Question

Which of the following statements is/are TRUE in relation to the Maximum Mixing Depth (or Height) ${Dmax}$ in the atmosphere?}

• A. $D_{\text{max}}$ is always equal to the height of the layer of unstable air.
• B. Ventilation coefficient depends on $D_{\text{max}}$.
• C. A smaller $D_{\text{max}}$ will have a smaller air pollution potential if other meteorological conditions remain the same.
• D. Vertical dispersion of pollutants occurs up to $D_{\text{max}}$.

Hint:

The ventilation coefficient and the vertical dispersion of pollutants are directly influenced by $D_{\text{max}}$. A smaller $D_{\text{max}}$ limits air dispersion and worsens air pollution potential.

Answer 1

The Correct Option is B, D

Statement (A): $D_{\text{max}}$ is not always equal to the height of the layer of unstable air. While the unstable air layer can contribute to $D_{\text{max}}$, the height can also vary depending on meteorological conditions and atmospheric stability. Hence, this statement is false.
Statement (B): The ventilation coefficient is related to $D_{\text{max}}$, as it indicates the efficiency of dispersion and mixing of pollutants. Larger $D_{\text{max}}$ usually results in higher ventilation, as the air mass can carry pollutants over a larger height. Hence, this statement is true.
Statement (C): While a smaller $D_{\text{max}}$ does generally result in higher air pollution potential due to reduced vertical mixing, the statement is not true in all cases. It would depend on other factors, so this statement is not universally true. Hence, this statement is false.
Statement (D): Vertical dispersion of pollutants occurs mainly up to $D_{\text{max}}$ because beyond this height, the pollutants cannot mix effectively with the surrounding air. Hence, this statement is true.
\boxed{\text{True Statements: (B) and (D)}}