Cellular energy allocation in mussels (Mytilus galloprovincialis) from the stratified estuary as a physiological biomarker

This study demonstrates the usefulness of cellular energy allocation (CEA) evaluations as a physiological biomarker to infer the occurrence of natural stress in native populations of mussels inhabiting the stratified estuary (Krka River estuary, Croatia). Sampling sites were selected based on their differences in the salinity and temperature. The CEA value was calculated as a ratio between available energy (E_a) and energy consumption (E_c). Generally, higher values of E_a were recorded in June than in November, which were especially evident in the storage components (carbohydrates and lipids), while the constitutive component (proteins) remained relatively constant. The highest E_c was recorded in mussels at estuarine site compared to coastal site, which may be caused by the energetically costly maintenance of osmotic balance. Decrease in CEA recorded in estuarine mussels may ultimately result in a lower amount of energy available for growth, reproduction, or defence against other stresses (e.g. pollution).     

AHP-based group decision making approach to supplier selection of irrigation equipment

Supplier selection is a complex task which assumes decision making in presence of many conflicting criteria and various parameters. If there are more than one decision maker, the problem shifts into a group context and it requires proper approach in mediating the decision making process and use of supporting multi-criteria methods and tools. This paper proposes group decision making approach for supplier selection based on analytic hierarchy process (AHP) that is combined with consensus convergence model, and two voting methods, non-preferential approval voting and preferential Borda count. Proposed approach utilized strengths of these methods thus enabling their adaption to the specific decision problem of supplier selection. An example of selecting a supplier of irrigation equipment in the company engaged in projecting, installing and maintenance of irrigation systems is used to explain and demonstrate how proposed approach can be implemented. Furthermore, this approach is viable as sufficiently general in supporting different selection processes in a field of water planning, management, and development and it can be adapted and applied on various group decision making problems.     

Structure analysis of geopolymers synthesized from clay originated from Serbia

The paper presents chemical and structural analysis of geopolymer materials which are obtained by alkali-activated calcined clay (metakaolin) originated from Serbia under strictly defined conditions. Characterization of the metakaolin and geopolymers molecular structure has been done using X-ray diffraction, scanning electron microscope, Fourier transform infrared spectroscopy and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. The paper presents the possibility of obtaining geopolymer structure and differences in chemical and structural characterization of these materials taking into account the concentration of NaOH as a variable parameter. The results of MALDI analysis of metakaolin and synthesized geopolymer structures using various matrix system: 2,4,6 trihydroxyacetophenone (THAP), α-cyano-4-hydroxycinnamic, 2,6 dihydroxyacetophenone and laser desorption/ionization, have shown that THAP matrix is the most appropriate for analysing these aluminosilicate materials.     

Geology of the San Isidro iron ore deposit,Venezuela

The iron ore deposits of Cuadrilatero Ferrifero de San Isidro represent the largest iron ore reserves in Venezuela. The district is a part of the iron metallogenic province of northern Guayana, one of the richest iron-bearing regions of the world. All presently known iron ore deposits of Venezuela are situated within this province: Cerro Bolivar, Altamira, Rondon, San Isidro, María Luisa, El Pao and others. Their total ore reserves amount to 2,000 million tons (disregarding the unenriched or slightly enriched iron-formation). The Imataca belt to which the iron ore deposits are confined consists of metamorphosed sedimentary and igneous rocks of Early Precambrian age, the oldest rocks presently known in South America. This belt extends some 450 km from the Orinoco delta southwesterly to the Cauro River. Iron ore is formed from banded iron-formation, a member of the Imataca complex, by removal of silica. The process of supergene enrichment is controlled to a certain degree by structural elements. There are five ore bodies in the San Isidro district, extremely varied in shape and size. Single bodies extend up to 3–4 km in length, approximately parallel to the regional structure pattern, and a few hundred meters in width. The morphology of the bottom of the ore bodies is rather irregular, particularly in transversal sections. Contacts between ore and the unaltered iron-formation beneath are gradational. Maximum vertical section through ore is 260 m; the average is 60 m approximately. The stratigraphic thickness of iron formation has been magnified by structural deformations. The primary stratigraphic thickness is estimated to be some 50–150 m. The iron ore is classified into two main types: a) hard, crustal ore, b) soft, friable ore. Hematite grains which remained after the leaching of silica, and goethite (as cement) are the two main constituents of crustal ore. Hematite and magnetite and a minor amount of quartz are almost the only constituents of friable ore. The crustal ore forms a 15–60 m thick mantle covering friable ore. The overall volume ratio between the friable and the crustal ore is about 2:1. However, it varies in different zones. The mean composition of iron ore on the basis of 10,800 chemical analyses is 64.41% Fe, 2.62% SiO₂, 0.6% Al₂O₃. The ore contains a minor amount of Mn, P, Ti (no S, As, Ba). The ore reserves amount to 750 million tons; in addition, 180–300 million tons of possible ore reserves are estimated.

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Zusammenfassung Die Eisenerzlagerstätten der Cuadrilatero Ferrifero de San Isidro beinhalten die größten Eisenerzreserven in Venezuela. Der Erzbezirk ist ein Teil der reichsten Eisenerzregionen der Welt. Alle bekannten Eisenerzvorkommen Venezuelas befinden sich in dieser Provinz (Cerro Bolivar, Altamira, Rondon, San Isidro, Maria Luisa, El Pao und andere). Die Gesamtvorräte werden auf etwa zwei Milliarden Tonnen geschätzt (ohne die nichtangereicherten oder nur wenig angereicherten Eisenquarzite). Die Imataca-Zone, an die die Eisenerzvorkommen angrenzen, besteht aus metamorphosierten sedimentären und magmatischen Gesteine des Archaikums, die ältesten bisher in Südamerika bekannten Gesteine. Die Imataca-Zone erstreckt sich ungefähr 450 km vom Delta des Orinoco in südwestlicher Richtung bis Rio Cauro. Die Eisenerze entstanden aus feingeschichteten (gebänderten) Eisenquarziten (Itabirite). Die Prozesse der deszendenten Anreicherung werden teilweise durch strukturelle Elemente bedingt. Fünf Erzkörper des San Isidro-Bezirks sind bekannt. Die Lagerstätten sind 3 bis 4 km lang und einige Hunderte Meter breit. Sie sind den regionalen Strukturen vorwiegend parallel gelagert. Die Morphologie der Erzkörperunterlage ist ziemlich unregelmäßig, besonders senkrecht zum Streichen. Der Kontakt zwischen dem Erz und den unterliegenden unveränderten Eisenquarziten ist stufenförmig. Das Erz ist durchschnittlich etwa 60 m mächtig, mit maximalen vertikalen Mächtigkeiten von 260 m. Die primäre stratigraphische Mächtigkeit des Eisenquarzites wurde durch strukturelle Deformationen vergrößert. Man kann die primäre Mächtigkeit auf 50–150 m schätzen. Das Eisenerz wird in zwei Typen klassifiziert: a) hartes Krustenerz, b) weiches, bröckeliges Erz. Die Hämatitkörner, die nach der Entfernung der Kieselsäure übrig blieben nebst Goethit (als Zement), sind die zwei wichtigsten Komponenten des Krustenerzes. Das weiche Erz enthält Hämatit, Magnetit und etwas Quarz. Das Krustenerz bildet eine 15–60 m mächtige Decke über dem bröckeligen, weichen Erz. Das Gesamtvolumenverhältnis zwischen dem weichen und harten Erz ist ungefähr 2:1. In anderen Zonen ist es jedoch unterschiedlich. Die durchschnittliche Zusammensetzung des Eisenerzes ist: Fe 64,41%, SiO₂ 2,62%, Al₂O₃ 0,6%; das Erz enthält auch etwas Mn, P, Ti (kein S, As, Ba). Die Eisenerzvorräte wurden auf 750 Millionen Tonnen berechnet, wozu wahrscheinlich weitere 180–300 Millionen Tonnen kommen.

     

Management of karst aquifers in Serbia for water supply

Karst aquifers represent one of the main sources of water supply in Serbia. Wide distributions of karstic areas, abundant reserves, and excellent quality of karst groundwater have been the reasons for its extensive use in water supply systems throughout the country. In Serbia, 70 karstic sources have been tapped for centralized water supply, with the assessed minimal capacity exceeding 4.5 m³/s. Most of the large cities of Eastern and Western Serbia currently use karst groundwater for water supply; however, due to unstable flow regime when only natural springflow is tapped, numerous problems arise during the recession period (summer–autumn). During the last two decades, after favorable conditions had been confirmed through hydrogeological survey and feasibility studies, several newly constructed systems for artificial control of karst aquifers (mostly in Eastern Serbia) resulted in significantly improved water supply.     

Heavy metals in sediments—problems concerning determination of the anthropogenic influence. Study in the Krka River estuary,eastern Adriatic coast,Yugoslavia

Factors that govern heavy metal concentration in sediments were examined by a combined analytical, geochemical, and geological approach. The constrains encountered in the determination of the anthropogenic influence are exposed. The region examined was the Krka River estuary located in the typical karst region of the eastern Adriatic, Yugoslavia.Sedimentological research revealed that: the Krka River (main water supplier) is almost free of suspended terrigenous material; the main supplier of suspended terrigenous matter of flysch origin is a small torrent-type Gudua Creek, and that this fine grained terrigenous material is sedimented mostly in the central enlarged part of the estuary, the Prokljan Lake.Three different groups of heavy metals were identified in recent sediments. Increased concentrations of nickel and zinc were found in estuarine sediments due to strongnatural enrichment in source rocks. Manganese and chromium were found to benaturally enriched and depleted in surface layer respectively, due to the different postdepositional geochemical behavior. Lead and copper concentrations were found to be increased in surface sediments in the central part of the estuary, apparently from anthropogenic source.     

The two polymorphs of TlPbSbS3 and the structural relations of phases in the system TlSbS2-PbS

Summary The synthetic TlPbSbS₃ represents a rare example of a sulphosalt with statistical distribution of Tl, Pb and Sb in the structure. Within the TlSbS₂-PbS system, TlPbSbS₃ is the end member of the solid solution series with TlSbS₂, but no solubility with PbS is detected. The high temperature-TlPbSbS₃ is orthorhombic and inverts at about 620 K to the low-temperature phase. The low-temperature modification of TlPbSbS₃ was structurally investigated by X-ray powder diffraction and by the Rietveld analysis of the data. The structure is monoclinic, with a = 4.1707(4) Å, b = 4.2856(4) Å, c = 12.157(1) Å, = 105.49(1)°, space group P2₁/c. Like in the high-temperature form, there is a cation disorder over the equivalent positions in the structure. The interatomic distances of (Tl, Ph, Sb) to S are 2.71, 2.72, 2.88, 3.15, 3.29, 3.51 (Å). There is a close similarity between the TlPbSbS₃ polymorphs and the and forms of SnS, as regards the atomic coordinations and the general structure types and the same type of phase transformation is supposed for both cases. The small differences in the structure type and symmetry, between the low temperature forms of SnS and TlPbSbS₃, result probably from stronger metal-metal interactions in the latter. A substitution-derivative relation to SnS type is established owing to the strong structural effect of the lone electron pairs of Tl and Sb. The substitution of Ag for Tl and Bi for Sb in ABCS₃ type compounds diminishes this effect and PbS type structures are produced.

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Die zwei Polymorphen von TlPbSbS₃ und die Strukturellen Beziehungen von Phasen in System TlSbS₂-PbS

Zusammenfassung Die synthetische Phase TlPbSbS₃ ist ein seltenes Beispiel von einem Sulfosalz mit der statistischen Verteilung von TI, Pb und Sb in der Struktur. In der TlSbS2-PbS Phasensystem, ist TlPbSbS₃ das Endmitglied der Mischkristallreihe, die sich im Richtung TlSbS₂ ausstreckt. Weitere Ausdehnung der Mischkristallreihe in der Richtung SbS konnte nicht bewiesen werden. Die Hochtemperatur-TlPbSbS₃ ist rhombisch und wird beim 620 K in die Tieftemperatur Modifikation umgewandelt. Die Tieftemperaturphase ist mit der Röntgenpulverdiffraktion und Rietveld Methode strukturell untersucht worden. Die ist monoklin, mit den Gitterkonstanten: a = 4.1707(4) Å, b = 4.2856(4) Å, c = 12.157(1) Å, = 105.49(1)°, Raumgruppe P2₁/c. Die statistische Verteilung von Kationen ist auch hier vorhanden. Die zwischenatomare Abstande (Tl, Pb, Sb)-S sind: 2.71, 2.72, 2.88, 3.14, 3.28, 3.51 (Å). Es besteht eine enge Verwandschaft zwischen den polymorphen Modifikationen von TlPbSbS₃ und den und Polymorphen von SnS, was die atomare Koordinationen und den generellen Strukturtypus betrifft, wobei ein ähnlicher Mechanismus der Phasenumwandlung für die beiden Fälle vermutet werden könnte. Die Differenzen in der Struktur und Symmetrie zwischen der Tieftemperaturmodifikationen von SnS und TlPbSbS₃ sind wahrscheinlich durch die bedeutende Metall-Metall Wirkungen in der zweiten verursacht. Die Phase TlPbSbS₃ ist ein substitution-derivative von der SnS Struktur, was durch die starke lone-electron-pair Aktivität von Kationen zu erklären ist. Die Ersetzung von Tl durch Ag und Sb durch Bi vermindert diese Aktivität und die entstandenen Strukturen sind in dem Fall dem PbS-Typus verwandt.

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With 3 Figures     

Inter-decadal Variability in Phytoplankton Community in the Middle Adriatic (Kaštela Bay) in Relation to the North Atlantic Oscillation

Evaluation of a 45-year data set of primary production (PP), a 30-year data set of phytoplankton biomass, and a 51-year data set of species composition shows an increase of phytoplankton biomass and abundance in the period from the mid-1980s to the mid-1990s. Phytoplankton biomass showed bimodal seasonal cycles, with winter and spring maxima, which did not change over the past 30 years. Diatoms were the most abundant functional group and they prevailed during the colder part of the year while the dinoflagellate contribution to the phytoplankton community increased in the warmer period from May to August. Diatoms showed a significant negative correlation with sea surface temperature (SST), while dinoflagellates were positively correlated with SST. An increase of phytoplankton abundance, particularly dinoflagellate, in the period from the mid-1980s to the mid-1990s coincided with years characterized by a high North Atlantic Oscillation (NAO) index. Primary production and chlorophyll a concentration in the spring period were negatively correlated with the NAO winter (DJFM) index, probably caused by increased precipitation associated with a low or negative NAO index. PP in winter during the mixing period was positively related to the NAO winter index associated with higher temperatures and dry conditions which brought more clear days and increased input of solar radiation.