In-depth analysis of the basic principles of differential absorption spectroscopy

Differential absorption spectroscopy (DOAS) is an air pollution monitoring technology that relies on spectral analysis. It uses changes in the absorption of light in a specific wavelength range to infer the concentration of trace gases in the atmosphere. This article aims to comprehensively introduce the principles, technical characteristics, application scope and future development trends of differential absorption spectroscopy so that readers can have a deeper understanding of it.

I. Introduction

The accelerated development of industrialization and urbanization has led to increasing air pollution. In order to effectively monitor and control air pollution, DOAS technology has attracted much attention as an efficient and sensitive monitoring method. By measuring the absorption changes of light in a specific wavelength range in the atmosphere, DOAS technology can retrieve the concentration of trace gases in the atmosphere, providing strong support for atmospheric environment monitoring.

2. Principle of DOAS

The core principle of DOAS technology is based on Beer-Lambert's law, that is, the absorption of light is proportional to the substance concentration and optical path. When light passes through the atmosphere, trace amounts of gas absorb some of the light, weakening the light intensity. DOAS technology can infer the concentration of trace gases by measuring the intensity changes of light before and after it passes through the atmosphere.

The main steps of DOAS technology include:

Spectral collection: Use a spectrometer to collect spectral data in the atmosphere, including the spectra of incident light and transmitted light.

Spectral processing: Preprocess the collected spectral data, such as denoising, normalizing, etc., to improve the signal-to-noise ratio.

Differential spectrum calculation: select a specific wavelength range and calculate the differential spectrum of incident light and transmitted light. The differential spectrum reflects the absorption of light by trace gases in the atmosphere.

Concentration inversion: Calculate the concentration of trace gases through an inversion algorithm based on the difference spectrum and the known absorption spectrum database.

3. Technical characteristics of DOAS

DOAS technology has the following salient features:

1. High sensitivity: It can detect extremely low concentrations of trace gases in the atmosphere with high sensitivity.
2. Excellent selectivity: By selecting the appropriate wavelength range and inversion algorithm, accurate measurement of specific gases can be achieved.
3. Real-time monitoring: It can realize real-time monitoring of trace gases in the atmosphere and provide timely data for pollution control.
4. Strong anti-interference ability: Eliminate the influence of some interference factors through differential calculation and improve the accuracy of data.

4. Application fields of DOAS

DOAS technology has broad application prospects in the fields of air pollution monitoring, industrial emission monitoring, urban planning and traffic emissions, and greenhouse gas monitoring. Its main applications include:

1. Air pollution monitoring: It can monitor sulfur dioxide, nitrogen oxides, ozone and other pollutant gases to provide data support for environmental quality assessment and control.
2. Industrial emission monitoring: It can monitor harmful gases, such as volatile organic compounds, ammonia, etc., which helps enterprises reduce emissions and green production.
3. Urban planning and traffic emissions: It can assess the impact of urban planning and traffic emissions on the atmospheric environment and provide scientific basis for urban management.
4. Greenhouse gas monitoring: Greenhouse gases such as carbon dioxide, methane, etc. can be monitored, which is helpful for global climate change assessment and emission reduction policy formulation.

5. Development Trend of DOAS

In the future, the development trends of DOAS technology mainly include:

1. Miniaturization of instruments: Miniaturization and portability of equipment are achieved to facilitate on-site monitoring.
2. Simultaneous monitoring of multiple components: Simultaneous monitoring of multi-component gases to improve efficiency.
3. High-precision inversion algorithm: Use advanced inversion algorithms to improve the accuracy and stability of concentration inversion.
4. Remote sensing monitoring technology: Combined with remote sensing technology, large-scale, high-resolution air pollution monitoring can be achieved.

6. Conclusion

As an efficient and sensitive means of monitoring air pollution, DOAS technology plays an important role in environmental protection and sustainable development. With the continuous advancement of technology, DOAS technology will play a greater role in various application fields and provide more reliable data support for environmental protection.