Development and deployment of a mid-cost CO2 sensor monitoring network to support atmospheric inverse modeling for quantifying urban CO2 emissions in Paris

• Published in: Atmospheric measurement techniques Vol. 17; no. 19; pp. 5821 - 5839
• Main Authors: Lian, Jinghui, Olivier, Laurent, Chariot, Mali, Lienhardt, Luc, Ramonet, Michel, Utard, Hervé, Lauvaux, Thomas, François-Marie Bréon, Broquet, Grégoire, Cucchi, Karina, Millair, Laurent, Ciais, Philippe
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 02.10.2024; European Geosciences Union; Copernicus Publications
• Subjects: Accuracy; Algorithms; Atmospheric monitoring; Calibration; Carbon dioxide; Carbon dioxide concentration; Carbon dioxide emissions; Carbon dioxide measurements; Cavity ringdown; Concentration gradient; Continental interfaces, environment; Control equipment; Cost analysis; Data analysis; Data processing; Data quality control; Effectiveness; Emission analysis; Emission inventories; Emissions; Environmental factors; Light rail transportation; Measuring instruments; Metropolitan areas; Modelling; Ocean, Atmosphere; Pollution monitoring; Power supply; Quality control; Real time; Sciences of the Universe; Sensors; Spectroscopy; Temperature requirements; Urban areas; Urban environments; Switzerland; Japan
• ISSN: 1867-1381; 1867-8548
• DOI: 10.5194/amt-17-5821-2024

To effectively monitor highly heterogeneous urban CO2 emissions using atmospheric observations, there is a need to deploy cost-effective CO2 sensors at multiple locations within the city with sufficient accuracy to capture the concentration gradients in urban environments. These dense measurements could be used as input of an atmospheric inversion system for the quantification of emissions at the sub-city scale or to separate specific sectors. Such quantification would offer valuable insights into the efficacy of local initiatives and could also identify unknown emission hotspots that require attention. Here we present the development and evaluation of a mid-cost CO2 instrument designed for continuous monitoring of atmospheric CO2 concentrations with a target accuracy of 1 ppm for hourly mean measurements. We assess the sensor sensitivity in relation to environmental factors such as humidity, pressure, temperature and CO2 signal, which leads to the development of an effective calibration algorithm. Since July 2020, eight mid-cost instruments have been installed within the city of Paris and its vicinity to provide continuous CO2 measurements, complementing the seven high-precision cavity ring-down spectroscopy (CRDS) stations that have been in operation since 2016. A data processing system, called CO2calqual, has been implemented to automatically handle data quality control, calibration and storage, which enables the management of extensive real-time CO2 measurements from the monitoring network. Colocation assessments with the high-precision instrument show that the accuracies of the eight mid-cost instruments are within the range of 1.0 to 2.4 ppm for hourly afternoon (12:00–17:00 UTC) measurements. The long-term stability issues require manual data checks and instrument maintenance. The analyses show that CO2 measurements can provide evidence for underestimations of CO2 emissions in the Paris region and a lack of several emission point sources in the emission inventory. Our study demonstrates promising prospects for integrating mid-cost measurements along with high-precision data into the subsequent atmospheric inverse modeling to improve the accuracy of quantifying the fine-scale CO2 emissions in the Paris metropolitan area.