Atmospheric Abundances, Trends and Emissions of CFC-216ba, CFC-216ca and HCFC-225ca

The first observations of the feedstocks, CFC-216ba (1,2-dichlorohexafluoropropane) and CFC-216ca (1,3-dichlorohexafluoropropane), as well as the CFC substitute HCFC-225ca (3,3-dichloro-1,1,1,2,2-pentafluoropropane), are reported in air samples collected between 1978 and 2012 at Cape Grim, Tasmania. Present day (2012) mixing ratios are 37.8 ± 0.08 ppq (parts per quadrillion; 1015) and 20.2 ± 0.3 ppq for CFC-216ba and CFC-216ca, respectively. The abundance of CFC-216ba has been approximately constant for the past 20 years, whilst that of CFC-216ca is increasing, at a current rate of 0.2 ppq/year. Upper tropospheric air samples collected in 2013 suggest a further continuation of this trend. Inferred annual emissions peaked 421 at 0.18 Gg/year (CFC-216ba) and 0.05 Gg/year (CFC-216ca) in the mid-1980s and then decreased sharply as expected from the Montreal Protocol phase-out schedule for CFCs. The atmospheric trend of CFC-216ca and CFC-216ba translates into continuing emissions of around 0.01 Gg/year in 2011, indicating that significant banks still exist or that they are still being used. HCFC-225ca was not detected in air samples collected before 1992. The highest mixing ratio of 52 ± 1 ppq was observed in 2001. Increasing annual emissions were found in the 1990s (i.e., when HCFC-225ca was being introduced as a replacement for CFCs). Emissions peaked around 1999 at about 1.51 Gg/year. In accordance with the Montreal Protocol, restrictions on HCFC consumption and the short lifetime of HCFC-225ca, mixing ratios declined after 2001 to 23.3 ± 0.7 ppq by 2012

First atmospheric observations of three chlorofluorocarbons

We report the first atmospheric observations of the Chlorofluorocarbons (CFCs) trifluorochloroethene, 3-chloropentafluoropropene and 4,4-dichlorohexafluoro-1-butene by means of Gas Chromatography with Electron Capture and Mass Spectrometric detection (GC-ECD-MS) in air samples taken at the Taunus Observatory operated by the University of Frankfurt (Main) and the Jungfraujoch High Altitude Research Station in Switzerland. These substances belong to a class of CFCs containing a double bond and are suspected to originate from the production and thermal degradation of widely used fluoropolymers like polychlorotrifluoroethene (PCTFE). Their atmospheric lifetimes are expected to be rather short. A quantitative calibration could only be derived for trifluorochloroethene but not for the other species by now. Thus, we use a relative sensitivity method to get a first indication of the observed atmospheric abundances. Identification was possible because of an air plume containing high concentrations of these substances. We suggest that the abundances found on this occasion originated from a local source. However, we have also observed the novel CFCs in air masses representative of background conditions, though with much lower concentrations. These species and some of their degradation products are toxic and could also be relevant for stratospheric and tropospheric ozone depletion

Introduction: Why Should We Study Migration Policies at the Interface between Empirical Research and Normative Analysis?

The text introduces the concept behind the Proceedings of the 2018 ZiF Workshop “Studying Migration Policies at the Interface between Empirical Research and Normative Analysis”. It explains why there is a need to study migration policies across disciplines, includes a short note on the current literature, and provides a look back at the workshop. DOI:10.17879/1519962468

GPS antenna designs

Application of the current GPS NAVSTAR system to civilian service requires that a right hand, circularly polarized, -160 dBW spread spectrum signal be received from an orbiting satellite, where the antenna environment is also moving. This presents a design challenge when inexpensive antennas are desired. The intent of this survey is to provide information on the antennas mentioned and to construct and test prototypes to determine whether the choice made by the industry, the quadrifilar helix, is the best. The helix antenna is currently the low cost standard for GPS. Prototype versions were constructed using 12 gauge wire and subminiature coaxial hardline. The constructed antennas were tested using a signal generator and a reference turnstile. A spectrum analyzer was used to measure the level of the received signal

GPS experiments

A method of collecting positional data has been devised using the Federal Aviation Administration (FAA) receiver built by Lincoln Labs which was originally designed for service as a long-term monitoring station. Modification of the receiver continues and this will allow its use as an aircraft navigator. Additional effort has been spent on the development of an experimental receiver or test bed receiver that would allow modification and implementation of new Global Positioning System (GPS) receiver design concepts

The Hydrographic and Wrecksearch Vessel "DENEB" as an Example for a Modern Survey Vessel

The Survey, Wrecksearch, and Research Ship (VWFS) "DENEB", built at the Peenewerft in Wolgast, is the latest in the fleet of the German Federal Maritime and Hydrographic Agency BSH (Bundesamt für Seeschiffahrt und Hydrographie). It is a sister-ship to the existing VWFS "ATAIR" and "WEGA" and is intended as a successor to the Survey Vessel "CARL FRIEDRICH GAUSS" and the old Survey and Wrecksearch Vessel "DENEB" taking over their tasks. The "DENEB", commissioned in the late fall 1994, is equipped with a currently unique combination of sensors and a prevailing system concept for navigation and hydrographic tasks, which changes the traditional concept of having an Operating Navigation System separated from the Hydrographic Survey System. The main operating area of this new vessel is the Baltic Sea, but other tasks will be performed in accordance with the requirements