Particulates

Satellite image of particulate pollution over Beijing, China.
Click on image for full size (219 Kb (JPEG))
NASA image courtesy the MODIS Rapid Response Team

Particulates, also called particulate matter, aerosols, or fine particles, are tiny particles of solid or liquid suspended in the atmosphere. They range in size from just a few molecules to large enough that they can no longer be carried by the air in the atmosphere. Coarse particulates have a diameter greater than 2.5 micrometers, and fine particles are less than 2.5 micrometers. Coarse particles usually contain rock and dust from wind erosion. Fine particles include soot, inorganic salts, and organic compounds.

In general, the smaller and lighter a particle is, the longer it will stay in the air. Larger particles (greater than 10 micrometers in diameter) tend to settle to the ground by gravity in a matter of hours whereas the smallest particles (less than 1 micrometer) can stay in the atmosphere for weeks and are mostly removed by precipitation.

There are both natural and anthropogenic sources of atmospheric particulates. The biggest natural sources are wind-blown dust, volcanoes, and forest fires. The biggest anthropogenic sources of particles are combustion sources, mainly the burning of fossil fuel in internal combustion engines (such as in automobiles and power plants), and wind-blown dust from construction sites and other land areas where the water or vegetation has been removed.

Some particles, such as dust from roads or elemental carbon (soot) from wood combustion, are emitted directly into the atmosphere. These are called “primary” particles. Other “secondary” particles are formed in the atmosphere from primary gaseous emissions. These include sulfates, formed from sulfur dioxide emissions from power plants and industrial facilities, and nitrates, formed from nitrogen oxides emissions from power plants, automobiles, and other types of combustion sources.

Particulate pollution contains microscopic solids or liquid droplets that are so small that they can get deep into the lungs and cause serious health problems. The size of particles is directly linked to their potential for causing health problems. Small particles less than 10 micrometers in diameter pose the greatest problems, because they can get deep into your lungs, and some may even get into your bloodstream.

Particulate pollution can also affect visibility. Fine particles are the major cause of reduced visibility (haze) in many parts of the world, including many of treasured natural parks and wilderness areas. Not all particles cause pollution. There are many natural sources of particles that are unrelated to air pollution. One common example is a cloud. Every cloud is made up of billions of particles (water droplets).


Particulates

Satellite image of particulate pollution over Beijing, China.
Click on image for full size (219 Kb (JPEG))
NASA image courtesy the MODIS Rapid Response Team

Particulates are tiny particles of solid or liquid suspended in the atmosphere. They are also called particulate matter, aerosols, or fine particles. Particulates vary in size from just a few molecules to so large that the air can’t hold them. Coarse particulates have a diameter bigger than 2.5 micrometers. They contain rock and dust from vehicles and factories. Fine particles are even smaller. They include combustion particles and organic and metal compounds.

In general, the smaller and lighter a particle is, the longer it will stay in the air. Larger particles (greater than 10 micrometers in diameter) tend to settle to the ground by gravity in a matter of hours whereas the smallest particles (less than 1 micrometer) can stay in the atmosphere for weeks and are mostly removed by precipitation.

There are both natural and human-made sources of particulates. The biggest natural sources are wind-blown dust, volcanoes, and forest fires. The biggest human sources of particles are combustion sources, like the burning of fossil fuel in cars and power plants, and wind-blown dust from construction sites and other land areas where the water or plants have been removed.

Some particulates, such as dust from roads or soot from wood combustion, are emitted directly into the atmosphere. These are called “primary” particles. Other “secondary” particles are formed in the atmosphere from primary particulates. These include sulfates, formed from sulfur dioxide emissions from power plants and industrial plants, and nitrates, formed from nitrogen oxides emissions from power plants, cars, and other types of combustion sources.

Particulate pollution contains solids or liquid droplets that are so small that they can get deep into a person’s lungs and make them very sick. Small particles cause more problems than big ones, because they can get deep into your lungs, and some may even get into your blood.

Particulate pollution can also affect visibility. Fine particles are the major cause of haze in many parts of the world, including many of treasured natural parks and wilderness areas. There are many natural sources of particles that are not air pollution. One example is a cloud. Every cloud is made up of billions of water droplets, which are particles.


Particulates

Satellite image of particulate pollution over Beijing, China.
Click on image for full size (219 Kb (JPEG))
NASA image courtesy the MODIS Rapid Response Team

Particulates are tiny particles that float in the air. They are also called particulate matter, aerosols, or fine particles. They come in different sizes, from just a few molecules to so big that the air can’t hold them. Bigger particulates are pieces rock and dust from cars and factories. Other particles are much smaller. They include aerosols, smoke and soot.

The smaller a particle is, the longer it will stay in the air. Big particles will fall to the ground in a few hours. Really small particles can stay in the air for weeks. They are washed out of the air by rain.

Some particulates are made from wind-blown dust, volcanoes, and forest fires. People make them too, by burning fossil fuels in cars and power plants, and making dust at construction sites and other places where the water or plants have been removed.

Some particulates are so small that they can get into a person’s lungs and make them very sick.

Particulates can make it hard to see through the air. They are the cause of haze in many parts of the world, including natural parks and wilderness areas. Some particles are natural, like the water droplets that make up clouds.



Page created January 27, 2006 by Dennis Ward.
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