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More than 500 years ago, Leonardo da Vinci sketched what he called "la turbolenza," comparing chaotic swirls atop flowing water to curly human hair. It turns out those patterns influence myriad phenomena, from the drag on an airplane's wings and the formation of Jupiter's red spot to the rustling of tree leaves.
Now add another to the list: the eradication of a pervasive fertilizer pollutant from streams. Scientists have long known that nitrate-loaded fertilizers run off from farms and city streets into bodies of water, sometimes creating giant "dead zones" hundreds of miles downstream. The prevailing view has been that hungry algae and bacteria in the bottom sediment control how fast nitrate can be removed. But an international team of researchers thought that physics might play a role, too. Churning water serves as a sort of escalator, whirling molecules of the pollutant down to streambeds in a pattern that's a vertical version of Leonardo's long-ago sketches. The study results have important implications for managing nitrate pollution near the source, before it flows to sensitive ecosystems.Image credit: Morvarid Azizian/University of California, Irvine
