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Fingerprinting Fugitive Dust

Finding the sources that contribute to the estimated 1000 tons of so-called “fugitive dust” entering the atmosphere each year is of increasing concern. Scientists at the US Department of Agriculture’s Agricultural Research Service (USDA-ARS) have shown that enzymes produced by soil microorganisms can be an effective tool in tracing the origin of dust. The researchers generated dust in the lab, thereby knowing its exact source, which is often difficult when collecting field data. The set of three soil enzymes used as a collective fingerprint are sensitive to climate, soil properties, and management, making them perfect candidates to profile soils over an entire region. Enzymes can also provide information about specific nutrient cycles or even organic matter decomposition. USDA-ARS soil microbiologist Veronica Acosta-Martinez (Lubbock, Texas) knew enzymes remained active in the soil for some time, but was surprised to find aryl sulfatase, typically the least predominant enzyme in these semi-arid soils, still present in the dust. “Enzymes are able to tell us about biochemical properties and the status of different soil processes”, she explains. Enzymes are the latest in a series of dust profiling tools. Past work has focused on using fatty acid methyl esters (FAME) to profile microbial communities, as well as inorganic factors to profile soil mineral and chemical characteristics. “By layering these measures together, we can get a nice idea of what the biology of a given soil looks like under different management systems”, notes USDA-ARS soil microbiologist Ann Kennedy (Pullman, Washington), who developed soil FAME profiles. By combining both organic and inorganic characteristics, the fingerprint becomes even more robust. “The more you describe a person, the easier it is to trace that person”, points out Acosta-Martinez. “We’re trying to do that with dust also.” Her research partner, soil scientist Ted Zobeck (Lubbock, Texas), is also working with others to develop additional profiling tools. Both Zobeck and Acosta-Martinez agree that enzymes alone can’t do the job. Zobeck is starting a project with Rich Arimoto of the Carlsbad Environmental Monitoring and Research Center (Carlsbad, New Mexico) to develop another tracing method, using radionuclides. “We’re the first ones looking directly at plutonium”, says Arimoto. This method has been overlooked in the past, due to the large sample size requirements and difficult analysis. According to Zobeck, “The overall goal of using these technologies is to identify types of cropping systems that have problems with dust, and to develop strategies to mitigate dust in the atmosphere”.