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Development and validation of a Benthic Flux Model for the Adriatic Sea

WORKSHOP W10 Progetto VECTOR. (Rimini, 10-11 settembre 2007). Development and validation of a Benthic Flux Model for the Adriatic Sea. Zaffagnini F. 1 , Vichi M. 1,2 , Frascari F. 3 , Spagnoli F. 4 , Marcaccio M. 5 , Bergamini C. 3.

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Development and validation of a Benthic Flux Model for the Adriatic Sea

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  1. WORKSHOP W10 Progetto VECTOR (Rimini, 10-11 settembre 2007) Development and validation of a Benthic Flux Model for the Adriatic Sea Zaffagnini F.1, Vichi M.1,2, Frascari F.3, Spagnoli F.4, Marcaccio M.5, Bergamini C.3 Keywords: Layer Model, Biogeochemistry, Diagenetic processes, Adriatic Sea Presenter: F. Zaffagnini fabio.zaffagnini@bo.ismar.cnr.it 1:CMCC 2:INGV 3:ISMAR CNR – Bo 4:ISMAR CNR – An 5:ARPA ER – Bo

  2. Geochemical Modelling:Objectives Find homogeneous biogeochemical regions in the Adriatic Sea Define initialization parameters for each facies Run the simulation and compare with available observations No predictive purposes 2/13

  3. Layer Model (BFM)‏ Geochemical Modelling Diagenetic processes: 2 approaches Level Model Explicit depth-profile resolution 3/13

  4. BFM: The Layer Model Pelagic System • 3 Layers governed by different diagenetic environments • Steady state analytical solutions are calculated (Berner equations) for each layer • Each layer considers integrated concentrations for every parameter • The evolution over time is determined through many transient solutions (Initial conditions  Equilibrium) • Only vertical diffusion! Berner (1980) Oxic K D1 K1 Suboxic D2 K2 Anoxic Dtot Benthic System 4/13

  5. The Model D Layer Depths Y Zoobenthos Predation D(1)‏ Yi(1)‏ Yi(2)‏ Yi(3)‏ Yi(4)‏ Yi(5)‏ Macrobenthos Detritivores Filter feeders Meiobenthos Infaunal predators Oxic layer D(2)‏ Anoxic layer G Dissolved Gases Respiration D(6)‏ Qc(6) penetration G(6)‏ Oxygen D(7)‏ Qn(6) penetration Ingestion/Egestion G(6)‏ Carbon dioxide D(8)‏ Qp(6) penetration D(9)‏ Qs(6) penetration Excretion K Nutrients Respiration Q Organic Matter K(1)‏ K1(1)‏ K2(1)‏ K(3)‏ K(4)‏ K1(4)‏ K2(4)‏ K(5)‏ Phosphate - Oxic Layer - Dentrification Layer - Anoxic Layer Nitrate Ammonium - Oxic Layer - Dentrification Layer - Anoxic Layer Silicate Dissolution Qi(1)‏ Q1i(1)‏ Qi(6)‏ Semi-ref. DOM - Oxic - Anoxic Particulate OM Oxidation Uptake/Release Uptake/Release Predation H Benthic Bacteria K Inorganic species Hi(1)‏ Hi(2)‏ Aerobic Anaerobic Chemotrophy K(6)‏ Reduction Equivalents Organic matter flow (C,N,P,Si)‏ Inorganic nutrient flow (N,P,Si)‏ Gas exchange (Bio)chemical reaction Boundary flow Living OrganicCFF (LFG)‏ Non-living OrganicCFF Inorganic CFF 5/13

  6. BFM: Output • Variations of concentration in the layers • Changes of the layers’ thickness • Fluxes of the major geochemical species all outputs expressed over time 6/13

  7. BFM: Adriatic Seabiogeochemical facies • 5 facies: • High reactivity • Medium reactivity • Low reactivity • Negligible reactivity • Coastline • First Station: S1 • Many data • Most complex area • Very reactive 1 4 5 3 2 Frascari et al. 1997 7/13

  8. BFM: Initialization From ISMAR – CNR database (1973-2005) Sediment & pore water data: • Nutrients • DOM and POM concentration and input • Chemical-Physical parameters • Benthic Fluxes 8/13

  9. BFM: Method Initialization of variables Assignment of values measured in station S1 Model run Check the evolution of variables over 10 years Estimate the required deposition rate of Organic Matter in order to: Maintain the initial conditions Obtain a credible equilibrium Stationary conditions (no seasonality) Absence of feedback from the pelagic system Numerical validity check 9/13

  10. BFM: Initialization Choice of the 3 layers’ thickness Fe in pore water D1=0.5 cm NO3 D2=7.5 cm Starting values POC NH3 Porosity 10/13

  11. BFM: Results Oxygen penetration depth Denitrification depth Oxygen in pelagic system POC 11/13

  12. BFM: Results Ammonium Phosphate Oxic Layer Oxic Layer Suboxic Layer Suboxic Layer !? Anoxic Layer Anoxic Layer 12/13

  13. BFM: Conclusions Considering a stationary input of oxygen and organic matter, we see: • Reached equilibrium of most variables similar to startup conditions • Some variables (i.e. phosphate) show problems Short term future purposes: • Fix problems and uncertainities • Add seasonality to external sources Medium term future purposes: • Apply the BFM to the other facies in Adriatic Sea • Couple the BFM with the Pelagic Model 13/13

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