Mass spectrometry and climate science. Part II

by Roland Hirsch

New technologies in mass spectrometry are advancing research in climate science

This is the second of a two-part posting based on a presentation prepared for the American Chemical Society’s National Meeting in March 2020. The meeting was cancelled, but the key points in that presentation (plus a couple of added examples based on new publications of relevant research) are in these two posts.

Reconstructing impacts of short term weather events

The first example in this part on the application of mass spectrometry to understanding recent climate and weather will look at a method used to obtain hourly to daily resolution short term weather events in the near past. There are a variety of ways of reconstructing past climate changes, but most of them do not have sufficient time resolution to identify short term weather events, such as extreme storms or heat or cold periods (“weather-timescale extreme events (WEEs …)”]). Yet the frequency and impact of such events could help developing better knowledge of past climate and its influencers.

A new study analyzed a marine bivalve in the South China Sea elemental ratios by NanoSIMS (Nano Secondary Ion Mass Spectrometry) to obtain daily to hourly resolution proxy records and confirm them using known daily weather for the location (Figure 7). The technique could be applied to fossil shells from the distant past to obtain similar weather information. The authors studied giant clam shells using the NanoSIMS technology to determine the iron/calcium (Fe/Ca) and strontium/calcium (Sr/Ca) ratios in different layers of the shells and were able to confirm the presence of nearby tropical cyclones (Figure 8) and also the impact of cold weather surges on the shells (Figure 9). [i]

Figure 7: D is the layers of the shell by autofluorescence; E and F are the NanoSIMS elemental ratios for indicated shell segments

Figure 8: Nearby tropical cyclones recorded in hourly Fe/Ca of Giant Clam shell obtained by NanoSIMS

Figure 9: Winter cold surges recorded in daily growth rate (green) and hourly Fe/Ca of Giant Clam shell (red)

Studying how aerosols impact the atmosphere

Understanding the makeup of different parts of the atmosphere and how they change is a major aspect of climate science, in addition to the study of air pollution and health impacts. Mass spectrometry plays a key role in this area (Figure 10).[ii]


Figure 10: Schematic of atmospheric chemistry analytical methods

Why are aerosols important for understanding climate?Couds reflect incoming solar radiation back into space and also absorb outgoing radiation, keeping that energy inside the Earth’s atmosphere. Aerosols are a key part of cloud formation, and the chemistry of aerosol particles influences the type of cloud they form. Thus aerosols have a major influence on the greenhouse effect, as well as on other aspects of weather and climate.

Many analytical techniques are used to analyze aerosol particles and to follow their behavior in the atmosphere. This essay is focused on mass spectrometry (MS), and several recently-published examples will showcase how the different types of MS can address specific aspects of aerosol chemistry:

  • Extractive Electrospray Ionization (EESI) to study metals in aerosols
  • EESI — Orbitrap MS to study organic compounds in aerosols
  • LC-EESI-TOF MS/MS to identify organic compound functional groups in aerosols (TOF means Time Of Flight)
  • TOF Chemical Ionization MS to follow reactions of sulfur-containing compounds in the atmosphere
  • Aerosol time-of-flight mass spectrometry (ATOFMS) and chemical ionization mass spectrometry (CIMS) to study formation of atmospheric chlorine-containing compounds due to rock salt aerosol particles

These are selected from many publications in this area to show the impact of mass spectrometry on the study of aerosols, but are not intended to cover all aspects of the field!

Also, while this essay is focused on mass spectrometric technologies and their applications in climate science, I hope that the limited details about these technologies do not get in the way of understanding their significance for climate research.

* * * * *

Metals are often found in aerosols, but are hard to measure accurately when the aerosols have to be transported to a laboratory. A new approach using Extractive Electrospray Ionization (EESI) with a portable Time-of-Flight MS system has enabled field measurements.[iv]

Figure 12: (a) Experimental mass spectrum of a mixture of zinc acetate, cadmium chloride hydrate, zinc acetate, cerium(III) acetate tetrahydrate, and barium acetate obtained with the EESI-TOF-MS. (b) Time series of an external mixture of lithium hydroxide monohydrate, lead acetate trihydrate, cadmium chloride hydrate, and cerium(III) acetate hydrate

* * * * *

Organic compounds in aerosols (organic aerosols or OAs) can have a substantial influence on how they develop and impact the atmosphere as they travel through it. It is difficult to characterize the many components of the OAs, especially since they are constantly changing as they travel in the atmosphere.

New mass spectrometric technology is making it possible to improve the accuracy and completeness of atmospheric OA measurements in real time. This enables measurement of secondary organic aerosols (SOAs) formed in atmospheric reactions as they happen. Extractive Electrospray Ionization combined with ultra high resolution Orbitrap enables measurements of OAs at relevant concentrations and a sufficient range of mass to cover the great variety of sizes of the OAs. [v] Figures 13 and 14 show examples of studies of a common OA, α-pinene.[vi]

Figure 13 (left): Mass spectra for unoxidized α-pinene (top), α-pinene oxidized at different concentrations (2nd and 3rd), and limonene oxidation products (bottom)


Figure 14 (right): SOAs produced from these two compounds (top and middle) and measurements of ambient air in summer

* * * * *

Functional groups are active sites in organic molecules, for example the aromatic ring that makes up benzene and is in the many compounds that include its ring, or the -OH functional group that is present in alcohols and sugars. Organic compounds with various functional groups are a significant component of aerosols, sourced, for instance, in atmospheric particulate matter. A new approach uses LC-ESI-TOF MS/MS to quantify organic aerosol functional groups in environmental samples. The scientists used this technique to study organic functional groups in air in Atlanta, Georgia, and the Long Island Sound, New York. An example of their results is shown in Figure 15.[vii]

Figure 15: Organic functional groups in aerosol compounds in two locations. The upper chart for each location expands the main chart to show the low concentration functional groups more clearly.

* * * * *

Dimethyl sulfide (DMS) is produced by phytoplankton in the oceans and is quite volatile. DMS is readily oxidized to form sulfur dioxide and sulfuric acid, among many products found in the atmosphere. There are several mechanisms for the oxidation and understanding them is important for modeling formation of aerosols and their climate impacts. A new study has used Time of Flight Chemical Ionization Mass Spectrometry to study sulfur compounds in air. The study was carried out in NASA aircraft missions that covered the air above the open Atlantic and Pacific oceans from 80º N to 85º S.

Hydroperoxylmethyl thioformate (HPMTF) was discovered to be a significant portion of the atmospheric sulfur and to play a major role in aerosol formation. The authors conclude: “Observationally constrained model results show that more than 30% of oceanic DMS emitted to the atmosphere forms HPMTF. Coincident particle measurements suggest a strong link between HPMTF concentration and new particle formation and growth. Analyses of these observations show that HPMTF chemistry must be included in atmospheric models to improve representation of key linkages between the biogeochemistry of the ocean, marine aerosol formation and growth, and their combined effects on climate.” [viii]

The paper includes a chart showing how the new information fits into the role of sulfur in aerosols, and the uncertainties in HPMTF chemistry in the air that need to be addressed in further research (Figure 16).

Figure 16: On the left: The basic mechanism of HPMTF formation. On the right: Concentrations observed using the NASA Atmospheric Tomography (ATom) mission, which used the Time of Flight Chemical Ionization Mass Spectrometry instrument

* * * * *

Atmospheric chlorine-containing aerosol particles are continually generated by sea spray. However, such particles are also observed far inland, especially in winter, due to use of rock salt and salt solutions to deice roads and sidewalks. More than 20 million tons of salt are used for this purpose in a typical winter in the United States alone. The chlorine in salt-containing aerosols leads to formation of nitryl chloride (ClNO2), which is a significant concern for health.

Just-published research used Aerosol Time-of-Flight Mass Spectrometry to measure the size and chemical composition of individual aerosol particles and used Chemical Ionization Mass Spectrometry to measure chemical compounds in the air in a winter period (February 17-18 and March 7-8) in an inland location adjacent to a roadway and sidewalk on which road salt and brine were applied during the study period.[ix] Their results are shown in Figure 17. The amount of ClNO2 is very low during the daytime as sunlight breaks the molecule into its reactive components, and increases overnight. The reactive components affect the levels of many atmospheric compounds and particulate matter, so having better experimental information is helpful in understanding this system.

Figure 17: On the left: Schematic diagram of the previous bulk method and the new single-particle method for measuring formation of nitryl chloride (ClNO2) from dinitrogen pentoxide (N2O5). On the right: Estimates using the bulk model (gray line) and using the single particle model (green line) and experimental measurements of ClNO2 using the new method (black line). Dashed blue lines represent modeled ClNO2 production from road salt only.

* * * * *

Biosketch Roland Hirsch has served the field of analytical chemistry in a 52-year career that spans teaching, research, and leadership at Seton Hall University, and 33 years of government service at the National Institutes of Health and the U.S. Department of Energy. Roland has been a leader of the ACS Division of Analytical Chemistry, as Councilor for 25 years, as Division Secretary for 4 years, Chair-Elect, Program Chair, and Chair, and as its Web Editor for 22 years. Roland organized the 50th-anniversary celebration of the Division and 25 years later, wrote the definitive history of the first 75 years of the Division, published in Analytical Chemistry in 2013. Roland has also been active in ACS Governance, including Chair of the Committee on International Activities, Secretary of the Committee on Nominations and Elections, Member of the Committee on Divisional Activities, Senior Chemists Task Force, Committee on Committees, and Liaison to the ACS Committee on Professional Training.

Based on a presentation prepared for the American Chemical Society National Meeting in Philadelphia in March 2020. It was to have been in the Division of Analytical Chemistry’s session “Advances in Mass Spectrometry”. The meeting was canceled, but this presentation was revised and made available on the web site for the meeting:

If you cannot access the presentation, please go to where you can obtain an ACS ID at no charge. It should allow you to sign in to view the presentation.


[i] H. Yan, et al., “Extreme weather events recorded by daily to hourly resolution biogeochemical proxies of marine giant clam shells”, PNAS (2020), and

[ii] P. Forbes, “Atmospheric Chemistry Analysis: A Review”, Anal. Chem. (2020), 92, 455-472.


[iv] S. Giannoukos, et al., “Real-Time Detection of Aerosol Metals Using Online Extractive Electrospray Ionization Mass Spectrometry”, Anal. Chem. (2020) 92, 1316−1325

[v] C.P. Lee, et al., “Online aerosol chemical characterization by extractive electrospray ionization – ultrahigh-resolution mass spectrometry (EESI-Orbitrap)” Envir. Sci. Technol., (2020), 54, 3871-3880


[vii] J.C. Ditto, T. Joo, J.H. Slade, P.B. Shepson, N.L. Ng, and D.R. Gentner, “Nontargeted Tandem Mass Spectrometry Analysis Reveals Diversity and Variability in Aerosol Functional Groups across Multiple Sites, Seasons, and Times of Day”, Environ. Sci. Technol. Lett. 2020, 7, 2, 60-69

[viii] P.R. Veres, et al., “Global airborne sampling reveals a previously unobserved dimethyl sulfide oxidation Mechanism in the marine atmosphere”, PNAS (2020), 117 (9) 4505-4510

[ix] S.M. McNamara, et al., “Observation of Road Salt Aerosol Driving Inland Wintertime Atmospheric Chlorine Chemistry”. ACS Central Science (2020), 6, 684-694.





9 responses to “Mass spectrometry and climate science. Part II

  1. Good call – IR and gamma ray spectroscopy has been a powerful method used to analyze particulate matter surrounding remote planetary bodies.

  2. Good to hear from you Roland. The short time frame work is fascinating. Almost makes me wish I had gone into analytical chemistry!

  3. Pingback: Mass spectrometry and weather science. Phase II – Daily News

  4. Progress does not stand still and it is excellent that new technologies in mass spectrometry advance research in the field of climatology. With the advent of complex modeling of the Earth system, a seamless approach to weather and climate forecasting, a more successful and reliable climate forecasting, and growing needs for a wider range of climate projections from global to local, measures to improve stability, adaptation and mitigation of the effects of WCRP are more in demand than ever .

  5. Mass Spec is a core methodology for palaeo climate reconstruction. It is one of the most important technologies in climate science for that reason. I work for the company Bruker that make some mass spectrometers, although I’m not an expert since I’m in a different part of the company working in xray tomography. So I’m grateful to Roland Hirsch for these valuable articles.

    Here’s an example. There have been three major glaciations over the last half billion years (the Phanerozoic) during which multicellular life has existed. They are the end-Ordovician, the end-Carboniferous and the current Pleistocene. After climate scientists (surviving ones at least) subscribed to the interpretation that CO2 dominantly controls global temperature, the Ordovician glaciation became problematic because it is a deep glaciation that occurred while atmospheric CO2 was high.

    Not only high – atmospheric CO2 increased in concentration as the end-Ordovician glaciation spread.

    Mass spectroscopy, specifically the measurement of carbon 12-13 isotope ratios, is central to reconstructing what exactly happened during this apparently anamalous glaciation.

    This study by Seth Young and colleagues, scientists from the USA, Canada and Estonia, performed an accurate and controlled reconstruction of carbon geochemistry over the Ordovician-Silurian ice age by looking at the 12/13 carbon ratio in both organic carbon and inorganic carbonate.

    Click to access Did_changes_in_atmospheric_CO2_coincide_20160504-5750-17f7bcu.pdf

    Here’s their mass-spec methodology:

    Powders for δ13Ccarb analyses were first roasted in a vacuum oven
    at 200 °C for 1 h to remove water and volatile organic contaminants.
    Then, 10–50 μg of carbonate was reacted at 70 °C with 3–5 drops of
    anhydrous phosphoric acid for 180–300 s. Stable isotope values were
    obtained using a Finnigan Kiel-III carbonate preparation device
    directly coupled to the dual inlet of a Finnigan MAT 253 isotope
    ratio mass spectrometer in the Saskatchewan Isotope Laboratory at
    University of Saskatchewan. Sample powders for δ13Corg analyses
    were accurately weighed and acidified using 6 N HCl to remove
    carbonate minerals. Insoluble fractions were then repeatedly rinsed in
    ultrapure water and dried at 85 °C. Remaining residues were weighed
    and homogenized, and then loaded into tin capsules. Samples were
    combusted with a Costech Elemental Analyzer and the resulting CO2
    gas analyzed for δ13C through a Finnigan Delta IV stable isotope ratio
    mass spectrometer under continuous flow using an open-split
    CONFLO III interface in the Stable Isotope Biogeochemistry Laboratory
    at The Ohio State University.

    Here’s what they found:

    The observed change in 13C through the Hirnantian Stage in
    Estonia and Anticosti Island can be interpreted to reflect atmospheric pCO2 levels that were relatively low immediately prior to the d13Ccarb excursion and then increased as ice sheets expanded (Figs. 5 and 6). Ultimately, this period of elevated pCO2 is followed by global deglaciation.

    This is not possible if CO2 is as dominant of global temperature as climate science currently believes. The word “ultimately” in the above means that glaciation persisted for a few million years under conditions of high atmospheric CO2. Then the glaciation ended, but this termination cannot have had anything to do with CO2, since an atmospheric cause resulting in no effect for millions of years and then suddenly a warming effect, is not credible.

    So climate scientists will work hard to blur and smudge the Ordovician high-CO2 glaciation the same as they blur and smudge the Holocene reconstruted climate and all other geological climate records that contradict the CO2 orthodoxy.

    But the facts will remain – the eco-extremist revisionists can’t destroy all the rocks in the world. Evidence such as that discovered by Seth Young and colleagues shows CO2 for what it is – just another parameter in a complex atmosphere-ocean-lithosphere system that goes up and down under multiple influences, but is much more an effect than a cause. Rising CO2 while glaciation spread and deepened, illustrates this fact clearly.

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