Atmospheric Physics and Chemistry Group

CO2 + O3 isotope exchange via O(1D) and stratospheric CO2

Dorota Mrozek

Stratospheric CO2 is anomalously enriched in 17O, leading to the most unusual three-isotope relation observed in nature to date, δ17O ~1.7 δ18O (Lämmerzahl et al. 2002) . It has been shown that the isotope anomaly is transferred from O3 to CO2 via O(1D). The anomaly can be used as a tracer of stratospheric chemistry and transport and ultimately causes an anomaly in the atmospheric O2 reservoir that is used to study biospheric productivity (ESR project 11). Nevertheless, the details of the transfer mechanism are not yet understood. We have recently established a promising new approach to study this isotope transfer: investigations of the isotope equilibrium between O2 and CO2 (Shaheen et al. 2007). The results show that the stratospheric observations cannot be explained by existing lab measurements, in contrast to earlier claims (Chakraborty & Bhattacharya 2003). Within the ITN, we will couple this new approach to ozone isotope characterization (LPMAA) to unravel the nature of the isotope exchange, in particular, whether or not further mass independent isotope effects are associated with the exchange process involving the CO3* intermediate.