Unusually high soil nitrogen oxide emissions influence air quality in a high-temperature agricultural region

Abstract

Fertilized soils have large potential for production of soil nitrogen oxide (NO x=NO+NO 2), however these emissions are difficult to predict in high-temperature environments. Understanding these emissions may improve air quality modelling as NO x contributes to formation of tropospheric ozone (O 3), a powerful air pollutant. Here we identify the environmental and management factors that regulate soil NO x emissions in a high-temperature agricultural region of California. We also investigate whether soil NO x emissions are capable of influencing regional air quality. We report some of the highest soil NO x emissions ever observed. Emissions vary nonlinearly with fertilization, temperature and soil moisture. We find that a regional air chemistry model often underestimates soil NO x emissions and NO x at the surface and in the troposphere. Adjusting the model to match NO x observations leads to elevated tropospheric O 3. Our results suggest management can greatly reduce soil NO x emissions, thereby improving air quality.