Look up in the sky. Air seems boundless and, for that reason, it is a resource often taken for granted. Above the state of Virginia alone rests over one trillion tons of it. But, just like water, not all of it is usable to you. Yet even with all of this volume, air must constantly be reused. In fact, the air you are breathing now was in someone else's lungs earlier. Air is the ultimate recyclable material!
Since oxygen is always being used to burn food into water and carbon dioxied, why doesn't it all get used up?
Photosynthesis. Green plants use light and carbon dioxide to produce glucose and oxygen. The use and reuse of oxygen is called the oxygen cycle.
Air is a mixture of invisible and odorless gases, mostly nitrogen and some oxygen. Water droplets, fine particles, and small amounts of other gases such as carbon dioxide, methane, ammonia, and argon are also part of the mix. If air is clean, we can neither see it, taste it, nor smell it.
Often what we can see or smell in the air is air pollution. Air pollution is any visible or invisible particle or gas found in the air that is not part of its normal composition. Some substances are so common and widespread, they build up in the air and become a hazard to human health.
The U.S. Environmental Protection Agency has developed health-based national air quality standards for six pollutants. They are: carbon monoxide, ozone, nitrogen dioxide, sulfur dioxide, particulate matter, and lead. In addition to these six criteria pollutants, standards have been set for over 120 toxic air pollutants (hazardous chemicals found in the air which are known or are suspected to cause cancer, genetic mutations, birth defects, or other serious illnesses in people even at low exposure levels). These contaminants include arsenic, benzene, beryllium, mercury, vinyl chloride, and radionuclides. Companies that produce such pollutants are required to use special equipment to control how much is emitted into the atmosphere.
Air pollutants have occurred naturally since the earth's formation. Particulate matter and gases are emitted from every corner of the globe: from volcanoes, tree pollen, forest fires, and decaying organic matter in oceans and wetlands.
Much air pollution, however, results from human activities - from burning coal, oil, wood, gasoline, and other fuels used to run factories, cars, farm and off-road vehicles, and construction equipment, and from power plants that generate heat and light for our homes and businesses. Burning these fuels produces smoke and gases (see chart on page 25.0). Smoke is made of tiny particles of soot and ash suspended in the air and called "particulate" matter. Sawdust from lumber mills, rock dust from quarries, and soil particles from bare earth are other examples of man-made particulates found in the air.
Once particulates are added to the air, they can chemically react to form pollutants that are even more dangerous. For example, when nitrogen oxides and chlorine interact with hydrocarbons in the presence of sunlight, ozone is formed. When it is formed at ground level, it acts as a powerful respiratory irritant that makes it hard for people to breathe, can damage lung tissue, and make respiratory ailments worse. High levels of ozone -- which means over 0.12 parts per million in an hour or over 0.08 ppm over 8 hours --, are frequently found in urban areas during hot summer months. When this happens, you are likely to hear a "Code Red Ozone Alert." Reading almost as high may cause an "air quality advisory" or Code Orange Alert. Though very infrequent, there have been Code Purple Ozone Alerts which are more severe than Code Red.
This is in sharp contrast to the ozone you may be most familiar with. That ozone, which exists in a layer found in the upper atmosphere (or stratosphere), provides a protective barrier against harmful radiation from the sun.
Ground-level ozone, the main ingredient of smog, is a colorless gas formed by the reaction of sunlight with vehicle emissions, gasoline fumes, solvent vapors, and power plant and industrial emissions. Ozone formation is most likely in hot, dry weather when the air is fairly still. Ozone pollution is one of the most serious problems in Virginia's urban areas. Symptoms felt include shortness of breath, chest pain when inhaling deeply, wheezing, and coughing. Children, people with respiratory disease, and individuals who exercise outdoors are at particular risk from high ozone levels. It can make these problems worse, send people to the hospital and can even damage lung tissue.
Pollutants of any sort can ride the air currents for long distances. Some of Virginia's pollution is carried in from sources in the Midwest, especially large coal-fired power plants. Air can "cleanse" itself to some degree by such processes as rain; otherwise dense, poisonous clouds would already cover the earth. Sometimes the weather does not permit this cleansing to happen, and the air stagnates due to a weather condition known as an inversion.
Normally, as you go higher up in the air, the temperature gets colder. Hot polluted gas from cars or smokestacks rises through the cooler air above and blows away. Sometimes a layer of warm air forms above the cooler air below (often in a valley like Roanoke or Charlottesville). When this inversion happens, the polluted air will rise up to the warm layer and then stop. In this way, a giant cloud of pollution can form over a community.
While the air may be cleansed after a good rain, many of the chemicals and small particles washed from the atmosphere become land or water pollution. In fact, scientists have estimated that as much as 25-30 percent of the nitrogen pollution in the Chesapeake Bay is a result of acid deposition. While "normal" rainfall has a pH of about 5.5, precipitation in Virginia can be up to ten times more acidic, ranging from 4.3 to 4.5.
Air pollution is dirty and it is expensive. More important, polluted air can make healthy people cough and wheeze. For people who are sick or especially ensitive, air pollution may worsen an existing condition and mean discomfort, limited activities, increased use of medication, and more visits to doctors and hospitals. A growing body of scientific studies suggests that air pollution has long-term effects on the lung's ability to function and contributes to the development of lung disease.
Our noses and sinuses have a built-in filtration system that traps large dust particles before they get into our lungs. And human lungs have a natural defense system that helps to protect us against some of the air pollutants breathed. But people respond differently to air pollution and very small particles are not filtered out. How people respond, or their level of risk, depends on several factors, including the amount of pollution in the air, the amount of air breathed in a given time, and their age and overall health.
INNOVATIONS AT THE MT. STORM POWER STATION
Virginia Power is getting into the pollution prevention act by using smokestack scrubbers to help reduce acid rain. At the Mt. Storm Power Station in West Virginia, smokestacks will be fitted with scrubbers that are expected to remove 95% of the sulfur dioxide from the smoke created by burning coal. (Sulfur oxides can mix with moisture in the air and become a component of acid rain.) The process works through a chemical reaction called neutralization when calcium in limestone, a base, mixes with sulfur dioxide, an acidic gas in the smoke, and creates calcium sulfate or gypsum. Some of the gypsum will be used to reclaim acidic water at mines near the plant. Virginia Power expects each of the scrubbers to remove about 55,000 tons of sulfur dioxide a year. This pollution prevention method is not only cost-effective for the power company, but also benefits air quality around the plant (including the Shenandoah National Park).
"Acid rain" is really rain, snow, or fog that contains sulfuric or nitric acid. Acid rain, or "deposition," forms when water vapor mixes with sulfur and nitrogen oxides. Sulfur and nitrogen come from natural sources like volcanoes, but are common by-products of the combustion of fossil fuels (coal and petroleum), which are burned principally to heat homes and generate electrical power. Sulfur dioxide and nitrogen oxides released during burning usually travel many miles before falling to the ground as acid rain. Acid is a measure on a pH scale ranging from 0, which is severely acidic, to 14, which is extremely alkaline, or basic. A value of 7 is neutral. Lemon juice has a pH of 2; baking soda, 8; a cola drink, 4; and pristine rain is about 5.6. Natural precipitation is about ten times less acidic than the average value of rainfall in Virginia - 4.3 (extremely acid). However, pH can vary from week to week (and rainstorm to rainstorm) from 3.5 to 5.0. Acid deposition levels in Virginia are comparable to other areas of the mid-Atlantic and Northeast regions of the U.S.
Sulfuric acid in the air can hurt the lungs of infants, children, and adults. It can contaminate drinking water by dissolving minerals from soil and pipes which are then carried into the water supply. Acid rain has been blamed for damaging trees and mountain streams in Virginia and the northeastern United States. High acidity levels can kill new fish eggs. Airborne nitrogen oxide is also believed to be responsible for an estimated 30 percent of the nitrogen pollution entering the Chesapeake Bay. Excessive nitrogen and other nutrients in the Bay overstimulate algae growth, thereby reducing the oxygen levels available for other plants and fish.
Scientific studies performed in the early '90s confirm that initial estimates of the national damage caused by acid rain were overstated. However, central Appalachian region ecosystems are severely stressed by acid deposition due to the low neutralizing capacity of local soils. The physical and chemical properties of these soils are such that they cannot buffer, or offset, the acid. This region of the state unfortunately receives a high rate of deposition of sulfur compounds from power plants in the Midwest.
Managing air is a complex undertaking because it is a substance constantly on the move. Air is affected by sunlight, dust particles, water vapor, and wind currents-factors which by their very nature are also moving.
When it comes to air pollution, technology has served as both a culprit and a cure. Devices used to control pollution from smokestacks and exhaust vents include:
Some emissions are pre-treated before being released. For example, some power plants spray a limestone slurry (a mixture of limestone and water) to neutralize the acid resulting from burning coal. Catalytic converters that help decrease emissions from automobiles are another example.
Of all the types of pollution, odors are probably the hardest to control because we can smell even tiny amounts of so many substances. (The nose is a great piece of monitoring equipment!) A new technology called biofilters actually uses bacteria to "eat" odors.
The U.S. Congress passed important federal air pollution laws, known collectively as the Clean Air Act (1963; and amended in 1967, 1970, 1977, and 1990). National air quality standards spelled out how clean the outdoor air has to be, and it is up to each state to see that its air meets these standards.
In 1966, the Virginia General Assembly passed the Virginia Air Pollution Control Law. The regulations are administered and enforced by the Department of Environmental Quality.
Some of the goals of the new Clean Air Act Amendments are listed here:
In Virginia, the Department of Environmental Quality works closely with the U.S. Environmental Protection Agency to monitor and evaluate hazardous air pollutants across the state. A computer model that estimates concentrations of 185 hazardous air pollutants statewide helps pinpoint regions of most concern. Data is collected every three years and added to the model and allows better evaluation of the state's air pollution strategies.
Virginia is working to achieve the requirements of the 1990 Clean Air Act, a federal law amended by Congress. One provision, Title IV, calls for reductions of sulfur dioxide of approximately ten million tons per year and two million tons of nitrogen oxides per year. Virginia's power plants are preparing to take steps necessary to reduce nitrogen oxides. Most of the reductions in pollutants will occur at large coal-fired power plants in the Midwest. Some of these individual plants emit more than all the sources in Virginia combined. Emissions fromthese large plants are released from very tall smokestacks and travel eastward, sometimes hundreds of miles, before returning to Earth in precipitation or dust.
Like so many other forms of pollution, the surest solution to air pollution is prevention. This means many things. It means wise transportation and community planning. It means adopting new processes and materials for industrial operators. It means each person doing their share by conserving the resources they use, particularly electricity and gasoline.