Soterios P. Varnavas

Hydrothermal metallogenic processes off the islands of Nisiros and Kos in the Hellenic Volcanic Arc

Abstract Two submarine hydrothermal fields off Nisiros and Kos islands in the eastern sector of the Hellenic Volcanic Arc have been investigated using analyses of submarine hydrothermal waters and sediments. Both the waters and the sediments were found to be enriched in Fe, Mn and Zn, together with As, Mo and V in the sediments only, resulting from seawater-rock interaction processes similar to those described from mid-ocean ridge systems. Differences found between the products of these processes in the two hydrothermal fields studied reflect differences between the rock types being leached, the physiographic and geological conditions present including the thickness and composition of the sediment column above the volcanic rocks, and the rates of mixing of hydrothermal solutions with normal seawater. The geochemical features described support possible sub-seafloor formation of metal sulphides at both of the hydrothermal fields studied.

Geochemical and sedimentological patterns in the thermaikos gulf, north-west Aegean sea, formed from a multisource of elements

Surface sediment samples from Thermaikos Gulf were analysed for organic carbon, Cd, Pb, Cr, Cu, Zn, Mn, Ni, Co and Fe and were subjected to grain size analysis. The results showed that Pb, Cu and Zn had the same source of pollution in the following order of importance: the sewage outfall, the industrial zone and the Axios River. The concentration of these metals increased with decreasing mean grain size, suggesting their association with the fine fraction of the sediments, the clays and the organic matter. Cadmium was more loosely correlated with the metals of the previous group, being derived from the community activities and also from the weathering of land-based ophiolitic rocks. Iron, Cr, Ni, Co and Mn are of natural origin, the weathering of mafic and ultramafic rocks being responsible for their enrichment. This was more apparent in the case of Ni, which was more enriched in the coarser and better sorted sediments, near the delta of the River Aliakmon.

Current status in wastewater treatment, reuse and research in some mediterranean countries

AbstractThe status of treated wastewater reuse as experienced in some Mediterranean Basin countries such as Greece, Israel, Italy and Cyprus is examined. General background information is given for each of these Mediterranean countries, including natural water resources, climatic conditions (temperature, rainfall), generated wastewater, crops cultivated and irrigated with effluent, and related aspects of reuse. The examined parameters include treatment strategies, wastewater reuse standards applied in each country, effluent reuse research in progress in the above target countries related to the treatment technologies, water quality, regulations, economics, public acceptance, risk assessment, benefits, keys for potential success and main constraints. Emphasis has been given to the benefits of treated wastewater reuse in integrated water resources management systems and its role for water cycle management, solving water scarcity issues mainly in arid and semi-arid regions of the Mediterranean basin. The exp...

A hydrothermal manganese deposit from the Eratosthenes Seamount, Eastern Mediterranean Sea

Abstract A manganese-crust horizon is described from the Eratosthenes Seamount, south of Cyprus in the Eastern Mediterranean Sea. Its morphological and geochemical features coupled with its geotectonic setting suggest that submarine hydrothermal activity is responsible for its formation.

Dispersion of bauxitic red mud in the Gulf of Corinth, Greece

Abstract Bauxitic red-mud slurry, discharged by an aluminium processing factory on the shelf of the Gulf of Corinth, Greece, is used as a tracer to examine sediment transport and dispersion processes in a tectonically active deep basin. The Gulf of Corinth is a silled elongate basin with a maximum depth of 860 m; it is characterised by high seismicity. The red mud is discharged through a pipeline at a depth of 100 m, where it forms an extensive deposit. Grab sampling has shown that the red mud extends over the slope and the abyssal plain up to a distance of 17 km from the mouth of the pipeline. It forms small scattered sheet-like deposits of up to 3 cm in thickness. The structures observed in the scattered patches of the red mud, which in some places are overlain by a thin veneer of grey/olive green (natural) sediments, suggest that the red mud is transported from the shelf to the abyssal plain by gravitative sediment flows. The flows are triggered by earthquakes. Granulometric and geochemical analyses of the red-mud samples show that the red mud, during its transport from the shelf to the abyssal plain, is subjected to mixing with the surrounding sediments. A different mixing ratio is determined, however, by reference to the various trace metals (Fe, Ni, Co, Pb).

Geochemical study of sediments from northern Euboekos Bay, Greece, with regard to the presence of submarine mineral deposits

Abstract Chemical analyses of surface sediment cores from northern Euboekos Bay, Greece show that this area is markedly enriched in metals (e.g. Ni, Cr, Mn) relative to Aegean Shelf sediments. These enrichments are partly related to the presence of an Fe-Ni ore body on the seafloor formed by the dumping of a metal-rich slag and partly to natural geological processes. In a zone on the northwestern coast of Euboea Island considerable enrichments of Ni, Cr and Mn are attributed to weathering of mafic and ultramafic rocks present on the island and probably extended onto the continental shelf. It is suggested that the geological and oceanographic conditions in this area are favourable for the formation of placer mineral deposits. Similar and even greater enrichments of Fe, Ni, Cr, Mn, Zn and Cu, identified in two older geological horizons, are associated with coarse sediments and may be the result of the following processes: (1) the weathering of ophiolitic rocks or Fe-Ni deposits, or both, extending from onshore below the seafloor; (2) the production of greater amounts of metal-rich weathering products in the past due to climatic changes; and (3) lowering of the sea level at times when metal-rich horizons were being formed closer to the continent.

Hydrothermal metallogenesis at the Wilkes Fracture Zone — East Pacific Rise intersection

Abstract Two hundred and eight sediment samples from 25 gravity cores obtained in and around the Wilkes Fracture Zone on the East Pacific Rise have been analysed in bulk for Mn, Fe, Ni, Co, Pb, Zn, Cu, Ba, Al, Si and CaCO3. Downcore metal variations suggest that, apart from the present hydrothermal event which is more intense on the crest of the rise and in the western part of the fracture zone, in the past, two hydrothermal events occurred: The end of the first event occurred about 121,000 yrs B.P. and that of the second event at about 85,000 yrs B.P. Both events are recognized throughout the study area. A third hydrothermal event is traced only on the crest of the rise, and occurred at about 16,000 yrs B.P. Generally, in the last 90,000 years the eastern part of the Wilkes Fracture Zone appears to have become less active in contrast to the western flank which has become more active. Geochemical partition analysis carried out on selected cores shows that the hydroxylamine HCl-soluble Fe, Mn, Ni, Cu and Zn decrease while the proportion of these metals associated with the HCl-soluble fraction increases with depth in the sediments. In addition, there is an increase in the proportion of the hydroxylamine HCl-insoluble residue with depth. From these data it is inferred that diagenetic transformation of phases occurs within the buried sediments leading to the formation of stable iron oxides and iron smectite. The element partition variations are most pronounced in the upper 40 cm of the sediments and are probably associated with oxidation-reduction reactions in which Mn, Fe-Mn, Fe oxides and organic material are involved. Reduction of Fe-Mn oxides may lead to the release of Mn, Cu and Zn which are subsequently incorporated in the newly formed goethite and smectite. The transformation of the metalliferous sediment constituents to more stable phases increases away from the crest of the rise because the environmental conditions for the formation of smectite become more favorable (i.e., lower temperature, older sediments, greater availability of Al, Si and Mg and greater physical contact between Fe oxy-hydroxides and SiO2 in the narrow basins).

Towards an understanding of the effect of road pollution on adjacent food crops: Zea mays as an example

This work is a preliminary study to test the hypothesis that major roads can have an adverse effect on the heavy metal composition of soil and food crops. Surface and subsurface soil samples were collected at increasing distances from the major road in the Araxos area and they were analysed for organic C, Al, Pb, Cd, Zn, Cu, Ni, Fe, Mn, Cr, Co, P, Ca, Mg and Na by inductively coupled plasma emission spectroscopy. Levels of Ca, Al, Mg and Fe were significantly increased in the surface and subsurface soils in the vicinity of the roadside. This increase was due to dust released from lorries carrying building materials originating from limestone quarries existing in the area. The impact of traffic on adjacent soils was also evidenced by a sharp increase in Pb, Mn, Fe and Al concentrations in the leaves and roots of Zea mays L.

Metal accumulation rates in East Pacific Rise metalliferous sediments

Abstract Metal accumulation rates at a number of stations on the East Pacific Rise fracture zone at 9°S are determined and their areal variations are examined. The accumulation rates of Mn, Fe, Cu, Zn and Ni show their highest values at the Rise crest—fracture zone intersection with zones of lower accumulation rates around this site. There is a negative correlation between the sedimentation rates and the concentrations of Mn, Fe, Cu, Zn and Ni which results from the dissolution of CaCO 3 in the deeper areas. The areal variations of the Al and Ca accumulation rates differ from those of the above metals. The Al accumulation rate is strongly influenced by the presence of volcanic ash. The areas with high Mn, Fe, Cu, Zn and Ni accumulation rates are characterized by low Al and Ca accumulation rates.

Αn Investigation of the Biogeochemical Properties of the Plant Species Οriganum majorana in Relation to its Soil Characteristics

A biogeochemical investigation was carried out on Origanum majorana grown on limestone substrate in Greece. Possible health risks from consumption of dried herbs and infusions were assessed. Macronutrients and essential and toxic metals were determined in the leaves of O. majorana plants and in their soil substrates. Toxic metals were measured in the herbal infusions. Macroelements were found generally in low concentrations for normally developing plants, except for Ca. The ratios N/P and N/K were found lower than the optimum range for normal growth, while the values of K/(Ca + Mg) ratio prevent the development of grass tetany. Manganese and arsenic were enriched in distinct samples. O. majorana plants can be used as indicators for soil environmental assessment. They can also be applied in phytoremediation methods in metal-polluted soils. Hazard indices were far below 1. Carcinogenic risks were found to be within the acceptable range. No health risk is anticipated by the consumption of the specific plants investigated in the present study.