Determination of NO, NO₂ and NOₓ Emissions: Methods and Importance

What are the Methods of Determination of Flue Gas Emissions?

Determination of Nitrogen Monoxide (NO), Nitrogen Dioxide (NO₂) and Nitrogen Oxide (NOₓ) Emissions

Oxides of nitrogen (NOₓ) is the common name for nitrogen monoxide (NO) and nitrogen dioxide (NO₂) gases. These gases are released from the combustion of fossil fuels and contribute significantly to air pollution. Measurement of NOₓ emissions is a critical process for controlling compliance with environmental health and air quality standards.

Why are NOₓ emissions important?

NOₓ emissions are at the root of environmental problems such as air pollution, acid rain, ozone depletion and global warming. The main sources of NOₓ emissions, especially in urbanized areas, are processes such as traffic, industrial activities and energy production. NOₓ emissions are regularly measured and controlled because it is a gas that can damage the respiratory system and poses a direct threat to human health.

Nitrogen oxides (NOx) are an interesting and important family of chemical compounds that pollute the air. Nitrogen oxides are a group of seven compounds. Among them, nitrogen dioxide (NO2) is the most common form of nitrogen oxides in the atmosphere produced by human activities. Nitrogen dioxide is not only a significant air pollutant in its own right, but also reacts in the atmosphere to form ozone and acid rain, which is present in ambient air.

Ozone, which forms the upper layer of the atmosphere, protects the earth from ionizing radiation from the sun. The US Environmental Protection Agency (EPA) has set standards for these ozone and nitrogen dioxides. It defines air quality levels to protect public health and public welfare from known or anticipated adverse effects of pollution. The limit value for nitrogen dioxide is 0.053 parts per million.

Nitrogen oxides are the most abundant nitrogen oxides in the air. Emissions of nitrogen oxides from combustion are mainly in the form of nitrogen monoxide. Except for nitrogen monoxide from soil, lightning and natural fires, nitrogen oxides are largely produced by human activity. Biogenic sources generally account for about 10 percent of total nitrogen monoxide emissions. Motor vehicles contribute about half of the nitrogen oxides emitted. Power plant boilers produce about 40 percent of emissions of nitrogen oxides from stationary sources.

Nitrogen dioxide is found in the atmosphere and in acid rain. When dissolved in water, it produces nitric acid. The existing ozone concentration is the product of both nitrous oxide and volatile organic compound (VOC) pollution.

Methods for the Determination of NOₓ Emissions

1. Refractive Infrared (IR) Spectroscopy: Measures the interaction of NOₓ gases with infrared light. IR spectroscopy is a highly effective method for determining emissions based on the molecular structure of gases.
2. Chemiluminescence Detection (CLD): CLD is a sensitive method for measuring nitrogen monoxide and nitrogen dioxide. NO gas reacts with ozone and emits light energy. This emitted light is measured by detectors to determine the NO concentration.
3. Gas Chromatography (GC): Gas chromatography is a method that separates and analyzes the composition of NOₓ emissions. GC provides accurate and detailed analysis of gas mixtures such as NOₓ.
4. Electrochemical Sensors: Used to detect NOₓ gases, electrochemical sensors measure emissions from combustion processes. They are preferred for instant measurements in the field due to their low cost and portability.
5. UV-Fluorescence Method: NO₂ gases emit fluorescence under ultraviolet (UV) rays. In this method, the amount of light emitted is used as an indicator of NO₂ concentration. The UV-fluorescence method is effective for NO₂ measurements at low concentrations.

Nanolab Laboratories Group continues to provide services within the scope of Determination of Nitrogen Monoxide (NO), Nitrogen Dioxide (NO₂) and NOₓ Emissions. We also provide services in Environmental Analysis.

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