Phthalates and Nonylphenols in Roskilde Fjord

• Constant concentrations of suspended matter in water and sediment(X w , X s ).• Equilibrium between dissolved and adsorbed substance (K d ).• Water volume is totally mixed along the vertical axis.• Only vertical diffusive flows in sediment (D sz ).• Dissolved concentration in sediment surface layer is equal to the dissolvedwater concentration.• 1 st order degradation of dissolved substance in water and sediment(k 1 ).• Increasing sediment depth in time due to sedimentation (S).6.4.1 Steady-state box-modelThe values in Table 24 and the model parameters are inserted in the generalsteady-state Equation 12.0 = Point sources + Freshwater sources +Water exchange +Atmospheric deposition + Sedimentation + Degradation ⇒ (12)For Roskilde Vig the mass balance becomes0 = CWWTP⋅ R WWTP ⋅ Q WWTP + C tot,f ⋅ Qf,vig( Q + Q Q ) +C w, vig ⋅ R w ⋅ bred-vig p,vig +Ctot, depvigw,vigvigf, vig⋅ A - C ⋅ S ⋅ A ⋅ R - k ⋅ C ⋅ A ⋅ h (13)sThe equations for Roskilde Bredning and narrow passage are describedanalogously. In the Vig equation C w,bred is unknown. In the Bredningequation C w,vig and C w,narr (boundary) are unknown and in the equation forthe narrow passage C w,bred is unknown. Through iteration in the watermodel the unknowns are determined.The calculated contributions and mean water concentrations are summarisedin Table 25.1-w,vigvigvig6.4.2 Numerical models (water and sediment model)The mass balance for the water compartment of the Vig and Bredning areas shown in Equation 13. The water balance in the narrow passage is describedwith the expressions below. Transport in the sediment is describedbelow irrespective of the model for the water.In Figure 35 a vertical section of the water-sediment system is shown.The considered horizontal and vertical mass fluxes are stated for eachcompartment.68