How Acid Rain Works

Acid rain can eat through stone and metal. It has accelerated the natural weathering process of this scarred stone angel's face.

Photographer: Michael Drager | Agency:

The Effects of Acid Rain

Forests rely on their soil's buffering capacity to protect them from acid rain. Acidic waters draw out soil toxins like aluminum. Trees take in the poisonous substances, and runoff dumps it in lakes, rivers and streams. Acid rain also dissolves helpful minerals and nutrients like calcium, magnesium and potassium before trees can absorb them. Acid rain rarely kills a forest outright but instead stunts its growth through years of soil degradation. Nutrient deprivation and exposure to toxins make trees more likely to topple in storms or die in cold weather.

Even trees in well-buffered soil can weaken in harsh acid fog. High-elevation forests soak in acidic clouds, which strip leaves of nutrients and break down trees' ability to resist cold. The bald peaks of the Appalachian Mountains tell of the poisonous effect of acid rain on high-elevation forests.

Materials and Finishes

Acid rain has the unsettling ability to erase and obliterate stone and metal, the most durable of materials. Old buildings, monuments and tombstones bear the smooth signs of acidic corrosion and deterioration. Acid deposition speeds up natural weathering caused by rain, sun, snow and wind.

Acid rain also mars automotive paint. The auto industry considers acid deposition one type of corrosive environmental fallout, along with tree sap, pollen and bird droppings. Acid markings leave irregular, etched shapes on horizontal surfaces. Repainting is the only way to fix a car finish disfigured by acid rain.

How Acid Rain Works

Photographer: Socrates­ | Agency:


Since acid rain can kill aquatic animals, weaken trees and dissolve stone, it seems like it could also scald or burn humans. But it doesn't affect people in the same way as it does fish or plants. Acid rain feels the same as regular rain -- it's even safe to swim in an acidic lake. But the sulfate and nitrate particulates of dry deposition can ­cause asthma, bronchitis and heart problems. The NOx in acid deposition also reacts with volatile organic compounds (VOCs) to form ground-level ozone. Ozone, or smog, aggravates and weakens the respiratory system.