Here is some basic understanding necessary in putting information together for urban air quality management
There are many pollutants and each of them have distinct source signatures. It is not wise to club them together. Commonly referred to pollutants are particulate matter (PM), sulfur dioxide (SO2), nitrogen oxides (NOx), carbon monoxide (CO), volatile organic compounds (VOC), ozone, and carbon dioxide (CO2)
The pollutant with most and immediate importance is PM
PM, SO2, NOx, CO, VOC, and CO2 are referred as primary pollutants and ozone as secondary pollutant (forms due to a series of chemical reactions between NOx and VOC species)
Urban emissions and urban concentrations are two distinct entities, both referring to pollution in their unique ways.
Emissions is rate at which a pollutant enters the environment – often referred in the units of grams per km, grams per hour, grams per day, or grams per kg of fuel burnt
On the other hand, concentrations is what we observe in the environment, after physical advection and chemical mixing of the emissions – often referred in the units of micro-gm per m3