Question

When a plume is sandwiched between inversions, it is known as
A. Fanning
B. Trapping
C. Lofting
D. Looping

Answer 1

Hint: A plume is referred to the distorted gaseous emission seen from the stack. The scattering of emitted gases from the stack is called plume. Just like a sandwich the plume fits or is trapped inside the inversion layers like ham in two bread pieces. The plume appears to be pressed from above and below.

Complete step by step answer:
Plume is the scattering of emitted gases from their production source. The production source is called the stack. The pattern for dispersion of plumes is different in different temperature conditions. The atmospheric temperature profile decides the dispersion pattern for the plumes.
-The inversion layers or inversion is the area where the temperature increases with increasing altitude. This is the opposite of the normal decrease in air temperature with an increase in altitude. The inversion layers have warmer air at the top and a less warm layer at the base. These inversion layers comprise atmospheric temperature profiles and thus decide the dispersion pattern for plumes.
-Now let us see what type of dispersion is observed when the plume is trapped or sandwiched between the two inversion layers.
-Fanning plume forms when stable environmental conditions exist above the stack and extreme inversion conditions exist on top of the plume. The plume takes the shape of horizontal flow.
-Trapping plume by its name suggests that it is formed when inversion condition prevails both above and below the stack and the plume is trapped in these inversion layers. In this, the plume is not freed to move up or down.
-A Lofting plume is formed when there are strong inversion conditions just below the opening of the stack. This plume is appropriate for the dissolution of gas pollutants as the plume is highly dispersed from above and does not deposit on the ground.
-A looping plume is formed under highly unstable atmospheric conditions. Due to extreme atmosphere and pressure, the plume lifts up and down rapidly in loops or waves. This has a high threat rate for the deposition of gas pollutants on the ground. Thus, the plume which is formed by sandwiching between inversion layers is trapping plume.
Hence, the right answer is option B.

Note: The trapping plume is not an ideal way of dispersing pollutants in the air. The stack for this type of plume can attain only a certain height and thus cannot go above a certain height. It should be noted that the plume rise is not only a function of environmental stability but also depends on the buoyancy of the exhaust gases.