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  • Izotopske in geokemične značilnosti lupinic školjke Mytilus galloprovincialis iz Jadranskega morja : diplomsko delo
    Kanduč, Tjaša
    The marine mussel Mytilus galloprovincialis lives attached to the surface of hard substrata where its exposure and relative immobility allow it to record changes in ambient seawater. In addition, ... because M. galloprovincialis deposits daily accretionary growth bands in the outer prismatic calcite layer of its shell, the shell contains a continuous record of seawater temperature and chemical conditions. Bivalves from most of their shell in the summer season. This means that this isotopic and geochemical composition of bivalve shells represent conditions in seawater primarily during the summer season. Samples of M. galloprovincialis were collected in October 1998 from coastal area of the Adriactic Sea (north, central, south). Determination of delta ▫$^18O$▫ and ▫$^13C$▫ was performd on calcite and aragonite of separate shell layers using a VARIAN MAT 250 mass spectrometer at the Jožef Stefan Institute. Multielement geochemical analysis was determined at ACTLAB in Onatrio (Canada), where they analysed major, minor and trace elements of the whole shell content using an ICP-MS. Molluscs, in general, are believed to exert only a minimal vital (metabolic) effect over their isotopic composition ( Jones, 1985), and thus their isotopic values are representative of environmental water conditions. Isotopic dis equilibrium may be, in part, due to kinetic effects that are inherent in fast growing areas of the shell (Mitchell, et al., 1994). Mytilus galloprovincialis uses aragonite and calcite to build its shell. Because aragonite is found to be enriched by 0,7 promille in ▫$^18O^$▫ and by 1 promille in ▫$^13C$▫ relative to coexisting calcite at the relevant temperatures (Grossman & Ku, 1986) we sampled the shell layers separately for isotopic analysis. We found out that, on average, aragonite is enriched by 1,07 promille in ▫$^13C$▫ and by 0,15 promille in ▫$^18O$▫. The ▫$^18O$▫/▫$^16O$▫ ratio of carbonate is determinated by the ratio in the water from which it is deposited and the temperature at which the deposition occurs.Most marine carbonates reflect the delta ▫$^13C$▫ of totaldissolved carbon (TDC) of the water in which they form their shell (Anderson & Arthur, 1983). The calculated temperatures for M. galloprovincialis shell growth from the investigated area range from 17,7 - 24,7°C for calcite and from 20,5 - 28,3°C for aragonite, according to the equation of Craig (1965) and Grossman & Ku (1986). According to our results of delta ▫$^18O$▫ and delta ▫$^13C$▫ in shell layers of M. galloprovincialis we can separeted the locations of the investigated area into three groups: those with more influence of fresh water,those with less influence of fresh water and those of marine environments. Results of delta ▫$^13C$▫ indicate that shells from locations influenced by fresh water inflow are enriched with ▫$^12C$▫. Fresh water contains more carbon originating from biogenic processes than marine water, which is generaly in isotopic equilibrium with atmosferic carbon dioxide. Previous investigations suggest that a record of heavy metal pollution may be found within the shells of bivalve molluscs (Bourgoin, 1989). Bivalves adsorb, absorb, accumulate, and concentrate a variety of pollutants, includingheavy metals. Minor elements substitute for calcium in the calcite or aragonite structure in accordance with ionic radius. In our case, the of M. galloprovincialis has proven to be a good indicator of pollution of Adriatic coastal area. We see the highest contents of manganese, barium, boron, arsenic, nickel in the shells of M. galloprovincialis from the locations Omiš and Bačvice (central Adritaic), where chemical and heavy industry is located, and where sewage is duniaed into the coastal area of sea.The highest concentrations of manganese were measured in the samples from Sv. Ivan (south Adriatic), where the Neretva River uotflows into the sea and carries contaminants from the industrial area of Mostar. An abundance of pollutants (boron, barium, nickel) were also found in shells from the industrial area of Zablače (central Adriatic); the main cause colud be municipal sewage. The highest concentartions of zinc, lead, copper were measured in samples from Pula, Rijeka and Gruž where there are also ports in addition ti industry. Positive correlations between delta ▫$^18O$▫, delta ▫$^13C$▫ and concentrations of sodium and molybdenum were found in M. galloprovincialis shell samples from the researched locations, and negative correlations betweendelta ▫$^18O$▫, delta ▫$^13C$▫ and cocentartions of strotium, magnesiumand tellurium. For more detailed geochemical and isotopic analysis itis necessary to sample growth bands of the M. galloprovincialis shells. The shells from the inevestigated locations should also be the same size and therefore the same age. In this case it would be possible to determine better correlations between measured quantittes.
    Vrsta gradiva - diplomsko delo ; neleposlovje za odrasle
    Založništvo in izdelava - Ljubljana : [T. Kanduč], 2000
    Jezik - slovenski
    COBISS.SI-ID - 224862

Knjižnica Signatura – lokacija, inventarna št. ... Status izvoda
NTF, Oddelek za geologijo, Ljubljana Geologija
D KANDUČ Tjaša Izotopske
IN: 000012912 		prosto - na dom, čas izposoje: 14 dni
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