The main sources of air pollutants are both natural and man-made. Naturally, carbon monoxide is produced by methane oxidation and bacterial decomposition. Oxides of nitrogen occur through lightning and bacteria. Sulfur dioxide forms from volcanic activity and bacteria. Particulates originate from sandstorms, volcanoes and fires. Volatile organic compounds are emitted by vegetation, bacteria, and methane-producing animals. Man-made sources include fossil fuel and industrial combustion, vehicular exhaust, smelting, and petroleum extraction/refining which release carbon monoxide, nitrogen oxides, sulfur oxides, particulates, and volatile organic compounds into the atmosphere.

1. O p tion E Environmental Chemistry Describe the main sources of carbon monoxide (CO), oxides of nitrogen (NO x ), oxides of sulfur (SO x ), particulates and volatile organic compounds (VOCs) in the atmosphere

2. Methane produced animals as a digestive gas (e.g. cows) Bacterial decomposition of organic matter in marshes and tropical regions (e.g. rice fields, rivers, lakes) Natural Sources of Carbon Monoxide

4. Man-made sources of Carbon Monoxide Factory combustion Power plants Combustion of Fossil fuels Vehicular exhausts

8. Man-made sources of Nitrogen Oxides E xhaust gases from internal combustion engines Wood and fuels Airplanes