Voedingsvraagstukke in Afrika*

Die uitnodiging van die Direkteur van die Afrika-Seminaar van die P.U. vir C.H.O. om die onderwerp „Voedingsvraagstukke in Afrika” voor te dra, word van harte deur my verwelkom en as ’n besondere voorreg beskou

Atmospheric aerosol measurements in the German Ultrafine Aerosol Network (GUAN) - part 3: Black carbon mass and particle number concentrations 2009 to 2014.

The German Ultrafine Aerosol Network (GUAN) is a cooperative effort to scientifically explore the health and climate-related properties of the atmospheric aerosol in Germany. This work presents results on the basis of long-term observations of particle number size distributions and equivalent black carbon (eBC) between 2009 and 2014. At 17 observation sites, we found variations in mean total particle number concentration (diameter range 20 to 800 nm) between 850 and 10,500 p. cm(-3), and in eBC mass concentration between 0.17 and 2.8 mu g m(-3). Time series trend analyses yielded a significant relative decrease in eBC mass concentration (median: -5%/year) and in total particle number concentration (median: -4%/year), which is rather consistent at almost all sites over Germany. The consistent downward trends suggest that air quality-related societal efforts, which have been targeted mainly at reductions of total particle mass emissions, have a beneficial effect on ambient total particle number, ultrafine particle number, and eBC mass concentrations as well

Long-term observations of tropospheric particle number size distributions and equivalent black carbon mass concentrations in the German Ultrafine Aerosol Network (GUAN)

The German Ultrafine Aerosol Network (GUAN) is a cooperative atmospheric observation network, which aims at improving the scientific understanding of aerosol-related effects in the troposphere. The network addresses research questions dedicated to both climate- and health-related effects. GUAN's core activity has been the continuous collection of tropospheric particle number size distributions and black carbon mass concentrations at 17 observation sites in Germany. These sites cover various environmental settings including urban traffic, urban background, rural background, and Alpine mountains. In association with partner projects, GUAN has implemented a high degree of harmonisation of instrumentation, operating procedures, and data evaluation procedures. The quality of the measurement data is assured by laboratory intercomparisons as well as on-site comparisons with reference instruments. This paper describes the measurement sites, instrumentation, quality assurance, and data evaluation procedures in the network as well as the EBAS repository, where the data sets can be obtained (<a href="http://dx.doi.org/10.5072/guan" target="_blank">doi:10.5072/guan</a>)