Air Polution Notes.docx

6 Pages

Earth & Environmental Sciences
Course Code
EESC 1175
Alan Kafka

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Geo Science Study Guide 3 Exam rd Air Pollution Troposphere & Stratosphere - their chemical makeup: what's similar? What's different? What role do these play in the human environment? Temperature variations define the atmosphere’s four principal layers: The troposphere, the stratosphere, the mesosphere, and the exosphere. The ozone layer is within the stratosphere. The atmosphere is composed primarily of nitrogen (78%), oxygen (20%), and argon (1%). Diatomic nitrogen (N )2is very stable, only broken down by high-energy lightning bolts and certain microorganisms. Argon is a noble gas and essentially inert. Oxygen is highly reactive. The troposphere is 70% Nitrogen and 20% Oxygen (O ). 2 The thin ozone layer in the upper stratosphere has a high concentration of ozone, a particularly reactive form of oxygen. This layer is primarily responsible for absorbing the ultraviolet radiation from the Sun. Ozone is a toxic chemical to living organisms that contributes to the formation of smog when present in the troposphere. In its natural environment in the stratosphere, however, ozone is critical to the structure of the atmosphere and the ability of life to exist on land. Ozone absorbs near ultraviolet wavelengths, preventing most of this radiation from reaching Earth’s surface where it would destroy living tissue and constrict life to living underground or in the ocean. This absorption of radiation in the stratosphere accounts for the stability of the stratosphere as it heats the air, causing warmer less dense air to sit stably over colder denser air. Tropospheric ozone also absorbs ultraviolet radiation, but this benefit is outweighed by the damage it causes when in proximity to living organisms. Thermal inversion - What are the general conditions for this? What special settings make some cities more vulnerable than others? • Restricted circulation in the lower atmosphere o Pollutants released from ground sources generally are warmer than the surrounding air and tend to rise o As an air mas these plumes will rise and cool o In certain situations a cool air mass will have a warm air mass overlying it, it will trap the rising warm pollutant-bearing air mass; this condition is made worse by an air mass with stagnant conditions • As more pollutants are dumped into the cooler air mass, they will become concentrated below the warm air mass • Eventually, the concentrations of pollutants may become very high and cause a health concern • Local topography – mountains, basins, valleys • Wind patterns may amplify the situation also Air pollution problems are naturally more severe when air is stagnant and pollutants are confined. Within the lower atmosphere, air temperature normally decreases as altitude increases. This is why mountaintops are cold places, even though direct sunlight is stronger there. In a thermal inversion, there is a zone of relatively warmer air at some distance from the ground. That is, going upward from the earth’s surface, temperatures decrease for a time, then increase in the warmer layer (inversion of the normal pattern), then ultimately continue to decrease at still higher altitudes. Inversions may become established in a variety of ways. Warmer air moving over an area at high altitude may move over colder air close to the ground, thus creating an inversion. Rapid cooling of near-surface air on a clear, calm night may also lead to a thermal inversion. Most air pollutants, as they are released, are warmer than the surrounding air – exhaust fumes from cars, industrial smokestack gases etc. Warm air is less dense than colder air, so ordinarily; warm pollutant gases rise and keep rising and dispersing through progressively colder air above. When a thermal inversion exists, a warm-layer becomes settled over a cooler layer. At that point, the pollutants are no longer less dense than the air above, so they stop rising. They are effectively trapped close to the ground and simply build up in the near-surface air. Every one of the six major acute air-pollution episodes of the 20 Century has been associated with a thermal inversion, as have many milder ones. The inversion concentrates the pollutants more strongly. Moreover, inversions can persist for a week or longer, once established, because the denser, cooler air near the ground does not tend to rise through the lighter warmer air above. Certain geographical or topographical settings are particularly prone to the formation of thermal inversions.As with most weather conditions, nothing can be done about a thermal inversion except to wait it out. • Los Angeles has the misfortune to be located where cool air blowing across the Pacific Ocean moves over the land and is trapped by the mountains to the east beneath a layer of warmed air over the continent. • Donora, Pennsylvania, lies in a valley where when a warm front moves across the hilly terrain, some pockets of cold air may remain in the valleys, establishing a thermal inversion. • Germany’s coal-rich Ruhr Valley suffered so from pollution trapped by a prolonged inversion during the winter of 1984-1985 that schools and many factories had to be closed and the use of private cars banned until the air cleared. Major types of urban-industrial air pollution. ForALL OF THEM give special consideration to: manmade vs. natural contribution, what manmade factors/industries/etc. are major contributors, any that create secondary pollution problems (smog, acid rain, etc.), harmful effects and why they are harmful. • Particulates (aerosols) – Characteristics? Origin and adverse impact to the environment? o 85% Natural and 15% Human-produced  85% Dust, 7% Industrial processes, 8% Combustion of fuels (stationary sources) Particulates include soot, smoke, ash from fuel (mainly coal) combustion, dust released during industrial processes, and other solids from accidental/deliberate burning of vegetation. Mostly generated by human activity from point sources.Additional particulates are added by many natural processes including volcanic eruptions, natural forest fires, and erosion of dust by wind, and by blowing salt spray off the sea surface.Aerosols include both particulates and fine liquid droplets in the air. • Coarse particles (PM ) 10 o Smoke, dirt, and dust from factories, farming, and roads o Mold, spores, and pollen o Sources: Desertification, volcanic eruption, fire, and farm lands • Fine Particles (PM )2.5 o Industrial sources:Airborne asbestos dust and heavy metals o Burning of crop residue from smoke and soot o Fossil fuel burning o Travel farther distance! The adverse impact depends somewhat on the nature of the particulates. o Dense smoke is unsightly. o Can accelerate melting ofArtic ice o Cleaning expenses increase with ash showers o Shown to be cancer-causing when inhaled o Can be chemically toxic • Lead once was a serious pollutant o Used in gasoline as an antilock additive, tons of lead was released into the atmosphere by internal combustion engines o High doses of lead can cause brain damage, depression, apathy, and other psychological disorders
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