In the real world, however, the situation is made more complex by the fact that (1) the emission occurs continuously; (2) dispersion of the pollutant occurs not only by diffusion but is aided (and thus rendered more complex from the analytical standpoint) by laminar or turbulent advection (movement) of wind, deposition, chemical reactions, confinement of air masses through the effects of topography, and/or the inversion phenomenon (trapping of polluted air due to differences in temperature of air masses); and (3) the pollutant emitted is really not confined to the box but is released from that enclosed space at a certain varying rate that depends on dynamic factors such as ambient temperature and wind speed.