A geochemical assessment of the middle and lower Mvoti river system,KwaZulu-Natal,South Africa

This paper presents one of the first investigations into the geochemical enrichment of the middle and lower Mvoti river system. Chemical elements are naturally present in aquatic sediments, but their concentrations tend to rise to potentially toxic levels via both natural and anthropogenic processes. This study evaluated the concentrations of aluminum, arsenic, boron, barium, cadmium, calcium, cobalt, chromium, copper, iron, lead, magnesium, manganese, molybdenum, nickel, phosphorous, selenium, silicon, strontium, titanium, vanadium and zinc, using inductively coupled plasma optical emission spectroscopy. The levels of elements present were used to assess their spatial distribution within the river and to determine the contamination factors and enrichment factors for each element. The pollution load index (PLi) is another contributing parameter that was calculated to determine the degree of pollution at each site. The results indicate that the sediments of the Mvoti are low to moderately polluted and deteriorating with time (average PLi value of 5.19), and that a major contributing factor to this contamination is natural sources.     

Der Bau der Betischen Kordillere und ihre Stellung im Mediterranen Orogen

Ohne ZusammenfassungÜbersetzung aus dem Holländischen von H.Cloos.Ich will nicht schließen, ohne meinen aufrichtigen Dank Herrn P.de WYKERSLOOTH auszusprechen, der so freundlich war, mir für diesen Artikel verschiedene wertvolle Angaben zu machen.     

A meteorological 80-m tower near Rotterdam

Construction, observation site and instrumentation are described of an 80-m meteorological observation tower, erected in Vlaardingen, The Netherlands, for studies in connection with air pollution problems along the Nieuwe Waterweg. From measurements made regularly in the period April 1967–April 1968 summaries are given of wind profile parameters and gustiness averages. Case histories are presented of an air pollution episode lasting several days, and of an hourly average wind direction difference of 120 ° over 70 m.     

Modeling Forest Emissivity at L-Band and a Comparison With Multitemporal Measurements

This letter describes recent advances in modeling forest emissivity at L-band. The formulation is based on a previously developed discrete model and includes a new representation of forest litter. Comparisons with multitemporal radiometric data collected in the framework of the ldquoBray 2004rdquo experiment, which was carried out within Les Landes forest, are shown and discussed. Input variables are given by using detailed ground measurements. In general, the model reproduces both absolute values and temporal variations of measured brightness temperature. The contribution of the litter to overall emission was found to be important.     

Temperature,composition, and f O2 effects on intersite distribution of Mg and Fe2+ in olivines

Single-crystal X-ray structure refinement of natural olivines equilibrated at high temperature under controlled oxygen fugacity (f _O2) conditions, coupled with a structure-energy model were used to establish the influence of T, f _O2 and bulk chemistry on intracrystalline disorder.The results are: 1) The k _D (k _D = [(Fe M1·Mg M2)/(Fe M2·Mg M1)]) factor describing site population on M1, M2 polyhedra increases from values lower than 1 at T below 400–600° C (depending on composition) to values higher than 1 at higher temperature. 2) The increase of k _D with T is quite regular. 3) At constant temperature and pressure, k _D increases with increasing fayalite content in the mixture; 4) Contrary to previous observations (Will and Nover 1979; Nover and Will 1981) varying f _O2, within the stability range of the substance, has a negligible influence on intracrystalline disorder. 5) As ancillary results, the model confirms the defect scheme of Nakamura and Schmalzried (1983) for the investigated solids. Moreover, it shows that cationic vacancies are always created on M 1 site at the expense of Mg ions, while trivalent iron is always stabilized on M2 site. This explains the marked anisotropies observed in Fe-Mg interdiffusion (Buening and Busek 1973; Misener 1974; Schock et al. 1989).     

Petrology of Santorini Volcano, Cyclades, Greece

The Pliocene to Recent lavas, dyke rocks, and cognate xenolithsof Santorini island group belong to four distinct series, eachof high-alumina basalt-andesite-dacite type. The oldest seriesincludes hornblende dacites and minor basaltic andesites. Theformer contain hornblende-rich cognate xenoliths of basalticcomposition, which consist essentially of crystals ‘floating’in residual acid liquid (glass). The chemical variation of theseries, like that of lavas of volcanic centres north-west ofSantorini, is of ‘calc-alkali’ type. The second and third series consist of a range of lavas frombasalt to rhyodacite. No hydrous mineral occurs as a stablephase. Augite is the phenocrystal pyroxene of basalts; augiteand hypersthene of andesites and dacites. The groundmass pyroxenesof basalts and most andesites are augite and pigeonite, whiledistinctive hornblende xenocryst-bearing andesites of the secondseries, and acid lavas of both second and third, carry augiteand hypersthene in the groundmass. Interstitial glass increasesin proportion from basalts to andesites, and forms a major componentof acid lavas. The second series, like the oldest, lacks absoluteiron enrichment. The third, however, shows weak iron enrichmentof andesitic relative to basaltic compositions. Of the youngest (historic) series, only the acid members (hyalodacites)have been extruded as lavas. The more basic members are representedby non-cumulate xenoliths of basaltic to andesitic compositionwhich, like those of the oldest series, consist of a mesh ofcrystals set in abundant glass. This modern series also displaysfeeble absolute iron enrichment. The compositional range of minerals other than plagioclase isvery limited in the two xenolithic series, but much greaterin the two lava series. Glass compositions are virtually constantwithin individual series. Estimates of temperatures and oxygenfugacities of Fe-Ti oxide mineral equilibration, and deductionsfrom liquid compositional trends indicate that the oldest serieswas characterized by higher f_O2, and f_H2O, and lower temperaturesthan the three younger, ‘dry’ series. Its silicaenrichment trend appears to have been controlled chiefly byfractionation of silica-poor hornblende, rather than magnetiteas in the younger series. The presence, in all series, of xenolithsof gabbroic cumulates, and the constancy of glass compositionssuggests that each series was generated by the tapping of adifferentiating highalumina basalt magma in a high level magmachamber.