Acid Rain. Acid Rain Overview Unusually Acidic Precipitation Extremely harmful to various ecosystems...

Acid Rain

Acid Rain Overview

• Unusually Acidic Precipitation• Extremely harmful to various ecosystems• Another term for wet acid deposition• The term was first coined in 1972• In the 70’s scientists began to realize the implications

and repercussions it has on the environment• In 1990 the Clean Air Act put a limit on the amount of

SO2 production of power plants , but while this has limited Acid rain it has not ended it or any of its lasting effects

Causes

• Acid rain is almost uniformly caused by human-made emissions – NO, NO2, CO2, SO2, SO3

• These are produced by electricity generation, factories, and motor vehicles

• Particularly harmful are the vast emissions of electrical power plants that utilize coal or other fossil-fuels

Causes• In the past short

smokestacks led to the destruction of local ecosystems

• The newer, taller smokestacks failed to solve the problem, however, and simply dispersed emissions across a wider area

Causes

• There are natural causes for acid rain as well, such as volcanic eruptions, forest fires, and lightning

• However these cause only a minute amount of acid rain in the greater scheme of things

• For example, the eruption of Mount Saint Helens released only about what one factory produces in a year

Chemical Process

• Previously mentioned sources emit harmful pollutants – The most common and most potent are NOx and

SO2

• The gases are dispersed via the wind to other locations

• At this point they dissolve into precipitation to form sulfuric acid, ammonium nitrate and nitric acid

Chemical Process

• Example:– Sulfur from burning oil and coal SO2

– SO2 is converted into SO3

– SO3 reacts with water to create sulfuric acid

– SO3(g)+H2O(l)H2SO4(aq)

Acidity of Acid Rain

• Pure water has neutral pH of 7. • Normal rainwater is slightly acidic, at around

5.6, due to the dissolution of CO2 from the surrounding atmosphere

• Acid rain typically has pH values between 3 and 4, but has been recorded to be as low as 2.7 in some cases, only a little above the acidity of battery acid, and in the range of that of vinegar

Effects

• 1. Pollution of Soil:– Higher acidity can kill microbes in soil by

denaturing their enzymes – Important nutrients, such as Magnesium and

Calcium, are leached away, changing the chemistry of the soil and affecting sensitive species

– Releases aluminum into the soil

Effects

• 2. Plant Life– Effected soil affects plants’

ability to withstand cold temperatures and insects, fight off disease, and reproduce

– The aluminum in the soil makes it difficult for plants to take up water

– The acid can also soak into their leaves and kill them killing the plant in the process

Effects

• 3. Erosion:– Acidity erodes stone, especially those with high

amounts of calcium carbonate. – The acid reacts with the calcium carbonate to create

gypsum (CaSO4·2H2O), which then flakes off: • CaCO3 (s) + H2SO4 (aq) CaSO⇌ 4 (aq) + CO2 (g) + H2O (l)

– This can destroy buildings and statues– Acid also increases the corrosion rate of metals such

as iron steel copper and bronze

Effects

• 4. Human Health:– The acid in the rainwater is too diluted to have

direct adverse effects, but the particulates responsible for acid rain do have an adverse effect

– Increased amounts of fine particulate matter in the air contribute to heart and lung problems including asthma and bronchitis

– The acidic water can corrode water pipelines. The high lead levels in water and sulfate pollution are harmful to human health

Effects

• 5: Pollution of Rivers and Lakes:– Fish can’t survive at the low pH of an acidic

environment– Whole populations of fish wind up dead, entire lakes

and rivers in Europe with no normal aquatic life left– Acid rain makes waters acidic and causes them to

absorb the aluminum, which makes its way from soil into lakes and streams

– At pHs lower than 5 most fish eggs will not hatch and lower pHs can kill adult fish