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N . Ogrinc “ J. Stefan” Institute, Dept. of Environ. Sci., Ljubljana, Slovenia J . Faganeli

Phosphorus regeneration and burial in near-shore marine sediments (the Gulf of Trieste, N Adriatic). N . Ogrinc “ J. Stefan” Institute, Dept. of Environ. Sci., Ljubljana, Slovenia J . Faganeli Marine Biological Station, Piran, Slovenia.

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N . Ogrinc “ J. Stefan” Institute, Dept. of Environ. Sci., Ljubljana, Slovenia J . Faganeli

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  1. Phosphorus regeneration and burial in near-shore marine sediments (the Gulf of Trieste, N Adriatic) N. Ogrinc “J. Stefan” Institute, Dept. of Environ. Sci., Ljubljana, Slovenia J. Faganeli Marine Biological Station, Piran, Slovenia

  2. Investigation of the biogeochemical cycling of phosphorous to elucidate the present and future naturally and anthropogenically induced changes in this coastal ecosystemusing  Aime . . .

  3. Pore water chemistry • Benthic flux experiment (oxic and anoxic conditions) • Sediment analysis – to reconstruct sedimentary phosphorus budget • Examination of historical changes of sedimentary P - (long core GT3)

  4. Location: N Adriatic sea area: approx. 500 km2 max. depth: 25m Inflow: river Isonzo in the N Water characteristics temperature at the bottom: 8-22oC salinity: 33-38.5 overlying water oxic, inlate summer hypoxia (occasionally anoxia) Some characteristics I

  5. AA1 Sampling locations -the Gulf of Trieste GT3 core length: 130 cm water depth: 25 m F

  6. Some characteristics II • Composition of the sediment: • clay and silt-sized materialcarbonates: mostly low-Mg calcite: biogenic, up to 70% • no carbonate fraction: quartz, illite, chlorite and mixed illite/montmorillonite • organic content: 0.3 – 0.7 wt.% • bioturbated: 10-15 cm

  7. Water samples: O2, nutrients, sulphide, sulphate, Fe, Mn Sediment samples: Organic C, Total N, Total P, Inorganic P, Total S, Reducible S, Total Fe, Total Mn Analyses

  8. Redfield: N:P = 16 Suspended particulate matter: N:P = 9 Sedimenting organic matter: N:P = 11 Surficial Sediment: N:P = 7 Previous results in the Gulf of Trieste

  9. Pore water I

  10. Pore water II

  11. P - remobilization • EXAFS - Goethite the predominant crystalline structure • Reduction of Fe oxide – 8% of the P flux • Precipitation and nucleation - fluoroapatite

  12. Incubation experiment I

  13. Incubation experiment II

  14. Pinput = Pefflux + Pburial Pburial = w TP  (1- ) w … sedimentation rate  … density  ...porosity E = Pefflux/Pinput ~ 50% Sedimentary P - budget

  15. Mass balance of particulate phosphorus

  16. Conclusions I Pore water and incubation experiment: • Degradation of organic matter is a principal mechanism of phosphate regeneration • The high C:N:P ratio of degradable sedimentary organic matter suggests precipitation of phosphates - fluoroapatite

  17. Conclusions II Sediment • The results of the tentative mass balance estimation indicate the preservation of TP in the form of fluoroapatite (about 50%) • Palaeoenvironmental reconstruction - the increase of TP, OP, TN and OC in the sediment core probably indicate the use of inorganic fertilizers and detergents after 1950

  18. 10thInternationalSymposium on theInteractions Between Sediments and Water Bled, Slovenia August 28th – September 2nd, 2005 www.icjt.org/iasws2005 E-mail: iasws@ijs.si Organized by: National Institute of Biology “J. Stefan” Institute

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