What is the correct sequence of events leading to acid deposition?

The correct sequence of events leading to acid deposition begins with the combustion of fossil fuels, which releases sulfur dioxide (SO2) and nitrogen oxides (NOx) into the atmosphere. These gases are significant precursors to acid rain.

After SO2 and NOx are emitted, they undergo a series of photochemical reactions in the atmosphere. This leads to the formation of secondary pollutants, specifically sulfuric acid (H2SO4) and nitric acid (HNO3). These acids are the result of the oxidation of SO2 and NOx in the presence of water vapor and sunlight.

Once these acids are formed, they can dissociate into their respective ions when they come into contact with moisture in the atmosphere. This dissociation process means that the acids become more soluble, allowing them to interact with precipitation.

最终，具有较高酸度的降水成为酸沉积物的形式，以雨、雪、雾或其他形式降落到地面。最终，这些酸性物质会影响土壤、水体和生态系统，导致酸化和其他环境问题。

This sequence highlights the transformation of emissions into harmful acids that are deposited back to the Earth's surface, affecting both natural ecosystems and human activities.