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Soils make smog too

California researchers say as much as 40 per cent 
of nitrogen oxides come from fertilizers

Maya Almaraz, a National Science Foundation post-doctoral fellow at UC-Davis and the study’s lead author, samples soils for NOx emissions in Palm Springs, California.

Internal combustion engines are typically blamed for smog in urban centres but researchers in California say fertilized fields need to be added to that list.

The scientists, from University of California-Davis, say they’ve found about 40 per cent of the nitrogen oxide emissions in the Golden State is coming from fertilized soils in the agriculture-rich Central Valley.

In the study, published January 31 in the journal Science Advances, the authors compared computer models with estimates collected from scientific flights over the San Joaquin Valley. Both the model and flight data suggested that between 25 and 41 per cent of NOx emissions come from soils with heavy nitrogen fertilizer applications.

Smog-forming nitrogen oxides, or NOx, are a family of air-polluting chemical compounds. They are central to the formation of ground-level ozone and contribute to adverse health effects, such as heart disease, asthma and other respiratory issues. NOx is a primary component of air pollution, which the World Health Organization estimates causes one in eight deaths worldwide.

Technologies like the catalytic converter have helped greatly reduce NOx emitted from vehicles in urban areas. But some of the state’s worst air quality problems are now in rural areas.

“We need to increase the food we’re making,” said lead author Maya Almaraz, a National Science Foundation post-doctoral. “We need to do it on the land we have. But we need to do it using improved techniques.”

The study suggests potential solutions for reducing NOx soil emissions, primarily through different forms of fertilizer management

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