OFFSHORE MEASUREMENTS OF CO 2 PLUMES The stability, precision and robustness of the system allows for measurement of CO 2 concentrations in remote locations and to track down plumes from ships, industries or bushfires. As an example, the Spectronus aided University of Wollongong scientists on-board the SS Southern Surveyor to chase CO 2 and other trace gas plumes from different sources as they circumnavigate Australia (Figure 7). Figure 8 (below). Time series of (a) CO2 and δ13C in CO2 and (b) CH4 and N2O during a 3-week campaign at the OzFlux tower site near Tumbarumba, SE Australia, November 2006. Seven-point vertical profiles of each species from 2-70m were measured every 30 min, colours represent measrements at heights above the surface shown in the legend. The top of the forest canopy is approx. 40m above the surface. Griffith, D. W. T., Deutscher, N. M., Caldow, C. G. R., Kettlewell, G., Riggenbach, M., and Hammer, S.: A Fourier transform infrared trace gas analyser for atmospheric applications, Atmos. Meas. Tech., 5, 2481-2498, 10.5194/amtd-5-3717-2012, 2012. TALL TOWER MEASUREMENTS Tall tower measurements help to broaden the knowledge on regional background pollution by measuring above the surface layer. Vertical profiles of trace gases and isotopic fractionation can also help in understanding C and H 2 O exchange. Using our manifold that staggers the measurements, differences in gas concentrations can be obtained between air parcels at different heights. Figure 7. Ship measurements of CO 2 plumes. Image supplied courtesy of University of Wollongong.
CO 2 , δ 13 C & TRACE GAS VARIATIONS One of the most important uses of δ 13 C measurements is in determining the strength of the different biosphere sinks. Since about half of the carbon dioxide we add to the atmosphere each year is absorbed into various sinks, it is important for future predictions to know where exactly that carbon dioxide goes. Figure 9. Trace gas variations in limestone caves. (Courtesy of Stephen Parkes, University of Wollongong, “The application of FTIR spectroscopy measuring stable isotopes of liquid water and water vapour: application to understanding speleothem growth”). Figure 9 shows a Spectronus involved in a preliminary study in a limestone cave in 2008. Annual growth layers in cave formations contain paleoclimatic information. The aim was to understand δ 13 C fractionation in speleothem layers, cave atmosphere and dripwaters. “ We purchased our Spectronus from ECOTECH in the fall of 2012 and installed the system at the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) facility located in the U.S. Southern Great Plain (SGP) in August 2013. Since then, the system has been performing well, and meeting our expectations. The deployment of a precise instrument for continuous measurement of CO 2 , CH 4 , CO, N 2 O mixing ratios, and 13 CO 2 isotopic ratios at the SGP 60 m tower, is opening up many new exciting research opportunities. S. Biraud, Lawrence Berkeley National Laboratory, USA. Figure 10. Isotopic ratios can help tracing sources using a Keeling plot. In this case, the intercept of the Keeling plot of δ 13 C vs 1 [CO 2 ] is -26.83 0.4‰, indicative of respiration from the dominant C3 plants in the forest. Griffith, D. W. T., Deutscher, N. M., Caldow, C. G. R., Kettlewell, G., Riggenbach, M., and Hammer, S.: A Fourier transform infrared trace gas analyser for atmospheric applications, Atmos. Meas. Tech., 5, 2481-2498, 10.5194/amtd-5-3717-2012, 2012. ecotech.com | 7