If anyone wants to have primary information about how the plume is formed and

1. Plume:
• The dispersion of emitted gases from the source of their
production is known as plume and the source is known as stack.

2. •NOTE: ELR (Environmental Lapse Rate)
• The environmental lapse rate (ELR), is the rate of decrease of
temperature with altitude in the stationary atmosphere at a given time
and location.
• As an average, the International Civil Aviation Organization (ICAO)
defines an international standard atmosphere (ISA) with a temperature
lapse rate of 6.49 K/km[15] (3.56 °F or 1.98 °C/1,000 ft) from sea level to
11 km (36,090 ft or 6.8 mi).
• Example : From 11 km up to 20 km (65,620 ft or 12.4 mi), the constant
temperature is −56.5 °C (−69.7 °F), which is the lowest assumed
temperature in the ISA.

3. •NOTE: ALR (Adiabatic Lapse rate)
• The process of expanding and contracting without exchanging heat is
an adiabatic process.
• When a parcel of air expands, it pushes on the air around it,
doing work (thermodynamics). Since the parcel does work but gains no
heat, it loses internal energy so that its temperature decreases. The
process of expanding and contracting without exchanging heat is
an adiabatic process.
• The rate of temperature decrease is 9.8 °C/km (5.38 °F per 1,000 ft)
(3.0 °C/1,000 ft).

4. What are the different types of plume classified on the basis of ELR and ALR ?
The diffusion or dispersion of pollutants into the atmosphere is
governed by the Environmental Lapse Rate (ELR) as well as
Adiabatic Lapse rate (ALR), i.e., atmospheric temperature
profile or atmospheric stability.

5. Coning Plume :
• It is calculated that when horizontal wind velocity exceeds 32km/hour
and under the condition of cloud blocking solar radiations at day time
and terrestrial radiation at night, neutral plume tends to form cone
like structure known as coning plume.
• Under sub-adiabatic conditions (ELR < ALR), when there is limited
vertical mixing and environment is slightly stable, the plume also
attains cone like structure and is coning plume.

7. Fanning Plume :
• Under extreme inversion condition (due to negative lapse rate),
fanning plume is obtained. Under condition of inversion, stable
environmental condition exists just above the stack and plume does
not move upwardly but horizontally.
• Occurs generally in less turbulence condition.

9. Looping Plume :
• Looping plume is of wavy character and occurs in super adiabatic
environment (ELR>ALR), which produces highly unstable atmosphere
because of rapid mixing.
• In an unstable atmosphere, rapid air movements take place vertically,
both upward and downward and the plume becomes a looping
plume.
• As a result of this, high concentrations of pollutants may occur near
the ground. To disperse these pollutants, it is advisable to design high
stack where atmosphere is generally super adiabatic.

11. Neutral Plume :
• Neutral plume occurs in neutral atmospheric conditions (ELR=ALR).
Such type of plume rises vertically in an upward direction.
• The upward lifting of the plume will continue till it reaches a height
where density and temperature of surrounding air are equal to it.

13. Lofting Plume :
• Under conditions of strong super adiabatic lapse rate just above the
stack and negative lapse rate (inversion) just below the opening of
stack, lofting plume is obtained.
• The upward mixing of plume is very rapid and turbulent, but
downward mixing is less because the downward movement is
prevented by inversion.
• The dispersion of pollutants therefore becomes rapid and pollutants
cannot come down to the ground. Such kind of a plume is ideal for
dispersion of air pollutants and protection of living beings to a great
extent.

15. Fumigating Plume :
• Fumigating plume is just opposite to lofting plume. Under conditions
of negative lapse rate (inversion) just above the stack and strong
super adiabatic lapse rate below the stack, the type of plume
obtained is known as fumigating plume.
• Under these set of conditions, the pollutants cannot escape above
the stack, rather they come down near the ground due to turbulence
and mixing. Fumigating plume is therefore extremely bad for
dispersion of pollutants.

17. Trapping Plume :
• When the inversion layer exists above the stack and as well as below
the stack, the plume neither goes up nor goes down, rather, it gets
confined or trapped between these two inversion layers.
• Such type of plume is therefore, termed as trapping plume.
• This plume is not ideal for dispersion of pollutants as it cannot go
above a certain height.