Abstract
Tra le sfide che l’umanità si trova ad affrontare, la chimica dell’atmosfera terrestre è quella che solleva più preoccupazione. Infatti, un’attendibile e accurata modellizzazione della chimica della troposfera terrestre è il primo passo per combattere il cambiamento climatico. I macro-obiettivi specifici del progetto sono due. Il primo è la messa a punto di una strategia integrata esperimento-teoria che coniughi calcoli cinetici accurati con un’innovativa strumentazione per il monitoraggio delle concentrazioni dei componenti di reazione per mezzo della spettroscopia rotazionale. Il secondo grande obiettivo è lo sviluppo di un database che raccolga in maniera critica tutti i dati accurati disponibili in letteratura e quelli ottenuti nel corso del progetto per quanto riguarda la chimica della troposfera. Lo scopo è di superare le presenti limitazioni degli attuali database, fornendo informazioni quantitative sulle rese di reazione in termini di abbondanza relativa dei vari prodotti e sulle proprietà molecolari degli inquinanti.
Results achieved
The GASCHEM4air project achieved its main scientific objective of developing an integrated computational-experimental framework for the investigation of gas-phase atmospheric reactions relevant to air-quality modeling. The project combined state-of-the-art quantum-chemical calculations with rotational spectroscopy to improve the mechanistic understanding and kinetic characterization of key atmospheric processes, while establishing the basis for a publicly accessible database of high-quality kinetic data. A major outcome of the project was the development of the Atmo-QC protocol, an advanced computational framework integrating automated exploration of reactive potential energy surfaces with high-level thermochemical calculations and kinetics based on the AITSTME (ab initio transition-state-theory-based master equation) methodology. Significant methodological advances were achieved through the implementation of automated PES exploration, the extension of accurate composite electronic-structure schemes to larger molecular systems, and the integration of these developments into a unified computational workflow. The resulting protocol enables accurate and efficient characterization of complex atmospheric reactions and represents a versatile tool for future kinetic investigations. The project identified critical gaps in the available kinetic data for several classes of atmospheric reactions and selected representative systems of particular relevance to polluted tropospheric and stratospheric chemistry. Detailed thermochemical and kinetic investigations were carried out for reactions involving OH radicals with ethylene, benzene, naphthalene, propanol, ketenimine, and related radicals, as well as for ozone-initiated reactions of olefins and hydrofluoroolefins. Particular attention was devoted to the two-step oxidation of aromatic hydrocarbons by OH followed by O₂ addition, a key process in the formation of secondary organic aerosols, and to the ozonolysis of hydrofluoroolefins, which is relevant to assessing the environmental impact of next-generation refrigerants. In addition, computational studies were extended to reactions associated with rocket emissions, addressing an emerging topic in atmospheric chemistry. On the experimental side, despite the impossibility of deploying the originally planned coupling of a chemical reactor with the broadband chirped-pulse microwave spectrometer due to delays associated with the relocation of the laboratory, an effective alternative strategy was successfully implemented using millimeter/submillimeter-wave spectroscopy. Although this approach did not allow the determination of quantitative rate constants and branching ratios with the desired accuracy, it provided reliable qualitative identification of reaction products, thereby enabling the experimental validation of the theoretically predicted reaction mechanisms. The project also established robust procedures for coupling spectroscopy with radical generation and developed dedicated software for the comparison and iterative refinement of experimental observations and theoretical predictions. Another important achievement was the realization of an integrated experiment–theory strategy that combines computational predictions with spectroscopic observations within a common workflow. Although the current implementation still requires expert intervention and is not yet fully automated, it proved robust and effective when applied to benchmark atmospheric reactions, demonstrating the feasibility of the proposed integrated approach and providing a solid basis for future automation once the new experimental infrastructure becomes fully operational. The project also produced the test version of the Atmospheric Chemistry Database, which combines critically evaluated literature data with the new kinetic and thermochemical results generated during GASCHEM4air. The database includes a dedicated section devoted to rocket-emission chemistry and has been designed as an expandable open-access resource to support atmospheric modeling and future developments. Overall, GASCHEM4air generated significant advances in computational methodology, experimental strategies, and atmospheric kinetic data. Despite the experimental limitations encountered, the project successfully delivered innovative tools, validated protocols, and new scientific knowledge that will contribute to improving the accuracy of atmospheric chemistry models and provide a strong foundation for future developments in integrated computational and spectroscopic studies of atmospheric reactions.Project details
Unibo Team Leader: Cristina Puzzarini
Unibo involved Department/s:
Dipartimento di Chimica "Giacomo Ciamician"
Coordinator:
ALMA MATER STUDIORUM - Università di Bologna(Italy)
Total Eu Contribution: Euro (EUR) 233.555,00
Total Unibo Contribution: Euro (EUR) 132.555,00
Project Duration in months: 24
Start Date:
30/11/2023
End Date:
29/11/2025
