Biophysical modeling of NO emissions from agricultural soils for use in regional chemistry-transport models

Arable soils are a significant source of nitric oxide (NO), a precursor of tropospheric ozone, and thereby contribute to ozone pollution. However, their actual impact on ozone formation is strongly related to their spatial and temporal emission patterns, which warrant high-resolution estimates. Here, we combined an agro-ecosystem model and a series of geo-referenced databases to map these sources over the 12 000 km2 administrative region surrounding Paris, France. The modeled NO emission rates from agricultural soils ranged from 1.5 to 11.1 kg NO-N/ha for the 14-month simulation period, and averaged 5.1 kg NO-N/ha. This corresponded to a mean emission factor of 1.7% for fertilizer-derived NO emissions. These emissions were characterized by a strong seasonal variability, being highest in May due to the fertilization of spring crops and lowest in wintertime. Their simulation was strongly sensitive to soil type and crop management practices, along with the resolution of the climate and soil input maps