Natural sources of sulfur in the atmosphere include evaporation from sea spray, volcanic fumes, and organic compounds.
Predominant form of anthropogenic sulfur is sulfur-dioxide from fossil-fuel combustion (coal and oil) and smelting of sulfide ores.
Sulfur dioxide is a corrosive gas which reacts with water vapor in the air to cause acid rain.
Nitrogen oxides are reactive gases formed when nitrogen is heated above 650oC in the presence of oxygen, or when nitrogen compounds are oxidized by bacteria.
Nitric oxide is further oxidized to give nitrogen dioxide, the reddish brown gas in smog.
Nitrogen oxides combine with water to make the nitric acid found in acid rain (along with sulfuric acid discussed earlier).
Excess nitrogen is causing fertilization and eutrophication of inland waters and coastal seas. It also encourages the growth of weeds that crowd out native species. Humans are responsible for 60% of emissions.
Predominant form of carbon in the air is carbon dioxide.
Increasing levels due to use of fossil fuels
Cause of global warming
Carbon monoxide is a colorless, odorless, toxic gas produced by incomplete fuel combustion.
Light pollution prevents us from seeing stars and is a serious problem for astronomers.
Indoor Air Pollution
EPA found indoor concentrations of toxic air pollutants are often higher than outdoor.
People generally spend more time indoors.
Smoking is the most important air pollutant in the U.S.
400,000 die annually from diseases related to smoking. This is 20% of all mortality.
Associated costs are estimated at $100 billion annually.
Chloroform, benzene and other chemicals can be found in homes at concentrations that would be illegal in workplace.
Indoor Air Pollution
Less Developed Countries also suffer from indoor air pollution.
Organic fuels make up majority of household energy.
Often burned in smoky, poorly ventilated heating and cooking fires.
Climate and Topography
Temperature inversions occur when a stable layer of warm air overlays cooler air, reversing the normal temperature decline with increasing height, and preventing convection currents from dispersing pollutants.
Rural areas downwind from major industrial areas often have significantly decreased visibility and increased rainfall.
Fine aerosols can be carried great distances by the wind.
3 km toxic cloud covers India for most of year, causing 2 million deaths/yr.
Cloud may also be disrupting monsoon rains on which harvests in South Asia depend
When cloud drifts over Indian Ocean at end of monsoon season, it may be changing El Nino patterns
Increasingly, sensitive monitoring equipment has begun to reveal industrial contaminants in places usually considered among the cleanest in the world (e.g. Antarctica).
Grasshopper transport - volatile compounds evaporate from warm areas; travel to poles where they condense and precipitate. Contaminants bioaccumulate in food webs. Whales, polar bears, sharks have dangerously high levels of contaminants.
Discovered in 1985 that stratospheric ozone levels over South Pole were dropping rapidly during September and October.
Occurring since at least 1960
Chlorofluorocarbons are the cause.
At ground-level, ozone is a pollutant, but in the stratosphere it screens UV radiation.
A 1% decrease in ozone could result in a million extra human skin cancers per year worldwide.
Decreased agricultural production and reduced plankton in the ocean, the basis of food chain
Ozone Hole Over Antarctic
Circumpolar vortex isolates Antarctic air and allows stratospheric temperatures to drop and create ice crystals at high altitudes.