Nature: Study of new particle formation from isoprene using MION

Understanding the chemistry of new particle formation in the upper troposphere is essential for improving climate models and predicting cloud formation. This study uncovered how isoprene-oxygenated organic molecules (IP-OOM) play a central role in nucleating new particles at -30°C to -50°C. The research demonstrated that trace amounts of sulfuric acid and iodine oxoacids can enhance nucleation rates by up to 100 times. These findings provide a crucial link between biogenic emissions from tropical forests and cloud condensation nuclei (CCN) formation, influencing Earth's radiative balance.

Br-MION2-CIMS: Unlocking Molecular Insights

This study relied on a combination of advanced chemical ionization mass spectrometry (CIMS) instruments, each optimized for different atmospheric species. The Br-MION2-CIMS, incorporating our MION2 technology, was critical in detecting and quantifying a broad range of highly oxygenated organic molecules (HOMs) and key oxidants that contribute to new particle formation.

The Br-MION2-CIMS provided high-sensitivity detection of the following species:

• IP-OOM (Isoprene-Oxygenated Organic Molecules) – Key drivers of new particle formation, including monomers (C5 species) and dimers (C10 species).
• Hydroperoxyl Radical (HO₂) – A critical oxidant that influences the formation of low-volatility organic molecules from isoprene.
• Nitrous Acid (HONO) – A key precursor in photochemical processes, influencing radical chemistry and oxidation pathways.
• Hydrogen Peroxide (H₂O₂) – Another important oxidant that contributes to secondary organic aerosol formation.
• Sulfur Dioxide (SO₂) & Sulfuric Acid (H₂SO₄) – Known contributors to nucleation, even in extremely low concentrations.
• Molecular Iodine (I₂) & Iodine Oxoacids (HIO₂, HIO₃) – These species help stabilize molecular clusters, boosting nucleation efficiency.
• Methanesulfonic Acid (CH₃SO₃H) – A sulfur-containing compound contributing to secondary particle growth.
• ISOPOOH & IEPOX (C₅H₁₀O₃) – Isomeric oxidation products of isoprene, playing a role in secondary organic aerosol formation.

Visualizing the Molecular Signatures of Nucleation

The Br-MION2-CIMS not only identified these critical species but also provided detailed molecular composition data of charged and neutral clusters, as shown in Figure 3 of the paper. This figure presents mass defect plots, illustrating how clusters grow step by step, with sequential additions of IP-OOM monomers and dimers.

By distinguishing between nitrate and non-nitrate species, the Br-MION2-CIMS revealed that nitrate-containing molecules were less effective in nucleation compared to their non-nitrate counterparts. These high-resolution insights were key to understanding how atmospheric conditions influence the chemistry of new particle formation.

Advancing Atmospheric Research with MION2

This study underscores the importance of using multiple chemical ionization techniques to achieve comprehensive coverage of volatile organic compounds (VOCs) and HOMs. The Br-MION2-CIMS played a key role in bridging this gap, measuring species at extremely low concentrations (<10⁵ cm⁻³) with high precision.

Reference: Shen, J., Russell, D.M., DeVivo, J. et al. New particle formation from isoprene under upper-tropospheric conditions. Nature 636, 115–123 (2024). https://doi.org/10.1038/s41586-024-08196-0

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