Stavros Kalaitzidis

Massive perturbation in terrestrial ecosystems of the Eastern Mediterranean region associated with the 8.2 kyr B.P. climatic event

The climatic perturbation at ca. 8.2 kyr B.P. is the strongest short-term climate anomaly within the Holocene. It is generally attributed to a meltwater-induced slowdown of the thermohaline circulation in the North Atlantic. Model simulations and available proxy data suggest that it was strongest in the high to middle latitudes around the North Atlantic. Based on new pollen data from Tenaghi Philippon, northeastern Greece, we provide evidence for a massive climate-induced turnover in terrestrial ecosystems of the Aegean region associated with the 8.2 kyr B.P. event. The reconstructed winter temperature decline of >4 °C is much stronger than suggested by model simulations and proxy data from more northern latitudes of Europe, although the latter provide a direct downstream response to a North Atlantic thermohaline circulation slowdown. We attribute this discrepancy to mesoclimatic effects; a stronger influence of the Siberian High during the 8.2 kyr B.P. event may have enhanced the katabatic air flow from the mountains bordering the study site via a larger, longer persisting snow cover. Our data demonstrate that high-amplitude temperature anomalies and increased seasonality connected to the 8.2 kyr B.P. event may also have occurred in the lower mid-latitudes, much farther south than previously thought. The magnitudes of these anomalies appear to have been strong enough to have seriously affected Neolithic settlers in the northeastern Mediterranean region.

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.

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.

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.

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%.

The upland holocene transitional mires of Elatia forest, northern Greece

Four small mires, located at an altitude of 1520 m in the forest complex of Elatia, western Rhodope Massif, northern Greece, were examined in terms of shape, physical and chemical features, plant communities, hydrologic regime, geotectonic setting, and developmental history. The data suggest that the terms bog or fen cannot strictly describe the mires. The mixed vegetation cover of both bog and fen species, the water supply regime (meteoric and surface), the low electrical conductivity, the slightly acidic to subneutral pH values, and the high ash contents support the notion that the mires at Elatia forest can be initially classified as transitional mires. This term is for the first time attributed to mires in Greece. Peat deposition at one of the sites was initiated c. 2,380 years ago but was intermittent to the present day.

EVALUATING CHARCOAL PRESENCE IN SEDIMENTS AND ITS EFFECT ON PHENANTHRENE SORPTION

Small amounts of charcoal in sediments can highly impact the sorption of organic compounds in single solute systems and at low relative concentrations. In the present study, the heterogeneous sorption behavior of charcoals is demonstrated through batch sorption experiments with phenanthrene. The utility of the black carbon content, as measured for soot materials, is evaluated as a measure of the nature of the charcoal material present in sediments. Black carbon content measurements improved predictions of sorptive properties through an additive model but were not sufficient in fully explaining the sorptive behavior observed for the sediments studied in the present work. This is also corroborated through the low and inconsistent measurements of black carbon content observed for laboratory-produced wood chars and natural charcoal samples. Since a quantitative means for prediction of sediment sorptive behavior is not readily available, a more detailed organic petrographical investigation of the charcoals present in sediment samples is pursued. This is a standard method that allows characterization of all (>1-2 μm) organic particles found in a sample. While petrographic methods provide a qualitative description of the sample, it is not possible to use the results to quantitatively predict the overall sorption properties based on this analysis alone. Thus, careful interpretation of qualitative (i.e. microscopy) and quantitative (i.e. black carbon fraction) results should lead us to the determination of a new quantitative property to be used as a predictive tool.

Petrographic Composition and Paleoenvironment of the Amynteo Lignite Deposit, Northern Greece

Maceral analyses along with proximate and elemental analyses were undertaken in order to determine the features of the Amynteo coal deposit and its depositional environment. The Amynteo coal has an eu-ulminite B reflectance of Rr = 0.21%, and in terms of lithotype belongs to matrix lignite. Huminite is the most abundant maceral group, consisting mostly of detrohuminite. Inertinite has relatively low percentages whereas liptinite concentrations are rather high. A ternary plot was applied as an indication of the depositional paleoenvironment. The results from the majority of the samples indicate origin in a topogenous setting. The peat accumulation was governed by a high groundwater level (wet telmatic to limno-telmatic facies). The depositional environment can be characterized as a reed-marsh environment, with occasional establishment of forest swamps.