Large cities such as Los Angeles and Sydney experience huge extents of photochemical smog. Photochemical smog is a combination of pollutants that occur when pollutants such as volatile organic compounds (VOC) and nitrogen oxide react in the presence of sunlight (EPA, 2004). This reaction leads to the formation of a brown haze that is commonly seen to cover cities. In most cases, photochemical smog occurs during summer. The primary pollutants undergo a number of chemical reactions to produce secondary pollutants. One of the secondary pollutants is the Ozone, which is a harmful substance if it occurs at the ground level. The major sources of primary pollutant include vehicles, industrial activities, and man-made combustions. Cities with the highest population of vehicles that are not well serviced are known to experience high pollution rates.
Sources of photochemical smog are both natural and man-made. The naturally produced pollutants usually cover large areas, hence less effective compared to man-made pollutants, which are concentrated within the source. Most of these sources are found in cities and that explains why photochemical smog is observed in cities (EPA, 2004). Researchers have shown that smog that develops away from the source of the pollutants is more harmful. This implies that although mostly observed in cities, smog that is swept with least dispersion can greatly affect areas away from the urban centers. Both location and prevailing weather affect the formation of photochemical smog. Cities located in areas where air movement is restricted have high chances of getting smog compared to those located in open areas. Similarly, unstable atmospheres encourage air movement hence, low chance of photochemical smog and vice versa. This implies that the time taken to form smog is directly proportional to the atmospheric temperature.
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City covered with smog (Source: http://www.conserve-energy-future.com/SmogPollution.php)
Photochemical smog affects both the environment and human health. When smog exceeds the natural background level, it causes an irritation of the respiratory tract. Cities that have uncontrolled hazardous smog have recorded various ailments and even cases of death as a result of smog effects on the respiratory system (Kingston, 2008). Ailments such as lung cancer, inflammation of the lung tissue and subsequent chest aches, irritation of the eyes, colds, pneumonia, and asthma are associated with exposure to photochemical smog. Also, heavy smog in the atmosphere reduces the amount of ultra violet radiation that reaches the earth surface this implies that the amount of vitamin D available for prevention of rickets is reduced (Kingston, 2008). The most vulnerable groups include the young, old, and those with pre-existing respiratory ailments. Photochemical smog on continuous exposure may result to death as the body is overwhelmed by it effects.
The environmental effect of photochemical smog is felt by both humans and plants. Humans experience difficulty with visibility and this is likely to cause accidents. Other than this, plants get poor growth and development hence causing enormous destruction to forests and crops. Food crops such as tomatoes and vegetables get pest and disease infection when exposed to photochemical smog (Rani at al., 2011). The ozone found in the photochemical smog kills many small animal species as they find it difficult to breath in a highly polluted environment. Lastly, smog affects materials such as fabric, rubber, and leads to corrosion.
Occurrence of photochemical smog can be reduced by ensuring that the amount of secondary pollutants is significantly reduced by minimizing emission of primary pollutants. Emission of nitrogen oxide can be reduced through catalytic reduction whereby a catalytic converter is fitted in the source so that it converts it before being emitted to the atmosphere (Rani at al., 2011). Volatile organic compounds can also be reduced by using alternative sources of energy instead of petrol. As industrialization continues to grow in many parts of the world, it is important to adopt the use of technology to reduce the amount of pollutants released to the atmosphere. This will subsequently reduce chances of chemical reactions that can lead to smog.
References
EPA (2004). Photochemical Smog. Retrieved from http://www.epa.sa.gov.au/8238_info_photosmog.pdf
Kingston, P. (2008). Atmosphere: Photochemical smog . Retrieved from https://www.ehp.qld.gov.au/state-of-the-environment/report-2007/contents/atmosphere_ photochemical_smog.html/
Rani, B., Singh, U., Chuhan, A. K., Sharma, D. & Maheshwari, R. (2011). Photochemical Smog Pollution and Its Mitigation Measures. Journal of Advanced Scientific Research , 2(4), 28-33
