Impact of the regional climate and substance properties on the fate and atmospheric long-range transport of persistent organic pollutants - examples of DDT and γ-HCH

摘要

A global multicompartment model which is based on a 3-D atmospheric generalcirculation model (ECHAM5) coupled to 2-D soil, vegetation and sea surfacemixed layer reservoirs, is used to simulate the atmospheric transports andtotal environmental fate of dichlorodiphenyltrichloroethane (DDT) andγ-hexachlorocyclohexane (γ-HCH, lindane).Emissions into the model world reflect the substance's agricultural usage in1980 and 1990 and same amounts in sequential years are applied. Fourscenarios of DDT usage and atmospheric decay and one scenario ofγ-HCH are studied over a decade.

The global environment is predicted to be contaminated by the substanceswithin ca. 2a (years). DDT reaches quasi-steady state within 3-4a in theatmosphere and vegetation compartments, ca. 6a in the sea surface mixedlayer and near to or slightly more than 10a in soil. Lindane reachesquasi-steady state in the atmosphere and vegetation within 2a, in soilswithin 8 years and near to or slightly more than 10a and in the sea surfacemixed layer. The substances' differences in environmental behaviour translateinto differences in the compartmental distribution and total environmentalresidence time, τ_overall. τ_overall≈0.8a forγ-HCH's and ≈1.0-1.3 a for the various DDTscenarios. Both substances' distributions are predicted to migrate innortherly direction, 5-12° for DDT and 6.7° for lindanebetween the first and the tenth year in the environment. Cycling in variousreceptor regions is a complex superposition of influences of regionalclimate, advection, and the substance's physico-chemical properties. As aresult of these processes the model simulations show that remote borealregions are not necessarily less contaminated than tropical receptor regions.Although the atmosphere accounts for only 1% of the total contaminantburden, transport and transformation in the atmosphere is key for thedistribution in other compartments. Hence, besides the physico-chemicalproperties of pollutants the location of application (entry) affectspersistence and accumulation emphasizing the need for georeferenced exposuremodels.