How can acid deposition affect the environment?
Acid deposition enters an ecosystem in a variety of forms and via a number of pathways. It may enter the soil directly or interact with the tree canopy as well as understory vegetation. Within the canopy, it may become more acidic as a result of the leaching of accumulated dry deposition or organic acid anions from the foliage. On the other hand, the acid precipitation may become less acidic through exchange processes of H+ for base cations in plant tissues. Up to 80% of the proton deposition may be buffered by the foliage. As a result of this, direct injury to the foliage has occurred close to point sources of pollution. Further away from the pollution source, indirect injury may occur including the acidification of soils, lakes and rivers. The direct effect of acid deposition on trees, as distinct from indirect effects acting through the soil are still unclear. Sulphur deposition has fallen greatly over the past 20 years as a result of emissions control measures and it is now conside
