Air and water pollution are the two areas where nature contributes its own forms of pollution, either by introducing gases and particulate matter into the atmosphere, or by introducing heavy metals and natural toxins into the water. Natural pollution occurs every day in ways that are barely noticeable, but the odd major event, such as certain types of volcanic eruptions, can produce massive amounts of particulate pollution.
Pollution is considered to be significant when plant and animal life are harmed in significant ways. In the atmosphere, the normal composition of gases includes nitrogen, oxygen, argon, carbon dioxide, smaller amounts of neon, krypton, helium and methane. When these are either out of balance or significant amounts of other substances enter the atmosphere, pollution is considered to have occurred.
The major atmospheric pollutants that are from natural causes are: carbon monoxide, the nitrogen oxides, the sulfur oxides, hydrocarbons and suspended particulate matter.
Carbon monoxide primarily comes as an oxidation of methane. Methane is produced in natural ways by the decay of organic matter on the Earths surface, with decay of chlorophyll as a secondary source. Carbon monoxide is the most prominent atmospheric pollutant by volume.
The Nitrogen Oxides include nitrogen dioxide, nitrous oxide, and nitric oxide. Nitrous dioxide is the most toxic, but nitrogen dioxide is not toxic, and is not even considered as a pollutant. These are predominantly natural in their source, as humans contribute less of these substances to the atmosphere. The main causes are soil decomposition, bacterial activity and lightening.
The Sulfur Oxides are mostly sulfur dioxide and sulfur trioxide. Sulfur dioxide is the majority of the oxides. Sulfur trioxide does not stay in the atmosphere for long, but it bonds with moisture and converts to sulfuric acid in water, becoming one of the components of acid rain. The Sulfur Oxides that are from nature form when hydrogen sulfide enters the atmosphere and oxidizes. Hydrogen sulfide comes from decomposition of organic matter. The larger proportion of the Sulfur Oxides are from human activity.
Hydrocarbons, composed mostly of hydrogen and carbon are the final and second most prominent atmospheric pollutant and there are thousands of them. The problem with hydrocarbons, which are relatively harmless in their natural state is that they become harmful when they suspend in the atmosphere and undergo chemical reactions. These are called secondary pollutants and include ozone Again, organic matter undergoing bacterial decomposition is the natural source of hydrocarbons.
Suspended particulate matter that can be in the form of smoke, mist (liquid) or dust. The largest natural cause is, surprisingly, tiny bubbles that burst at the surface of the oceans, releasing salt into the atmosphere at microscopic levels. The suspended particles, depending on their composition, can attract to other particles and clump, or they can be broken down in the atmosphere from larger particles. As a result, the composition of dust storm material and volcanic eruptions can result in a variety of reactions in the atmosphere.
The natural sources of water pollution comes from organic matter, metals and oxygen reducing substances that result from natural land erosion and introduction to the waterways, or the settling of suspended particles on the water. Water pollution is mostly human in origin, however. The natural functions and compositions of the water structure are compromised when some substances undergo chemical reactions or the biomass interferes with the natural processes that go on in aquatic and marine biomes.