Which one of the following is included while estimating Air Quality Index (AQI)?

Concept

An Air Quality Index converts the measured concentration of each designated ambient-air pollutant into a sub-index. The overall AQI is determined from these pollutant sub-indices, so only species explicitly included in the framework enter the calculation.

Application

1. In India's National AQI, the designated pollutants are PM10, PM2.5, nitrogen dioxide (NO2), sulfur dioxide (SO2), carbon monoxide (CO), ozone (O3), ammonia (NH3), and lead (Pb).

2. Among the listed nitrogen oxides, NO2 is the species named in this pollutant set. N2O, N2O3, and N2O5 are chemically different compounds.

Contrast

• N2O is nitrous oxide, a distinct long-lived greenhouse gas.

• N2O3 is dinitrogen trioxide, associated with nitrous acid chemistry.

• N2O5 is dinitrogen pentoxide, the acid anhydride of nitric acid.

Cross-check

The official pollutant list uses the formula NO2, with one nitrogen atom and two oxygen atoms; that formula is different from every other offered oxide.

Therefore, the included pollutant is nitrogen dioxide (NO2).