Temperature-compensated ppb-level sulfur dioxide detection system based on fourier transform ultraviolet differential optical absorption spectrum method

Abstract

Sulfur dioxide (SO2) is a toxic gas which poses a great threat on environmental protection and human health even at low concentration. Hence, considerable attention has been devoted to achieve accurate SO2 monitoring at ppb level. In this work, we report on a ppb-level SO2 detection system via deep ultraviolet differential optical absorption spectroscopy (DUV-DOAS). A novel concentration-retrieval algorithm and spectral data-processing method were proposed to overcome the ubiquitous cross-sensitivity. The differential optical density (DOD) signal of SO2 component was identified and decomposed by FFT (fast Fourier transform) from overall DOD signal of gas mixture, followed by a reconstruction by IFFT (Inverse fast Fourier transform) after frequency domain filtering. Via this method, SO2 DOD signal was accurately extracted regardless of strong interference from NO, NO2 and NH3, indicating a remarkably enhanced SO2 selectivity. Besides, a detection limit (DL) of 4 ppb and a quantitation limit (QL) of 20 ppb were achieved, which are among the best cases of related reports thus far. Moreover, a compensation model was offered to compensate for deviations caused by gas temperature variation and thus enhance the system accuracy and adaptability.