Modelling transport and deposition of persistent organic pollutants in the European region

Persistent organic pollutant (POP) transport and deposition in Europe were investigated using calculations with the TREND model based on high-resolution 1990 emission estimates. Lindane (γ-HCH) and benzo(a)pyrene were chosen to represent components found predominantly in the gas and particle phases, respectively. Atmospheric lifetimes and dispersion of gas-phase POPs are primarily determined by their solubility in water and degradation rate in soils and vegetation; they have much longer lifetimes over land than over water surfaces. Model calculations indicate that γ-HCH has the potential for dispersion throughout the hemisphere, with most of it ending up in large water bodies. Spatial distribution patterns of calculated concentrations in precipitation correlated well with those of wet deposition measurements around the North Sea, but the absolute values were too low by a factor of three. Sensitivity analyses suggest that it is the emission data rather than other model parameters that are responsible for the underestimation. For (particle-phase) B(a)P the size distribution of its carrier particles and its atmospheric degradation rate are the most important, and the most uncertain, parameters affecting dispersion and transport. Results here indicate general overestimation of concentrations by a factor of two or less, but insufficient measurements limit uncertainty analyses and validity of conclusions.