Acid Precipitation

Environmental ScienceSpring 2011

Explain the causes of acid precipitation Explain how acid precipitation affects

plants, soils, and aquatic ecosystems Describe three ways that acid precipitation

affects humans Describe ways that countries are working

together to solve the problem of acid precipitation

Acid Precipitation: precipitation such as rain, sleet, or snow that contains a high concentration of acids

Burning of fossil fuels releases oxides of sulfur and nitrogen

When oxides combine with water in atmosphere, form sulfuric acid and nitric acid and falls to ground as acid rain

Acidic water flows over and through ground, into lakes, rivers, etc.

Can kill living things and result in decline or loss of some local animal and plant populations

pH (power of hydrogen): measure of how acidic or basic a substance is ◦ Lower the pH number, more acidic ◦ Higher the pH number, more basic ◦ Each whole number on the pH scale indicates a

tenfold change in acidity

Pure water = pH of 7 Normal precipitation is slightly acidic,

because atmospheric carbon dioxide dissolves into precipitation and forms carbonic acid ◦ Has pH of 5.6

Acid precipitation has pH of less than 5.0

pH of precipitation varies between different geographic areas◦ Eastern US and Canada ranges from 4.2 to 4.8◦ Most acidic precipitation in North America occurs

around Lake Erie and Lake Ontario pH of 4.2

Can cause drop in pH of soil and water Acidification: increase in concentration of

acid of soil and water

Acidification can:◦ Changed balance of soil’s chemistry ◦ Some nutrients are dissolved and washed away ◦ Can cause aluminum and other toxic materials to

be released and possibly absorbed by roots of plants

◦ Aluminum can cause root damage ◦ Sulfur dioxide can clog openings on surfaces of

plants

Aquatic animals adapted to live in environment with particular pH range

Acid precipitation alters this range, can kill organisms

Causes aluminum to leach out of soil, can accumulate in gills of fish and interfere with oxygen and salt exchange, fish are suffocated

Acid shock: sudden influx of acidic water that causes a rapid change in the water’s pH ◦ Occurs in spring, when acidic snow melts ◦ May kill large numbers of fish ◦ Affects reproduction of fish and amphibians,

produce fewer eggs, eggs often do not hatch, offspring hat do hatch can have birth defects and reproduction prblems

Toxic materials such as aluminum and mercury can be released and find their ways into crops, water and fish

Correlation between acid precipitation and respiratory problems

Decreases in fish can influence livelihood of commercial fishers and sport fishing industry and forestry industry

Can dissolve calcium carbonate in common building materials, such as concrete, marble, and limestone

Monuments are being dissolved by acid precipitation

Problem: pollutants may be released in one area and fall to ground hundreds of km away

Ex. Half of acid precipitation that falls in southeastern Canada results from pollution produced in northeastern US

International problem led to Canada-US air quality agreement