Design of atmospheric composition monitor based on ultraviolet optical absorption technology

Abstract

An open path atmospheric composition monitor is designed based on ultraviolet differential absorption technology. Dark current correction and diode response correction are used to improve the detection limit and Savitzky-Golay filter is used to improve the measurement accuracy. The experimental results show that the designed system has the ability to measure NO and NO₂ in real time with reasonable accuracy. The detection limit of the system is about 0.25 ppm for NO and 0.28 ppm for NO₂. When the concentration level of the target gases is below 100 ppm, the system has good linearity and high measurement accuracy, i.e., the measurement accuracy is about 2% for NO and about 4% for NO₂. The detection limit of dark current can be improved by about 5 to 10 ppb, and the correction of diode response can improve the detection limit by around 30 ppb. Moving window average can improve the detection limit at low concentration levels but will generate more errors at higher concentration levels. Generally, the designed system meets the requirement of measuring multi-species air pollutants in real time and accurately.

Keywords

Moving Window / High Concentration Level / Open Path / High Measurement Accuracy / Move Window Average

References

[1] Committee on the Medical Effects of Air Pollutants. The Quantification of the Effects of Air Pollution on Health in the United Kingdom, 2008, London, UK, Government Department of Health

[2] SigristM. W.. Air Monitoring by Spectroscopic Techniques, 2004, London, Wiley

[3] Philip Nathaniel Martin, Measurements of Atmospheric Trace Gases Using Open Path Differential UV Absorption Spectroscopy for Urban Pollution Monitoring, Imperial College London, 2003.

[4] MellqvistJ., RosenA.. Quant. Spectrosc. Radiat. Transfer, 1995, 56: 178

[5] TangG. H.. Meas. Sci. Technol., 2009, 20: 56

[6] LeeJ. S.. Journal of the Korean Physical Society, 2002, 41: 693

[7] PundtI., MettendorfK. U.. Applied Optics, 2005, 44: 4985

[8] Li S W, Application of Kalman Filtering and Wavelet Transform in DOAS, International Conference on Information Acquisition, Weihai, China, 2006.

[9] StutzJ., PlattU.. Applied Optics, 1996, 35: 6041

[10] WangR.-b., FengH.-y.. Journal of Optoelectronics · Laser, 2010, 21: 50

[11] WangY., GuN., ChenX.-d., YuD.-y.. Journal of Optoelectronics · Laser, 2009, 20: 36

[12] ZengZ.-l., QuX.-m., LongK.-p.. Journal of Optoelectronics · Laser, 2009, 20: 42

[13] JinX., LiJ.. IEEE Transactions Geosciences and Remote Sensing, 2008, 46: 479

[14] LeveltP. F., van den OordG. H. J., DobberM. R.. IEEE Transactions Geosciences and Remote Sensing, 2006, 44: 1093