In: Civil Engineering
X -value is taken as the downwind distance from stack at (0,0,0) to the point at which we want to calculate the concentration..It is given in the figure shown above.
This is the guassian dispersion equation
For maximum downwid concentration ,y value = 0,because the pollutant concentraion is maximum along the plume centreline
The variables z &y are function of X thats how the X distance downwind is incorporated in the guasssian equation.
the value of z &y are taken from pasquil curve
this implies x- distance is taken for the downwind pollutant concentration using guassian plume model