gradients of primarily emitted toxics around point sources are typical,
especially if there are no other nearby sources of the pollutants.
emissions can lead to relatively homogeneous concentrations of toxics on the
urban scale. However, if a monitor is
placed close to any source type, gradients may be observed.
|Very close to a
roadway or near a construction site, mobile source air toxics may be seen in
higher concentrations. A few hundred
|away from the
roadway, for example, concentrations typically fall to more normal levels.