ACID DEPOSITION AND FOREST ECOSYSTEMS Chapter 3.11

Acid Deposition Technology is great in many ways but it also contributes to acid deposition.

Progress? Coal-burning plants, cars, and trucks, metal smelters, and oil refineries provide energy, transport, and materials for the industrial world, but at the same time produce oxides of sulfur and nitrogen, among the most dangerous of air pollutants.

The Problem of Combustion Sulfur dioxide (SO2) and Nitrogen oxides (NOx) are released into the atmosphere by burning fossil fuels and metal ores. If Sulfur and Nitrogen enter the atmosphere they may combine with water droplets to form acids. Because of the Water Cycle the acids return to the surface of the Earth in the form of snow or rain, called ACID PRECIPITATION.

Acid Rain is 40X more acidic than normal rain.

ACID PRECIPITATION KILLS: Fish Soil Bacteria Aquatic Plants Terrestrial Plants The sulfur and nitrogen oxides released from tailpipes and smokestacks do not always enter the water cycle in the atmosphere.

Some areas are more susceptible to the affects of acid rain while other are more resistant. Some types of soils are basic and can neutralize the acid. The unfortunate thing is that most of southeastern Canada does not offer natural protection against acid rain.

Sulfur and nitrogen compounds may remain airborne and settle out in the dry state – DRY DEPOSITION Dry Deposition enter the water cycle and form acid as it combines with water found on the ground, (ie. run-off, dew, the inside of your lungs!). CAN BE FOUND: Dew on lawns Surface of lakes Water inside your respiratory tract

THE EFFECTS OF ACID PRECIPITATION Direct effects on Humans: Medical effects Accelerated respiratory problems Examples: Asthma, bronchitis Cause eyes to water Irritate skin Dissolving marble statues Corroding metal Dulling car finishes Damage to buildings

Effects on Ecosystems Damage to leaves Damaged to tissues of trees become more susceptible to fungal or bacterial infections.

EFFECTS OF ACID RAIN Important to Nitrogen Cycle Acid falls to soil Promotes growth of moss Kills Bacteria Releases aluminum in the soil Reduces nutrients in trees Damage tree roots

pH – Potential Hydrogen pH is a measure of the acidity or alkalinity (basic) in the solution. What pH stands for is not clear. Measured using pH meter pH is a scale from 0 – 14 where: 0 – 6.9 = Acidic 7.0 = neutral 7.1-14 = Basic 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 A pH of 3 is 10 times more acidic than pH of 4 More Basic More Acidic

pH of Normal rain water pH of Acid Rain pH of 5.6 Range from 4.5 to 5.6; average 5.0

pH Scale

pH corresponds to the concentration of Hydrogen Ie. Low pH = high H

Class Work/Homework Read and Review pages 116 -118 in the text. Answer Questions #1-4 page 118