Environmental pollution and decontamination. Process. Smog. Bullnyacadmed00109-0137. Photochemical Smog. Table of Contents (a). Introduction (b). Development of Photochemical Smog (c). Chemistry of Photochemical Smog (d). Photochemical Smog and the Okanagan Valley (a). Introduction The industrial revolution has been the central cause for the increase in pollutants in the atmosphere over the last three centuries. Major Chemical Pollutants in Photochemical Smog: Sources and Environmental Effects (b).
Certain conditions are required for the formation of photochemical smog. 1. 2. Early morning traffic increases the emissions of both nitrogen oxides and VOCs as people drive to work. 3. Precipitation can alleviate photochemical smog as the pollutants are washed out of the atmosphere with the rainfall. 4. (c). The previous section suggested that the development of photochemical smog is primarily determined by an abundance of nitrogen oxides and volatile organic compounds in the atmosphere and the presence of particular environmental conditions. Sunlight. NO + RO2 »»» NO2 + other products (d). 1.
Photochemical pollution - CITEPA. Details Last Updated on Tuesday, 11 September 2012 14:55 LPhotochemical (or photo-oxidant) pollution involves a series of complex phenomena leading to the formation of ozone (O3) and other oxidising compounds (such as hydrogen peroxide, aldehydes, peroxyacetyl nitrate or PAN) from primary pollutants, called precursors: nitrogen oxides (NOx), non-methane volatile organic compounds (NMVOC), carbon monoxide (CO) and methane (CH4) and the energy from solar ultra-violet (UV) radiation. This type of ozone-laden atmospheric pollution, often called "smog", occurs in the lower layer of the atmosphere, called the troposphere, 0 to 8-10 km above the Earth's surface. The estimated lifetime of ozone is about 22 days, but it is much shorter – only 1 or 2 days – in the layer 0 to 2 km above the Earth's surface).
Ozone and photochemical oxidants are secondary pollutants. The chemical reactions involved are complex but can be represented fairly simply. UV radiation dissociates NO2: O + O2 → O3 [b] Scale: