An Analysis of Historical and Present Dust Deposition on the Columbia Plateau

Most soils on the Columbia Plateau are derived from windblown sediments deposited over the last 15,000 years, although dust deposition has been ongoing in the region for two million years resulting in loess deposits up to 75 m (250 ft) thick. Many of the soils contain significant amounts of fine particulates and if exposed when dry can produce massive clouds of dust during high wind events that may be carried for hundreds of miles or farther in turbulent eddies (Busacca and Sweeney, 2004). The windblown dust and fallout can permeate and settle almost everywhere in the environment where people work and live. The question that needs to be addressed for scientific and policy purposes is to what extent human activities have contributed to the overall “dustiness” of the region. In other words, is the environment of the Columbia Plateau today more or less dusty compared with pre-agricultural times? The answer to this question is important from the standpoint of knowing whether farming and land development are/were contributing more or less significantly to the decline of regional air quality from dust transport and deposition than before human intervention occurred. Geologic studies in regions other than the Columbia Plateau indicate that windblown sediment fluxes were 10 to 40 times higher at the peak of the last Ice Age about 18,000 years ago than they are today (Busacca and Chandler, 2002). However, as these authors point out, wind erosion intensity is subject to cycles of climate change (over decades to centuries) and variability (over months to years) that can affect sediment transport and dustiness to a far greater extent than might occur with human intervention. Wind erosion has been an ongoing part of the climate history of the Columbia Plateau dating back to the Pleistocene Epoch, or Ice Ages (Busacca, 1991).