Multi-channel wavelength-resolved Albedometer for Black Carbon Measurement – MABCaM
High-precision measurements of black carbon
Black carbon (BC), also called soot, is part of fine particulate matter pollutant (PM2.5). It warms the atmosphere by absorbing sunlight and is considered as the third most powerful climate-forcing agent in the atmosphere after CO2 and CH4 [http://www.ipcc.ch/report/ar5/wg1/]. The uncertainties associated to BC radiative forcing are, for now, larger than 70% and are mainly related to actual measurement techniques [J. Geophy. Res.: Atmos. 118 (2013) 5380]. BC has been also identified as the most harmful air pollutant in terms of its adverse impacts on human health [REVIHAAP, Technical Report, World Health Organization (2013)]. The most widely used measurement methods are filter-based online aethalometry and off line thermal optical analysis. However, such filter-based methods suffer from non linearity due to the loading of the filter, which may lead to a large measurement bias [Aerosol Sci. Technol. 42 (2008) 1033]. In this proposal, we proposed to develop a novel Black Carbone Analyzer, based on an innovative broadband optical cavity, for direct and filter-free optical measurements of wavelength-dependent optical extinction and absorption of BC and other aerosols in the major spectral region of the solar radiation (300-2000 nm). Such a broad wavelength band from the UV to the near-IR is recommended by European Environment Agency [EEA Technical report No 18/2013], which can provide additional information on particle size (due to scattering wavelength dependence by fine particles) and aerosol chemical composition (because of their wavelength selective absorptions) [J. Geophys. Res. 113 (2008) D16203].
High-finesse optical cavities, based on prism in SiO2 or CaF2, have been demonstrated with broadband wavelength region from 400 to 2000 nm (?>400 nm is limited by the available light source). Effective reflectivities of R=99.925% for prisms in CaF2 and R=99.984% for prisms in SiO2 were achieved. Cavity enhanced absorption spectroscopy of NO2, NO3, and H2O vapor were investigated to determine the achieved prism reflectivity in the spectral range from 400 nm to 1600 nm. In parallel, multi-wavelength photoacoustic spectrophone has been developed for filter-free direct measurement of BC and other aerosols' absorption.
(1) New ANR project ICAR-HO2 (2020-2024)
Based on the expertise acquired in optical cavity from the project ANR-MABCaM, we proposed to develop an innovative spectroscopic instrument for direct optical measurement of hydroperoxyl (HO2) radicals using cavity enhanced Faraday rotation spectroscopy. HO2 radicals play a major role in the atmospheric chemistry. The measurement of their concentration is vital to identify a lack in the understanding of gas phase oxidation processes. Many efforts have been made in the last decades to develop sensitive instruments for a reliable quantification of HO2 radicals, a difficult task due to their high reactivity and their subsequently low concentrations (~pptv, parts per trillion per volume). However, these instruments are most of the time very costly, bulky and request calibration and chemical conversion (leading to interferences). A compact, cost-effective, scientific instrument will be developed for an absolute, direct measurement of HO2 concentration in the atmosphere. This PRC proposal, entitled «An Innovative Compact instrument for AtmospheRic HO2 monitoring«, has been submitted to the ANR program in the «Domaine « Sciences de l’environnement », Axe 1.3 : Innovations scientifiques et technologiques pour accompagner la transition écologique«, in collaboration with the GSMA (Reims University) and the PC2A (Lille University).
(2) New PIA project SEAM (2021-2025)
Thanks to the expertise acquired in optical measurement of carbonaceous particles in the ANR-MABCaM project, a new project entitled “Smart Eco-efficient Air quality Monitoring system” (SEAM), responding to the call for projects « Economie Circulaire – Ecoefficience dans l'Industrie, l'Agriculture et l'Eau » launched by ADEME, is selected in 2021 in the framework of the PIA program on « Démonstrateurs et Territoires d’Innovation de Grande Ambition ». This new project, led by the ENVEA group with the LPCA as a partner, aims to significantly reduce the cost and environmental impact of air quality measurement stations by developing a new technology for measuring the concentration of several regulated gaseous compounds and also particles.
Scientific production related to the project MABCaM includes:
- 11 articles in international journals or book (including 2 in revision for publication)
- 1 book «Advances in Spectroscopic Monitoring of the Atmosphere«, edited by Weidong Chen (PI of the MABCaM project), Dean S. Venables, Markus W. Sigrist, ISBN: 978-0-12-815014-6, Elsevier (2021)
- 15 presentations in international conferences (including 5 invited talks)
- 1 invited talk in 6th International WORKshop on Infrared Technologies at Princeton University (2019) in USA
- 3 presentations in national conferences (including 1 invited talk)
- 2 PhD thesis funded by the HdF Region and the The Eiffel Excellence Scholarship Program, respectively.
- 1 paper in SPIE Newsroom, 12 June 2017 (DOI: 10.1117/2.1201704.006896) distributed to a large public of the Optics and Photonics community (SPIE)
Global efforts to mitigate climate change have largely focused on reducing emissions of carbon dioxide (CO2), which is responsible for 55-60% of current anthropogenic radiative forcing on warming impact. Because of its long lifetime (~ 130 years [Sonnemann 2013]) in the atmosphere, long-lasting CO2 will remain the primary driver of long-term temperature rise even if new CO2 emissions dropped to zero. A "fast-action" climate mitigation strategies is therefore strongly needed to provide more sizeable short-term benefits than CO2 reductions by reducing emission of short-lived climate pollutants (SLCPs) having atmospheric lifetimes of less than 20 years [Zaelke 2013], which would lead to short-term drops in atmospheric concentrations and hence slow climate change over the next several decades.
Black carbon (BC), one of the most important SLCPs with an atmospheric lifetime of about one week, warms the atmosphere by absorbing sunlight. BC is considered as the third most powerful climate-forcing agent in the atmosphere after CO2 and CH4 [IPCC 2013]. The uncertainties associated to BC radiative forcing are, for now, larger than 70% and are mainly related to actual measurement techniques that provide limited information to distinguish BC from other aerosols and to its optical properties [Bond 2013]. BC has been also identified as the most harmful air pollutant in terms of its adverse impacts on human health [WHO 2013].
Despite intensive efforts over the past decades, no widely accepted standard measurement method exists for the determination of BC. The most widely used methods are filter-based online aethalometry and off line thermal optical analysis. However all filter-based photometers suffer from non linearity due to the loading of the filter, which may lead to a large measurement bias [Lack 2008].
In this proposal, we propose to develop a novel Black Carbone Analyzer based on an innovative multi-channel aerosol albedometer for direct and filter-free simultaneous measurements of wavelength-dependent optical extinction and absorption of BC and other aerosols in the major spectral region of the solar radiation (300-2000 nm). This all integrated compact photonic albedometer consists of two main devices : (1) an innovative broadband optical cavity coupled to a high-sensitivity CCD spectrometer to form a BroadBand Cavity enhanced Extinctiometer (BBCE) for wavelength-resolved extinction measurements; (2) a multi-microphone enhanced Photoacoustic Absorptionmeter (PA) for wavelength-dependent integrated absorption measurements. Both devices are coupled to a single broadband high-brightness photonic light source.
The implementation of the advanced photonic technologies will significantly improve the instrument performance allowing for the determination of high quality data of BC and other aerosols, such as BC and BrC fractions, their optical parameters (single scattering Albedo and complex refractive index), derived from the measured spectral data over the full spectral regions of 300-2000 nm, with a lower uncertainty of ~ 5% (compare to 20-35% of the filter based techniques [Lack 2006]). Based on the expertise acquired in our previous work, the measurement sensitivity and precision of the proposed multi-channel BBCE-PA albedometer are expected to be ~ 0.1 Mm-1 and ~ 0.5 Mm-1, respectively, with a higher temporal resolution of approximately 1 minute (compared to 1-10 minutes requested by European Environment Agency [EEA 2013]).
After validation and characterization in laboratory, the BBCE-PA albedometer will be tested and calibrated in the Environnement S.A field test laboratory, and then validated via intensive field intercomparison with other field-established instruments on national and European observation network sites (like ORAURE and ACTRIS).
Project coordination
Weidong CHEN (Laboratoire de Physicochimie de l'Atmosphère)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
Partner
EnSA Environnement S.A
LOA Laboratoire d'Optique Atmosphérique
LPCA Laboratoire de Physicochimie de l'Atmosphère
Help of the ANR 438,552 euros
Beginning and duration of the scientific project:
December 2016
- 36 Months
