Major and minor elements (incl. Ag, As, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sr, V, Zn) have been determined in recent sediments from the Gulf of California upwelling area and Black Sea sapropels in order to reinterpret their chemical composition in view of reliable seawater and plankton data. The chemistry of the Gulf of California sediments reflects regeneration processes which occur in the water column; i.e. only a small fraction (<10%) of elements like Cd, which in seawater are coupled to the »labile« nutrients (C, N, P), is buried in the sedimentary column. In contrast, elements like the more resistant nutrients (Si) undergo a deeper regeneration cycle (Ba). Several trace metals which are present in comparatively higher concentrations in seawater (As, Mo, U, V) and at the same time are reactive under reducing conditions and/or are able to form stable Sulfides, are fixed in the sediments during early diagenesis. The early diagenetic behavior of Ba is closely related to bacterial sulfate reduction. The formation of barite concretions is discussed. Anoxic conditions in the water column act as ideal traps for a number of redox sensitive and/or stable sulfide forming elements. A simple trace metal balance calculation shows that the chemical composition of Black Sea sapropels is controlled by fluvial and Mediterranean seawater element input and the accumulation rate of terrigenous detrital material.

Geochemistry of recent TOC-rich sediments from the Gulf of California and the Black Sea

A field study was conducted over a 30 mo period to examine movement of Cd, Tl, and V through the profile of a Coastal Plain soil (Typic Kandiudult) and the availability of these trace metals to bush bean (Phaseolus vulgaris L) plants The metals were applied to field plots as dissolved salts and mixed into the surface 75 cm The greatest concentration of all three metals was observed in the surface soils, with a steep decrease occurring down to the 75 to 15 cm depth Thallium was the most mobile of the three metals; approximately 15% of the applied Tl and <3% of the applied Cd and V moved below the surface 75-cm region during the 30-mo experiment Extractable concentrations of all three metals in the surface soils decreased significantly (P ≤005) during the initial 18 mo after treatment No further decrease occurred between 18 and 30 mo The presence of Al- and Fe-oxides and small amounts of clay minerals and organic matter in this highly-weathered, low cation-exchange soil were likely responsible for the retention of the trace metals Bioavailability, as measured by concentrations and total amounts of metals in root and aboveground tissues of plants, did not change significantly between 18 and 30 mo These data suggest that bioavailability of Cd, Tl, and V decreased over time as a result of transformation of these elements into unavailable forms and not to leaching These changes in bioavailability occurred soon after application, becoming negligible after 18 mo

Temporal Changes in Cadmium, Thallium, and Vanadium Mobility in Soil and Phytoavailability under Field Conditions

There is sufficient evidence today to assume that selenium has beneficial effects on the growth of plants, and that it is both an essential and toxic trace element for animal and man This review article intends to show the involvement of selenium in the environment and in biology Attention is paid, in large, to the occurrence, distribution and accumulation of the element in the eco- and biosphere, but also to toxic effects, interactions with concomitant elements and to the essentiality to animals and humans Special emphasis is, however, placed on the determination of selenium at trace levels with consideration of systematic errors in environmentally relevant materials A comprehensive literature search was carried out in order to provide an appropriate overview of the most commonly used analytical methods and their limitations

A Survey of selenium in the environment and a critical review of its determination at trace levels

In aluminous metapelites the ratio H2O+/K2O decreases with increasing metamorphic grade and degree of reaction. This ratio is a very practical indicator for the progress of the mineral reconstitution during progressive metamorphism. With decreasing values of the ratio H2O+/ K2O the Cu concentration and the following element ratios also decrease either continuously or in stepwise fashion: Tl/K2O, Ba/K2O, Pb/K2O, Bi/K2O, Hg/K2O, Sr/Na2O, Zn/(Fe2++Mg), Cd/(Fe2++Mg); Rb/K2O remains approximately constant. In the aluminous metapelites of the Damara Orogen in Namibia the following losses occur between the biotite isograd and anatexis: 61% Cu, 20% Tl, 34% Ba, 59% Pb, 86% Bi, 46% Hg, 30% Sr, 25% Zn, 31% Cd. Thus the potential of regional metamorphism to form hydrothermal deposits in the low grade environment should not be neglected.

Loss of metals from pelites during regional metamorphism

Volcanic activity started about 20 Ma before present with quartz tholeiites (QTh), had a climax with alkali olivine basalts (AOB) 13 to 14 Ma ago and ended 7 Ma ago with nepheline basanites (NB) and olivine nephelinites (ON). AOB covers 73% of the volcanic area. About 250 basalts and peridotite xenoliths were sampled for investigation. An upper mantle layer ranging from about 90 to 60 km depth has been conditioned for a preferential alkali basalt production by advection of H2O-CO2-fluids containing Si, Al, Ca, K, Na, P as major constituents beside numerous incompatible minor elements. At the onset of the geodynamically triggered mantle conditioning locally restricted diapirism into shallow depth has caused formation of olivine tholeiite magmas (OTh) at about 1,300° C by partial melting. All of these OTh primary melts intruded due to a favourable compressibility into granulites of the lower crust. The rare QTh basalts are their derivative magmas which have been slightly contaminated in the crust. Magmas of the subsequent alkali basaltic volcanism (AOB, bAOB, NB, ON, MON) formed by in-situ partial melting at about 75 to 90 km depth after depression of the peridotite solidi by fluids to temperatures ≦1,200° C. Except many AOB these magmas are primary melts as characterized by olivine/melt distribution coefficients of Mg/Fe2+ (KD=0.29 to 0.34), by Ni concentrations (260 to 330 ppm) and the occurrence of peridotite xenoliths. Rapid rise of gas charged melts due to saturation in CO2 prevented separation of olivine etc. and of xenoliths. The sequence of magmas from OTh to ON (or MON) is formed from decreasing proportions of orthopyroxene (opx) and increasing contributions of clinopyroxene (cpx) and phlogopite (ph) at almost equal proportions of spinel (sp). Incongruent melting of opx (and cpx) for OTh, AOB, NB and ON is correlated with precipitation of olivine. The average xenolith composition (73% ol, 18% opx, 7% cpx, 1.1% sp and 1.3/0.5% ph) was used to model the sources of the investigated melts by 9 incompatible elements and to calculate degrees of partial melting. The occurrence of garnet cannot be reliably excluded by modelling on the basis of HREE distribution coefficients. The average xenolith composition was used for modelling because of its resemblance with worldwide sampled depleted mantle inclusions. For avoiding to exhaust at least one mineral of the model mantle in the support of the norm composition of OTh, AOB, NB and MON magmas the degrees of partial melting cannot exceed 12.5%, 6%, 6% and 4% respectively. Mantle containing about 500 ppm K (and the correlated incompatible elements), like the average of 36 xenoliths, allows to explain the formation of OTh magmas. AOB, NB and ON melts require peridotite with slightly less than 1,500 ppm K, 670 ppm P and proportions of the correlated elements LREE, Sr, Ba, Zr, Rb, Cs, Ta, Th, Hf, U, which are higher than their abundance in primitive mantle rocks. About 20% of the xenoliths have this composition. Metasomatism of fluids with these elements must have been an immediate precursor of the alkali basaltic volcanism. Otherwise the preservation of a local disequilibrium in 87Sr/86Sr ratios between cpx cores and total rock at upper mantle temperatures cannot be explained.

Origin of the Tertiary basaltic volcanism in the northern Hessian Depression

Determination of arsenic, bismuth, cadmium, selenium, and thallium by atomic absorption spectroscopy with a volatilization technique

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Determination of arsenic, bismuth, cadmium, selenium, and thallium by atomic absorption spectroscopy with a volatilization technique