 Atmosphere composition mostly Nitrogen (76.6 %), Oxygen (23.1 %), and other gases  Chemical materials cycle through the atmosphere as they do in other reservoirs › Residence Times (Table 17.1) › Influenced by amounts present in a given reservoir  CO 2 – 4 years  O million years  N 2 – 44 million years

 Air pollution is costly  $40 billion – Worldwide annual expense of forest-product harvest reduction due to air pollution  $16 billion annual U.S. expense ( direct costs)  Medical costs are enormous: › Illness › Medical treatment › Absenteeism › Loss of production

1. Gaseous pollutants › CO and CO 2 › SO 2 › NO, NO 2 › Ozone and CFCs 2. Particulates › Soot › Smoke › Ash (from burning coal) › Dust (released from industrial processes) › Other solids release by burning › From 35 million tons/year (mainly combustion) to 180 million tons/year (mostly industrial)

 CO – carbon monoxide › Not very abundant in the atmosphere but deadly › Odorless, tasteless and invisible – toxic to animals › Very short residence time but easily added to the atmosphere by common anthropogenic sources (automobiles)  CO 2 - carbon dioxide › Essential for life of plants (photosynthesis) › Product of plant respiration, combustion, and volcanic eruptions › Short residence time and easily fluxes between oceans and atmosphere

 More than 50 million tons of sulfur dioxide (SO 2 ) are emitted worldwide each year mainly from coal combustion  SO 2 - sulfur dioxide forms acid rain › very short residence time (days or hours) › By product from combusting coal › SO 2 + H 2 O + ½ O 2 = H 2 SO 4 (sulfuric acid) and will lower the pH of rain to below 5.6, the pH of uncontaminated rain fall › Can contribute to acid rain causing lung and eye irritation › Becomes a contributor to water pollution

 Complex geochemistry › oxygen and nitrogen are very abundant in the atmosphere › high temperatures cause nitrogen and oxygen to form nitrogen oxide compounds  2NO 2 + H 2 O + ½ O 2 = 2HNO 2 (nitric acid)  NO 2 + strong sun light will produce photochemical smog  NO 2 can breakdown in sun light to NO and will react with common oxygen (O 2 ) to form ozone (O 3 )  Ozone inhibits photosynthesis in plants and can cause severe medical problems to people in urban areas where abundant automobiles are in operation

 Ozone (O 3 ) is a ‘chemically out of place pollutant’ › In upper atmosphere (stratosphere) the ozone layer absorbs harmful ultraviolet radiation › Ozone forms as O 2 + ½ O 2 = O 3 › At ground level it is very harmful to plants and animals › A thick ozone layer is beneficial to life on earth › Periodically, an ozone hole forms over either pole. This allows more ultra violet radiation to enter the lower atmosphere › CFCs attack ozone and can destroy, or thin, the ozone layer › CFCs build up their concentration in the upper atmosphere, have a residence time of about 100 years, and breakdown into various by-products including chlorine monoxide (ClO) › One ClO can destroy many ozone molecules

 Lead - once a serious pollutant › Used in gasoline as an antiknock additive, tons of lead were released into the atmosphere by internal combustion engines › Unleaded fuels have reduced lead in air pollution  High doses of lead can cause brain damage, depression, apathy, and other psychological disorders

 Acidity is reported on the pH scale. › An acid solution has more Hydrogen-ions (H + ) › A basic solution would have fewer  Acid rain has more acid than normal rain › Certain gases in the atmosphere will complex with atmospheric water plus oxygen to form acids  Acid rain is harmful to plants, health of rivers and lakes, and animals  Acid rain causes increases in the build up of heavy metals (lead, zinc, selenium, copper, and aluminum) leached from rocks and soils  Toxic levels are then found in our waterways, fish, and fish eaters

Rain water that has a pH less than 5.6 is environmentally harmful “acid rain” Rain water that has a pH greater than 5.6 is likely contaminated by an alkaline particle. This higher pH can also be harmful if different from the natural pH of local ecosystems

 Rain down wind of an industrial or populated areas have greater acidic conditions › Generally, industrial areas have notably higher sulfur dioxide emissions than non-industrial areas › Urban areas, with automobiles, generally have higher nitrogen oxide emissions than areas without autos  Local geology can reduce the acidity of waterways that receive acid rain. › Limestone can neutralize acidic water; granite can not

1. Thermal Inversion › Pollutants released from ground sources generally are warmer than the surrounding air and tend to rise › As an air mass these plumes will rise and cool › 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, and local wind patterns may amplify the situation also

2. Air pollution can impact local weather › Reduce visibility › Reduce air quality › Modify air temperature › Produce acid rain › Produce abnormal rain

 Air Quality Standards – Clean Air Act (1970) › Designed to protect public health, clear the visible pollution in the air, and prevent damage to crops  Control Methods › Trapping or scrubbing emissions › conversion techniques that reduce the emission of harmful compounds to less harmful ones

 Automobile Emissions – strong legislation creates the Environmental Protection Agency (EPA) › Goal to reduce automobile emissions › Limited success achieved by requiring the use of catalytic converters in new cars and increased fuel economy standards for all new cars  Cost and Effects – it has increased abatement and control cost while limited areas of success have occurred

 Also requires the control (abatement) of dust (solid particulate).  Methods of dust control include › Using water trucks on construction sites to minimize dust › Using bag houses and water sprays in crushing and milling operations › Applying soil palliatives for longer term dust control