Air quality management commonly aims to mitigate nitrogen oxide (NOx) emissions from combustion, reducing ozone (O3) and particulate matter (PM) pollution. Despite such ongoing efforts, regulations have recently proven ineffective in rural areas like the Salton Sea Air Basin of Southern California, which routinely violates O3 and PM air quality standards. … We conducted a source apportionment of NOx (an important precursor to both O3 and PM) using nitrogen stable isotopes of ambient NO2, which revealed a significant contribution from soil-emitted NOx to the regional budget. …. Inorganic fertilizer amendments are not regulated, leading to over-application and nutrient leaching into the surrounding environment, such as the groundwater, local water sources, atmosphere, and soils24,28. The objective of this work is to understand the implications of agricultural practices in arid agroecosystems of the SSAB on regional air quality.