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Pollutant-Specific Scale of Multimedia Models and Its Implications for the Potential Dose
journal contribution
posted on 2000-11-16, 00:00 authored by Edgar G. Hertwich, Thomas E. McKoneThe spatial range is a generic indicator for how far
pollutants are likely to travel. It also indicates the appropriate,
pollutant-specific area of a multimedia model, which is
the square of the spatial range. Formulations of the spatial
range can be based on advective or dispersive transport.
They differ in whether they take the extent and shape
of the earth's surface into account. We suggest the common
element of the different approaches is that all account
for the persistence and mobility of pollutants. The mobility
is the expected travel speed and depends on the
partitioning. This paper extends the concept of a pollutant-specific model scale through the introduction of a
characteristic atmospheric scale height. It is the height of
the atmosphere that would be needed to contain all the
pollutant if the entire atmosphere had ground-level
concentration, taking into account deposition and degradation.
We define the spatial range as the expected advection-driven travel distance of a pollutant molecule released to
a specific compartment. This novel analytical formulation
is more comprehensive but encompasses all previous
advection-based proposals of a spatial range. We evaluate
the spatial range and scale height of 288 chemicals for
releases to air, surface water, and surface soil. We find a
strong correlation between the spatial range for air
releases and the scale height because both depend on
persistence. We investigate the effect of the spatial scale
on calculations of the human toxicity potential, a screening-level risk indicator based on toxicity and potential dose. The
product of model area and potential dose is found to be
the same for calculations using a fixed model area and those
using the pollutant-specific spatial scale. The introduction
of the scale height, however, can change the potential
dose by more than 1 order of magnitude.