Particulates
Particulates, alternatively referred to as particulate matter (PM) or fine particles, are tiny particles of solid or liquid suspended in a gas or liquid. In contrast, aerosol refers to particles and the gas together. Sources of particulate matter can be man made or natural. Particulate Matter[1]—(Water quality) In water pollution, particulates can either be in a solid or dissolved state. Solid particulates can be removed by filters or settle from the water, and is referred to as insoluble particulate matter. Whereas, dissolved particulate matter in water is collected by allowing the water to evaporate, leaving behind the dissolved particulate matter. Salt is an example of dissolved particulate matter. Some particulates occur naturally, originating from volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray. Human activities, such as the burning of fossil fuels in vehicles, power plants and various industrial processes also generate significant amounts of aerosols. Averaged over the globe, anthropogenic aerosols—those made by human activities—currently account for about 10 percent of the total amount of aerosols in our atmosphere.[citation needed] Increased levels of fine particles in the air are linked to health hazards such as heart disease, altered lung function and lung cancer.
The chemical composition of the aerosol directly affects how it interacts with solar radiation. The chemical constituents within the aerosol change the overall refractive index. The refractive index will determine how much light is scattered and absorbed.
Effects of aerosols on electromagnetic radiation
All aerosols both absorb and scatter solar and terrestrial radiation. This is quantified in the Single Scattering Albedo (SSA), the ratio of scattering alone to scattering plus absorption (extinction) of radiation by a particle. The SSA tends to unity if scattering dominates, with relatively little absorption, and decreases as absorption increases, becoming zero for infinite absorption. For example, sea-salt aerosol has an SSA of 1, as a sea-salt particle only scatters, whereas soot has an SSA of 0.23, showing that it is a major atmospheric aerosol absorber.
Aerosols, natural and anthropogenic, can affect the climate by changing the way radiation is transmitted through the atmosphere. Direct observations of the effects of aerosols are quite limited so any attempt to estimate their global effect necessarily involves the use of computer models. The Intergovernmental Panel on Climate Change, IPCC, says: While the radiative forcing due to greenhouse gases may be determined to a reasonably high degree of accuracy... the uncertainties relating to aerosol radiative forcings remain large, and rely to a large extent on the estimates from global modelling studies that are difficult to verify at the present time [1].
A graphic showing the contributions (at 2000, relative to pre-industrial) and uncertainties of various forcings is available here.
Health effects
The effects of inhaling particulate matter have been widely studied in humans and animals and include asthma, lung cancer, cardiovascular issues, and premature death. The size of the particle is a main determinant of where in the respiratory tract the particle will come to rest when inhaled. Because of the size of the particle, they can penetrate the deepest part of the lungs.[2] Larger particles are generally filtered in the nose and throat and do not cause problems, but particulate matter smaller than about 10 micrometers, referred to as PM10, can settle in the bronchi and lungs and cause health problems. The 10 micrometer size does not represent a strict boundary between respirable and non-respirable particles, but has been agreed upon for monitoring of airborne particulate matter by most regulatory agencies. Similarly, particles smaller than 2.5 micrometers, PM2.5, tend to penetrate into the gas-exchange regions of the lung, and very small particles (< 100 nanometers) may pass through the lungs to affect other organs. In particular, a study published in the Journal of the American Medical Association indicates that PM2.5 leads to high plaque deposits in arteries, causing vascular inflammation and atherosclerosis — a hardening of the arteries that reduces elasticity, which can lead to heart attacks and other cardiovascular problems <ref name="pope"> {{cite journal
- ^ Compiled by James Vennie. Authors include: Gary Horton (Nevada Division of Water Planning), "Understanding Lake Data," Byron Shaw, Christine Mechenich and Lowell Klessig (University of Wisconsin - Stevens Point), Ken Wagner - CLM (ENSR, Northborough, MA), Libby McCann (Adopt-a-Lake and Project WET Wisconsin) (2007). "North American Lake Management Society - Water-Words Glossary". Retrieved 2008-03-02.
{{cite web}}: CS1 maint: multiple names: authors list (link) - ^ Region 4: Laboratory and Field Operations - PM 2.5 (2008).PM 2.5 Objectives and History. U.S. Environmental Protection Agency.