A New Analytical-Theoretical Method to Assess Past Changes in the Oxidising Capacity of Atmospheres

Terrestrial plants are the largest emitter of volatile organic compounds in the atmosphere. These compounds undergo chemical transformations during their transport to polar regions. Determining the transformation products in ice cores could provide information on how the past atmosphere reacted to abrupt climate changes, analogous to the present changes, thus contributing to knowledge around global uncertainties. Analysing organic compounds in ice cores represents an analytical challenge due to their low concentrations and limited sample availability. In this project, we aim at pushing mass spectrometry capability to its limits to allow, for the first time, for a continuous flow analysis of ice cores, gradually melted in continuous, for the determination of organic compounds with high time resolution in the archive. This novel method, once operational, can be applied to a range of ice cores but is especially useful for older ice cores, given the compact stratification of deeper segments, to retrieve paleoclimatic information that would otherwise be lost using traditional methods. Given that the target analytes are being transformed in the atmosphere during their transport to polar regions, a theoretical model, combining reactivity and global transport, will be developed to infer average concentrations of the atmospheric oxidants with which the target analytes have reacted during their atmospheric lifetime. Validation of the theoretical framework will be done by comparing model results of oxidant concentrations with direct measurements available for recent years.