Kimon Christanis

Geological factors influencing the concentration of trace elements in the Philippi peatland, eastern Macedonia, Greece

Abstract Six peat samples obtained from the Holocene and the Weichselian of the Philippi peat deposit, eastern Macedonia, Greece, were analyzed for 48 trace elements by Inductively Coupled Plasma–Mass Spectrometry (ICP–MS). The ash contents of these samples were also determined. Most of the trace elements are associated with the minerals in the peat, while Ge, Mo, Pb, Se, Ta, Tl, U, and W display a greater affinity with the organic matter. Compared with crustal averages (Clarke concentrations), the Philippi peat is enriched in some elements (Ag, As, Au, Cd, Mo, Se, Te, U, and W) because of the respective mineralizations in the area. The Philippi peat is also enriched in Cr, Cu, Mo, Pb, Sc, Sn, T, V, Y, and Zn in comparison with typical fen peats, as well as in As, Cr, Mo, Se, and U in comparison with typical coals. Climatic and hydrogeological conditions strongly influenced the peat-forming environment resulting in a differentiation between Holocene and Weichselian peat. Generally, the Holocene peat contains lower concentrations of trace elements in the northern and southern part of the fen, than the Weichselian one. The opposite trend is observed in the fen area close to the western basin margins.

How quality and quantity of organic matter affect polycyclic aromatic hydrocarbon desorption from Norwegian harbor sediments

The desorption behavior of phenanthrene, pyrene, and benzo[a]pyrene was investigated for three Norwegian harbor sediments and their respective particle size fractions using the Tenax desorption method. Rate constants for rapidly, slowly, and very slowly desorbing fractions were on the order of 10(-1), 10(-2) to 10(-4), and 10(-4) to 10(-6)/h, respectively. Relatively small amounts were present in the rapidly desorbing fractions (F(rapid): < 6% for phenanthrene, 3-19% for pyrene, and 1-12% for benzo[a]pyrene). With the exception of benzo[a]pyrene, these F(rapid) values were generally lower than median F(rapid) values obtained from more than 100 literature values for native polycyclic aromatic hydrocarbons (PAHs) (22% for phenanthrene, 29% for pyrene, and 8% for benzo[a]pyrene). To understand which parameters influence PAH desorption, relations between desorption behavior and the sediment characteristics were investigated. A significant positive correlation was found between the extent of slow and very slow desorption and the ratios of black carbon to total organic carbon, as well as the temperature at which 50 and 90%, respectively, of the organic matter was oxidized, as obtained from oxidation-only Rock Eval analysis. Thus, black carbon-bound PAHs probably desorb slowly and very slowly. Furthermore, significant positive correlations between desorption behavior and the average particle size were observed, which could be explained by retarded intraparticle diffusion.

Enhanced seasonality of precipitation in the Mediterranean during the early part of the Last Interglacial

The deposition of sapropels in the eastern Mediterranean Sea is thought to occur during intervals of intensified African monsoon and increased precipitation in the Mediterranean borderlands. Speleothem and pollen records, however, reveal conflicting evidence for a Mediterranean-wide precipitation increase, suggesting that seasonal changes in the hydrological regime may be important. Using a multiproxy record, we present the first independent evidence for seasonality of precipitation during the early Last Interglacial (ca. 130–119 ka) from the Tenaghi Philippon peatland in northeast Greece. During the early part of the interglacial, mineralogical, macrofossil, and pollen records from the same core show a shift from mire to lacustrine conditions simultaneous with an expansion of sclerophyllous vegetation and the presence of acicular aragonite, indicating the onset of highly evaporative summer conditions. This indicates enhanced seasonality of precipitation and reconciles the apparent incongruity between Mediterranean pollen and speleothem records. It also provides evidence for significantly increased winter precipitation coeval with the deposition of sapropel S5, one of the most prominent sapropels of the Pleistocene. We suggest that in addition to the summer African monsoon component, increased winter precipitation from the northern Mediterranean borderlands may have contributed to maintaining reduced surface-water salinities in the Mediterranean Sea over the entire year.

Influence of historical industrial epochs on pore water and partitioning profiles of polycyclic aromatic hydrocarbons and polychlorinated biphenyls in Oslo Harbor, Norway, sediment cores

Contaminant levels in urban harbor sediments vary with contaminant emission levels, sedimentation rates, and sediment resuspension processes such as propeller wash. Levels of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) are decreasing in many urban harbors, as heavily contaminated sediments that accumulated during past decades are being buried by less-contaminated sediments. However, PAHs and PCBs remain a concern in areas where burial is slow or resuspension processes re-expose heavily contaminated older layers. Chronostratigraphic sediment core studies typically characterize contaminant level histories by using total sediment concentrations, C(sed) , and do not determine the freely dissolved porewater concentrations, C(pw) , which provide a better measure of bioavailability. Here both C(sed) and C(pw) profiles were established for PAHs and PCBs in dated sediment cores from diverse areas of Oslo Harbor, Norway. Sediment-porewater partitioning profiles were established alongside profiles of various sorbing carbonaceous phases, including total organic carbon (TOC), black carbon, and diverse carbonaceous geosorbents identified by petrographic analysis. Stratigraphic trends in carbonaceous phases and C(sed) could be associated with different industrial epochs: hydropower (post-1960, approximately), manufactured gas (∼1925-1960), coal (∼1910-1925), and early industry (∼1860-1910). Partitioning was highly variable and correlated best with the TOC. Hydropower-epoch sediments exhibit decreasing C(sed) with time and a relatively strong sorption capacity compared with the manufactured-gas epoch. Sediments from the manufactured-gas epoch exhibit substantial PAH and metal contamination, large amounts of coke and char, and a low sorption capacity. Reexposure of sediments of this epoch increases risks to local benthic species. Implications on natural recovery as a sediment management strategy are discussed.

Responses of Lumbriculus variegatus to Activated Carbon Amendments in Uncontaminated Sediments

Activated carbon (AC) amendment is a recently developed sediment remediation method. The strong hydrophobic organic contaminant sorption efficiency of AC has been shown in several studies, but effects on benthic organisms require more investigation. The AC induced effects on egestion rate, growth and reproduction of Lumbriculus variegatus were studied by applying bituminous coal based AC in three different particle size fractions, namely <63 μm (90%, AC(p)), 63-200 μm (AC(m)) and 1000 μm (AC(g)), to natural uncontaminated (HS) and artificial sediment (AS). Egestion rate, growth and reproduction decreased with increasing AC concentration and finer AC particle fractions, effects being stronger on HS than on AS sediment. Lipid content in AS was reduced already at the lowest AC doses applied (AC(p) and AC(m) 0.05%, AC(g) 0.25%). In addition, hormesis-like response was observed in growth (AS) and reproduction (AS, HS) indicating that AC may disturb organisms even at very low doses. Potential ecological effects need to be further evaluated in an amendment- and site-specific manner.

Scanning electron microscope studies of the Philippi peat (NE Greece): initial aspects

The ash contents (on dry basis) of the Philippi peat range up to 46 wt.%, indicating increased inorganic supply to the fen. The acquisition of backscattered electron images (BEI) using scanning electron microscope (SEM) provided an initial differentiation between the inorganic fraction and the organic matter. Spectral patterns obtained from several inorganic particles, in combination with X-ray diffraction studies, revealed the abundant occurrence of carbonates, clay minerals, quartz, feldspars, gypsum and pyrite. Clay minerals, quartz grains and feldspars tend to incorporate into humodetrinite, while carbonates and pyrite occur both in humodetrinite and empty cell lumens of humotelinite. Elemental microprobe X-ray mapping of the elements Ca, P, S, Si, Al and Fe provided an initial fingerprint of the elemental distribution and can be a useful tool for understanding the relationship between minerals and macerals within coals.

Characteristics of scales from the Milos geothermal plant

Samples of scales have been studied using X-ray diffraction, elemental analysis and scanning electron microscopy. Analyses have also been made of brine and steam samples. The scale consists of heavy metal sulfides and silicon compounds which account for 90-100% of the deposited mass. The composition of the scale depends on the location with respect to the fluid flashing point. Samples in the vicinity of this point largely consist of metal sulfides (PbS, ZnS and CuFeS/sub 2/), while the percentage of silica and possible of other silicon compounds tends to increase farther downstream. In all the samples, a significant part of the iron is not in the form of sulfide and is possibly bound into the silica matrix by some kind of ion-bridging. It is also observed that a silicon - rich layer adheres to the metal surface, even in places where sulfides are the main constituents of the scale.

Mineral matter in the Philippi peat in relation to peat/lignite-forming conditions in greece

The Upper Weichselian and Holocene layers of the 190 m thick peat sequence in the Philippi basin (NE Greece) are studied by means of their mineralogical and geochemical features. The ash contents range between 11.4 and 53.4% and inorganic carbon contents range between 0.5 and 5.7%. X-ray diffraction (XRD) analysis revealed that Mg-calcite, quartz, clay minerals, K-feldspars, plagioclases, and chlorites are the dominant minerals in the peat. Lime, pyrite, siderite, apatite, iron-oxides, weddellite, and basaluminite occur subordinately. During Upper Pleniglacial and Late Glacial times, clastic sedimentation prevailed in the palaeomire. Peat was enriched in Fe, K, Ti, As, Cr, Cu, Ni, Rb, Th, Y, Zn, and Zr. In Early Holocene, authigenic sedimentation of Ca-rich material dominated. Peat became enriched in As, Br, Se, Sr, and U. In Middle Holocene, fluctuations of the water table in the mire resulted in the deposition of both authigenic and clastic minerals. The Late Holocene peat is intensely damaged due to drainage and cultivation. The mineral matter features of the Upper Weichselian peat are identical to the features of many Greek lignites.

A study of scale deposition: An analogue of meso- to epithermal ore formation in the volcano of Milos, Aegean arc, Greece

Abstract The viability of boiling as a mechanism for meso- to epithermal ore formation has been tested in the Milos volcano, Aegean Island Arc, by investigating rates of deposition and composition of scale, and by drawing an analogy between the results and actual field occurrences on the island. Milos offers ideal conditions for such testing: it consists of predominantly felsic volcanic rocks with numerous late-stage hydrovolcanic (phreatic) breccias. A geothermal system is at present active in the area, with numerous terrestrial and submarine hot spring outlets and kaoline and bentonite alteration zones. AuAg bearing polymetallic, as well as manganese and barite ore deposits, occur on the island; scaling tests were made possible after the installation of a 2 MW geothermoelectric plant on Milos. The rates of scale deposition were measured during different test times and analyses made on the chemistry and mineralogy of scales from the Milos plant; the results indicate that the rates of scale deposition are higher near the flashing valve, and that the metals Pb, Cu, Zn are deposited as sulphides in the vicinity of the flashing point, particularly PbS, which has the lowest solubility and, to a lesser degree, Cu-sulphide. ZnS is the dominant sulphide downstream. Higher scaling rates are observed in tests which are suspect of a higher incidence of two-phase flow in the pipe. Pressure, temperature and salinity conditions of the hydrothermal fluid are conducive to phase separation in the upper parts of the Milos geothermal system and down to a depth of 1000–1100 m but, as scaling tests indicate, self-sealing of the system could rapidly halt hydrothermal flow and ore formation; however, hydrovolcanic (phreatic) explosions may initiate new cycles of ore-deposition. The metals have mainly precipitated as sulphides, except for Fe, which is found mostly in the siliceous matrix of the scale. The paragenesis of the metals in the Milos scales is similar to those of AuAg bearing polymetallic deposits on the island. Domains with signs of multiple episodes and craters of hydraulic fracturing, argillic alteration, siliceous sinters and gossaneous cappings, should be targeted on Milos for exploration for meso- to epithermal polymetallic and precious metal ores.

Preliminary comparative analyses of two Greek leonardites

Two leonardite benches occur in the lignite basins of Achlada (NW Greece) and Zeli (Central Greece). In this study, we present some initial results concerning chemical composition (C, H, N and S), kind of inorganic matter, contents of free-humic acids, and the petrological features. Both samples are classified as lignites and display similar values of carbon contents. The Zeli-sample displays higher hydrogen and lower sulphur contents than the sample from Achlada. Nitrogen in both cases remains below the detection limit. Increased silicate inorganic influx, consisting mainly of clay minerals, affected both benches. The organic matter is low to moderately gelified and intensely fragmented, with attrinite being the predominant maceral. Inertinites are almost absent, whereas liptinites occur with low values. Values of free-humic acids are similar, ranging up to 50 wt%.