Assessing long-range transport potential of persistent organic pollutants

An analysis is presented of the factors controlling the potential for the long-range transport (LRT) of persistent organic pollutants subject to degrading reactions and reversible transport to other environmental media. The approach adopted generalizes those developed previously by van Pul et al, and Bennett et al, to estimate a characteristic travel distance (CTD) or a half-distance (analogous to a half-life) for a substance present in a mobile medium such as air and subject to reversible transport to other media such as soil and water. For substances discharged to immobile media, such as pesticides to soil, an effective travel distance (ETD) is defined as the distance that, for example, 1% of the discharged chemical may be transported. It is shown that existing multimedia box models can be used to estimate CTD and that a simple relationship exists between CTD and overall environmental persistence, which can be displayed graphically. CTDs in air and water are calculated illustratively for 18 chemicals, and recommendations are made regarding ranking or grouping chemicals according to their potential for LRT.