The stability class influences sigma_y and sigma_z because it defines:

The stability class influences sigma_y and sigma_z because it defines:

• A. The color of the plume
• B. The turbulence and mixing in the atmosphere
• C. The chemical composition
• D. The deposition rate

Answer: (B)

The main idea here is that sigma_y and sigma_z describe how far a plume spreads horizontally and vertically due to atmospheric turbulence. The stability class is a shorthand for how turbulent and well-mixed the atmosphere is. A stable atmosphere has less turbulence, so the plume spreads less and sigma_y and sigma_z are smaller. An unstable atmosphere has more turbulence and mixing, so the plume disperses more and sigma_y and sigma_z are larger. The stability class thus directly sets how much the plume can spread as it travels. The other options don’t relate to dispersion: color doesn’t affect mixing, chemical composition isn’t what the stability class measures, and deposition rate is about removal processes, not the turbulent spread.

The main idea here is that sigma_y and sigma_z describe how far a plume spreads horizontally and vertically due to atmospheric turbulence. The stability class is a shorthand for how turbulent and well-mixed the atmosphere is. A stable atmosphere has less turbulence, so the plume spreads less and sigma_y and sigma_z are smaller. An unstable atmosphere has more turbulence and mixing, so the plume disperses more and sigma_y and sigma_z are larger. The stability class thus directly sets how much the plume can spread as it travels. The other options don’t relate to dispersion: color doesn’t affect mixing, chemical composition isn’t what the stability class measures, and deposition rate is about removal processes, not the turbulent spread.