Abstract
The turbidity interference caused by suspended particles in water seriously affects the accuracy of ultraviolet-visible spectroscopy in detecting water quality chemical oxygen demand. Based on this, the application of ultraviolet-visible spectroscopy to detect water quality chemical oxygen demand usually requires physical and mathematical methods to correct the spectral baseline interference caused by turbidity. Because of the slow response speed and unstable compensation effect of traditional correction methods, this paper proposes to use a compressed sensing algorithm to perform baseline correction and achieve good results. In the experiment, we selected formazin turbidity solution and sodium oxalate standard solution and carried out the research on the algorithm of turbidity correction for detecting chemical oxygen demand of water quality by ultraviolet-visible spectroscopy. The experiment obtains the absorption spectra of different concentrations of formazine turbidity solutions and the same concentration of sodium oxalate with different turbidity standard solutions at 210∼845 nm and analyzes the nonlinear effect of absorbance on turbidity. This article uses standard solution experiments to explore the compressed sensing theory for turbidity correction, and through the correction of the absorption spectrum of the actual water sample, it verifies the feasibility of the compression theory for turbidity correction. The method effectively corrects the baseline shift or drift of the water quality ultraviolet-visible absorption spectrum caused by suspended particles, while retaining the absorption characteristics of the ultraviolet spectrum, and it can effectively improve the accuracy and accuracy of the ultraviolet-visible spectroscopy water quality chemical oxygen demand detection.
Highlights
COD is a parameter for calibrating organic pollutants in waterbodies, and it is an important index parameter for evaluating water quality [1]
Ultraviolet-visible spectroscopy is widely used in the field of water quality testing due to its fast, real-time, low maintenance cost, and no secondary pollution advantages [2]. e UV-visible spectroscopy method for detecting water quality COD has been studied by different teams. e team of Tianjin University Zhao [3] used the principle of ultraviolet spectroscopy to design and complete the online water quality COD detection instrument, which realized the real-time online detection of water quality COD. e team of Hou of Zhejiang University [4] used UV-Vis spectroscopy to integrate with other water quality detection methods to improve water quality detection performance
Tang et al [5] used a multivariate scattering correction method to effectively eliminate spectral shifts and shifts caused by turbidity scattering; Wu et al [6] studied a turbidity interference compensation Journal of Spectroscopy algorithm based on the Mie scattering theory to improve the soluble organic matter detection accuracy of the content
Summary
COD (chemical oxygen demand) is a parameter for calibrating organic pollutants in waterbodies, and it is an important index parameter for evaluating water quality [1]. Ultravioletvisible spectroscopy methods for detecting COD in water quality are gradually being updated, but in turbid waters, turbidity shifts the UV-Vis spectral curve of the water sample upward, and the shift is not proportional to the turbidity, which interferes with the direct measurement of COD using ultraviolet-visible spectroscopy [2]. The detection of water quality by ultraviolet-visible spectroscopy mostly uses multiple wavelength points or subbands for correction, which requires a large amount of experimental data support and cannot adapt to rapid changes in turbidity, and the compensation effect is unstable. This paper proposes the use of compressed sensing theory to correct the nonlinear rise of turbidity in UV-visible spectroscopy detection, select the standard solution of COD and turbidity, and analyze the influence factors of turbidity on COD in the whole UV-visible spectrum. This paper proposes the use of compressed sensing theory to correct the nonlinear rise of turbidity in UV-visible spectroscopy detection, select the standard solution of COD and turbidity, and analyze the influence factors of turbidity on COD in the whole UV-visible spectrum. e effect of turbidity on COD absorption spectrum is expressed sparsely, and the effect of turbidity on COD absorption spectrum is deducted from the original spectrum to realize turbidity correction
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