Measurements of ozone-depleting substances at the Cape Verde Observatory

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This project will expand our atmospheric halocarbon GC-MS measurements at the Cape Verde Observatory (CVO) to include a wider range of established and emerging ozone depleting substances. The student will also collect new air and seawater VSLS chlorine measurements at Cape Verde to investigate and parametrise in situ ocean production. The student will test and harmonise column combinations with those used by other groups to allow comparison of relative retention times for new halocarbon species, establish calibration scales for compounds not previously measured at CVO via an intercomparison programme, and establish a program of monthly seawater sampling upwind of the CVO for measurements of CH2Cl2, CHCl3 and other, predominantly natural, VSLS by purge and trap GC-MS. Simultaneous analysis of CFC-11 concentrations in seawater will allow calculation of the excess CH2Cl2 and CHCl3 "saturation anomalies", required to assess whether in-situ oceanic production is occurring. These saturation anomalies will be analysed for patterns and trends that correlate with, for example, chlorophyl-A, coloured dissolved organic material and dissolved organic carbon abundances, to allow scale-up of these emissions to the tropical ocean. Thus, the project will determine patterns and trends in emerging anthropogenic ozone depleting substances and better constrain natural emissions of short-lived ozone depleting compounds not controlled under the Montreal Protocol.