Regional Basic Professional Training Course in Korea

❙ 345 ❙
5. SITING CONSIDERATIONS
(σx = σy = σh = (Aht) kh and σz = (Azt) kz ). There were only two stability categories: neutral
and weak diffusion. The limit between these two classes was the vertical temperature
gradient. Parameters2 used in the formulation of standard deviations were adjusted on the
extremely numerous distributions observed of pollutants in suspension resulting from
short‐duration emissions [5.6].
In the French‐German model [5.7], standard deviations no longer come from
experimental data, but result from considerations of the atmospheric turbulence spectra
and their influence on the diffusion process. There are three stability categories, the limit
between the classes is a function of either vertical temperature gradient and wind speed or
both fluctuations of wind direction and wind speed.
This new set of standard deviations corrects problems that occurred when using Doury's
(overestimation of concentrations for high wind speeds) or Pasquill's (overestimation of
concentrations for low wind speeds) standard deviations.
Under stable meteorological conditions, for a puff, whose initial dimensions that are
small relative to its dimensions at the instant of observation, the concentration per unit
volume (along x, y and z) at instant t can be written as:
AV(
x,
y,
z,
t)
⎡
2
2⎤
2
2
QE 1 ( x−x
⎡ ⎛ ⎞ ⎛ + ⎞⎤
oo−ut)
( y−yo)
1(
z−zo)
1(
z zo)
exp−
⎢ + ⎥•⎢exp
⎜
⎜−
⎟
⎟+
exp ⎜
⎜−
⎟
3
2
2
2
⎥
2 ( 2π)
σ σ σ 2⎢⎣
σx
σy
⎥⎦
⎣ ⎝ 2 σz
⎠ ⎝ 2 σz
⎠⎦
= 2
x y z
in which AV = activity per unit volume in air
Q = quantity of activity released
E = specific law for increase or decrease of activity
e.g. radioactive decay or depletion by dry or wet deposition