Assessing the long-range transport potential of polybrominated diphenyl ethers: a comparison of four multimedia models.

Data from a comprehensive literature search of environmentally relevant physical-chemical properties for nine polybrominated diphenyl ethers (PBDE), ranging from a monobrominated congener to the fully brominated decabromodiphenyl ether, were evaluated and adjusted to achieve both internal and interhomologue consistency. These data were then used in four model-based long-range transport potential (LRTP) assessment methods. The models TaPL3-2.10, ELPOS-1.1.1, Chemrange-2, and Globo-POP-1.1 were found to yield comparable predictions. A comparison of the LRTP estimates for the PBDEs with those of benchmark chemicals (polychlorinated biphenyls [PCBs]) suggest that the lower-brominated congeners have a LRTP comparable to that of PCBs known to be subject to significant LRT, whereas the highly brominated congeners have a very low potential to reach remote areas. This is in agreement with field measurements in remote regions that indicate that the lighter components of commercially produced PBDE mixtures predominate. Deviations between Chemrange and the models based on the concept of a characteristic travel distance were due to differences in the assumed height of the air compartment, which influences the relative importance of atmospheric degradation and deposition processes. The three models assuming a uniform temperature of 25 degrees C may underestimate the LRTP of the smaller congeners. Only atmospheric parameters had a notable influence on the LRTP estimates by TaPL3, ELPOS, and Chemrange. whereas the relative enrichment of chemicals in the Arctic calculated by Globo-POP is additionally sensitive to the parameters related to the interaction of temperature with air-surface exchange and degradation in surface compartments.