Polluting `tar balls'
CARBON-BEARING particles, called `tar balls' have been found to pollute air over Hungary, Indian Ocean, and southern Africa by an international team of scientists. Forming in smoke from wood fires and agricultural and forest burning, tar balls in the lower atmosphere are a concern, they say. The team, report their findings in the Journal of Geophysical Research..
``They are abundant in biomass (vegetal) smoke,'' says an Arizona State University resesarcher. ``Tar balls occur in a variety of atmospheric environments that are affected by human activities,'' he says.
``Tar balls may look like soot which consists of spheres,'' says a Hungarian researcher. Each soot sphere is made of graphitic layers that are concentrically wrapped with other soot spheres, he says. Tar balls, on the other hand, are just individual spheres and do not form chains or clusters. ``Optical properties of a particle depend on the graphitic structure. The more ordered the graphitic structure, the darker the colour,'' explain the team. ``Dark particles absorb sunlight and thereby heat the atmosphere.'' Tar balls may also be absorbing sunlight while black soot is the major absorber of sunlight in the atmosphere.
- Our Bureau
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