nitrogenoxid

Nitrogen oxides, collectively referred to as NOx, are reactive nitrogen-oxygen compounds produced by the high-temperature oxidation of nitrogen and by atmospheric chemistry. The most important species are nitric oxide (NO) and nitrogen dioxide (NO2). In certain conditions, related oxides such as dinitrogen trioxide (N2O3), dinitrogen tetroxide (N2O4), and dinitrogen pentoxide (N2O5) can form and interconvert with NO and NO2.

Natural sources include lightning and microbial processes in soils and water. Human activities are major contributors, especially combustion of fossil fuels in vehicles, power plants, and industrial processes. NOx formation increases with engine load, fuel quality, and temperature, and it is also produced in some chemical manufacturing processes.

NOx influence air quality and climate through several mechanisms. NO2 is a reddish-brown gas that contributes to urban smog and can irritate the respiratory system. NOx participate in photochemical reactions that generate ozone at ground level, a key component of smog. They also contribute to acid rain, nutrient pollution, and atmospheric deposition, affecting ecosystems and visibility.

Industrial use centers on the production of nitric acid and various organic synthesis pathways, where NOx serve as reagents or intermediates. In environmental management, NOx are controlled to reduce air pollution, using technologies such as catalytic converters, low-sulfur fuels, and selective catalytic reduction. Regulatory frameworks commonly set emission limits and monitoring requirements to limit their environmental and health impacts.