icon alerte

 

Fact file

Nitrogen oxides (NOx) are made up of a mixture of nitric oxide (NO) and nitrogen dioxide (NO2). They are produced during combustion phenomena by the high-temperature oxidation of nitrogen (N2) in the air and, to a lesser extent, of the nitrogen contained in fuels. The majority of these emissions come in the form of nitric oxide (NO), which has a short lifespan in the atmosphere and can oxidise to nitrogen dioxide (NO2). Monoxide and nitrogen dioxide thus form a dynamic equilibrium and that is why they are studied together.

NO2 is used for the calculation of the Belgian air quality index, BelAQI

 

Origin of pollution

Anthropogenic emissions come mainly from combustion processes and the main sources of nitrogen oxides are energy-intensive sectors. In Wallonia, the transport sector is responsible for half of anthropogenic emissions, compared with approximately 30% for the industrial sector. In urban areas, where traffic emissions are predominant, the concentrations of nitrogen oxides in the air can even be considered to be characteristic of traffic density and conditions.

 

Health effects

At the concentrations usually found in air, nitric oxide is not considered toxic.

Nitrogen dioxide is an oxidant and an irritant to the respiratory tract, especially the bronchi. People suffering from asthma or chronic respiratory pathologies form the at-risk population when it comes to this pollutant. In children, it increases sensitivity to pathogens.

Epidemiological studies have shown that an increase in nitrogen dioxide concentrations was accompanied in particular by an increase in the number of deaths from cardiovascular causes.

In addition to its direct impact on health, nitrogen dioxide is a precursor to ozone (see ozone fact file). In addition, in the atmosphere, it can turn into nitric acid and react with ammonia NH3 to form secondary aerosols.

 

Environmental impact

Nitrogen oxides participate in the acidification of the environment and their fallout promotes environmental eutrophication. Indeed, the nitrogen supply exceeds the absorption capacity of certain ecosystems and creates an imbalance by favouring certain species with, consequently, an exhaustion of biodiversity.

As a precursor to ozone, nitrogen dioxide has an indirect impact, through the formation of ozone, on crop yields.

 

The situation in Wallonia

Nitrogen oxides participate in the acidification of the environment and their fallout promotes environmental eutrophication. Indeed, the nitrogen supply exceeds the absorption capacity of certain ecosystems and creates an imbalance by favouring certain species with, consequently, an exhaustion of biodiversity.

As a precursor to ozone, nitrogen dioxide has an indirect impact, through the formation of ozone, on crop yields.

 

Measurement methods

Nitric oxides are measured continuously and in real time using monitors using the principle of chemiluminescence.

Find out more :http://www.awac.be/index.php/2017-03-28-09-19-01/emission-de-nox

The protection of your data is our priority. By continuing to browse our site, you accept the use of cookies which enable us to provide you with quality data, ensure the smooth running of the website and measure its audience.
I understand