In Gaussian dispersion, which type of receptor typically experiences strong ground reflection effects?

In Gaussian dispersion, which type of receptor typically experiences strong ground reflection effects?

• A. Ground-level receptors
• B. Elevated receptors
• C. Receptors near the surface at half the height
• D. Receptors well above the boundary layer

Answer: (A)

Ground reflection effects arise because the ground acts as a boundary that the plume cannot cross. In Gaussian dispersion, the standard way to handle this is by introducing an image source below the ground so the boundary condition is satisfied. The observed concentration at a receptor is then the sum of the real plume and the image plume. The image contribution is most significant when the receptor is near the ground, where the direct and reflected paths are similar in scale and interfere strongly. As the receptor height increases, the influence of the image source fades, so receptors well above the surface experience much weaker ground reflection effects. That’s why ground-level receptors show the strongest ground reflection impacts.

Ground reflection effects arise because the ground acts as a boundary that the plume cannot cross. In Gaussian dispersion, the standard way to handle this is by introducing an image source below the ground so the boundary condition is satisfied. The observed concentration at a receptor is then the sum of the real plume and the image plume. The image contribution is most significant when the receptor is near the ground, where the direct and reflected paths are similar in scale and interfere strongly. As the receptor height increases, the influence of the image source fades, so receptors well above the surface experience much weaker ground reflection effects. That’s why ground-level receptors show the strongest ground reflection impacts.