Persistence and spatial range as endpoints of an exposure-based assessment of organic chemicals

An approach to the classification of environmental chemicals in terms of exposure-based quantities is presented. First, the spatial range of environmental chemicals is introduced as the counterpart of the persistence, and mathematical definitions are given for the calculation of both persistence and spatial range from exposure data. Persistence and spatial range serve as proxy measures that reflect the influence of many different transport and degradation mechanisms without the details of these mechanisms being discussed individually. Secondly, a one-dimensional model of the global circulation is set up in analogy to previous unit-world models; besides atmospheric and oceanic long-range transport, the model covers diffusive and nondiffusive phase transfer processes as well as net first-order degradation. CCl3F and 1-butanol are used as benchmarks representing long-range/long-term and short-range/short-term exposure. As a first test of the model, the distribution behavior of these two chemicals is quantified in terms of the three spatial ranges of the phases soil, water, and air.