Mineral dust is a term used to indicate
atmospheric aerosolsParticulates, alternatively referred to as particulate matter 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...
originated from the
suspension of
mineralA mineral is a naturally occurring solid formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties. A rock, by comparison, is an aggregate of minerals and/or mineraloids, and need not have a specific...
s constituting the
soilSoil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics. It is composed of particles of broken rock that have been altered by chemical and...
, being composed of various oxides and carbonates. Human activities lead to 30% of the dust load in the
atmosphereAn atmosphere is a layer of gases that may surround a material body of sufficient mass, by the gravity of the body, and are retained for a longer duration if gravity is high and the atmosphere's temperature is low...
. The
SaharaThe Sahara , , "The Greatest Desert") is the world's largest hot desert. At over 9,000,000 square kilometres , it covers most of Northern Africa, making it almost as large as the United States or the continent of Europe. The desert stretches from the Red Sea, including parts of the Mediterranean...
is the major source of mineral
dustDust is a general name for minute solid particles with diameters less than 20 thou . Particles in the atmosphere arise from various sources such as soil dust lifted up by wind, volcanic eruptions, and pollution...
, which subsequently spreads across the Mediterranean and
CaribbeanThe Caribbean is a region consisting of the Caribbean Sea, its islands , and the surrounding coasts...
seas into northern
South AmericaSouth America is the southern continent of the Americas, situated entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere...
,
Central AmericaManagua
Guatemala City
San Salvador
San Pedro Sula
Panama City
San José, Costa Rica
Santa Ana, El Salvador
León
San Miguel|-|}...
,
North AmericaNorth America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific...
, and
EuropeEurope is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally divided from Asia to its east by the water divide of the Ural Mountains, the Ural River, the Caspian Sea, the Caucasus Mountains , and the Black Sea to the southeast...
. The
Gobi DesertThe Gobi is the largest desert region in Asia. It covers parts of northern and northwestern China, and of southern Mongolia...
is another source of dust in the atmosphere, which affects eastern
AsiaAsia is the world's largest and most populous continent, located in the eastern and northern hemispheres. It covers 8.6% of the earth's total surface area and with approximately 4 billion people, it hosts 60% of the world's current human population.Asia is traditionally defined as part of the...
and western North America.
It is mainly constituted of the oxides (SiO
2, Al
2O
3, FeO, Fe
2O
3, CaO, and others) and carbonates (CaCO
3, MgCO
3) that
constitute the
Earth's crustIn geology, a crust is the outermost solid shell of a rocky planet or moon, which is chemically distinct from the underlying mantle. The crusts of Earth, our Moon, Mercury, Venus, Mars, Io, and other planetary bodies have been generated largely by igneous processes, and these crusts are richer in...
.
Global mineral dust emissions are estimated 100-500 millions of tons per year, of which the largest part is
attributed to deserts.
Although this aerosol class is usually considered of natural origin, it is estimated that about 30% of the
mineral dust load in the atmosphere could be ascribed to human activities through
desertificationDesertification is the degradation of land in arid and dry sub-humid areas, resulting primarily from man-made activities and influenced by climatic variations...
and land
misuse.
Large dust concentrations may cause problems to people having respiratory problems, forcing them to stay
indoors while dust aerosols are in the area.
Another notable effect of dust clouds is prettier
sunsets"Sunsets" is a song released as the third single from Australian rock band Powderfinger's fifth studio album, Vulture Street. The single was released on 4 January 2004 in Australia and New Zealand....
, thanks to the increased number of particles
in the
skyThe sky is the part of the atmosphere or of outer space visible from the surface of any astronomical object. It is difficult to define precisely for several reasons. During daylight, the sky of Earth has the appearance of a deep blue surface because of the air's scattering of sunlight. The sky is...
, which the
SunThe Sun is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 99.86% of the Solar System's mass....
may reflect off of.
The Sahara is the major source on Earth of mineral dust (60-200 millions of tons per year).
Saharan dust can be lifted by
convectionConvection is the movement of molecules within fluids . Convection is one of the major modes of heat transfer and mass transfer...
over hot desertic areas, and can thus reach very high altitudes; from there it can be transported worldwide by winds, covering distances of thousands of kilometers.
Mineral dust is a term used to indicate
atmospheric aerosolsParticulates, alternatively referred to as particulate matter 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...
originated from the
suspension of
mineralA mineral is a naturally occurring solid formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties. A rock, by comparison, is an aggregate of minerals and/or mineraloids, and need not have a specific...
s constituting the
soilSoil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics. It is composed of particles of broken rock that have been altered by chemical and...
, being composed of various oxides and carbonates. Human activities lead to 30% of the dust load in the
atmosphereAn atmosphere is a layer of gases that may surround a material body of sufficient mass, by the gravity of the body, and are retained for a longer duration if gravity is high and the atmosphere's temperature is low...
. The
SaharaThe Sahara , , "The Greatest Desert") is the world's largest hot desert. At over 9,000,000 square kilometres , it covers most of Northern Africa, making it almost as large as the United States or the continent of Europe. The desert stretches from the Red Sea, including parts of the Mediterranean...
is the major source of mineral
dustDust is a general name for minute solid particles with diameters less than 20 thou . Particles in the atmosphere arise from various sources such as soil dust lifted up by wind, volcanic eruptions, and pollution...
, which subsequently spreads across the Mediterranean and
CaribbeanThe Caribbean is a region consisting of the Caribbean Sea, its islands , and the surrounding coasts...
seas into northern
South AmericaSouth America is the southern continent of the Americas, situated entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere...
,
Central AmericaManagua
Guatemala City
San Salvador
San Pedro Sula
Panama City
San José, Costa Rica
Santa Ana, El Salvador
León
San Miguel|-|}...
,
North AmericaNorth America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific...
, and
EuropeEurope is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally divided from Asia to its east by the water divide of the Ural Mountains, the Ural River, the Caspian Sea, the Caucasus Mountains , and the Black Sea to the southeast...
. The
Gobi DesertThe Gobi is the largest desert region in Asia. It covers parts of northern and northwestern China, and of southern Mongolia...
is another source of dust in the atmosphere, which affects eastern
AsiaAsia is the world's largest and most populous continent, located in the eastern and northern hemispheres. It covers 8.6% of the earth's total surface area and with approximately 4 billion people, it hosts 60% of the world's current human population.Asia is traditionally defined as part of the...
and western North America.
Characteristics
It is mainly constituted of the oxides (SiO
2, Al
2O
3, FeO, Fe
2O
3, CaO, and others) and carbonates (CaCO
3, MgCO
3) that
constitute the
Earth's crustIn geology, a crust is the outermost solid shell of a rocky planet or moon, which is chemically distinct from the underlying mantle. The crusts of Earth, our Moon, Mercury, Venus, Mars, Io, and other planetary bodies have been generated largely by igneous processes, and these crusts are richer in...
.
Global mineral dust emissions are estimated 100-500 millions of tons per year, of which the largest part is
attributed to deserts.
Although this aerosol class is usually considered of natural origin, it is estimated that about 30% of the
mineral dust load in the atmosphere could be ascribed to human activities through
desertificationDesertification is the degradation of land in arid and dry sub-humid areas, resulting primarily from man-made activities and influenced by climatic variations...
and land
misuse.
Large dust concentrations may cause problems to people having respiratory problems, forcing them to stay
indoors while dust aerosols are in the area.
Another notable effect of dust clouds is prettier
sunsets"Sunsets" is a song released as the third single from Australian rock band Powderfinger's fifth studio album, Vulture Street. The single was released on 4 January 2004 in Australia and New Zealand....
, thanks to the increased number of particles
in the
skyThe sky is the part of the atmosphere or of outer space visible from the surface of any astronomical object. It is difficult to define precisely for several reasons. During daylight, the sky of Earth has the appearance of a deep blue surface because of the air's scattering of sunlight. The sky is...
, which the
SunThe Sun is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 99.86% of the Solar System's mass....
may reflect off of.
Saharan dust
The Sahara is the major source on Earth of mineral dust (60-200 millions of tons per year).
Saharan dust can be lifted by
convectionConvection is the movement of molecules within fluids . Convection is one of the major modes of heat transfer and mass transfer...
over hot desertic areas, and can thus reach very high altitudes; from there it can be transported worldwide by winds, covering distances of thousands of kilometers. The dust combined with the hot dry air of the Sahara Desert often forms an atmospheric layer called the
Saharan Air LayerThe Saharan Air Layer is an intensely dry, warm and sometimes dust-laden layer of the atmosphere which often overlies the cooler, more-humid surface air of the Atlantic Ocean. In the Sahara Desert region of North Africa, where it originates, it is the prevalent atmosphere, extending from the...
which has significant effects on tropical weather, especially as it interferes with the development of hurricanes. There is a large variability in the dust transport across the Atlantic into the
CaribbeanThe Caribbean is a region consisting of the Caribbean Sea, its islands , and the surrounding coasts...
and Florida from year to year. Due to the
trade windThe trade winds are the prevailing pattern of easterly surface winds found in the tropics near the Earth's equator. The trade winds blow predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere...
s, very large concentrations of mineral dust can be found in the tropical Atlantic, reaching the Caribbean; moreover episodic transport to the Mediterranean region as well as
Northern EuropeNorthern Europe is the northern part or region of Europe. The United Nations defines Northern Europe as including the following countries and dependent regions:** ** ** Ireland** Svalbard and Jan Mayen** ** Channel Islands: and...
is observed. In the Mediterranean region, Saharan dust is important as it represents the major source of nutrients for
phytoplanktonPhytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτον , or "plant", and πλαγκτος , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye...
and other aquatic organisms. Saharan dust carries the fungus
Aspergillus sydowiiAspergillus is a genus of a few hundred molds found throughout much of nature worldwide. Aspergillus was first catalogued in 1729 by the Italian priest and biologist Pier Antonio Micheli. Viewing the fungi under a microscope, Micheli was reminded of the shape of an aspergillum , and named the genus...
and others. Aspergillus borne by Saharan dust falls into the
Caribbean SeaThe Caribbean Sea is a sea of the Atlantic Ocean situated in the tropics of the Western hemisphere, bounded to the south and west by the American landmass, with the North Atlantic Ocean proper to the northeast and the Gulf of Mexico to the northwest...
and possibly infects coral reefs with Sea Fan disease (
aspergillosisAspergillosis is the name given to a wide variety of diseases caused by fungi of the genus Aspergillus. The most common forms are allergic bronchopulmonary aspergillosis, pulmonary aspergilloma and invasive aspergillosis. Most humans inhale Aspergillus spores every day...
).
It also has been linked to increased incidence of pediatric
asthmaAsthma is a predisposition to chronic inflammation of the lungs in which the airways are reversibly narrowed. Asthma affects 7% of the population of the United States, and 300 million worldwide...
attacks in the Caribbean. Since 1970, dust outbreaks have worsened due to periods of drought in Africa. Dust events have been linked to a decline in the health of
coral reefCoral reefs are aragonite structures produced by living organisms, found in marine waters containing few nutrients. In most reefs, the predominant organisms are stony corals, colonial cnidarians that secrete an exoskeleton of calcium carbonate...
s across the Caribbean and Florida, primarily since the 1970s.
Dust from Subsaharan May Affect Frequency of Hurricanes
According to a
NASAThe National Aeronautics and Space Administration is an agency of the United States government, responsible for the nation's public space program. NASA was established by the National Aeronautics and Space Act on July 29, 1958, replacing its predecessor, the National Advisory Committee for...
article, NASA satellites have shown that "the chilling effect of dust was responsible for one-third of the drop in North Atlantic sea surface temperatures between June 2005 and 2006, possibly contributing to the difference in hurricane activity between the two seasons." There were only 5 hurricanes in 2006 and compared with 15 in 2005.
It is known that one the major factors that create hurricanes is warm water temperatures on the surface of the ocean. One theory holds that dust from the Sahara desert caused surface temperatures to be cooler in 2006 than in 2005. Evidence shows that surface temperatures dropped by one third because of the Subsaharan dust.
Asian dust
In Eastern Asia, mineral dust events originated in springtime in the Gobi Desert (Southern Mongolia and Northern China) gives rise to the phenomenon called
Asian dust.
The aerosols are carried eastward by prevailing winds, and pass over China, Korea, and Japan.
Sometimes, significant concentrations of dust can be carried as far as the Western United States.
Areas affected by Asian dust experience decreased visibility and health problems, such as sore
throat and respiratory difficulties.
The effects of Asian dust, however, are not strictly negative, as it is thought that its deposition
enrichs the soil with important trace minerals.
An American study analyzing the composition of Asian dust events reaching Colorado associates them to
the presence of
carbon monoxideCarbon monoxide is a colorless, odorless and tasteless gas, yet very toxic to humans. It consists of one carbon atom and one oxygen atom, connected by a covalent double bond and a dative covalent bond...
, possibly incorporated in the air mass as it passes over industrialized
regions in Asia.
Although dust storms in the Gobi desert have occurred from time to time throughout history,
they became a pronounced problem in the second half of the 20th century due to intensified agricultural
pressure and
desertificationDesertification is the degradation of land in arid and dry sub-humid areas, resulting primarily from man-made activities and influenced by climatic variations...
.
Printed Media
- Kubilay and Saydam, "Trace elements in atmospheric particulates over the Eastern Mediterranean: concentration, sources, and temporal variability", Atmospheric Environment 29, 2289-2300 (1995).
- Morales, "The airborne transport of Saharan dust: a review", Climate Change 9, 219-241 (1986).
- Loyë-Pilot et al., "Influence of Saharan dust on the rain acidity and atmospheric input to the Mediterranean", Nature 321, 427-428 (1986).
- Sokolik and Toon, "Direct radiative forcing by anthropogenic airborne mineral aerosols", Nature 381, 681-683 (3075).
- Tegen and Fung, "Contribution to the atmospheric mineral aerosol load from land surface modification", Journal of Geophysical Research 100, 18707-18726 (1995).
External links