Acid Deposition

Acid rain has a pH less than 5.6

The pH of natural rain is 5.6 CO2 + H2O  H2CO3 (carbonic acid) Carbon dioxide in the atmosphere mixes with water and forms carbonic acid, making rain slightly acidic.

What causes acid deposition? The primary air pollution is sulphur dioxide and nitrogen oxides Sulfur oxides come from: Burning coal in the production of electricity and the smelting of ores SOx + H2O  H2SOx (sulfurous and sulfuric acid) Nitrogen oxides comes from: Fuel combustion in vehicles NOx + H2O  HNO2 (nitrous acid) + HNO3 (nitric acid)

Sulfur oxides and water become sulfurous and sulfuric acid The primary pollutants: sulfur oxides and the nitrogen oxides become secondary pollutants: nitric acid and sulfuric acid. Sulfur oxides and water become sulfurous and sulfuric acid Nitrogen oxides become nitrous and nitric acids

Acid precipitation can travel long distances by prevailing winds http://www.thepetitionsite.com/1/chamalapura-coal-based-fired-thermal-power-plant-project

Acid deposition can be snow, fog, or rain.

Burning coal in the USA is a major contributor to acid rain

Combustion of coal produces carbon dioxide and sulfur dioxide

Transportation causes nitrogen monoxide to be emitted

Effects of acid rain Direct effects are effects that occur because of the acidity of the rain. Indirect effects occur because of an action that the acid rain causes which then harms the environment.

Direct effects on lakes Most living organisms, like fish, do not survive in water with a pH level lower than 5.0 Growing aquatic plants like algea, stop growing, due to low pH.

Species of fish that are directly harmed by water with a low pH At pH 5, most fish eggs cannot hatch. At lower pH levels, some adult fish die.

Direct effects on plants It can alter the protective waxy surface of leaves, lowering disease resistance. It may inhibit plant germination and reproduction.

Direct effect on soil It accelerates soil leaching and removal of nutrients, such as calcium, potassium and magnesium ions. It makes some toxic elements, such as aluminum, more soluble. High aluminum concentrations in soil can prevent the uptake and use of nutrients by plants.

http://www.eoearth.org/article/Acid_rain

Analyze this chart How does acid deposition affect nutrients and substances in the soil?

Indirect effect on lakes: Aluminum ions are leached from the soil into lakes As acid rain flows through soils in a watershed, aluminum is leached from soils into the lakes and streams located in that watershed. The increased aluminum levels are directly toxic to fish.

Forests Acid deposition leaches nutrients to the subsoil, making them unavailable for tree roots. Acid deposition in clouds directly harms the foilage (leaves and needles) of trees, especially in mountain forests

Compare the healthy forest in Chile to one that has been impacted by acid rain http://www.learner.org/courses/envsci/visual/visual.php?shortname=acid_rain

Effect on ecosystems and food chains As lakes and streams become more acidic, the numbers and types of fish and other aquatic plants and animals that live in these waters decrease.

Buffering Capacity: The ability of soils to neutralize acid depends on its composition Limestone contains carbonates, which neutralize acid rain.

Limestone soils have high buffering capacities as the calcium carbonate is able to neutralize acids from acid rain.

Granite has low buffering capacity

When acid rain falls on areas that are high in granite, the acid is not neutralized, making these areas prone to damage from acid rain.

Damage to forests by acid rain has increased in Norway Damage to forests by acid rain has increased in Norway. The rocks are mostly granite here.

Damage caused by acid rain depends on: 1) the amount of industry and automobiles 2) the direction of the winds that carry the pollution 3) the composition of the soil.

The socioeconomic consequences of acidification Acid deposition causes accelerated corrosion, fracturing, and discoloration of buildings, structures, and monuments. Lower productivity in fisheries, forestry, and agriculture translates to lower profits and fewer jobs for some important industries.

Acid rain and building structures Acids are corrosive to limestone, sandstone and marble and metals

Acids corrode metals and break down limestone and marble

Effect on humans There is a link between this pollution and respiratory problems in sensitive populations such as children and asthmatics. Acid deposition can increase the levels of toxic metals such as aluminum, copper, and mercury in untreated drinking water supplies.

Reduction of nitrogen monoxide and sulfur dioxide emissions Catalytic converter changes nitrogen oxides to nitrogen gas Energy saving Avoiding coal power plants Sulfur can be washed from coal Alkaline Scrubbers can remove sulfur dioxide from emissions

Catalytic converters lower NOx emissions Unburnt hydrocarbons Carbon monoxide and nitrogen oxides are converted to nitrogen gas, carbon dioxide and water

Low sulfur coal produces less acid rain, but it is more expensive Low sulfur coal has 0 to 1% sulfur in it. The most common coal is high sulfur coal of about 2-4% sulfur.

Sulfur can be removed from coal before burning the coal. http://news.bbc.co.uk/2/hi/sci/tech/4468076.stm

Alkaline Scrubbers Removes sulfur oxides before emission The mixture of sulfur dioxide and lime makes a solid calcium sulfate.

Alkaline scrubber at work Limestone is added to remove the sulfur dioxide from the emissions

USA: Acid Rain Program (Example of an international agreement) The original Clean Air Act from 1970 was changed because of the acid deposition flow from the United States to Canada. In 1990 the Clean Air Act was changed to reduce 50% of SO2 emissions and 33% of N0x emission in the United States.

Power that does not burn coal

Quick summary of ways to reduce Acid Deposition 1) reducing energy use and the air pollution by improving air efficiency. 2) Switching from burning coal to natural gas, wind power, solar power, hydroelectric power or nuclear power 3) Removing sulfur from coal before burned. 4) Removing of sulfur dioxide using alkaline scrubbers 5) Removing Nitrogen oxides from motor vehicles exhaust using catalytic converters

Liming Lakes Liming is adding limestone and calcium carbonate (CaCO3) to increase the acidity of soils and lakes to a more basic pH. It is expensive

Soil Conditioner adding lime

Liming study in Sweden • Lime treatment neutralizes the acidity of the lake. • However, not all plant and fish species return to the lake even after liming. info1.ma.slu.se/IKEU/PDF-Poster/.../Kalkning_mot_forsurn.effekt.pdf