the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
The realization of autonomous, aircraft-based, real-time aerosol mass spectrometry in the upper troposphere and lower stratosphere
- 1Max Planck Institute for Chemistry (Otto Hahn Institute), Particle Chemistry Department, Mainz, Germany
- 2Institute for Physics of the Atmosphere, Johannes Gutenberg University Mainz, Germany
- 3Leibniz Institute for Tropospheric Research, Leipzig, Germany
- 1Max Planck Institute for Chemistry (Otto Hahn Institute), Particle Chemistry Department, Mainz, Germany
- 2Institute for Physics of the Atmosphere, Johannes Gutenberg University Mainz, Germany
- 3Leibniz Institute for Tropospheric Research, Leipzig, Germany
Abstract. We report on the developments that enabled the field deployment of a fully-automated aerosol mass spectrometer, specially designed for high-altitude measurements on unpressurised aircraft. The merits of the two main categories of real-time aerosol mass spectrometry, i.e. (a) single particle laser desorption and ionization, and (b) continuous thermal desorption / electron impact ionization of aerosols, have been integrated into one compact apparatus with the aim to perform in-situ real-time analysis of aerosol chemical composition. The demonstrated instrument, named ERICA (European Research council Instrument for the Chemical composition of Aerosols), operated successfully aboard the high-altitude research aircraft M-55 Geophysica at altitudes up to 20 km, while being exposed to ambient conditions of very low atmospheric pressure and temperature. A primary goal of those field deployments was the in-situ study of the Asian Tropopause Aerosol Layer (ATAL). During 11 research flights, the instrument operated for more than 49 hours and collected chemical composition information of more than 150,000 single particles combined with quantitative chemical composition analysis of aerosol particle ensembles. This paper presents in detail the technical characteristics of the main constituent parts of the instrument, as well as the design considerations for its integration into the aircraft and its autonomous operation in the upper troposphere and lower stratosphere (UT/LS). Additionally, system performance data from the first field deployments of the instrument are presented and discussed, together with exemplary mass spectrometry data collected during those flights.
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Antonis Dragoneas et al.
Status: open (extended)
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RC1: 'Comment on egusphere-2022-33', Anonymous Referee #1, 21 Apr 2022
reply
Review of Dragoneas et al.
This manuscript describes the design and operation of a new mass spectrometer for aerosol analysis aboard a high-altitude aircraft. It combines a single-particle laser ionization instrument with a thermal desorption/electron impact method. The manuscript is largely clear and appropriate for publication. This is a novel instrument and a paper describing it is worth publishing.
Mostly I have minor comments below. In thinking about an instrument description manuscript it is important to consider not only if what is presented is correct but also what might be missing from the manuscript. A few things should be added:
1) For both the single particle and thermal desorption mass spectrometers, please list some dimensions and voltages. The energy of the ions is especially important since it affects detection at the MCP. The electric field across the ion source is also important for understanding the ionization processes. Simply calling it an Ionwerks spectrometer is not sufficient.
2) In a bipolar mass spectrometer, one or both detectors must be floating at high voltage. Please describe in detail how the signals are coupled to ground and what preamplifiers are used.
3) Describe the spot size for the ionization laser. A 10 mJ pulse has very different implications depending on how tightly it is focused.
4) What fraction of laser shots in the single particle instrument result in spectra? Is this a function of particle size?
5) It might be helpful to show an isotope ratio plot as a diagnostic of the linearity of the single particle spectrometer. 41K versus 39K, 54 and 56Fe, or 32 and 34S would be possibilities. There are other contributions to the peaks but a scatter plot will show a locus of points along the isotope ratio.
6) What detection limits were achieved for the thermal desorption (AMS) spectrometer?
Technical comments:
Line 61: The strong statement about quantitation is not true. SPMS instruments can be quantitative both for types of particles and components within particles:
Cornwell et al., Direct Online Mass Spectrometry Measurements of Ice Nucleating Particles at a California Coastal Site, JGR, 2019.
Cziczo, et al., Ablation, Flux, and Atmospheric Implications of Meteors Inferred from Stratospheric Aerosol, Science 291, 1772 (2001);
Froyd et al., A new method to quantify mineral dust and other aerosol species from aircraft platforms using single-particle mass spectrometry, Atmos. Meas. Tech., 12, 6209–6239, 2019
Qin et al., Comparison of Two Methods for Obtaining Quantitative Mass Concentrations from Aerosol Time-of-Flight Mass Spectrometry Measurements, Anal. Chem. 2006, 78, 6169-6178
Line 72: It is worthwhile to mention that a bipolar SPMS has been flown at lower altitudes: Pratt et al., Anal. Chem. 2009, 81, 1792–1800, Development and Characterization of an Aircraft Aerosol Time-of-Flight Mass Spectrometer
Line 105: Please mention the model of the PMT.
Line 131. Having the motor outside is potentially much cleaner than the motor inside the vacuum. Is the organic background in the AMS region lower than in a stock Aerodyne AMS?
Line 145. An AMS has previously been flown on a stratospheric balloon. Although not built by Aerodyne, it was an AMS: it included an aerodynamic lens, vaporizer, shutter for the particle beam, and a mass spectrometer. Schreiner et al., A mass spectrometer system for analysis of polar stratospheric aerosols, Review of Scientific Instruments 73, 446 (2002); https://doi.org/10.1063/1.1430732.
Line 178: I found the discussion of changing pressure confusing – the instrument is in a pressure vessel, only talked about later. Readers will think the electronics are exposed to changing pressure.
Line 203: interesting point about fire safety
Circa line 220: Given the radiative cooling, it is surprising that the instrument couldn’t just stay fairly indefinitely in low power mode with a modest external fan blowing on the pressure chamber rather than a dedicated air conditioning unit. Radiative cooling with a 10 to 20C temperature difference is hundreds of watts.
Circa line 300: I appreciate the detailed and readable description of the inlet.
Line 530: Just as a side note, it is interesting the Geophysica allowed you to have your own transmitter on the plane.
Line 665: I am convinced the gold is from contamination; you don’t need to mention space debris.
Section 4.4 first paragraph: You can probably reduce the number of times the same references are cited in successive sentences.
Figure 4: I think Figure 4 belongs in supplemental.
What supplemental material is there is appropriate and appreciated. One could also consider a digital file of the spectra shown in the figures in the manuscript.
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RC2: 'Comment on egusphere-2022-33', Anonymous Referee #2, 09 May 2022
reply
The manuscript by Dragoneas et al. entitled “The realization of autonomous, aircraft-based, real-time aerosol mass spectrometry in the upper troposphere and lower stratosphere” describes the development and technical details of a combined instrument to measure single particle (laser ablation-based) and ensemble aerosol chemical composition with a thermal desorption/electron ionization system. In total the instrument has three separate time-of-flight mass analyzers.
The description of the instrument is quite thorough and the description of the development storyline, especially during early deployments, is nice to see.
It would be nice to see more descriptions of how the SP and TD/EI mass spectrometry systems work together to provide a more complete dataset than is currently possible. Do the data sets from ERICA-LAMS and ERICA-AMS strongly educate one another in the context of UT/LS deployments? Such a demonstration would highlight the (already fair) statement that the two aerosol MS approaches are complementary. Perhaps some of this material is published in other papers on this instrument, but herein lies the confusion that can ensue without a good overview, in what is truly an instrument development paper. How does the output of this instrument and its unique configuration/construction/engineering/implementation advance science? It would be entirely germane to discuss the complementarity of the LAMS and AMS subsystems in the context of the UT/LS studies that have been indicated in the paper already. There is a short mention of this concept toward the end of the paper, but it is perhaps the most important advancement that this instrument affords from a data collection perspective (of course the high-altitude capabilities are clear).
What fraction of the particles that enter the inlet trigger an ERICA-LAMS spectrum, compared to the particle mass that is detected by the ERICA-AMS part of the instrument during these high altitude flights? Is there a notable improvement in the quality of data obtained by this instrument above and beyond that afforded by other aircraft-ready instruments? The easy answer is an unqualified “yes” – but the answer remains to be demonstrated. There could certainly be devils in the details, and it would be helpful to evaluate the limitations of the instrument in the UT/LS environment.
Overall, the paper is well written, detailed, and is certainly commensurate with the quality of AMT after consideration of the comments in this review.
Antonis Dragoneas et al.
Antonis Dragoneas et al.
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