Air & Air Pollution

Earth's atmosphere:

• mixture of gases that forms a layer about 250 miles thick around the earth
• bottom 5 - 11 miles (7 - 16 km) contains most (75%) of the air

• Composition of clean, dry air:

Air pollution

• presence of chemicals in the atmosphere in quantities and duration that are harmful to human health and the environment
• Types of air pollutants:
• Primary pollutants - products of natural events (like fires and volcanic eruptions) and human activities added directly to the air
• Secondary pollutants - formed by interaction of primary pollutants with each other or with normal components of the air

Major Classes of Air Pollutants:

• Carbon oxides (CO & CO2)
• sources = incomplete combustion of fossil fuels
• transportation, industry, & home heating
• CO2 is an important greenhouse gas
• CO (carbon monoxide)
• the most abundant pollutant know to affect human health
• combines with hemoglobin & may create problems for infants, the elderly, & those with heart or respiratory diseases

• Sulfur oxides (mainly SO2, or sulfur dioxide)
• source = combustion of coal & oil (esp. coal)
• SO2 released in the U.S. comes from:
• utilities 69.5%
• industrial manufacturing processes 12.7%
• industrial combustion 11.6%
• transportation 3.7%
• other sources 2.5%.
• can react with gases in atmosphere to form sulfuric acid ('acid rain')
• 20 million tons released in U.S. every year
• Exposure to SO2 can cause impairment of respiratory function, aggravation of existing respiratory disease (especially bronchitis), and a decrease in the ability of the lungs to clear foreign particles. It can also lead to increased mortality, especially if elevated levels of particulate matter (PM) are also present. Groups that appear most sensitive to the effects of SO2 include asthmatics and other individuals with hyperactive airways, and individuals with chronic obstructive lung or cardiovascular disease. Elderly people and children are also likely to be more sensitive to SO2.

• Nitrogen oxides - NO (nitric oxide) & NO2 (nitrogen dioxide)
• source = motor vehicles & industry (burning fossil fuels)
• can react with other gases in atmosphere to from nitric acid (HNO3) ('acid rain')

• Volatile organic compounds (hydrocarbons) - methane, benzene, propane, & chlorofluorocarbons (CFC's)
• source = motor vehicles (evaporation from gas tanks), industry, & various household products
• 18 million tons released each year in U.S.
• Concentrations of many VOCs are consistently higher indoors than outdoors. A study by the EPA, covering six communities in various parts of the United States, found indoor levels up to ten times higher than those outdoors-even in locations with significant outdoor pollution sources, such as petrochemical plants.
• Eye and respiratory tract irritation, headaches, dizziness, visual disorders, and memory impairment are among the immediate symptoms that some people have experienced soon after exposure to some organics. At present, not much is known about what health effects occur from the levels of organics usually found in homes. Many organic compounds are known to cause cancer in animals; some are suspected of causing, or are known to cause, cancer in humans.

• Suspended particulate matter
• solid particles (e.g., dust, soot, & asbestos) & liquid droplets (e.g., pesticides)
• sources = power plants, iron/steel mills, land clearing, highway construction, mining, & other activities that disturb or disrupt the earth's surface
• act as respiratory irritants; some are known carcinogens (e.g., asbestos)
• can aggravate heart/respiratory diseases

• Toxic compounds
• trace amounts of at least 600 toxic substances (such as lead and mercury) produced by human activities
• Mercury is an element that occurs naturally in the earth’s crust. Most people and wildlife can generally tolerate the extremely low levels of this naturally occuring substance. When mercury enters the body it becomes concentrated in tissue, an effect known as bioaccumulation. Because this element is toxic at very low concentrations, even slight increases in the minute concentrations naturally present in the environment can have serious effects on humans and wildlife.

Once mercury enters the water it can be converted to its most toxic form, methyl mercury, by bacteria or chemical reactions. Methyl mercury is absorbed by tiny aquatic organisms, which are then eaten by small fish. The chemical is stored in the fish tissue and is passed on at increasing concentrations to larger predator fish. People and wildlife at the top of the food chain are consequently exposed to elevated amounts of methyl mercury through the contaminated fish they consume.
• sources of mercury = burning coal and waste (such as medical wastes)

 
• Photochemical oxidants
• mainly ozone
• Because sunlight has a critical role in its formation, ozone pollution is principally a daytime problem in the summer months. The presence of hydrocarbons and nitrogen oxide in sunlight with little air movement leads to the generation of ozone. These two compounds are produced by cars, trucks, factories, and power-generating plants or wherever gasoline, diesel fuel, kerosene, oil, or natural gas are combusted. These gases combine together with sunlight, producing ozone. Urban areas with heavy traffic and large industrialized communities are primary areas for ozone problems.
• The greatest concern about ozone pollution is the potential damage it may inflict on human health. High concentrations of ozone are especially hazardous to children, the elderly, and people with respiratory problems. Each year many food crops are damaged by ozone. Ozone also damages rubber, nylon, plastics, dyes, and paints.
• EPA provides maps showing levels of ozone pollution:

Ozone Animation
8-hour Average Concentration
(Yellow = moderate ozone levels;
Orange = Unhealthy for sensitive groups, e.g., those with respiratory diseases such as asthma)
Wednesday, 25 July 2001
Source: EPA
 

Source: Environmental Protection Agency
Map shows where pollutants exceeded EPA standards in September, 1996.

Smog

• forms from mixture of primarily nitrogen oxides (from vehicles), volatile organic compounds, & sunlight
• complex mixture of gases but primarily ozone
• more common in cities with sunny, dry, warm climates, such as Los Angeles, Denver, Salt Lake City, Sydney, & Mexico City

Effects of Air Pollution on Human Health

• Much evidence links air pollutants to respiratory & other diseases in humans
• Examples of air pollution-related diseases:
• Pulmonary irritation & impaired lung function:
• chronic bronchitis
• emphysema
• Cancer
• Systemic toxicity:
• Lead
• Mercury
• Increased susceptibility to disease

Effects of Air Pollution on other animals & plants:

• Wild & domestic animals probably affected in the same ways as humans
• Plants damaged by ozone, sulfur dioxide, & acids:
• ozone - weakens pine needles & makes them more susceptible to insects & diseases
• sulfur dioxide - suppresses growth
• acid - damages leaves & needles & also removes nutrients

Acid Precipitation

Where do acids come from?

• Nitric oxide & sulfur dioxide released primarily from electric power plants & motor vehicles
• SO2 + water vapor + ozone ---> H2SO4
• NO + sunlight + O2 ---> NO2 + various atmospheric gases ---> HNO3

http://www.epa.gov/airmarkets/acidrain/

Acid Transport

• Prevailing winds transport the compounds, sometimes hundreds of miles, across state and national borders.

Source: EPA

Average annual pH of rainfall:

The pH scale and acid rain:

• Acid rain is measured using a scale called "pH." The lower a substance's pH, the more acidic it is. Pure water has a pH of 7.0. Normal rain is slightly acidic because carbon dioxide dissolves into it, so it has a pH of about 5.5. As of the year 2000, the most acidic rain falling in the US has a pH of about 4.3.

Effects of Acid Deposition

• acidification of lakes and streams
• Acid rain causes a cascade of effects that harm or kill individual fish, reduce fish population numbers, completely eliminate fish species from a waterbody, and decrease biodiversity. As acid rain flows through soils in a watershed, aluminum is released from soils into the lakes and streams located in that watershed. So, as pH  in a lake or stream decreases, aluminum levels increase. Both low pH and increased aluminum levels are directly toxic to fish. In addition, low pH and increased aluminum levels cause chronic stress that may not kill individual fish, but leads to lower body weight and smaller size and makes fish less able to compete for food and habitat. Generally, the young of most species are more sensitive to environmental conditions than adults. At pH 5, most fish eggs cannot hatch. At lower pH levels, some adult fish die. Some acid lakes have no fish.
• contributes to damage of trees
• Acid rain does not usually kill trees directly. Instead, it is more likely to weaken trees by damaging their leaves, limiting the nutrients available to them, or exposing them to toxic substances slowly released from the soil. Quite often, injury or death of trees is a result of these effects of acid rain in combination with one or more additional threats. Acidic water dissolves the nutrients and helpful minerals in the soil and then washes them away before trees and other plants can use them to grow. At the same time, acid rain causes the release of substances that are toxic to trees and plants, such as aluminum, into the soil.
• Forests in high mountain regions often are exposed to greater amounts of acid than other forests because they tend to be surrounded by acidic clouds and fog that are more acidic than rainfall. Scientists believe that when leaves are frequently bathed in this acid fog, essential nutrients in their leaves and needles are stripped away. This loss of nutrients in their foliage makes trees more susceptible to damage by other environmental factors, particularly cold winter weather.
• accelerates the decay of building materials and paints, including irreplaceable buildings, statues,and sculptures that are part of our nation's cultural heritage.

Controlling Acid Deposition

• Clean up smokestacks and exhaust pipes
• Almost all electricity comes from burning fossil fuels like coal, natural gas, and oil. Acid deposition is caused by two pollutants that are released into the atmosphere, or emitted, when these fuels are burned: sulfur dioxide (SO2) and nitrogen oxides (NOx). Coal accounts for most U.S. sulfur dioxide (SO2) emissions and a large portion of NOx emissions. Sulfur is present in coal as an impurity, and it reacts with air when the coal is burned to form SO2. In contrast, NOx is formed when any fossil fuel is burned.
• Options for reducing SO2 & NOx emissions
• using coal containing less sulfur, washing the coal, and using devices called scrubbers to chemically remove the SO2 from the gases leaving the smokestack.
• Power plants can also switch fuels; for example burning natural gas creates much less SO2 than burning coal. Certain approaches will also have additional benefits of reducing other pollutants such as mercury and carbon dioxide.
• catalytic converters reduce NOx emissions from cars. These devices have been required for over twenty years in the U.S., and it is important to keep them working properly.
• Use alternative energy sources
• There are other sources of electricity besides fossil fuels. They include: hydropower, wind energy, geothermal energy, and solar energy. There are also alternative energies available to power automobiles, including natural gas powered vehicles, battery-powered cars, fuel cells, and combinations of alternative and gasoline powered vehicles.
• Take action as individuals
• Individuals can contribute directly by conserving energy, since energy production causes the largest portion of the acid deposition problem. For example, you can:
• Turn off lights, computers, and other appliances when you're not using them
• Use energy efficient appliances: lighting, air conditioners, heaters, refrigerators, washing machines, etc.
• Keep your thermostat at 68 F in the winter and 72 F in the summer.
• Carpool, use public transportation, or better yet, walk or bicycle whenever possible

Global Warming

• Some greenhouse gases occur naturally in the atmosphere, while others result from human activities. Naturally occuring greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Certain human activities, however, add to the levels of most of these naturally occurring gases:
• CO2
• methane
• emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from the decomposition of organic wastes in municipal solid waste landfills, and the raising of livestock.
• nitrous oxide
• Hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), & sulfur hexafluoride (SF6)
• These compounds are potent greenhouse gases. In addition to having high global warming potentials, SF6 and many HFCs and PFCs have extremely long atmospheric lifetimes, resulting in their essentially irreversible accumulation in the atmosphere. Sulfur hexafluoride, itself, is the most potent greenhouse gas the IPCC has evaluated.
• generated in a variety of industrial processes

Source: EPA

• CO2 levels in the atmosphere have risen substantially

What do we know?

• Since 1860, the mean global temperature has risen 0.7 - 1.3 degrees Fahrenheit
• 10 of the 15 years from 1980 - 1994 were among the hottest in the 113-year recorded history of temperature measurement
• 1998 was the warmest year of the last century based on thermometer data and the warmest of the last millenium based on proxy temperature data.
• The IPCC (Intergovernmental Panel on Climate Change) concluded in 1995 that human activities were influencing global climate
• In 2001, the IPCC issued its Third Assessment Report stating that "most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations". IPCC points out a number of features of the climate system, like intensity of rainstorms, that have already changed and estimates that warming of the coming century will reach 1.4°C-5.8°C (2.5°F-10.4°F) if emissions are not limited. IPCC finds that warming of between 1°C-2°C (1.8°F-3.8°F) is likely to pose high risks to unique and threatened ecosystems, and to lead to increases in the risk of extreme climate events.

Possible Effects of a Warmer World

• Changes in food production

Source: http://www.fao.org/NEWS/FACTFILE/FF9721-E.HTM

• Reductions in biodiversity
• Plants and animals generally react to consistently warmer tempartures by moving to higher latitudes and elevations. Recent studies reveal that some species have already started to shift their ranges, consistent with warming trends. Many populations and species may become more vulnerable to declining numbers or extinction if warming occurs faster than they can respond or if human development presents barriers to their migration.
• Rise in sea level
• Warmer temperatures increase melting of mountain glaciers and cause ocean water to expand. Largely as a result of these effects, global sea level has risen 4 to 10 inches over the past 100 years. With additional warming, sea level is projected to rise from half a foot to 3 feet more during the next 100 years. On average, 50 to 100 feet of beach are lost for every foot of sea-level rise.
• More extreme weather
• climate change will lead to more hurricanes, floods, and droughts
• Threats to human health
• Intergovernmental Panel on Climate Change (IPCC), is a United Nations-sponsored organization made up of 2,500 scientists from around the world. The IPCC projects that more frequent and more severe heat waves will be an early effect of global warming. Events such as the deadly stretch of hot days that killed 669 people in the Midwest during the summer of 1995 and 250 in the Eastern United States in July 1999 are likely to become more common.
• As temperatures rise, disease-carrying mosquitoes and rodents move into new areas, infecting people in their wake. Global warming will likely put as much as 65% of the world's population at risk of infection—an increase of 20%. Scientists at the Harvard Medical School have linked recent U.S. outbreaks of dengue ("breakbone") fever, malaria, hantavirus and other diseases to climate change.

Slowing Global Warming

• Cut fossil fuel use
• Car makers could dramatically increase the fuel economy of their cars and trucks.
• Most electric utilities still use coal to produce electricity, spewing millions of tons of carbon dioxide and other pollution into the atmosphere every year. Part of the problem could be solved by converting these plants to burn cleaner natural gas.
• Improve energy efficiency
• Our cars and light trucks, home appliances and power plants could be made much more efficient by simply installing the best current technology. Energy efficiency is the cleanest, safest, most economical way to begin to curb global warming.
• We could do much more to save energy in our homes and office buildings. More energy efficient lighting, heating and air-conditioning could keep millions of tons of carbon dioxide out of our air each year.
• Reduce deforestation & plant trees
• Because global vegetation and soils contain about three times as much carbon as the planet's atmosphere, terrestrial ecosystems offer an opportunity to absorb and store (sequester) a significant amount of  carbon dioxide from the atmosphere. By planting trees, preserving forests, and changing cultivation practices to increase soil carbon, for example, it is possible to increase the size of carbon sinks.
• Slow human population growth

Any progress in meeting these objectives?

• Only 4 MDCs (Great Britain, Denmark, Germany, & Norway) have produced plans to substantially reduce CO2 emissions
• CO2 emissions by LDCs are increasing about 5%/year
• Overall, global CO2 emissions are still increasing 2-3%/year

Greenhouse Gas Emissions in the U.S.
Source: EPA

• Governments should be leading the way to a fundamentally new energy direction based on clean renewable energy, like wind or solar power. But at present many governments instead use taxpayers money to support the agenda of the companies which continue to spend billions of dollars on development of coal, oil or gas - the climate-damaging fossil fuels.

Useful links:

Climate Ark - The Premier Climate Change & Renewable Energy Portal

EPA's Global Warming Site

Global Warming: Early Warning Signs

Guide to the Climate Change Negotiation Process

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