PARENT SESSION

1L (1) - Exposure Modelling
Hall 4
1:45 PM - 3:30 PM, Wednesday, 30 April 2003
Chair: Lammel, G.¹, ¹
Co-chair: Dachs, J.², ²

(WE4/14) Simulating the environmental fate of organic chemicals using poly-parameter linear free energy relationships.

Breivik, Knut¹, Wania, Frank², ¹ NILU - Norwegian Institute for Air Research, Kjeller, Oslo, Norway² University of Toronto at Scarborough, Toronto, Ontario, Canada

ABSTRACT- Reliable estimates of environmental phase partitioning are essential for accurate predictions of the environmental fate of organic chemicals. Current environmental fate models use single-parameter linear free energy relationships (SP-LFERs) to quantify equilibrium phase partitioning. The applicability of such SP-LFERs is limited because no single parameter is able to describe appropriately all the molecular interactions that contribute to environmental phase distribution processes. Environmental partitioning coefficients such as Koc predicted by SP-LFERs may thus have errors of up to an order of magnitude. Ranges for several environmental partitioning equilibria are identified, where such errors can result in significantly different fate predictions. We propose that it is possible to reduce such errors and uncertainties by implementing poly-parametric LFER (PP-LFER) approaches in multimedia fate models. A Mackay level III model was modified such that the partitioning properties of chemicals are characterised by five linear solvation energy parameters rather than vapour pressure, water solubility and octanol-water partition coefficient. A comparison of modified and unmodified model for a set of organic chemicals shows that the approach chosen to simulate environmental phase partitioning can have a large impact on model output, including long-range transport potential, overall persistence and concentrations in various media. It is argued that PP-LFER based environmental fate models are applicable to a much wider range of organic substances, in particular those with polar functional groups. Obstacles to the full implementation of PP-LFER in multimedia fate models are currently the lack of solute descriptors for some chemicals of environmental concern and suitable regression equations for some important environmental phase equilibria, in particular for the partitioning between gas and particle phase in the atmosphere.

Key words: LFERs, Environmental Phase Partitioning, Multimedia Models, Fate