Criegee intermediates are reactive intermediates that are implicated in transforming the composition of Earth’s troposphere and in the formation of secondary organic aerosol, impacting Earth’s radiation balance, air quality and human health. Yet, direct identification of their signatures in the field remains elusive. Here, from particulate and gas-phase mass-spectrometric measurements in the Amazon rainforest, we identify sequences of masses consistent with the expected signatures of oligomerization of the CH₂OO Criegee intermediate, a process implicated in ozonolysis-driven aerosol formation. We assess the potential contributions of oligomerization through laboratory ozonolysis experiments, direct kinetic studies of Criegee intermediate reactions, and high-level theoretical calculations. Global atmospheric models built on these kinetics results indicate that Criegee intermediate chemistry may play a larger role in altering the composition of Earth’s troposphere than is captured in current atmospheric models, especially in areas of high humidity. However, the models still capture only a relatively small fraction of the observed signatures, suggesting considerable underestimates of Criegee intermediate concentrations and reactivity and/or the dominance of other, presently uncharacterized, oxidation mechanisms. Resolving the remaining uncertainties in emission inventories and the effects of atmospheric water vapour on key chemical reactions will be required to definitively assess the role of Criegee intermediate oligomerization reactions.

Criegee中间体是反应性中间体，涉及改变地球对流层的组成和形成二次有机气溶胶，影响地球的辐射平衡、空气质量和人类健康。然而，在现场直接识别他们的签名仍然难以实现。在这里，通过亚马逊雨林中的颗粒物和气相质谱测量，我们确定了与 CH ₂ OO Criegee 中间体低聚的预期特征一致的质量序列，该过程涉及臭氧分解驱动的气溶胶形成。我们通过实验室臭氧分解实验、Criegee 中间反应的直接动力学研究和高级理论计算来评估低聚的潜在贡献。基于这些动力学结果建立的全球大气模型表明，克里吉中间化学物质在改变地球对流层成分方面可能比当前大气模型中所捕获的作用更大，特别是在高湿度地区。然而，这些模型仍然只捕获了观察到的特征的相对一小部分，这表明对 Criegee 中间浓度和反应性和/或其他目前尚未表征的氧化机制的主导地位的估计被大大低估。需要解决排放清单中剩余的不确定性以及大气水蒸气对关键化学反应的影响，才能明确评估 Criegee 中间低聚反应的作用。