Research on decoupling Cl2 and PM slow-changing noise in open-path UV-DOAS detection

Ultraviolet differential optical absorption spectroscopy (UV-DOAS) has been successfully applied in long-distance detection of polluting gases in atmosphere. However, the traditional DOAS method will fail if gas absorption signals are annihilated in noisy signals. To address this issue, chlorine (Cl₂) was selected as the target gas. In this paper, a DOAS experimental system for open-path detection was developed, and an algorithm for decoupling slow-changing signals of Cl₂ and particle matters (PM) was proposed. Firstly, the weight analysis of full spectrum band was carried out based on synergy interval partial least squares (Si-PLS). As a result, low SNR band, Cl₂ feature absorption band and non-feature band were matched according to their contribution. Secondly, an equivalent scattering model was established to obtain the light intensity attenuation of PM in the non-feature band. Finally, the signal decoupling was realized by deducting the PM attenuation spectrum from the absorption band of Cl₂. This study provides a new feasible method for large scale detection of Cl₂ leakage in open environments.