Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 4 2 2004 10.5194/acpd-4-1339-2004 http://www.atmos-chem-phys-discuss.net/4/1339/2004/ http://www.atmos-chem-phys-discuss.net/4/1339/2004/acpd-4-1339-2004.html http://www.atmos-chem-phys-discuss.net/4/1339/2004/acpd-4-1339-2004.pdf 1339 1370 2004-03-08 Modelling atmospheric transport of persistent organic pollutants in the Northern Hemisphere with a 3-D dynamical model: DEHM-POP K. M. Hansen kmh@dmu.dk J. H. Christensen J. Brandt L. M. Frohn C. Geels Department of Atmospheric Environment, National Environmental Research Institute, Roskilde, Denmark The Danish Eulerian Hemispheric Model (DEHM) is a 3-D dynamical atmospheric transport model originally developed to describe the atmospheric transport of sulphur into the Arctic. A new version of the model, DEHM-POP, developed to study the atmospheric transport and environmental fate of persistent organic pollutants (POPs) is presented. During environmental cycling, POPs can be deposited and re-emitted several times before reaching a final destination. A description of the exchange processes between the land/ocean surfaces and the atmosphere is included in the model to account for this multi-hop transport. The α-isomer of the pesticide hexachlorocyclohexane (α-HCH) is used as tracer in the model development. The structure of the model and processes included are described in detail. The results from a model simulation showing the atmospheric transport for the years 1991 to 1998 are presented and evaluated against measurements. The annual averaged atmospheric concentration of α-HCH for the 1990s is well described by the model; however, the shorter-term average concentration for most of the stations is not well captured. This indicates that the present simple surface description needs to be refined to get a better description of the air-surface exchange proceses of POPs.