Oliver Chadwick on why there’s more dust in the air

Oliver Chadwick: We have evidence that suggests that now the planet is much dustier than it was just a few hundred years ago.

Oliver Chadwick of the University of California at Santa Barbara studies dust and how it moves around the world. He said one reason Earth has gotten dustier is connected to the rise of modern agriculture. When you clear land for agriculture, you remove trees and other plants – exposing loose dirt beneath to passing winds. And how far that dust might travel depends on its weight.

Oliver Chadwick: The finest portion can be lofted high enough into the atmosphere so that it will move long distances around the planet.

Agricultural chemicals from the fields, such as fertilizers and pesticides, can get carried along with the dust. Airborne dust can change habitats that are near – or far – from the fields, said Chadwick.

Oliver Chadwick: All parts of the planet are interconnected. And the atmosphere will carry particulate matter or solutes around the planet.

Urban activities such as construction and transportation also generate a lot of dust, Chadwick said.

Oliver Chadwick: Clearly, there is a public health concern with dust because not all dust is derived from soil and therefore relatively benign. Some of it comes from construction materials; some of it comes from industrial processes.

Chadwick said that it’s farmers’ best interest to keep dust levels low.

Oliver Chadwick: In the process of minimizing dust they’re also minimizing loss of fertility, and maintaining fertility costs money. But there’s only so much that agricultural efforts can do in this regard.

Dust had an important role in shaping our planet long ago. Chadwick said there are areas of the Earth that owe most of their soil and its fertility to the accumulation of dust.

Oliver Chadwick: We actually have whole regions that are made up of soil that was composed of dust. We have a term for this soil material that we have received from the German science term: ‘Loess.’ Loess soils are found all around the world, particularly in areas that were impacted by Glaciers in the past. In those areas there was a tremendous amount of dust that was blowing around and accumulating and that fine-grain dusty material that now makes up the soils has a lot of fertility. So the areas of the Midwest, areas in the Palouse region of Washington State, in the Ukraine, in the Pampas area in Argentina – some of these are the richest grain-growing areas in the world and these are dust-derived soils.

Scientists are able to analyze how much of a region’s soil is composed of dust by studying the mineral content in soil samples.

Oliver Chadwick: If the dust has different properties than the soil that it’s falling on, we can actually use the differences to help us determine how much dust has fallen in the past and influenced the soils.

Chadwick explained that dust globally has quartz in it. The presence of quartz in a soil can indicate a past falling of dust in the region.

August 23, 2010

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