Characterization of Regional Combustion Efficiency using ΔXCO: ΔXCO2 Observed by a Portable Fourier-Transform Spectrometer at an Urban Site in Beijing

Abstract

Measurements of column-averaged dry-air mole fractions of carbon dioxide and carbon monoxide, CO 2 (XCO 2 ) and CO (XCO), were performed throughout 2019 at an urban site in Beijing using a compact Fourier Transform Spectrometer (FTS) EM27/SUN. This data set is used to assess the characteristics of combustion-related CO 2 emissions of urban Beijing by analyzing the correlated daily anomalies of XCO and XCO 2 (e.g., ΔXCO and ΔXCO 2 ). The EM27/SUN measurements were calibrated to a 125HR-FTS at the Xianghe station by an extra EM27/SUN instrument transferred between two sites. The ratio of ΔXCO over ΔXCO 2 (ΔXCO:ΔXCO 2 ) is used to estimate the combustion efficiency in the Beijing region. A high correlation coefficient (0.86) between ΔXCO and ΔXCO 2 is observed. The CO:CO 2 emission ratio estimated from inventories is higher than the observed ΔXCO:ΔXCO 2 (10.46 ± 0.11 ppb ppm −1 ) by 42.54%–101.15%, indicating an underestimation in combustion efficiency in the inventories. Daily ΔXCO:ΔXCO 2 are influenced by transportation governed by weather conditions, except for days in summer when the correlation is low due to the terrestrial biotic activity. By convolving the column footprint [ppm (µmol m −2 s −1 ) −1 ] generated by the Weather Research and Forecasting-X-Stochastic Time-Inverted Lagrangian Transport models (WRF-X-STILT) with two fossil-fuel emission inventories (the Multi-resolution Emission Inventory for China (MEIC) and the Peking University (PKU) inventory), the observed enhancements of CO 2 and CO were used to evaluate the regional emissions. The CO 2 emissions appear to be underestimated by 11% and 49% for the MEIC and PKU inventories, respectively, while CO emissions were overestimated by MEIC (30%) and PKU (35%) in the Beijing area.

Observed decade-long improvement of combustion efficiency in the Yangtze River Delta region in China

“…The measurement conducted in the Netherlands by Super et al (2017) found the mean ratios in different cities varying from 2.0-3.9 ppb ppm −1 in 2014-2015, and a ratio of 3.01-6.80 ppb ppm −1 in France from 2013 to 2014 was measured by Ammoura et al (2016). Moreover, the ∆CO/∆CO 2 ratio is in the range of 10.5-60.2 for other cities in China (Liu et al 2018, Xia et al 2020, Che et al 2022, Li et al 2022. Therefore, there is still a long way to go for China to improve its combustion efficiency.…”

“…Studies of combustion efficiency using the observed atmospheric ∆CO/∆CO 2 ratio, especially long-term ones, are even more limited in China. The majority of ∆CO/∆CO 2 ratio studies are concentrated in the areas around Beijing (Han et al 2009, Wang et al 2010, Turnbull et al 2011b, Liu et al 2018, Che et al 2022, Li et al 2022. Our study area, the Yangtze River Delta (YRD) region, covers the alluvial plains surrounding the Yangtze River estuary with an area of around 350 000 square kilometers and is home to over 240 million people.…”

“Urban Respiration” Revealed by Atmospheric O2 Measurements in an Industrial Metropolis

“…According to the MEIC inventory 45 The neglect of human respiration can cause underestimations of emission ratios (ER, e.g., ΔCO/ΔCO 2 and ΔNO x /ΔCO 2 ) derived from direct measurements since the observed CO 2 is misattributed to fossil fuel emissions. A lot of open-air observational studies impute the higher inventoryderived ER to overestimation by emission inventories, 29,30,47 while excellent agreements between local inventory CO/CO 2 ratio for the traffic sector and the observed ΔCO/ΔCO 2 ratio are obtained in a tunnel study, in which CO 2 and pollutants (CO, NO x , and VOCs) measurements were performed in a road tunnel in Paris, 48 which is close to the origin of the air mass. It is worth stressing that the neglect of human respiration may not necessarily indicate that ERs from previous observations are incorrect, and bias may also occur in ERs derived from inventory.…”

Monitoring greenhouse gases (GHGs) in China: status and perspective

“…A similar ground-based highresolution FTIR observatory at Xianghe has also passed the TCCON quality inspection and joined the TCCON network in 2021 (Yang et al, 2020c). Furthermore, a few affiliations started to operate the portable EM27/SUN FTIR spectrometers and became COCCON members in recent three years (Frey et al, 2019;Liu et al, 2022;Che et al, 2022). 4.…”