Remote Sensing Of CO₂ Column Concentration And Emission Flux In Urban Areas Based On Ground-based FTIR

Carbon dioxide（CO₂）in the atmosphere,as the primary anthropogenic greenhouse gas,has a significant impact on the Earth’s climate and human living environment.Therefore,monitoring the source and sink of CO₂is particularly important.Fourier transform infrared spectroscopy（FTIR）is an important method for high-precision detection of greenhouse gas column concentrations in the atmosphere.It has advantages such as continuous observation,insensitivity to vertical gas transmission,and minimal impact from ground source emissions.Therefore,using FTIR technology to observe the column concentration and emission flux of CO₂in the atmosphere is of great significance for mastering carbon emissions in key urban areas and monitoring carbon source and sink information.This article is based on ground-based Fourier transform infrared spectroscopy technology to carry out remote sensing monitoring of CO₂column concentration in key urban areas and calculate its emission flux.Based on the solar absorption spectrum observed by a portable FTIR spectrometer（EM27/SUN）,an inversion algorithm for observing CO₂in the atmosphere was studied;Verify the accuracy of the observation data of the portable FTIR spectrometer using a ground-based high-resolution FTIR spectrometer,and monitor the instrument linetype;Based on a ground-based portable FTIR spectrometer,the CO₂column concentration data of Chongqing Atmospheric Environment Comprehensive Observation Super Station in August 2022 were obtained,and the temporal variation of CO₂column concentration in that month was analyzed;Studied the method of comparing ground-based observation data with satellite remote sensing data,and compared and analyzed it with OCO-2 satellite data;Combined with HYSPLT backward trajectory software,potential sources and transport trajectories of CO₂gas masses centered around observation stations were analyzed.Finally,based on the portable FTIR spectrometer,a CO₂mobile vehicle monitoring experiment was carried out around a power plant in Hefei,and the CO₂column concentration distribution around the power plant was successfully obtained,and the CO₂emission flux was calculated;Compare the experimental results with publicly available carbon emissions data from power plants to verify the accuracy of the observation results.Firstly,the reliability and data accuracy of the portable FTIR spectrometer were tested.Correlation analysis was conducted on the daily average concentration of carbon dioxide（XCO₂）observed by portable FTIR spectrometers and ground-based high-resolution FTIR spectrometers.The results showed that the XCO₂correlation coefficient R of the two synchronous observations was 0.97,indicating a high degree of correlation.Secondly,in the laboratory’s instrument line monitoring,it was found that the average amplitude modulation efficiency of the spectrometer was 0.99,with a standard deviation of 0.005,and the average loss of amplitude modulation efficiency was 0.01（1%）,much lower than 10%.The average measurement value of phase error is 0.003 rad,which is much less than 0.02 rad.The amplitude modulation efficiency loss and phase error value of the spectrometer are very small,indicating that the instrument linetype has reached the ideal linetype for inverting greenhouse gas data,which can ensure the reliability of subsequent field experiments.In the one-month CO₂column concentration observation results of the Chongqing Atmospheric Environment Comprehensive Observation Super Station,it was found that the CO₂column concentration showed certain fluctuations throughout the entire observation period,with measured values ranging from 412.7 to 418 ppm.Starting from August 2nd,the CO₂column concentration gradually increased and reached its highest value on August 6th;Subsequently,it gradually declined until reaching its lowest point on August 17th,and then showed a fluctuating upward trend.We studied the method of comparing ground-based remote sensing and satellite remote sensing data.By comparing the measured XCO₂with OCO-2 satellite telemetry results,we found that the correlation coefficient between them was 0.61,indicating a moderate correlation.Finally,in the cluster analysis of air masses and potential CO₂source analysis,it was found that the concentration contribution was mainly distributed in a sheet-like pattern,from high to low,in the southwestern part of Chongqing,the southeastern part of Guizhou Province,the southeastern part of Sichuan Province,the border between western Hunan Province and Guizhou Province,and the border area between Guangxi Zhuang Autonomous Region and Guizhou Province.Among them,the air masses from the southeast direction of Guizhou Province are the most affected by the southeast monsoon,accounting for 52.02%.Due to the influence of southerly winds,the air masses from the border between Guizhou Province and Guangxi Zhuang Autonomous Region account for 35.08%,while the air masses from the northeast of Sichuan Province only account for 12.9%.However,the CO₂concentration of the air masses in this direction is slightly higher.Finally,a mobile vehicle experiment was conducted on a power generation company in Hefei using a portable FTIR spectrometer to monitor its CO₂emissions,obtain the distribution of CO₂around the area,and analyze it in conjunction with meteorological data.Studying the algorithm for measuring greenhouse gas emissions flux on mobile vehicles,it was found that the CO₂emissions flux from the power plant on September 17,2021 was 135.75 kg/s,and on September 18,it was 140.36kg/s.The data matches the CO₂emissions（approximately 137.5kg of carbon dioxide per second）provided by the power plant in its annual report.Through in-depth research on the method of detecting atmospheric CO₂column concentration using ground-based FTIR technology,the monitoring of key urban areas and the monitoring of CO₂emission values from power plant emission sources have been completed.It has been demonstrated that ground-based FTIR technology has the ability to accurately and high-precision observe CO₂in the atmosphere,providing ground-based verification for satellite observations and valuable observation results for studying the spatiotemporal distribution of CO₂and emissions in key urban areas.