Long-range atmospheric transport and total environment fate of persistent organic pollutants: A study using a general circultion model

Persistent bioaccumulative contaminants in pristine, remote regions like the Arctic are of great concern due to the hazard they pose to the ecosystems. These substances have been transported to the Arctic via atmosphere, ocean currents, rivers or biota (migratory birds or mammals). At least for semivolatile organic compounds on global to medium scales, long-range transport is most efficient in the atmosphere. For the first time, a three dimensional atmosphere global general circulation model (ECHAM4 and ECHAM5), is used, to study the long-range transport of persistent organic pollutants, and their fate in the multimedia environment. ECHAM4 used a horizontal resolution of 3.75° x 3.75°, and ECHAM5 2.8° x 2.8°. Both of them use a terrain following 19 level vertical resolution, 1000 - 10 hPa. The models comprise a fully developed atmospheric compartment, soil with a 'bucket model' hydrology, two-dimensional vegetation surface and a mixed layer ocean. The transport and fate of two persistent organic pollutants, DDT and γ-HCH, which are subject to regulations, were studied. These two agrochemicals differ considerably in their physico-chemical properties. DDT is more lipophilic while γ-HCH is more hydrophilic. Similar trends of multicompartmental behaviour were predicted by both versions of the model. Model experiments show that, while the strongest emission occurs in the tropics, the Arctic is contaminated. This long-range transport was quantified. The long-range transport potential of γ-HCH is higher than that of DDT. All the experiments show that DDT is more persistent than γ-HCH in the total environment, while γ-HCH is more persistent in the oceanic reservoir