Which of the following is not gaseous air pollutant?

Air pollutants are broadly classified into gaseous and particulate matter. Oxides of sulphur (SOx) and oxides of nitrogen (NOx) are primary gaseous pollutants emitted from industrial processes and fuel combustion [3]. Hydrocarbons, often referred to as Volatile Organic Compounds (VOCs), are also classified as organic gases [5]. In contrast, smoke is defined as a form of particulate matter consisting of tiny solid or liquid particles suspended in the atmosphere [4]. While gaseous pollutants exist in a molecular state, smoke is a visible aerosol composed of soot and other particulates resulting from incomplete combustion [4]. Therefore, smoke is categorized as a particulate pollutant rather than a gaseous one [4].

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > 20.1. Composition of The Earth's Atmosphere > p. 270
2. [3] Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 17: Contemporary Issues > 1. Air Pollution > p. 38
3. [5] https://www.cdc.gov/air-quality/pollutants/index.html
4. [2] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > iii) Gaseous Waste > p. 25
5. [4] https://afdc.energy.gov/vehicles/emissions-pollutants