What is dry deposition and how does it differ from wet deposition in the context of acid rain?

• A. Dry deposition is direct transfer of gases/particles to surfaces; wet deposition is removal by precipitation; both deliver acids to ecosystems.
• B. Dry deposition is rain; wet deposition is snow only.
• C. Dry deposition occurs only in deserts; wet deposition only in forests.
• D. Dry deposition removes acids; wet deposition adds acids to atmosphere.

Answer: (B)

Dry deposition is the direct transfer of acidic gases and fine particles from the air to surfaces (soil, water, vegetation) without the involvement of precipitation. Wet deposition, on the other hand, is the removal of these acids from the atmosphere by precipitation, such as rain, snow, or fog, delivering acids to surfaces when it occurs. In the context of acid rain, both pathways move acids from the atmosphere to ecosystems, but the key difference is whether precipitation is involved. Snow is still precipitation, so it falls under wet deposition, not dry deposition, whereas rain is also wet deposition. That’s why the statement that dry deposition is rain and wet deposition is snow is not accurate—the correct distinction is direct deposition to surfaces versus deposition via precipitation.