DUST

Presented by

Dianne Q. Robinson, PhDHampton University, Hampton, Virginia

What is DUST?

“On Earth, dust forms when rocks are broken down into sand and smaller particles. These particles, called mineral dust, can be blown

by the wind and suspended in the atmosphere.”

“ Desert dust contains common crustal minerals, such as silica,

calcium carbonate, and iron oxides.”

DUST FACT:

“The deserts on Earth are huge sources of dust, with the Sahara and Gobi Deserts as the main sources.

Desert dust is one of many types of tiny particles found in our atmosphere called aerosols.”

Sources of dust…

Above: African dust blowing into the Atlantic Ocean

African Dust Storms

This image shows dust blowing from Baja California.

Dust Storm• A large body of small

airborne particles.

• Particles ranging from small sand particles to smoke to volcanic ash.

• Can travel thousands of miles, crossing continents and oceans, affecting the entire ecosystem of the Earth.

Above: A dust storm over Pakistan.

• Dust storms are a major part of our planet’s ecosystem.

supply nutrient poor areas with nutrients from all over the world.

balancing force in the world’s weather systems.

> cool the oceans and aid in cloud creation, as well as reflect different wavelengths of light.

Importance of Dust Storms

Clouds versus Dust Clouds

This diagram shows the difference in light frequency reflection from clouds to dust.

• Flux of African dust has increased dramatically since 1970 due to the ongoing drought in the Sahara and Sahel regions.

• The dust flux from Africa to the atmosphere has been estimated in approximately 1 billion tons per year.

Desertification

Desertification vulnerability of Africa Risk of human-induced desertification

The main causes of the spreading deserts in Africa are climate, humans, and livestock.

Desertification

Transportation of Dust

Transportation of Dust

• Wind picks up the dust and carries it up into the atmosphere, up to 2 kilometers.

• This airborne dust can remain there for days, depending on the size of the particles and the strength of the wind propelling it.

Taklimakan Dust Storm

• A dust storm originating from China’s Taklimakan Desert in May of 2007, traveled around the world in just 13 days, depositing dust into the Pacific Ocean just after it completed its circuit.

• Enlarged image on next page…

Dust storm growing over the Taklimakan Desert.

Taklimakan Dust Storm

The cloud measured 3 kilometers tall, 2000 kilometers long and was 8 to 10 kilometers above the surface of the earth, it moved at about 36 kilometers per hour, and had a mass of about 800 million kilograms.

A cold front over the desert created strong surface winds which drove the dust so high that the jet stream caught it, and carried it around the world.

Source Regions

• Most dust storms originate in China and Africa.

• They carry dust across the oceans, affecting major weather systems, and local ecosystems.

The orange area is the Sahel Desert.

The Sahel is a good example of a perfect

climate for dust.

The Sahel is the area between the Sahara Desert and the southern grasslands.

The Sahel is responsible for one-third of the world’s dust production.

Years of drought and over-use of the soil have depleted the aquifer, and left the land vulnerable to the wind.

Transportation of DustThis diagram shows the

major global wind systems which carry dust.

African dust storm blowing towards the Mediterranean Sea.

Dust Seasons• China’s dust season runs primarily in the spring

(March - May).• Africa’s dust seasons are complex in that the dust

never stops, only changes direction.• Dust from Africa travels to the U.S. during the summer

in the northern hemisphere (May - November).• African dust travels to Middle and South America

during the summer of the southern hemisphere (December - April)

• Through both seasons, dust drifts up to Europe, affecting their air quality.

Libyan dust blowing across the Atlantic Ocean.

The two tones of dust are two different material compositions.

Africa

South America

United StatesAug 29 Aug 26 Aug 25 Aug 24 Aug 23 Aug 22 Aug 21 Aug 20 Aug 19

NASA’s Terra Satellite Observations From a Multi-angle Imaging SpectroRadiometer (MISR) instrument

Dust from the Sahara Desert Reaches Houston, Texas

Components:• Minerals (e.g. aluminosilicates, calcium

carbonate)• Metals (Hg, Fe+3 )• Radioactive isotopes ( e.g. Be-7, Pb-

210,)• Pesticides (e.g. DDT)• Bioaerosols

Primary bioaerosols include:• Pollen• Fungi• Bacteria• Viruses• Biological products (spores, mycotoxins,

endotoxins)• Insects• Fragmentary particles linked

to anthropogenic activities such as agriculture

Saharan Dust Composition

Impacts of Dust• Dust could effect every

aspect of our climate, from temperature, to weather.

• Dust storms have affected the topsoil composition for a few regions already.

• They can carry many small particles, from minerals to viruses.

A dust storm during the Dust Bowl in the Midwest.

Climate Earth radiative budget

Cloud physical & radiative propertiesPrecipitation

Hurricane suppressant

Nutrient depositionOcean fertilization

Plankton productivity/algal blooms

Human HealthRespiratory

Cardiovascular Other infections

Ecosystem HealthAspergillosis (soft corals)

Plant pathogens

Impacts of Saharan Dust

Detrimental Effects

> Dust could carry viruses across the world, making containment and quarantine nearly impossible.

> There is a clear link between dust and asthma.

A dust storm in the Sahel, and a satellite picture of that storm (top-right).

Detrimental Effects … continued

A coral formation with Black Band Disease

> Diseases can be carried by dust to other parts of the world.

> Coral reefs are a good example of the disease transportation.

> Caribbean Coral has been one of the hardest hit coral systems by dust borne disease.

Impacts of Saharan Dust:Ecosystem Health

Saharan dust is an important source of fungal spores from species that are not common in the Caribbean region.

We have been identified over 13 species of pathogenic species (i.e. Aspergillus fumigatus, A. flavus, P. citrinum). Some are environmental allergens and agents of asthma and infection.

Most of these species are considered opportunistic, primarily affecting immunocompromised hosts. Fusarium equiseti and Curvularia brachyspora are known plant pathogens.

Aspergillus sydowii, responsible of Aspergillosis in soft corals, has not been isolated from our samples.

ASPERGILLOSIS

First reported in sea fans Gorgonia ventalina and G. flabellum in mid 90s (Smith 1996).

Dead tissue surrounded by purple halo that can lead to death of colony.

The pathogen has been described as Aspergillus sydowii (Smith 1996).

A. sydowii has been isolated from Saharan dust samples.

However other Aspergillus species (A. flavus) has been found in necrotic tissue of sea fans (A. Zuluaga, personal communication).

Healthy Gorgonia ventalina

• Aspergillosis is one of the most important diseases affecting corals in the Caribbean Region.

Aspergillosis

Aspergillus sydowii

Photos courtesy of Hector Ruiz and Juan Torres

Coral Reef Bleaching

African dust blowing across the Caribbean Sea

> Dust storms cool the oceans, lessening the strength of hurricanes by reflecting solar radiation back into space.

> Dust storms carry nutrients all over the world to stimulate ecosystems.

> African phosphorus carried by dust to the Amazon to stimulate growth, thus helping to remove carbon dioxide from the air.

Beneficial Affects

Satellites

Earth Probe

CALIPSO

Terra Aqua

Satellite Evidence

A large cloud of dust being blown into the air over Africa.

Satellite Evidence…continued

Dust from the Western Sahara being blown into the atmosphere, then blown over to Central America,

losing strength as it passed over the Atlantic Ocean.

Images from Earth Probe satellite.

Satellite evidence…continued

Chinese Dust storm tracked across the Pacific Ocean, landing in the U.S. and Canada in

April, 2001.

A RECENT NASA PUBLICATION:“Understanding Earth: The Journey of Dust”