Dust plays role in damage of pollution
By Jan TenBruggencate
Advertiser Science Writer
Dust trapped in Europe's alpine glaciers is confirming discoveries by Hawai'i researchers that airborne pollutants are changing the atmosphere.
Scientists are finding that dust particles gather pollutants and can trap heat within the atmosphere.
Barry Huebert, an oceanographer at the University of Hawai'i, has collected air samples while flying over parts of Asia and the Pacific and studied the dust they contain. He said dust blown off the Gobi Desert and other dry areas picks up carbon particles from burning fossil fuels. That makes the dust darker and more effective at absorbing heat.
As it blows over cities, the dust is exposed to urban pollution. Nitric oxides, also created by burning fossil fuels, react with carbonates in the dust to create nitrates. These attract water, making the dust particles bigger and more likely to scatter light, preventing it from reaching the Earth's surface.
Huebert helped work on the Atmospheric Characterization Experiment-Asia, which also showed that dust forms distinct layers in the atmosphere.
"We did one profile over the Yellow Sea off North Korea and found 13 different layers in the lowest 5.5 kilometers (3.4 miles) of the atmosphere," he said. Some layers were predominantly a single type of particle, some were clear, and some were made up of other kinds of dust. The combination, he said, makes it extremely difficult to model how the atmosphere behaves.
His colleague, atmospheric chemist Urs Baltensperger of the Swiss Laboratory of Atmospheric Chemistry at the Paul Scherrer Institute near Zurich, said ice cores in Alpine glaciers have shown trends in the components of atmospheric dust over Europe since 1750.
Before the start of the Industrial Revolution around 1850, dust had a stable proportion of carbon from wood fires across the continent. There followed a gradual rise in the amount of carbon attached to dust, and in sulfur compounds, both associated with the burning of fossil fuels.
"We see a factor of three increase in carbon, but with sulfates a factor of 10," Baltensperger said.
In recent decades, research shows a decrease in sulfur compounds corresponding to the use of low-sulfur fuels and new filtering technologies. Acidic nitrogen compounds, also associated with fossil-fuel burning, remain high, he said.
In Europe, acidic pollutants today are associated with acid rain, which has acidified Nordic lakes and damaged European forests.
Baltensperger said the historical data being extracted from glaciers in the Alps gives an important perspective on the effects of pollution on climate. He hopes other glaciers, including those in China, will be probed for information they can provide about airborne dust.
"This is a very important archive to see what's going on," he said.
Huebert and Baltensperger were among the speakers at an East-West Center workshop last week, "Air Pollution as a Climate Forcing," sponsored by the International Pacific Research Center at the University of Hawai'i's School of Ocean and Earth Science and Technology.
Reach Jan TenBruggencate at jant@honoluluadvertiser.com or (808) 245-3074.
