Retrieval of SO₂ concentration from UV camera image based on immuneoassay of light dilution effect

SO₂ UV camera has rapidly become integral in remote sensing applications of polluted gases by virtue of its simple structure, high spatiotemporal resolution, and extensive monitoring range. However, as the monitoring distance increases, atmospheric aerosol scattering induces light dilution effects, which significantly compromise measurement accuracy, and conventional calibration methods face limitations in effectively compensating for light dilution without incurring high instrumentation costs. To overcome these challenges, this paper proposes a light dilution effect-immune calibration method (LDECM) tailored for dual-channel UV camera systems. Instead of measuring the distance and visibility from the UV camera to the emission source, the method utilizes only the raw images acquired by the two channels of the UV camera to retrieve the image of the SO₂ column concentration, which is not affected by the light dilution effect. Results from simulations and field experiments show that this method effectively eliminates the influence of light dilution and distance, and compared with the differential optical absorption spectroscopy (DOAS) calibration method, the retrieval results are very close, with an average error reduction of approximately 5.5%. Additionally, emission rates derived from the SO₂ column amount data produced by both methods show a goodness of fit of 0.95, underscoring the accuracy and reliability of the proposed approach. The proposed light dilution effect-immune calibration method offers operational simplicity and strong spectral adaptability, providing an effective means for remote sensing monitoring of SO₂ gas.