Nitrogen Dioxide Monitoring
Nitrogen dioxide is a pollutant gas that can be found in the air in both urban and rural environments. It is created as a by-product of combustion processes, as well as certain industrial processes, such as the production of cement, fertilizer and some metal ores. Nitrogen dioxide is a colorless and mostly odorless gas, but at high concentrations it can have an irritating odor. Overall, it is considered to be an air pollutant because it can cause respiratory disorders, especially in those with existing conditions, and it can aggravate the effects of ozone, sulfur dioxide, and other air pollutants.
Monitoring the concentrations of nitrogen dioxide in a given area is an important part of air quality control. The EPA, as well as state and local regulatory agencies, closely monitor the levels of nitrogen dioxide for compliance with the National Ambient Air Quality Standards and other air quality laws. Nitrogen dioxide monitoring is typically conducted using either chemiluminescence or ultraviolet fluorescence technology, and is sometimes combined with carbon monoxide monitoring.
In chemiluminescence, measurement is done by oxidizing the nitrogen dioxide with ozone. The nitrogen dioxide is then mixed with a solution of sodium hydroxide and potassium hydroxide in a reaction chamber. As the reaction proceeds, light is produced and the light intensity is measured to determine the concentration of nitrogen dioxide.
In ultraviolet fluorescence, the ultraviolet radiation produced by a lamp is passed through the nitrogen dioxide. The radiation is then absorbed by the nitrogen dioxide molecules, which then emit energy at a different wavelength. This energy is measured and used to calculate the concentration of nitrogen dioxide in the sample.
Both of these methods have their advantages and drawbacks. The chemiluminescence method is more accurate, but is also more expensive and it requires more maintenance than the ultraviolet fluorescent method. Additionally, the chemiluminescence method can only detect nitrogen dioxide in concentrations over 0.55 parts per million (ppm). On the other hand, the ultraviolet fluorescent method is much less expensive and is able to detect concentrations above 0.05 ppm. It is also simpler to maintain, although it is slightly less accurate than the chemiluminescence method.
In addition to the traditional techniques for measuring nitrogen dioxide, there are also other methods available. These techniques include laser-induced breakdown spectroscopy, mass spectrometry and absorption spectroscopy. The availability of these methods depends on the instruments used, as some may not be suitable for measuring nitrogen dioxide in certain situations.
Nitrogen dioxide monitoring is essential in order to ensure compliance with air quality regulations, limit public health risks, and protect the environment from the harmful impacts of this pollutant. For these reasons, it is important to make sure that monitoring of nitrogen dioxide is performed regularly, using a reliable equipment and techniques. Monitoring can help to identify the sources of nitrogen dioxide emissions, which can then be addressed to reduce emissions and thus improve air quality.
