Tuesday, January 31, 2017

Acid Rain and Ground Water pH

An important measure of water quality is its pH.   The letters (pH) describe the acidic or basic nature of a substance.  Scientifically a liquid’s pH is a measure of the concentration of hydrogen ions (H+ ) it contains.  The Danish biochemist S.P.L. Sorenson originally proposed the concept or the pH scale in 1909 as a method to describe the “acidity” of beer. 

The pH scale ranges from 0 to 14 with a value of 7 indicating a neutral pH (neither acidic nor basic].  Distilled water has a pH of 7.  Basic (or alkaline) solutions (i.e. bleach and ammonia) have values greater than 7.  Acidic solutions (i.e. battery acid, lemon juice, and vinegar) have values less than 7.  Each unit change in pH is equal to a 10-fold (10 times) change in the pH.  The table shows the approximate pH value for some common substances.

Rain and snow (the principal sources of ground water) have pH values near 5.6, if they are relatively free of pollution.  However, in many areas of the United States “acid rain” is now the norm because of pollution emissions from sources such as coal-fired power plants and car exhaust.  Acid rain can have pH values near 4.  There are concerns that acid rain is having effects on vegetation and aquatic fauna. Once on the ground, some of the acidic precipitation infiltrates downward to mix with ground water and can affect the ground water pH.  

The pH of ground water will vary depending on the composition of the rocks and sediments that surround the travel pathway of the recharge water infiltrating to the ground water.  Ground water chemistry will also vary depending on how long the existing ground water is in contact with a particular rock.  The chemical composition of the bedrock tends to stabilize (buffer) the pH of the ground water.  The longer the contact time, the larger the effect of the rock chemistry on the composition and pH of the ground water.  Ground water passing through carbonate-rich rocks (e.g., limestones and marbles) will usually have pH values greater than 7 as the acidic water is “neutralized.”  If the geology of the aquifer containing the ground water has few carbonate rocks (e.g., sandstones, metamorphic granitic schists and gneisses; volcanic rocks, etc.) the ground water will tend to remain acidic.

Acidity in water is not in itself harmful to health. Many popular beverages have considerable acidity or alkalinity. The concern for acidity in drinking water is that even mildly acid water can dissolve lead or copper that may in plumbing pies and fixtures.  In theory, there should be no lead content in homes built since 1987.  However for millions of homes there is the potential for a problem.  For this reason, the United States Environmental Protection Agency has determined that drinking water should have a pH between 6.5 and 8.5 in order to limit the concentration of dissolved contaminants from acidic waters or the build up of scale deposits from alkaline water.  

It is a good idea to test the pH when a new well is drilled (check again after six months of use), when you move to a new home, or if your well has never been tested.  If the pH is not within the EPA recommended range then it may be necessary to increase the pH of the water with limestone or marble chips or to reduce the pH with caustic soda (sodium hydroxide) treatments.  These treatments are not expensive, not difficult to maintain, and can be easily installed by a professional.  Test your water to make sure you actually need the pH adjusted before you install any equipment.

Acid Rain Various Effects

Acid rain is rain that contains nitric and sulfuric acid. Snow and fog can also contain nitric and sulfuric acid, and the dangerous effects are the same whether the acid is falling to the earth by rain or snow, or dancing in the air via fog. Any precipitation or dust particle that contains abnormal levels of sulfur dioxide and nitrogen oxides is considered acid rain. Acid rain primarily affects the United States, Europe, and China.

Acid rain directly affects the chemical and pH balances in ground water. The excess aluminum created by acid rain makes aquatic environments such as the sea, lakes, and streams, toxic. The animals that can withstand the imbalance of the water's natural minerals might survive, but quickly lose their food source as the weaker creatures die off. Animals that cannot withstand the chemical imbalances die, fail to reproduce, become deformed due to bone decalcification, or fail to grow normally. Algae growth is increased by acid rain, and rock scaling microbial and invertebrate herbivores lose habitation and die.

Acid rain leaches calcium out of the soil when it is absorbed by the earth. This directly affects the mineral levels of the soil and the creatures, such as snails, that rely on that calcium for shell growth. Consequently, snails die off and birds, which eat them for calcium, lay eggs with shells that are weak and brittle and therefore fail to hatch. Decreased calcium also creates excess aluminum in the soil, preventing trees and other plant life from absorbing water. Weakened plant life cannot tolerate extreme temperatures or fight off insects and disease.

Those seeking an expensive paint job on their car might want to think twice in areas directly affected by acid rain. The excess sulfur dioxide and nitrogen oxides in acid rain damages automobile paint and corrodes surfaces. It is believed that the acid rain causes the damage as it dries on, and evaporates from, the surface. Auto and paint coating manufacturers are trying to develop protective coatings that prevent acid rain corrosion.

Acid rain directly impacts forest ecosystems and their inhabitants. The damage to the forest trees and plants is widespread. Acid rain damages leaves as it falls. Acid rain runoff from the trees and forest floors infiltrates the forest's water supplies; runoff that doesn't enter the water supply is absorbed by the soil. The consequence of this is just as it is for any soil or water source infected with acid rain: the plants and creatures die off, and the creatures that rely on those plants and smaller creatures lose their food source and die, as well.

Plants and animals aren't the only victims of acid rain. Acid rain is dangerous to humans. The same sulphate and nitrate particles that directly affect the soil and water pH balances can cause serious damage to the respiratory system if inhaled deeply. A damaged respiratory system means decreased oxygen in the blood supply, which eventually damages the heart. Studies show an increase of chronic conditions, such as asthma and bronchitis, in people who are regularly exposed to acid rain.

Preventing acid rain is the only way to stop its deadly impact on the environment. Acid rain is caused by pollution. It is released into the air naturally during a volcanic eruption, but the primary cause of excess nitric and sulfuric acid in the environment is manmade. Conserving energy is the number one way humans can prevent acid rain. Using less energy at home decreases the need for power plants. People also need to get out of their car. Using public transportation, biking or walking to destinations leaves fewer cars on the road, less emissions in the air, and a decreased dependency upon fossil fuels. Finally, manufacturing plants can reduce the emissions that cause acid rain by using scrubbers to clean and remove the dangerous chemicals from the pipes before they are released into the air. 

Liming lakes and rivers

Acidification of lakes and rivers is one of the most serious environmental problems in Norway. Acid rain is a threat to aquatic biodiversity: it has resulted in the loss or depletion of more than 15 000 fish stocks. Liming is an effective way of reducing the damage.

Acidification of Norway’s lakes and rivers is mainly caused by pollutants from other countries that are transported in the atmosphere and deposited as acid rain. This problem can only be reduced through international agreements to reduce releases of pollutants.

Critical loads for deposition of acid rain are still being exceeded in much of the southern half of Norway. Liming makes lakes and rivers less acidic, improving the water chemistry and providing better conditions for fish and other freshwater organisms. The Norwegian authorities provide substantial funding for liming of many rivers and lakes.

The Norwegian Environment Agency has drawn up an action plan for liming for the period 2011–15.
Damage worsened as pollution rose

Acidification started in Norway with the Industrial Revolution in the 1800s, and continued to worsen until the 1970s. In 1925, it was discovered that fish mortality was caused by acid water, but the links with acid rain were not understood until the 1950s. More and more fish stocks were damaged as the problem spread, leading to losses of aquatic biodiversity generally.

When the situation was at its worst, 30 % of mainland Norway was affected, and one in five species disappeared from the most acidic river systems. More than 15 000 fish stocks were wiped out or depleted: Norway lost 25 of its salmon stocks, and at least 20 others were depleted. The damage was worst in Vest-Agder and Aust-Agder counties in the far south of the country.

Liming improves water quality

Liming programmes started in the mid-1980s, and 21 salmon rivers and 2 500 lakes and streams are now limed regularly. The effects are documented by monitoring water chemistry, fish, benthic animals and aquatic vegetation.

Many years of liming combined with reductions in acid deposition have improved water quality to the extent that ecosystems are recovering. The lower acidity (higher pH) improves conditions directly, and also means that less aluminium – which is highly toxic to many aquatic species – is released from soils. Both salmon stocks and their prey species are recovering, although there is still a considerable potential for further improvement of species diversity.

Since 2000, however, the positive trend has levelled off, and no major improvement is expected after 2010. Acid rain (sulphur and nitrogen deposition) is still a serious threat to freshwater biodiversity in Norway. About 10 % of mainland Norway is now damaged by acidification, with the most serious effects in the southernmost and westernmost parts of the country.

Sensitive to acid rain

Much of the southern half of Norway has thin soil cover on bedrock consisting of acidic rocks such as gneiss and granite. These areas are very sensitive to acid rain. The liming programme is most extensive in the counties that are worst affected – Aust-Agder, Vest-Agder, Rogaland and Hordaland – and will have to be continued until critical loads for acidification of surface water are no longer exceeded.

Critical loads are used to express how much acidification different ecosystems can absorb without damage. In Norway, freshwater ecosystems are particularly sensitive to acidification, and critical loads are therefore low.

Linked to fossil fuels

Acid rain is mainly caused by combustion of fossil fuels. Power plants, industrial processes and transport are the major sources of the emissions that cause acid rain. About 90 % of the sulphur and nitrogen deposited in Norway originates in other countries, especially the UK, Germany and Poland. This means that the amount of acid rain falling on Norway is to a large extent determined by developments elsewhere in Europe.

Sulphur emissions in Europe have been greatly reduced in the past 20–30 years. In Eastern Europe, this is partly a result of economic problems that have led to the closure of factories and lower energy production. In Western Europe, cuts in emissions have generally been achieved by installing emission abatement technology at industrial plants and by switching to the use of low-sulphur fuels. Motor vehicles and other mobile sources are an important source of nitrogen emissions, and this has made it more difficult to reduce releases of nitrogen. 

International agreements on cuts in emissions

Since 1980, total deposition of sulphur in precipitation in Norway has been reduced by about 75 %, while the corresponding figure for nitrogen is about 35 %. The reductions have largely been brought about by countries taking action to meet their commitments under international agreements.

Several binding protocols have been adopted under the Convention on Long-range Transboundary Air Pollution, including the Gothenburg Protocol, which entered into force in 2005. There are 26 parties to the Protocol, which in its first phase set emission ceilings for 2010 for sulphur, nitrogen oxides (NOx) and other pollutants. In 2012, new national emission reductions were agreed to be achieved in 2020 and beyond.

Sunday, January 29, 2017

Acid Deposition In UK

Acid rain is a general name for many phenomena including acid fog, acid sleet, and acid snow. Although we associate the acid threat with rainy days, acid deposition occurs all the time, even on sunny days.

Acid Deposition is the scientific term used to describe "Acid Rain". When atmospheric pollutants such as sulphur dioxide and nitrogen oxides mix with water vapour in the air, they are converted to sulphuric and nitric acids. These acids make the rain acidic, hence the term "acid rain". Rain returns the sulphur and nitrogen acids to Earth, and in high concentrations, can cause damage to natural environments including forests and freshwater lakes. This form of acid deposition is known as wet deposition. A second method of acid deposition is known as dry deposition. Whilst wet deposition involves the precipitation of acids, dry deposition occurs when the acids are first transformed chemically into gases and salts, before falling under the influence of gravity back to Earth. Sulphur dioxide, for example, is deposited as a gas and as a salt.

The gases present in acid deposition are found to occur naturally in the environment. They are given off from a number of sources including volcanic eruptions and the rotting of vegetation. They become a problem when humans produce the gases in large amounts, and at high concentrations by the burning of fossil fuels.

The distances that pollutant gases travel means that acid deposition is an international or transboundary problem. This means that acid pollutants are not necessarily deposited in the same country where they were produced.

Acidic Emissions In Uk

Rain water is naturally acidic as a result of carbon dioxide dissolved in water and from volcanic emissions of sulphur. However, it is the chemical conversion of sulphur and nitrogen emissions from power stations, factories, vehicles and homes, where fossil fuels are burnt, that we call acid rain. These waste gases are carried by the wind, sometimes over long distances, and can in time be converted into sulphuric and nitric acids.

Natural sources of sulphur dioxide (SO2) include releases from volcanoes, oceans, biological decay and forest fires. Actual amounts released from natural sources in the world are difficult to quantify; in 1983 the United Nations Environment Programme estimated a figure of between 80 million and 288 million tonnes of sulphur oxides per year. Man-made sulphur dioxide emissions result from combustion or burning of fossil fuels, due to varying amounts of sulphur being present in these fuels. Worldwide emissions of SO2 are thought to be around 69 million tonnes per year.

Levels of sulphur dioxide from combustion sources in the UK have declined in recent decades. Between 1970 and 1999, UK sulphur dioxide emissions fell by 82% due to recession, restructuring of industry, substitution of fuels (for example natural gas) and air pollution control technology. Power station emissions fell by 73% over the same period, but the percentage of UK emissions from power stations has actually increased to 65% of the 1999 total compared to 45% of the total in 1970.

Natural sources of nitrogen oxides (NOx) include volcanoes, lightening strikes and biological decay. Estimates range from between 20 million and 90 million tonnes per year NOx released from natural sources, compared to around 24 million tonnes from human sources world-wide. Nitrogen oxides are produced when fossil fuels are burned. The major sources of NOx in the UK in 1999 were road transport (44%), power stations (21%) and industry (including iron and steel, and refineries) (12%). Emissions of nitrogen oxides from road transport increased during the 1970s and 1980s before decreasing again during the 1990s. For example, in 1970, emissions of NOx from road transport in the UK were 0.769 million tonnes by in 1990 they had risen to over 1.31 million tonnes NOx. Since then, however, emissions from transport have been declining due to improvements in vehicle technology, such as the use of catalytic converters, and the use of cleaner fuels. In 1999 they were 0.714 million tonnes, lower than in 1970.

The geographical distribution of human acidic emission sources is not even. Nitrogen and sulphur emission sources are heavily concentrated in the Northern Hemisphere, particularly in Europe and North America. As a result, precipitation is generally more acidic in these countries, with an acidity in the range pH 4.1 to pH 5.1. �Normal� or �unpolluted� rainfall has a pH of 5.6.

Acid Rain

Acids form when certain atmospheric gases (primarily carbon dioxide, sulfur dioxide, and nitrogen oxides) come in contact with water in the atmosphere or on the ground and are chemically converted to acidic substances. Oxidants play a major role in several of these acid-forming processes. Carbon dioxide dissolved in rain is converted to a weak acid (carbonic acid). Other gases, primarily oxides of sulfur and nitrogen, are converted to stronq acids (sulfuric and nitric acids).

Although rain is naturally slightly acidic because of carbon dioxide, natural emissions of sulfur and nitrogen oxides, and certain organic acids, human activities can make it much more acidic. Occasional pH readings of well below 2.4 (the acidity of vinegar) have been reported in industrialized areas.

The principal natural phenomena that contribute acid-producing gases to the atmosphere are emissions from volcanoes and from biological processes that occur on the land, in wetlands, and in the oceans. The effects of acidic deposits have been detected in glacial ice thousands of years old in remote parts of the globe. Principal human sources are industrial and power-generating plants and transportation vehicles. The gases may be carried hundreds of miles in the atmosphere before they are converted to acids and deposited.

Since the industrial revolution, emissions of sulfur and nitrogen oxides to the atmosphere have increased. Industrial and energy-generating facilities that burn fossil fuels, primarily coal, are the principal sources of increased sulfur oxides. These sources, plus the transportation sector, are the major originators of increased nitrogen oxides.

The problem of acid rain not only has increased with population and industrial growth, it has become more widespread. The use of tall smokestacks to reduce local pollution has contributed to the spread of acid rain by releasing gases into regional atmospheric circulation. The same remote glaciers that provide evidence of natural variability in acidic deposition show, in their more recently formed layers, the increased deposition caused by human activity during the past half century.