Acid RainWhat is acid rain? Acid rain is the term for pollution causedwhen sulfur and nitrogen dioxides combine with atmosphericmoisture. The term ‘acid rain’ is slightly misleading, and wouldbe more accurate if deemed ‘enhanced acid rain’, as rain occursacidic naturally.
Acidity is measured on what is know as the pHscale. Fourteen is the most basic, seven is the most neutral, andzero is the most acidic. Pure rain has a pH level of 7, which isexactly neutral. The acidity of rain is determined by the pH ofpure water in reaction with atmospheric concentrations ofcarbon dioxide, resulting in carbonic acid. These particlespartly dissociate to produce hydrogen ions and bicarbonateions. A bicarbonate atom is an ion formed by one hydrogenatom, one carbon at atom, and three oxygen atoms, and is veryeffective in natural waters at neutralizing hydrogen ions andreducing acidity.
The dissociation results in the natural acidityof pure rain, which is moderately acidic at a pH of 5. 7. Rainless than 5. 7 is considered ‘acid rain’, meaning it has reactedwith acidic atmospheric gases other than carbon dioxide, suchas sulfur dioxide and nitrogen dioxide. Sulfur dioxide isproduced by electric utilities, industrial, commercial andresidential heating, smelters, diesel engines and marine and railtransport, which creates sulfuric acid in rain.
Nitrogen dioxidewill also react with the rain, caused largely by transportation(cars, trucks, planes, etc. ) and electric utilities, producingnitric acid. There is a certain degree of naturally occurringacidity in rain water. This acid is from reaction with alkalinechemicals, found in soils, lakes and stream, and can occasionallyoccur when a volcano erupts as well. Bacterial action in soilsand degasing from oceanic plankton also contribute to theacidity found in rain.
More than 90% of the sulfur and 95% ofthe nitrogen emissions which occur in North America are due tothe pollution created by humans. 1 How Is Acid Rain Formed?Acid rain consists mainly of acids formed in the atmosphere. Itconsists of the oxides of sulfur, SO2 and SO3, and of nitrogenNO and NO2. Let us examine the major contributor to acidrain, sulfur oxides. Natural sources which emit sulfur dioxideinclude volcanoes, sea spray, plankton and rotting vegetation. Despite these natural occurrences, the burning of fossil fuels(such as coal and oil) can be largely blamed for the emissions.
The chemical reactions begin as energy from sunlight, in theform of photons, hit ozone molecules (O3) to form free oxygen(O2), as well as single reactive oxygen atoms (O). The oxygenatoms react with water molecules (H2O), producing electricallycharged, negative hydroxyl radicals (HO). These hydroxylradicals are responsible for oxidizing sulfur dioxide andnitrogen dioxide, which produces sulfuric acid and nitric acid. Some particles will settle to the ground (in the form of aciddeposition) or vegetation can absorb some of the SO2 gasdirectly from the atmosphere. When sulfur dioxide comes incontact with the atmosphere, it oxidizes and forms a sulfateion. It becomes sulfuric acid as it joins with hydrogen atoms inthe air and falls down to earth.
Oxidation occurs most in clouds,especially in heavily polluted air, where other compounds suchas ammonia and ozone help to catalyze the reaction, increasingthe amount of sulfur dioxide changing to sulfuric acid. Not allof the sulfur dioxide is converted to sulfuric acid, and it is notuncommon for a substantial amount to float up into theatmosphere, move to another area, and return to earth as sulfurdioxide, unconverted. S (in fossil fuels) + O2 =* SO2 2 SO2 +O2 =* 2 SO3 Much of the sulfur dioxide is converted to sulfurtrioxide in the atmosphere SO3 + H2O =* H2SO4 The sulfurtrioxide can then dissolve within water to form sulfuric acidNitric oxide and nitric dioxide are mainly from power plantsand exhaust fumes. Similar to sulfur dioxide, reactions areheavily catalyzed in heavily polluted clouds where iron,manganese, ammonia and hydrogen peroxide are present. Also,the formation of nitric acid can trigger further reactions whichrelease new hydroxyl radicals to generate more sulfuric acid.
The following is a typical reaction, which is direct combinationof nitrogen and oxygen at the high temperature inside a carengine. N2 + O2 + heat =* 2NO 2NO + O2 =* 2NO2 Thisnitrogen monoxide immediately reacts with oxygen and formsnitrogen dioxide in the following reaction 3NO2 + H2O =*2HNO3 (aq) + NO The nitrogen will then dissolve in water inthe atmosphere and produce nitric acid There are several otherpotential contributors to acid rain. These include oxidation byproducts of alkene-ozone reactions, oxidation by reactions ofNxOy species and oxidation by peroxy radicals. Each of thesereactions, however prove to be minor contributors and arerather insignificant.
How Is Acid Rain Harmful? EnvironmentalHazards Aquatic Ecosystems Acid rain has an effect onvirtually all ecosystems it touches. Perhaps the most prominent,and equally as troubling is the harmful results it produces whenin contact with lakes, streams and ponds. Scientists studyingthe effects of acid rain went to a lake about 135 km away fromthe Ontario- Manitoba border called Lake 223. This lake, sofar north acid rain did not reach it, was extremely healthy, andwas a perfect setting to explore the effects of acid rain onaquatic ecosystems.
In 1974, scientists began to add sulfuricacid into the lake. The acid was added very slowly, and it wasfour years later when they saw a major change. The freshwatershrimp began to die out. Fathead minnows stopped reproducingand began to vanish. As the scientists continued adding acid toLake 223 in low amounts, large algae mats began to form andcrayfish became unhealthy and died.
Seven years after thebeginning of the experiment, the lake trout stoppedreproducing, and most of the fish species, leeches, crawfish andmayflies began to die. In 1984, the scientists stopped addingthe acid. Without the addition of deadly sulfuric acid, the lakeslowly began to recover. Some of the fish species began torecover, however some of the scientists estimated it would takeone hundred years for the lake to fully recover, even withoutthe addition of any more acid.
Fish can still live in a lake with alow acid level, however they will get sick and not grow toproper proportions. Often the fish will not reproduce, andeventually, as the acid level increases, all the fish will die. Theacid will also ‘leach’ metals from the bottom of the lake. Thereare metals contained within the mud and rocks of the lakebottom, however they remain not dangerous as long as they arenot released. The acid will draw out these harmful metals anddissolve them in the water, resulting in the deterioration anddisappearance of a species.
One of these damaging metals isaluminum, which will coat and burn the gills of the fish as itintakes the polluted water. Some fish found in acidic lakescontain higher levels of mercury in their bodies, which isharmful to humans, resulting in the government telling society tolimit the amount of fish they eat from certain lakes and rivers. If the numbers of one species or group of species changes inresponse to acidification, the ecosystem of the entire body ofwater is likely to be affected through the predator-preyrelationships. Let us examine how acid rain is dangerous to fish. A freshwater fish’s respiration consists of a ‘trade’ ofhydrogen ions (H+) in their blood for sodium ions (Na+) fromthe water around them. If the concentration of hydrogen ions inthe water is increased, which is essentially what happens whenpH falls, there are (proportionally) fewer sodium ions.
Fish areforced to absorb more hydrogen while finding it harder toobtain sodium. The acidity of their blood increases, while thesalt content drops. An experiment involving brown trout showedthat at a pH of 5. 2 or lower, this process was fatal to thisspecies, and is likely deadly to many other trout species. Thefollowing chart shows the steps typical to freshwater fish asthe acidity increases. (Fig 1-1) ACIDITY LEVEL (pH)EFFECTS ON AQUATIC LIFE 7 Neutral, H+ and H- are inbalance 6.
8 Shells of clams and snails become thinner, due tolack of hazardous calcium ions in the water 6. 6 The viability ofeggs of the fathead minnow is reduced, rain can have and fewereggs hatch 6. 5 Lake trout begin to have difficulty reproducing,clams and snails become scarcer, green algae growth increases 6Several clam and snail species disappear, several trout speciespopulations decrease, the smooth newt is gone, smallmouth bass,walleyes and spotted salamanders have difficulty reproducing,several mayfly species cease to lay eggs 5. 8 Copepods (acritical link of crustaceans in the marine food chain) are gone,crayfish have trouble regrowing exoskeleton after molting 5.
7Several algae species decrease, while filamentous green algaeincreases, plankton decreases 5. 5 Rainbow trout, fatheadminnows and smallmouth bass lose considerable population,walleyes, brook trout, roach, lake trout and shiners don’treproduce, leeches and mayfly larvae vanish. 5. 4 Crayfishreproductivity is impaired. 5 Snail and clams are extinct. Allbut one species of crayfish are extinct, brook trout, walleyesand most bullfrogs are gone, most fish species experiencereproduction difficulties, zooplankton population begins todrop, green and green-blue algae mats have largely spread 4.
8Leopard frog numbers decline 4. 5 Mayflies and stonefliesvanish, a slowing in growth rate and oxygen uptake of bacteriais notable 4. 2 The common toad disappears 4 The oxygen outputof Lobelia plants declines 75% 3. 5 Virtually all clams, snails,frogs, fish and crayfish vanish 2. 5 Only a few species ofacid-tolerant midges, bacteria and fungi are alive 2 Inpractical terms, the lake is sterile Two hundred and twentylakes in Ontario have been found acidified, meaning their pH isless that 5.
1 year round. 2 Terrestrial Plant Life It is muchmore difficult to solve the mystery of forest destructioncompared to that of a lake. This is partially because trees liveso much longer than fish do, and acid rain damage in trees maynot show up for thirty or forty years. It is also very difficultto replicate forest conditions in a laboratory, such as insects,cold winters, pollution, elevation and abrupt changes in rainfall. Each of these conditions put stress on the trees and can beconsidered variables. Many scientists are convinced thatbecause of the complexity of a forest ecosystem, it is nearlyimpossible to prove the death of forests is due to pollution inthe form of acid rain, but deduce from many experiments it is amain factor in forest destruction.
Deciduous trees are like airfilters, and screen particles that pass through the air aroundthem. These particles collect on the leaves of the tree, andstudies have shown that when these particles contain acid theycan cause damage to the leaves. The leaves are the part of thetree that help make food, hence any damage to the leaves willresult in harm to the health of the entire tree. Coniferous treesare vulnerable to the harmful effects of acid rain as well.
Thetree’s needles are designed to nourish the tree after they fallto the ground. Each needle houses whole colonies of microscopicbacteria and algae that help the tree change nitrogen into foodat the roots. Acid rain will often burn away this material,thereby reducing adequate food supply, and weakening thetree’s health. After the damage has been done to leaves andneedles, acid rain harms the trees even more through the soil.
Soil has a level of acid. Acid in the soil can do damage to thetrees by releasing aluminum, which, once in contact with acid,becomes highly poisonous to forests. The aluminum will enterthe tree’s hairlike roots, choking them, and when these becomeclogged, the upper branches are no longer nourished. Eventhough there may be plenty of moisture in the soil, the tree candie of thirst.
Scientists have discovered that the aluminumcontent in soil has tripled since the 1960s. 3 Acid rain also killsimportant organisms on the forest floor. The process ofdecomposition is interrupted as the acid kills many of thebacteria and fungi that live on the forest floor. At a pH levelof 4. 0, the earthworm dies, further damaging the decompositionprocess.
Without earthworms and bacteria to decompose thedebris consisting of animal and bird droppings, twigs and deadleaves, the materials continue to build on the forest floor. When debris builds up, seedlings from the trees are not able tosurvive, because they can not work their way down to the soilto root. This causes the forest to slowly disappear, as oldertrees die, and the forest will not be able to rejuvenate itself. Acid rain is hardest on trees high up in mountains, because it isoften covered in mist or fog, literally bathing the trees in anacidic atmosphere. Trees also suffer because of changes in thesoil. Acid rains leach metals (draw metals out of mud and rocks)in the soil, and the trees in turn intake these harmful metalsthrough their roots.
Figure 1-2 shows the damage that acid raincan to do a forest Human Health It is known that the earthcontains many metals that are potentially dangerous to humans,such as lead, mercury, and aluminum. Most of the time thesemetals are harmless because they are in the soil, bonded toother elements. The problem occurs when acid detaches thesemetals from the rocks and soils, and can be carried deep intothe ground and make their way to underground streams. Thesestreams eventually connect to our water sources. Medicalresearchers have found these metals can be dangerous, and onrare occasion, is even fatal.
Aluminum has been found to killpeople who have kidney problems, and can also collect in braintissue. Some scientists even suspect that aluminum deposits onthe brain cause Alzheimer’s disease. (A disease that results inmemory loss, nervous system problems, and death. Acid rain isknown to irritate the whole respiratory system, beginning withmucous membranes in the nose and throat, all the way to tissuein the lungs. Consequently, acid rain has an increased effect onpeople with respiratory problems.
The U. S. Council onEnvironmental Quality estimates health-related problems dueto acid precipitation cost the United States $2 billion peryear. 4 In August 1987, over one hundred people were treatedfor eye, throat, and mouth irritation when 1. 8 metric tonnes ofhighly toxic sulfur dioxide gas leaked from an Inco plant nearSudbury, Ontario. Even Fig 1-2 This picture shows how aconiferous forest has been virtually destroyed.
Acid rain isblamed for the destruction of terrestrial ecosystems aroundthe world. without accidents, the sulfur dioxide regularlyemitted from Inco smokestacks has been linked to chronicbronchitis in Inco employees. 5 Drinking Water Acid raindamages drinking water in various ways. Thus far, amounts ofmetals in drinking water have been minimal, however the factthat metals even leak into the water is troubling to scientists. Since metals remain in the body once ingested, over time, smallamounts accumulate into large quantities, and it has yet to beconcluded how large an amount will prove to be harmful tohumans. Acid rain causes damage by loosening metals off metalwater pipes.
Modern plumbing uses plastic tubing, but oldersystems have copper pipes. The copper pipes are held togetherby a mixture of tin and lead. Lead is known to be extremelydangerous to humans, even in small amounts, and will causedamage to the brain and nervous system. A study that was donein Ontario found that water sitting in plumbing pipes for tendays contained hazardous levels of copper and lead. Thisdiscovery could be a widespread danger, since often people willgo on vacation and not shut off the plumbing, allowing water tosit and absorb these dangerous metals. Acid rain can alsodissolve the reinforcements that occur around large waterpipes.
In some parts of the United States, asbestos is used toreinforce the cement bases that hold water pipes. Asbestos isnot dangerous when bound to the cement, but is highlydangerous when separated, and has been linked to cancer andother serious diseases. Many health officials worry that looseasbestos will find it’s way to the city’s water when acid raincomes in contact with the cement. Effects On Man MadeStructures Scientists are becoming increasingly concerned withacid rain’s destruction of the ‘built environment’. There areobjects in our built environment that are irreplaceable.
Historic landmarks and statues, old cathedrals and temples,paintings and sculpture – all are part of the built environmentand are slowly being damaged. Some of these objects arepractical, making life easier, safer or more comfortable. Manyfactors determine how much damage acid rain will do, includingthe amount of rain, the location, and direction of wind. Allinfluence the amount of corrosion done.
Areas that have a largeamount fog or humidity tend to suffer more than dry areas,which is why many steel bridges located over water get rustedand corroded by acid. When metal is decayed, it cannot takethe same amount of stress of weight as when it was originallycreated. Acid rain has been blamed in several collapses ofbridges around the world. Acid rain corrodes the steel trackused on railroads, thus the tracks must be constantly checked. Metal in air planes can also be eaten away by acid rain. TheUnited States Air Force spends more that $1 billion every yearto repair or replace damaged parts.
6 A study done in Swedenshowed that metal rusts four times faster in areas that receivea lot of acid rain. This figure is staggering, and yet, metal isnot the only material damaged by acid rain. Houses andbuildings made of brick and stone are affected as well. Acidrain can dissolve the mortar, which is used in cement to holdbricks together.
When the mortar is worn away, the brickscrumble more easily, because they shift and cannot stay intactagainst the heavy weight of the bricks pressuring from above. The corrosive effects of acid rain are particularly obvious onlimestone, because it is composed of calcium carbonate, which ishighly reactive with acid rain. Tombstones made of marble(which is metamorphosed or heated limestone) have been badlydamaged, while older tombstones made of slate remain intact. Famous buildings such as the Taj Mahal, The United StatesCapitol building and the Lincoln Memorial in Washington, are allbeing continually damaged by acid rain.
Statues made of bronzeand copper are particularly susceptible to corrosion. Thesestatues turn green naturally, and this covering, called a patina,acts as a protective shield against the elements. Acid rain eatsaway at the patina, and where the acid dissolves the greencovering, it leaves a streaky black coat. This process ruinsstatues throughout the world. How Does Acid Rain Affect theEconomy? Canada/American Relations Canada is particularlysusceptible to the effects of acid rain.
Its geographicallocation places it directly in the path of a large amount of U. S. emission, and the granite bedrock of the Canadian Shield has apoor buffering quality. (A buffer is a material that canchemically weaken acid soil and is less harmful to theenvironment, such as lime or baking soda.
) The lack of such aquality renders Eastern Canada highly vulnerable to damage dueto United States pollution. Canada suffers more from acid rainthan the United States does, even though much of the pollutionoriginates in the United States. Acid rain costs Canadianshundreds of millions of dollars every year. To try and decreasethe large amounts of money the pollution is costing tax payers,Canada has passed laws to force its electrical companies to cutdown on harmful emissions. However, no matter what laws arepassed in Canada, it is not possible to stop U.
S. power plantsfrom sending acid in its direction. Figure 1-3 displays amountsof emissions created by the United States and Canada. TheGavin power plant is an excellent example of how the UnitedStates sends tonnes of acid to Canada every year.
Every hour,this power plant burns 600 tonnes of coal. The higher thesmokestack, the further the dangerous gases will travel, and theGavin smokestack is 1 103 feet tall. 7 Obviously, The Gavin cannot be solely blamed for the pollution, but it is power plantssuch as these that have caused trouble between the twocountries. It is estimated that about 50% of the sulfatedeposited in Canada derived from American sources. 8 Sixty ofthe largest plants and thus largest polluters are located in theOhio Valley, a short distance away from vulnerable Canadianland. In 1980, Canada and the United States signed aMemorandum of Intent, an agreement that both countries wouldmake acid rain control a priority.
They both promised to focuson developing ideas to cut down the amount of sulfur dioxideand nitrogen oxide emissions being pumped into the air. In thepast, Canada has presented devastatingly large figures to theUnited States, in an attempt to have them change laws andregulations regarding pollution. Unfortunately, the attemptsthus far have been unsuccessful, as the US government requestsmore testing and studies instead of altering laws. In the recentpast, the negotiations between Canada and United Statesrepresentatives have been hardly reminiscent of efforts putforth by Canadian officials. Many U.
S. politicians still qualifyacid rain as a ‘minor’ problem, and it is treated as such,according to Raymond Robinson, chairman of the CanadianEnvironmental AssBibliographyWhat is acid rain? Acid rain is the term for pollution causedwhen sulfur and nitrogen dioxides combine with atmosphericmoisture. The term ‘acid rain’ is slightly misleading, and wouldbe more accurate if deemed ‘enhanced acid rain’, as rain occursacidic naturally. Acidity is measured on what is know as the pHscale. Fourteen is the most basic, seven is the most neutral, andzero is the most acidic.
Pure rain has a pH level of 7, which isexactly neutral. The acidity of rain is determined by the pH ofpure water in reaction with atmospheric concentrations ofcarbon dioxide, resulting in carbonic acid. These particlespartly dissociate to produce hydrogen ions and bicarbonateions. A bicarbonate atom is an ion formed by one hydrogenatom, one carbon at atom, and three oxygen atoms, and is veryeffective in natural waters at neutralizing hydrogen ions andreducing acidity. The dissociation results in the natural acidityof pure rain, which is moderately acidic at a pH of 5. 7.
Rainless than 5. 7 is considered ‘acid rain’, meaning it has reactedwith acidic atmospheric gases other than carbon dioxide, suchas sulfur dioxide and nitrogen dioxide. Sulfur dioxide isproduced by electric utilities, industrial, commercial andresidential heating, smelters, diesel engines and marine and railtransport, which creates sulfuric acid in rain. Nitrogen dioxidewill also react with the rain, caused largely by transportation(cars, trucks, planes, etc.
) and electric utilities, producingnitric acid. There is a certain degree of naturally occurringacidity in rain water. This acid is from reaction with alkalinechemicals, found in soils, lakes and stream, and can occasionallyoccur when a volcano erupts as well. Bacterial action in soilsand degasing from oceanic plankton also contribute to theacidity found in rain.
More than 90% of the sulfur and 95% ofthe nitrogen emissions which occur in North America are due tothe pollution created by humans. 1 How Is Acid Rain Formed?Acid rain consists mainly of acids formed in the atmosphere. Itconsists of the oxides of sulfur, SO2 and SO3, and of nitrogenNO and NO2. Let us examine the major contributor to acidrain, sulfur oxides. Natural sources which emit sulfur dioxideinclude volcanoes, sea spray, plankton and rotting vegetation.
Despite these natural occurrences, the burning of fossil fuels(such as coal and oil) can be largely blamed for the emissions. The chemical reactions begin as energy from sunlight, in theform of photons, hit ozone molecules (O3) to form free oxygen(O2), as well as single reactive oxygen atoms (O). The oxygenatoms react with water molecules (H2O), producing electricallycharged, negative hydroxyl radicals (HO). These hydroxylradicals are responsible for oxidizing sulfur dioxide andnitrogen dioxide, which produces sulfuric acid and nitric acid.
Some particles will settle to the ground (in the form of aciddeposition) or vegetation can absorb some of the SO2 gasdirectly from the atmosphere. When sulfur dioxide comes incontact with the atmosphere, it oxidizes and forms a sulfateion. It becomes sulfuric acid as it joins with hydrogen atoms inthe air and falls down to earth. Oxidation occurs most in clouds,especially in heavily polluted air, where other compounds suchas ammonia and ozone help to catalyze the reaction, increasingthe amount of sulfur dioxide changing to sulfuric acid. Not allof the sulfur dioxide is converted to sulfuric acid, and it is notuncommon for a substantial amount to float up into theatmosphere, move to another area, and return to earth as sulfurdioxide, unconverted. S (in fossil fuels) + O2 =* SO2 2 SO2 +O2 =* 2 SO3 Much of the sulfur dioxide is converted to sulfurtrioxide in the atmosphere SO3 + H2O =* H2SO4 The sulfurtrioxide can then dissolve within water to form sulfuric acidNitric oxide and nitric dioxide are mainly from power plantsand exhaust fumes.
Similar to sulfur dioxide, reactions areheavily catalyzed in heavily polluted clouds where iron,manganese, ammonia and hydrogen peroxide are present. Also,the formation of nitric acid can trigger further reactions whichrelease new hydroxyl radicals to generate more sulfuric acid. The following is a typical reaction, which is direct combinationof nitrogen and oxygen at the high temperature inside a carengine. N2 + O2 + heat =* 2NO 2NO + O2 =* 2NO2 Thisnitrogen monoxide immediately reacts with oxygen and formsnitrogen dioxide in the following reaction 3NO2 + H2O =*2HNO3 (aq) + NO The nitrogen will then dissolve in water inthe atmosphere and produce nitric acid There are several otherpotential contributors to acid rain. These include oxidation byproducts of alkene-ozone reactions, oxidation by reactions ofNxOy species and oxidation by peroxy radicals. Each of thesereactions, however prove to be minor contributors and arerather insignificant.
How Is Acid Rain Harmful? EnvironmentalHazards Aquatic Ecosystems Acid rain has an effect onvirtually all ecosystems it touches. Perhaps the most prominent,and equally as troubling is the harmful results it produces whenin contact with lakes, streams and ponds. Scientists studyingthe effects of acid rain went to a lake about 135 km away fromthe Ontario- Manitoba border called Lake 223. This lake, sofar north acid rain did not reach it, was extremely healthy, andwas a perfect setting to explore the effects of acid rain onaquatic ecosystems. In 1974, scientists began to add sulfuricacid into the lake. The acid was added very slowly, and it wasfour years later when they saw a major change.
The freshwatershrimp began to die out. Fathead minnows stopped reproducingand began to vanish. As the scientists continued adding acid toLake 223 in low amounts, large algae mats began to form andcrayfish became unhealthy and died. Seven years after thebeginning of the experiment, the lake trout stoppedreproducing, and most of the fish species, leeches, crawfish andmayflies began to die.
In 1984, the scientists stopped addingthe acid. Without the addition of deadly sulfuric acid, the lakeslowly began to recover. Some of the fish species began torecover, however some of the scientists estimated it would takeone hundred years for the lake to fully recover, even withoutthe addition of any more acid. Fish can still live in a lake with alow acid level, however they will get sick and not grow toproper proportions. Often the fish will not reproduce, andeventually, as the acid level increases, all the fish will die. Theacid will also ‘leach’ metals from the bottom of the lake.
Thereare metals contained within the mud and rocks of the lakebottom, however they remain not dangerous as long as they arenot released. The acid will draw out these harmful metals anddissolve them in the water, resulting in the deterioration anddisappearance of a species. One of these damaging metals isaluminum, which will coat and burn the gills of the fish as itintakes the polluted water. Some fish found in acidic lakescontain higher levels of mercury in their bodies, which isharmful to humans, resulting in the government telling society tolimit the amount of fish they eat from certain lakes and rivers. If the numbers of one species or group of species changes inresponse to acidification, the ecosystem of the entire body ofwater is likely to be affected through the predator-preyrelationships. Let us examine how acid rain is dangerous to fish.
A freshwater fish’s respiration consists of a ‘trade’ ofhydrogen ions (H+) in their blood for sodium ions (Na+) fromthe water around them. If the concentration of hydrogen ions inthe water is increased, which is essentially what happens whenpH falls, there are (proportionally) fewer sodium ions. Fish areforced to absorb more hydrogen while finding it harder toobtain sodium. The acidity of their blood increases, while thesalt content drops. An experiment involving brown trout showedthat at a pH of 5.
2 or lower, this process was fatal to thisspecies, and is likely deadly to many other trout species. Thefollowing chart shows the steps typical to freshwater fish asthe acidity increases. (Fig 1-1) ACIDITY LEVEL (pH)EFFECTS ON AQUATIC LIFE 7 Neutral, H+ and H- are inbalance 6. 8 Shells of clams and snails become thinner, due tolack of hazardous calcium ions in the water 6. 6 The viability ofeggs of the fathead minnow is reduced, rain can have and fewereggs hatch 6.
5 Lake trout begin to have difficulty reproducing,clams and snails become scarcer, green algae growth increases 6Several clam and snail species disappear, several trout speciespopulations decrease, the smooth newt is gone, smallmouth bass,walleyes and spotted salamanders have difficulty reproducing,several mayfly species cease to lay eggs 5. 8 Copepods (acritical link of crustaceans in the marine food chain) are gone,crayfish have trouble regrowing exoskeleton after molting 5. 7Several algae species decrease, while filamentous green algaeincreases, plankton decreases 5. 5 Rainbow trout, fatheadminnows and smallmouth bass lose considerable population,walleyes, brook trout, roach, lake trout and shiners don’treproduce, leeches and mayfly larvae vanish.
5. 4 Crayfishreproductivity is impaired. 5 Snail and clams are extinct. Allbut one species of crayfish are extinct, brook trout, walleyesand most bullfrogs are gone, most fish species experiencereproduction difficulties, zooplankton population begins todrop, green and green-blue algae mats have largely spread 4.
8Leopard frog numbers decline 4. 5 Mayflies and stonefliesvanish, a slowing in growth rate and oxygen uptake of bacteriais notable 4. 2 The common toad disappears 4 The oxygen outputof Lobelia plants declines 75% 3. 5 Virtually all clams, snails,frogs, fish and crayfish vanish 2. 5 Only a few species ofacid-tolerant midges, bacteria and fungi are alive 2 Inpractical terms, the lake is sterile Two hundred and twentylakes in Ontario have been found acidified, meaning their pH isless that 5.
1 year round. 2 Terrestrial Plant Life It is muchmore difficult to solve the mystery of forest destructioncompared to that of a lake. This is partially because trees liveso much longer than fish do, and acid rain damage in trees maynot show up for thirty or forty years. It is also very difficultto replicate forest conditions in a laboratory, such as insects,cold winters, pollution, elevation and abrupt changes in rainfall.
Each of these conditions put stress on the trees and can beconsidered variables. Many scientists are convinced thatbecause of the complexity of a forest ecosystem, it is nearlyimpossible to prove the death of forests is due to pollution inthe form of acid rain, but deduce from many experiments it is amain factor in forest destruction. Deciduous trees are like airfilters, and screen particles that pass through the air aroundthem. These particles collect on the leaves of the tree, andstudies have shown that when these particles contain acid theycan cause damage to the leaves. The leaves are the part of thetree that help make food, hence any damage to the leaves willresult in harm to the health of the entire tree. Coniferous treesare vulnerable to the harmful effects of acid rain as well.
Thetree’s needles are designed to nourish the tree after they fallto the ground. Each needle houses whole colonies of microscopicbacteria and algae that help the tree change nitrogen into foodat the roots. Acid rain will often burn away this material,thereby reducing adequate food supply, and weakening thetree’s health. After the damage has been done to leaves andneedles, acid rain harms the trees even more through the soil. Soil has a level of acid.
Acid in the soil can do damage to thetrees by releasing aluminum, which, once in contact with acid,becomes highly poisonous to forests. The aluminum will enterthe tree’s hairlike roots, choking them, and when these becomeclogged, the upper branches are no longer nourished. Eventhough there may be plenty of moisture in the soil, the tree candie of thirst. Scientists have discovered that the aluminumcontent in soil has tripled since the 1960s. 3 Acid rain also killsimportant organisms on the forest floor.
The process ofdecomposition is interrupted as the acid kills many of thebacteria and fungi that live on the forest floor. At a pH levelof 4. 0, the earthworm dies, further damaging the decompositionprocess. Without earthworms and bacteria to decompose thedebris consisting of animal and bird droppings, twigs and deadleaves, the materials continue to build on the forest floor. When debris builds up, seedlings from the trees are not able tosurvive, because they can not work their way down to the soilto root.
This causes the forest to slowly disappear, as oldertrees die, and the forest will not be able to rejuvenate itself. Acid rain is hardest on trees high up in mountains, because it isoften covered in mist or fog, literally bathing the trees in anacidic atmosphere. Trees also suffer because of changes in thesoil. Acid rains leach metals (draw metals out of mud and rocks)in the soil, and the trees in turn intake these harmful metalsthrough their roots. Figure 1-2 shows the damage that acid raincan to do a forest Human Health It is known that the earthcontains many metals that are potentially dangerous to humans,such as lead, mercury, and aluminum. Most of the time thesemetals are harmless because they are in the soil, bonded toother elements.
The problem occurs when acid detaches thesemetals from the rocks and soils, and can be carried deep intothe ground and make their way to underground streams. Thesestreams eventually connect to our water sources. Medicalresearchers have found these metals can be dangerous, and onrare occasion, is even fatal. Aluminum has been found to killpeople who have kidney problems, and can also collect in braintissue.
Some scientists even suspect that aluminum deposits onthe brain cause Alzheimer’s disease. (A disease that results inmemory loss, nervous system problems, and death. Acid rain isknown to irritate the whole respiratory system, beginning withmucous membranes in the nose and throat, all the way to tissuein the lungs. Consequently, acid rain has an increased effect onpeople with respiratory problems. The U.
S. Council onEnvironmental Quality estimates health-related problems dueto acid precipitation cost the United States $2 billion peryear. 4 In August 1987, over one hundred people were treatedfor eye, throat, and mouth irritation when 1. 8 metric tonnes ofhighly toxic sulfur dioxide gas leaked from an Inco plant nearSudbury, Ontario. Even Fig 1-2 This picture shows how aconiferous forest has been virtually destroyed.
Acid rain isblamed for the destruction of terrestrial ecosystems aroundthe world. without accidents, the sulfur dioxide regularlyemitted from Inco smokestacks has been linked to chronicbronchitis in Inco employees. 5 Drinking Water Acid raindamages drinking water in various ways. Thus far, amounts ofmetals in drinking water have been minimal, however the factthat metals even leak into the water is troubling to scientists. Since metals remain in the body once ingested, over time, smallamounts accumulate into large quantities, and it has yet to beconcluded how large an amount will prove to be harmful tohumans. Acid rain causes damage by loosening metals off metalwater pipes.
Modern plumbing uses plastic tubing, but oldersystems have copper pipes. The copper pipes are held togetherby a mixture of tin and lead. Lead is known to be extremelydangerous to humans, even in small amounts, and will causedamage to the brain and nervous system. A study that was donein Ontario found that water sitting in plumbing pipes for tendays contained hazardous levels of copper and lead. Thisdiscovery could be a widespread danger, since often people willgo on vacation and not shut off the plumbing, allowing water tosit and absorb these dangerous metals.
Acid rain can alsodissolve the reinforcements that occur around large waterpipes. In some parts of the United States, asbestos is used toreinforce the cement bases that hold water pipes. Asbestos isnot dangerous when bound to the cement, but is highlydangerous when separated, and has been linked to cancer andother serious diseases. Many health officials worry that looseasbestos will find it’s way to the city’s water when acid raincomes in contact with the cement.
Effects On Man MadeStructures Scientists are becoming increasingly concerned withacid rain’s destruction of the ‘built environment’. There areobjects in our built environment that are irreplaceable. Historic landmarks and statues, old cathedrals and temples,paintings and sculpture – all are part of the built environmentand are slowly being damaged. Some of these objects arepractical, making life easier, safer or more comfortable. Manyfactors determine how much damage acid rain will do, includingthe amount of rain, the location, and direction of wind. Allinfluence the amount of corrosion done.
Areas that have a largeamount fog or humidity tend to suffer more than dry areas,which is why many steel bridges located over water get rustedand corroded by acid. When metal is decayed, it cannot takethe same amount of stress of weight as when it was originallycreated. Acid rain has been blamed in several collapses ofbridges around the world. Acid rain corrodes the steel trackused on railroads, thus the tracks must be constantly checked.
Metal in air planes can also be eaten away by acid rain. TheUnited States Air Force spends more that $1 billion every yearto repair or replace damaged parts. 6 A study done in Swedenshowed that metal rusts four times faster in areas that receivea lot of acid rain. This figure is staggering, and yet, metal isnot the only material damaged by acid rain. Houses andbuildings made of brick and stone are affected as well.
Acidrain can dissolve the mortar, which is used in cement to holdbricks together. When the mortar is worn away, the brickscrumble more easily, because they shift and cannot stay intactagainst the heavy weight of the bricks pressuring from above. The corrosive effects of acid rain are particularly obvious onlimestone, because it is composed of calcium carbonate, which ishighly reactive with acid rain. Tombstones made of marble(which is metamorphosed or heated limestone) have been badlydamaged, while older tombstones made of slate remain intact.
Famous buildings such as the Taj Mahal, The United StatesCapitol building and the Lincoln Memorial in Washington, are allbeing continually damaged by acid rain. Statues made of bronzeand copper are particularly susceptible to corrosion. Thesestatues turn green naturally, and this covering, called a patina,acts as a protective shield against the elements. Acid rain eatsaway at the patina, and where the acid dissolves the greencovering, it leaves a streaky black coat. This process ruinsstatues throughout the world. How Does Acid Rain Affect theEconomy? Canada/American Relations Canada is particularlysusceptible to the effects of acid rain.
Its geographicallocation places it directly in the path of a large amount of U. S. emission, and the granite bedrock of the Canadian Shield has apoor buffering quality. (A buffer is a material that canchemically weaken acid soil and is less harmful to theenvironment, such as lime or baking soda.
) The lack of such aquality renders Eastern Canada highly vulnerable to damage dueto United States pollution. Canada suffers more from acid rainthan the United States does, even though much of the pollutionoriginates in the United States. Acid rain costs Canadianshundreds of millions of dollars every year. To try and decreasethe large amounts of money the pollution is costing tax payers,Canada has passed laws to force its electrical companies to cutdown on harmful emissions.
However, no matter what laws arepassed in Canada, it is not possible to stop U. S. power plantsfrom sending acid in its direction. Figure 1-3 displays amountsof emissions created by the United States and Canada. TheGavin power plant is an excellent example of how the UnitedStates sends tonnes of acid to Canada every year. Every hour,this power plant burns 600 tonnes of coal.
The higher thesmokestack, the further the dangerous gases will travel, and theGavin smokestack is 1 103 feet tall. 7 Obviously, The Gavin cannot be solely blamed for the pollution, but it is power plantssuch as these that have caused trouble between the twocountries. It is estimated that about 50% of the sulfatedeposited in Canada derived from American sources. 8 Sixty ofthe largest plants and thus largest polluters are located in theOhio Valley, a short distance away from vulnerable Canadianland.
In 1980, Canada and the United States signed aMemorandum of Intent, an agreement that both countries wouldmake acid rain control a priority. They both promised to focuson developing ideas to cut down the amount of sulfur dioxideand nitrogen oxide emissions being pumped into the air. In thepast, Canada has presented devastatingly large figures to theUnited States, in an attempt to have them change laws andregulations regarding pollution. Unfortunately, the attemptsthus far have been unsuccessful, as the US government requestsmore testing and studies instead of altering laws.
In the recentpast, the negotiations between Canada and United Statesrepresentatives have been hardly reminiscent of efforts putforth by Canadian officials. Many U. S. politicians still qualifyacid rain as a ‘minor’ problem, and it is treated as such,according to Raymond Robinson, chairman of the CanadianEnvironmental Ass
