Study offers insight into Saharan dust migration

Aug 22, 2013
Credit: Luca Galuzzi / Wikipedia

Satellite pictures of Saharan dust clouds have been in the news all summer, but to Shankar Chellam, they have just raised more questions.

How much impact did the Saharan have on Houston's air? Is it more toxic than our home-grown dust?

Chellam, a professor in the department of civil and environmental engineering at the University of Houston's Cullen College of Engineering, is searching for answers to those and other questions.

Clouds of African dust often migrate across the Atlantic Ocean during summer months, affecting Houston's air quality from mid-June through mid-September. Chellam said it's especially prevalent in late August and early September.

The dust, whipped up by sandstorms in northwest Africa and carried by across the Atlantic Ocean, takes about 10 days to two weeks to reach the United States and, ultimately, Houston.

Chellam said he collaborates on the project with Joseph Prospero, professor emeritus of marine and at the University of Miami.

Chellam became interested after he noticed "the most curious coincidence" as he was collecting data on outside plants along the Houston Ship Channel in 2008.

He began the project expecting that the plants would emit a constant amount of pollution, as measured from just beyond their property lines. But he discovered that on some days they emitted relatively little, while emissions were much higher on other days.

"What we quickly realized was that the impact of the varied with time," he said. "We naively had gone into our research expecting that if we took three months of data, we would get an average."

A five-day period in July and August 2008 showed a large variation. That coincided with an influx of Saharan dust, Chellam said.

To determine the actual impact of the Saharan dust required scientific detective work. Chellam and his team determined the "fingerprint" of the African dust, allowing them to differentiate it from other types of pollutants in their samples: industrial dust, vehicle pollutants and smoke from wildfires, among other things.

"There are millions of sources of pollution," he said.

His lab works with African dust collected in Barbados, before it has picked up other contaminants along the route to the United States. Still, he said, the metals in the dust are distinct.

That finding allowed him to determine that a spike in pollution levels in the 2008 readings reflected the arrival of Saharan dust. A paper on those findings has been accepted for publication in in the journal Environmental Science and Technology. In addition to Prospero, his co-authors include Ayse Bozlaker, a post-doctoral researcher working with Chellam, and Matthew Fraser of Arizona State University.

Work by other scientists has linked the dust migration with coral reef stresses and other environmental problems, but the impact on human health is less clear.

Chellam, whose research does not extend into health impact, said he would expect it to affect people with asthma and other respiratory problems.

"But clearly more research is needed," he said. "The composition of the dust is not the same" as other industrial and vehicle dust.

"And if the composition is different, the health impact may be different," he said.

Explore further: Arctic sea ice helps remove CO2 from the atmosphere

Related Stories

'Refinery dust' reveals clues about local polluters

Jan 12, 2009

Cloaked in the clouds of emissions and exhaust that hang over the city are clues that lead back to the polluting culprits, and a research team led by the University of Houston is hot on their trails.

Saharan dust impacts West African monsoon precipitation

Mar 21, 2011

(PhysOrg.com) -- Africa's Saharan Desert is the largest source of mineral dust in the world, covering more than 3 million square miles and causing dust particles to blanket African skies. According to Pacific ...

Dust storm shrouds Tokyo in haze

Mar 10, 2013

A huge dust storm hit Tokyo Sunday, blanketing the city with brown dust that darkened the skies and rapidly transformed what had been a clear and sunny day.

Study shows links between dust and breast milk

Aug 13, 2013

Concentrations of organic compounds called brominated flame retardants in New Zealand samples of dust and breast milk are "well below" limits imposed by international authorities, researchers from the College ...

Recommended for you

Arctic sea ice helps remove CO2 from the atmosphere

52 minutes ago

Climate change is a fact, and most of the warming is caused by human activity. The Arctic is now so warm that the extent of sea ice has decreased by about 30 pct. in summer and in winter, sea ice is getting ...

Kiribati leader visits Arctic on climate mission

Sep 20, 2014

Fearing that his Pacific island nation could be swallowed by a rising ocean, the president of Kiribati says a visit to the melting Arctic has helped him appreciate the scale of the threat.

User comments : 0