Question

Which plume occurs when there is a strong lapse rate above the surface inversion?
A. Fanning
B. Looping
C. Trapping
D. Lofting

Answer 1

Hint:- Plume is defined as the path and extent in the environment for dispersion of gaseous effluents from the chimney or in simple words, it is a path consisting of one fluid moving through another fluid. The nature of a plume that radiated from any stack depends on the stability of localized air.

Complete Answer:-
Fanning: In this lapse rate is negative because in the existence of inversion the diffusion of stack gas is low, because of the absence of turbulence. A plume spreads horizontally in very stable air, with limited vertical mixing. Looping is a kind of plume that has a wavy character. It primarily happens in a highly uncertain environment because of the emitted pollutants that undergo rapid mixing. The high degree of turbulence enables the distribution of the plume quickly resulting in a high concentration near the stack before diffusion is complete.
Trapping is defined as the situation in which a plume is entrapped in between 2 inversions and can neither go up and nor will be let down and an inversion layer exists above as well as below the emission. source. Lofting is a kind of plume that happens when there is a strong lapse rate above the surface inversion. In this case, dispersion is sudden upward, but downward dispersion cannot penetrate the inversion layer under these conditions, emission will not touch the surface.
Thus, the right option is D.

Note:- Another type of plume behaviour are:
● Conning: It is known as conning because its shape is like a cone. In this case, the plume reaches the surface at a greater distance than with loping.
● Fumigation: When the air destabilizes, the pollutants radiated into the environment are brought quickly to the surface level.