Nitrogéndioxid

Nitrogéndioxid (NO₂) is a toxic, reddish-brown gas with a sharp, biting odor that belongs to the family of nitrogen oxides, often referred to as NOx. It is a key air pollutant formed through the reaction of nitrogen oxides (NOx) with volatile organic compounds (VOCs) in the presence of sunlight, a process known as photochemical smog. NO₂ is also produced naturally during volcanic eruptions, lightning strikes, and forest fires, but human activities, particularly the combustion of fossil fuels in vehicles, power plants, and industrial facilities, are the primary sources of atmospheric NO₂.

Nitrogéndioxid plays a significant role in atmospheric chemistry, contributing to the formation of ground-level ozone, a harmful pollutant linked to respiratory issues and environmental damage. It also participates in the removal of methane, a potent greenhouse gas, from the atmosphere. However, its presence in high concentrations poses serious health risks, including respiratory irritation, aggravation of asthma, and increased susceptibility to lung infections. Long-term exposure has been associated with chronic respiratory diseases and cardiovascular effects.

Industrially, NO₂ is used as a nitrating agent in the production of nitric acid, which is essential for manufacturing fertilizers, explosives, and dyes. It is also employed in the synthesis of various organic compounds. Due to its hazardous nature, strict regulations govern its emission levels in both industrial and vehicular sources to protect public health and the environment.

Monitoring and controlling NO₂ levels are critical components of air quality management programs. Technologies such as catalytic converters in vehicles and selective catalytic reduction (SCR) systems in power plants help reduce NO₂ emissions. Additionally, public awareness campaigns encourage energy-efficient practices to minimize its production.