Effects of African dust deposition on phytoplankton in the western tropical Atlantic Ocean off Barbados

Bioassay incubation experiments conducted with nutrients and local atmospheric aerosol amendments indicate that phosphorus (P) availability limited phytoplankton growth in the low-nutrient low-chlorophyll (LNLC) ocean off Barbados. Atmospheric deposition provides a relatively large influx of new nutrients and trace metals to the surface ocean in this region in comparison to other nutrient sources. However, the impact on native phytoplankton is muted due to the high ratio of nitrogen (N) to P (NO3:SRP > 40) and the low P solubility of these aerosols. Atmospheric deposition induces P limitation in this LNLC region by adding more N and iron (Fe) relative to P. This favors the growth of Prochlorococcus, a genus characterized by low P requirements and highly efficient P acquisition mechanisms. A global three-dimensional marine ecosystem model that includes species-specific phytoplankton elemental quotas/stoichiometry and the atmospheric deposition of N, P, and Fe supports this conclusion. Future increases in aerosol N loading may therefore influence phytoplankton community structure in other LNLC areas, thereby affecting the biological pump and associated carbon sequestration

Chemical composition of medieval glass from excavations in West Germany

Investigations of excavated glass fragments from the Roman-Frankish cemetery at Krefeld-Gellep, the Carolingian imperial palace with glassworks at Paderborn, the monasteries and towns of Corvey, Höxter and Brunshausen-Gandersheim and several glassworks in the Bramwald, Hils, Spessart and Eichsfeld areas allow conclusions on the sequence of major medieval glass types. Exhaustion of Imports of trona-soda or soda raw glass and increased needs caused the introduction of woodash as domestic alkali and earth alkali source for glass manufacture at about 800 AC. Early woodash glass from 800 to 1000, woodash glass from about 1000 to 1400 and woodash-lime glass from about 1400 to post-medieval times were the major glass types. They were accompanied by minor Imports of soda-lime and soda-ash glass objects, the latter since about 1300. From about 1100 to 1400 woodash-lead and lead glass have been produced from the P bO byproducts of the silver metallurgy. Galena from the Harz Mountains was a major source of lead for lead glass in northwestern Europe. The average production of a medieval glassworks was in the order of 15 t glass per year and its requirements for ash and fuel about 30001 wood. The number of glassworks in Germany during the late medieval period (moving after 5 to 30 years from one to another location) is tentatively estimated to be in the order of 40. Their main furnaces were constructed for about 1400 C working temperature. The occurrence of the medieval chemical glass types in a sequence allows some rough dating of glass fragments

Chemical characteristics (REE, etc.) of Paleozoic and Mesozoic graywackes and sandstones from Central Europe

During the Variscan orogeny in Central Europe, partial melting in the lower continental crust formed granitic magmas, which intruded into the upper crust and left compounds of Ca (plus Eu2+), Mg, etc. in the lower crust. From the late Paleozoic decomposition of the tonalitic upper crust, sedimentary graywackes were produced reflecting the composition of this crust. The repeated reworking of the sedimentary cover caused the formation of sands. Sandstones as their products of consolidation contain increasing fractions of quartz and decreasing feldspar from Carboniferous and Triassic to Cretaceous age. A distinct negative Eu anomaly characterizes the majority of these rocks. The latter is imprinted by the Variscan magmatism. Quartz as used for numerous Medieval wood ash glasses is marked for its Central European origin by a distinct negative Eu anomaly in contrast to many soda glasses produced outside Germany mostly with a small or none Eu anomaly