| The detection and tracing of pollutants is of great significance to the prevention and control of air pollution.Volatile organic compounds(VOCs)in the atmosphere are typical atmospheric pollutants,which have serious harm to the atmospheric environment.What is more,most VOCs also pose a great threat to human health.At present,most of the traditional atmospheric VOCs detection technologies cannot realize the online monitoring of VOCs pollutants.In this paper,the in-situ online detection and traceability of atmospheric VOCs pollutants have been studied.A set of on-line laser detection system for VOCs pollutants was developed by using laser induced breakdown spectroscopy(LIBS)and Raman spectroscopy technology.At the same time,combined with machine learning algorithm,the online source tracing research of atmospheric VOCs pollutants was carried out.Specific work includes:(1)The test of LIBS laser detection system and the research of key parameters of LIBS technology.For the LIBS experimental platform,the laser detection capability of the system was tested with zinc metal as the experimental sample.The influence of laser energy on the intensity of spectral lines and plasma temperature was also studied.The special relationship between the intensity of characteristic spectral lines and plasma temperature was found,which provided a strong guarantee for LIBS spectral research.(2)In situ laser detection of typical VOCs pollutants.The LIBS technology was used to test the spectrum of synthetic mothballs(p-dichlorobenzene)and natural mothballs(camphor),which are common in life.The characteristic spectral lines of chlorine element are detected and marked in the LIBS spectrum of synthetic mothballs.At the same time,the real-time monitoring of VOCs pollutants produced by mothballs was carried out through LIBS technology,and the online detection of VOCs pollutants was successfully realized.In addition,the Raman spectra of two VOCs(p-dichlorobenzene and camphor)were measured,and their Raman characteristic peaks and corresponding molecular vibration modes were calculated based on density functional theory(DFT),thus realizing the detection of VOCs molecular structure.(3)Real-time laser detection of sulfur compounds and their combustion products in the atmosphere.Based on LIBS experimental system,the spectrum of typical atmospheric sulfide carbon disulfide was detected.The characteristic spectra of sulfur element was clearly observed in the LIBS spectrum of gaseous carbon disulfide and its combustion products.At the same time,it was found that the intensity of spectral line in the carbon disulfide flame spectrum is much stronger than the spectra of the gas sample experiment.Further research showed that the state of the experimental sample has an impact on the LIBS detection signal.(4)On-line traceability of atmospheric VOCs pollutants and their isomers.Two VOCs pollutants(fluorobromobenzene and dibromoethane)and their isomers were tested by LIBS technology.The corresponding characteristic peaks of halogen element bromine were observed in LIBS spectrum.Then comparing the LIBS spectra of different samples,it was found that for VOCs with different molecular formulas,although the spectra are completely the same in elemental composition,there are still significant differences in the relative intensity of the spectral lines and other information.Finally,Finally,in light of the shortcomings of traditional LIBS technology in identifying isomers,the machine learning algorithm was introduced to realize the rapid identification of VOCs pollutant isomers.In this paper,based on laser spectroscopy and machine learning algorithm,a set of online detection and identification system of atmospheric VOCs pollutants and their isomers was developed,which provides experimental basis for online monitoring and tracing of VOCs pollutants in the atmospheric environment and plays a positive role in the prevention and control of atmospheric pollution. |
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