1. Section #3: Acid Precipitation
Air
Section #3:
Acid Precipitation

2. Acid Precipitation
precipitation such as rain, sleet, or snow that contains a high concentration of acids
it is a secondary pollutant caused by the chemical reaction between water in the atmosphere & the sulfur dioxide & nitrogen oxides that are released from burning fossil fuels

3. Acid Precipitation
the sulfuric acids & nitric acids that are produced will flow over & through the ground into rivers, lakes, & streams
acid precipitation can kill living organisms resulting in a decline in animal & plant populations

4. How Acid Precipitation Forms

5. pH a number that measures how acidic or basic a substance it
the pH scale runs from 0-14
the lower the number, the more acidic a substance is
the higher the number, the more basic a substance it
each whole number on the scale indicates a tenfold change in acidity

6. pH Scale

7. Normal pH pure water has a pH of 7 which is neutral
normal precipitation is slightly acidic (~ 5.6) because CO2 in the atmosphere forms carbonic acid
if the pH is less than 5.0, then the precipitation is considered acidic
pH varies with each geographic area

8. Affect on Soils & Plants
plant communities have adapted over long periods of time to the acidity of the soil in which they grow
significant & quick changes in the acid level is called acidification

9. Acidification changes the balance of a soil’s chemistry
an increase in the acid levels can cause some nutrients to be more easily dissolved & washed away by rainwater
can also cause aluminum & other toxic metals to be released & absorbed by plant roots
acids can also clog the stomata on plant surfaces

10. Acidification of a Forest

11. Affect on Aquatic Ecosystems
just like plants, aquatic organisms have adapted to live within a particular pH range
even a slight increase in acid levels can lead to death

12. Acid Shock
a sudden influx of acidic water that causes a rapid change in the water’s pH
this often occurs in the spring when acidic snow that accumulated in the winter melts & rushes into bodies of water

13. Acid Shock
this causes large #s of fish in a population to die & affects the reproduction of fish & amphibians
organisms produce fewer eggs, most do not hatch, & those that do often have birth defects &/or cannot reproduce themselves

14. Fish Killed by Acid Shock

15. Combating Acidification
some states in the U.S. and some countries will try to counteract the effects of acid precipitation on aquatic organisms by spraying powdered limestone on acidified lakes in the spring to help restore natural pH levels in the lake

16. Affect on Humans
when soil acidity increases, toxic metals such as aluminum & mercury can be released into the environment
these toxic metals can then find their way into the human body through crops, water, & fish
this can poison the human body & even cause death at high levels

17. Affect on Humans
there is also a correlation between large amounts of acid precipitation received by a community & an increase in respiratory problems by children in that community
industries (commercial fishing, logging) may struggle because of the damage from acid precipitation

18. Affect on Structures
a common building material, calcium carbonate, found in concrete & limestone is dissolved by acid precipitation
some of the world’s most important & historic monuments (especially those made of marble) are slowly being eaten away

19. Acids Eating Rocks

20. International Conflict
very hard to control because acid precipitation may form over one region or country but actually fall to the ground several kilometers away
for example, most of the acid precipitation that falls in Canada was actually produced in OH, IN, PA, IL, MO, WV, and TN

21. Global Problems

22. International Cooperation
Canada & the U.S. signed an Air Quality Agreement in 1991 where both countries agreed to reduce acidic emissions that flow across the Canada-U.S. border
more agreements will have to be formed in the future to fight the acid precipitation problem

23. Question?
Should the country that releases significant amounts of pollutants into the air that falls as acid precipitation in another country be expected to pay some of the cost of clean-up? Why or why not?