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Abstract

Various scenarios of DDT and ß-HCH global emis-sions of the years 1970-1990 have been used to study the sensitivity of the multicompartmental fate of these sub-stances towards location and mode of entry during the first two years upon entry. A multicompartment chemis-try-transport model with 3.75°*3.75° horizontal resolution has been used, based on an atmospheric general circula-tion model. ß-HCH is expected to be the more mobile but less persistent substance. Persistence in the total environment, ?overall, ranged from 1.5-1.8 years for the DDT and from 0.6-1.2 years for the ß-HCH scenarios. Compartmental distributions and residence times were found to be strongly influenced by the scenario of entry. Emissions in the trop-ics rather than in mid latitudes and application to vegeta-tion rather than to the soil tend to enhance the mobility and to limit the persistence. The changing geographic application pattern of DDT in 1970-1990, which was caused by the phasing out in many countries during this period, went along with sig-nificant changes in the environmental fate of DDT: the number of completed atmospheric cycles ('hops') in-creased and the residence times in the ground compart-ments decreased correspondingly. The north-south shift in the application pattern, which occurred in this time pe-riod, was expected to have given rise to increased disper-sion over the globe.