Chapter 1
The Air Pollution Problem

1.1 The Role of Water and Air

1.1.1 Water

Water on the Earth is part of a closed cycle called the hydrologic cycle, that is affected by both the energy of the Sun and the gravitational pull of Earth's Moon. This results in the tides, evaporation of water, and its condensation to form precipitation in various forms. Only 1% of the water on the Earth participates in the short-term water cycle that is used for human consumption. Most water is outside the scope of human interaction and is stored in the oceans, ice caps, and deep groundwater aquifers and moves on time scales of several thousand years or more.

The gravitational pull of the Moon plays an interesting role in the movement of water on the Earth. The tides are caused primarily by the Moon's gravity. The Sun's gravity also plays a role, but the Moon is more important because it exerts more than twice as much gravitational influence as the Sun because the Moon is so much closer. The gravitational forces of the moon essentially pull the water on the Earth into an elliptical shape. The water bulges toward the moon, and equally on the opposite side, which shrinks the water on the perpendicular sides. As the Earth rotates, it passes through these high and low bulges which we experience and high and low tides.

Water on the Earth is believed to have been brought to the surface by comets that collided with the Earth early in its history. This water is a prerequisite for all life on the Earth, and it is liquid water that is the prerequisite, not steam or ice. Thus, water must exist at temperatures constrained by the boiling and freezing points of this unique material for life to flourish.

Over the course of history, human life has revolved around access and proximity to water. Those who maintained close proximity to clean water survived to learn again and reproduce, whereas those who did not disappeared. Environmental concerns took hold at about 3,000 b.c.e. Urban areas on the Indian continent developed sanitation programs such as underground drains and public baths. Aspects of health were integrated with daily activities including personal hygiene, health education, dietary practices plus food, and environmental sanitation.

Water is the original renewable resource and carries a rich history. The water molecules contained in the fruit eaten yesterday may have fallen as rain last year in a distant place or even millennia ago by one's ancestors.

The overall amount of water on the surface of the Earth has remained fairly constant over time. The hydrologic cycle describes this movement from place to place. The vast majority (96.5%) of water on the surface of the Earth is contained in the oceans. Solar energy heats the water at the ocean surface, and some of it evaporates to form water vapor. Air currents take the vapor up into the atmosphere along with water transpiring from plants and evaporating from soil. The cooler temperatures in the atmosphere cause the vapor to condense into clouds. Clouds move around the world until the moisture capacity of the cloud is exceeded, and the water falls as precipitation. Most precipitation in warm climates falls back into the oceans or onto land, where the water flows over the ground as surface runoff. Runoff can enter rivers and streams, which transport the water back to the oceans; it can accumulate and be stored as freshwater in lakes; or it can soak into the ground as infiltration. Some of this water may infiltrate deep into the ground and replenish aquifers that store huge amounts of freshwater for long periods of time.

1.1.2 Air

Earth's atmosphere is currently composed primarily of nitrogen and oxygen, but this composition has greatly changed over time. The air composition exposed to the first primitive cells was quite different to the "normal" composition of air today. Some scientists believe that Earth's earliest atmosphere probably contained almost no free oxygen. The oxygen in today's atmosphere is likely the result of several million years of photosynthesis.

Over the history of the Earth, plants and animals have had to adapt to changes in the environment. These changes occur extremely slowly through evolution. However, when environmental changes occur more rapidly than a species' ability to adapt, some species cannot adapt fast enough and oftentimes do not survive. This is the main concern with the human effect on the environment and atmosphere. The average air temperature and composition has certainly changed over the history of the Earth, but human contributions have caused significantly faster changes compared to the natural rate of change. The concern among scientists is that Earth's inhabitants' natural adaptation capabilities might not be adequate to meet this challenge. The current concentrations of air are provided in Tables 1.1 and 1.2, listing two key physical parameters of concern in the air pollution field.

Table 1.1 Concentration of current air at sea level.

Component Concentration (vol %) Nitrogen (N2) 78.0 Oxygen (O2) 20.99 Carbon dioxide (CO2) 0.03 Argon (Ar) 0.94 Neon (Ne) 0.0015 Helium (He) 0.0005 Krypton (Kr) 0.00005 Xenon (Xe) 0.000006 Hydrogen (H2) 0.01 Methane (CH4) 0.0002 Nitrous oxide (N2O) 0.0004

Note: Not including particulate, PM, and water vapor.

Table 1.2 Physical properties of selected gases of concern.

Gas Molecular weight Density (lb/ft3) Air 29 0.079 Ammonia, NH3 17 0.048 Carbon dioxide, CO2 44 0.12 Carbon monoxide, CO 28 0.078 Hydrogen, H2 2 0.006 Methane, CH4 16 0.045 Nitrogen, N2 28 0.078 Oxygen, O2 32 0.089

1.2 Early History of Air Pollution

Air pollution is not a new phenomenon. Natural phenomena such as volcanoes, windstorms, forest fires, and decaying organic matter contribute substantial amounts of air pollutants. Plants and trees also emit organic vapors and particles. The Earth, for the most part, is able to keep up with natural air pollution with natural cleaning systems.

Air pollution has been an issue since the first person discovered fire. This pollution was quite insignificant at first, especially when fire was kept outdoors. Humans did not significantly affect the environment until relatively recent times. This is due to two reasons: (1) the human population has been large for only a small part of recorded history, and (2) the bulk of human-made produced air pollution is intimately related to industrialization. Humans did not begin to alter the environment until they began to live in communities.

Recognition of pollutants as health hazards has rarely resulted in pollution reduction or control; traditionally, only when personal survival is at stake has effective action been taken. Unfortunately, the control of pollutants rarely takes place prior to public outcry, even though the technology for controlling pollutants may be available.

Air pollution issues date back to the reign of the English King Edward I (1271-1307), where a protest was conducted by the nobility against the use of "sea" coal. Under later kings such as Richard (1377-1399), and later under Henry V (1413-1422), England took steps to regulate and restrict the use of coal through taxation and regulation of the transportation of coal in London. Other legislations, parliamentary studies, and literary comments appeared sporadically during the next 250 years. In 1661, a pamphlet was published by the Royal Command of Charles II entitled "Fumifugium; or the Inconveniences of Air and Smoke in London Dissipated; Together with Some Remedies Humbly Proposed." The paper was written by John Evelyn, one of the founding fathers of the Royal Society. Later, in 1819, a Select Committee of the British Parliament was formed to study smoke abatement.

Air pollution was a fact of life during the first half of the 20th century. The smoke problem in London peaked around December 1952; during this "air pollution episode," approximately 4,000 people died, primarily of respiratory problems. Similar issues were recorded around the same time period in Pennsylvania, New York City, Tennessee, St. Louis, and Pittsburgh. Additionally, details of these often-referenced episodes are available in the literature [1].

Smoke (particulates) and acid gases produced by the burning of coal have been significant air pollutants for more than 400 years. The use of oil and gas has reduced this problem somewhat; however, local natural resources (and hence costs) currently dictate the choice between coal, oil, and gas for stationary energy conversion.

The internal combustion engine in the...