This study was primarily initiated to understand the consistently moderate levels of nitrogen oxides (NOx) in Indian cities in spite of increasing NOx emissions. The research objective was to understand NO formation as a NOx function, and other atmospheric constituents. For this purpose, air quality monitoring was conducted at four locations in Delhi city, India (during October?November, 2000), representing various land–use patterns. The NO levels were found to be 4.9?15.1 ?gm in PM and 7.3?21.9 ?gm in PM. The high NO levels could provide a plausible explanation for moderate NOx concentration levels in Delhi city.

Keywords: nitrogen oxides, NOx emissions, atmospheric nitrate, particulate matter, PM25, PM10, sulphate, potassium, sodium, organic matter, crustal matter, migration pathways, sustainable development, sustainability, India, air quality, air pollution