the long range transport potential of OCPs, empirically from network concentrations, and theoretically from model calculations yielded a comparable classification. In order to have consistent input data for these model simulations, a complete set of partitioning properties (aqueous solubility, octanol-water partition coefficient, vapor pressure, Henry's law constant, octanol-air partition coefficient) for fourteen OCPs was derived by compiling, evaluating, selecting, and adjusting all measured values reported in the literature. Large scale PAS networks are suitable for monitoring compliance with, and effectiveness of, regulatory control measures, and for establishing experimentally the atmospheric long-range transport behavior of POPs.

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