top 14 acid precipitation

7/30/2019 Top 14 Acid Precipitation

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CHEM115 Environmental Chemistry

Background source:

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CHAPTER 14 (part 1)

ACID PRECIPITATION




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Acid Precipitation

Acid precipitation involves deposition of

hailstones, rain and snow.

The main causes include the presence of

sulfuric (H2SO4) and nitric (HNO3) acid

which are formed by oxidation of sulfur

dioxide (SO2) and nitrogen oxides (NOx).




Background source:


Formation of Acid Rain

Source: Botkin&Keller, 2003. Environmental Science. 4th ed. Chapter 23.




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Sulfur dioxide and nitrogen oxides in theatmosphere reacts with water vapor to form

sulfuric and nitric acids.

i. SO2 + H2O H2SO3 (sulfurous acid)

ii. SO3 + H2O H2SO4 (sulfuric acid)iii. 2 NO2 + H2O HNO2 + HNO3 (nitrous and nitric acids)



• These acids travel long distances with

prevailing winds and be deposited as acid

precipitation.

• Sulfate and nitrate particles can also be

deposited as dry deposition and changes

into sulfuric and nitric acid later where

there is moisture.


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Negative effects on:

• Lake and aquatic ecosystems

• Trees and soils• The atmosphere

• Architecture

• Materials• Humans

Consequences




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Effect on Aquatic Ecosystem

Acidic chemicals can enter the water directly.

Surface run-off which washes nutrients out of soil thatenters the water.

Spring acid-shock can occur. The aquatic ecosystem doesnot have enough time to adjust to the sudden change.

Acid in water may affect the fish direct and indirect ways of which both will lead to death of fish and weak reproductionof fish.



• Spring acid-shock :When snow melts rapidly in

spring due to a sudden temp change, any acids

and chemicals in the snow are released into thesoil. The melted snow then runs off into streams

and rivers and gradually makes its way into lakes.

The introduction of these acids and chemicals

causes a sudden dramatic change in the pH of the lakes – hence, the term ‘acid shock’

Example: fish have disappeared from lakes in Scandinavia.

Records show that an increase in acidity has been traced

to acid rain, the result of industrial processes in other

countries particularly Germany and Great Britain.



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Effects on Trees and Soils

•Minerals such as calcium and magnesium

in soils can be washed away.

•Overtime, when soil becomes too acidic.

• Aluminum from clay minerals is freed and

taken up by the plants. The plants gradually

become starved of their vital nutrients and

poisoned by aluminum.





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Acidic aerosols affect stomata in leaves and

hinder photosynthesis.

Ammonium sulfate

further increases soilacidification which

encourages the growth

of pests.

Source: http://www.grandfather.com/conservation_interpretation/images/acidrain.jpg



• Ammonia from ground-level biological decay

processes reacts with droplets of atmospheric

sulfuric acid to form ammonium sulfateH2SO4 + 2NH3 > (NH4)2SO4

which can form on the surfaces of trees. When

ammonium sulfate reaches the soil, it reacts to

form both sulfuric and nitric acids, further

increase soil acidification. These conditions also

stimulate the growth of fungi and pests because

trees under stress release chemicals such asterpenes, with the latter attracting pests such as

ambrosia beetle.



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Loss of nutrients also results in weakeningof trees, making them more susceptible todisease.

As trees weaken and die, there is lesshabitat and food for birds and animals.



The dying trees also allow more light through to

the forest floor , changing the temperature andwater content of soil at the surface. This affects

the ecosystem.

The trees allow more light as they are stripped of

leaves. It affects the ecosystem because the

amount of light reaching the ground can affect

the surface temperature and water and thuschange what grows on the floor and what lives in

the soil



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Effects on Atmosphere

Atmospheric sulfates, nitrates and acids can

cause haze.

It reduces visibility and interfere withatmospheric energy processes by absorbing

sunlight.





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Effects on Architecture

Acid particles and precipitation depositedonto stone buildings, monuments causestone damage

Limestone and marble turn into gypsum(calcium sulfate) upon contact with the acid.

Gypsum is soluble and can be washed off the stone by rain.





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Building materials such as paint, plasticsand steel may be damaged by acid. Iron

exposed to acid and oxygen will rapidly

dissolve and be washed away.





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Effects on Materials

Acid rain can damage materials like fabric,

books, works and water pipelines.

Metals leaching from water pipelines may

enter and accumulate in human bodies.





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Effects on Humans

Long-term exposure to acidic aerosols issaid to cause:

dry coughs

Headaches

eye irritation

nose and throat irritation

aggravating respiratory

pulmonary diseases.





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Control of Acid Precipitation

The main one:Decrease the emissions of sulfur dioxide

and nitrogen oxides.

-Reducing electricity consumption

-Reducing on-road vehicle exhaust

-Reducing manufacturing shipping




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Thank you

top 14 acid precipitation

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