| Abstract
| - The spatial range is a generic indicator for how farpollutants are likely to travel. It also indicates the appropriate,pollutant-specific area of a multimedia model, which isthe square of the spatial range. Formulations of the spatialrange can be based on advective or dispersive transport.They differ in whether they take the extent and shapeof the earth's surface into account. We suggest the commonelement of the different approaches is that all accountfor the persistence and mobility of pollutants. The mobilityis the expected travel speed and depends on thepartitioning. This paper extends the concept of a pollutant-specific model scale through the introduction of acharacteristic atmospheric scale height. It is the height ofthe atmosphere that would be needed to contain all thepollutant if the entire atmosphere had ground-levelconcentration, taking into account deposition and degradation.We define the spatial range as the expected advection-driven travel distance of a pollutant molecule released toa specific compartment. This novel analytical formulationis more comprehensive but encompasses all previousadvection-based proposals of a spatial range. We evaluatethe spatial range and scale height of 288 chemicals forreleases to air, surface water, and surface soil. We find astrong correlation between the spatial range for airreleases and the scale height because both depend onpersistence. We investigate the effect of the spatial scaleon calculations of the human toxicity potential, a screening-level risk indicator based on toxicity and potential dose. Theproduct of model area and potential dose is found to bethe same for calculations using a fixed model area and thoseusing the pollutant-specific spatial scale. The introductionof the scale height, however, can change the potentialdose by more than 1 order of magnitude.
|
