Phthalates and Nonylphenols in Roskilde Fjord

The vertical flux is a combination of sedimentation of particles, extractionof molecular substance through sediment suction, atmosphericdeposition and freshwater sources.∂ CsN wz = - D sz ⋅ - S ⋅ R ⋅ C + C∂ zz=0q f,narrq p,narr+ ⋅ C tot,f + ⋅ Cbbs w,narr tot,deptot,p (17)The first term in Equation 17 is the boundary condition at the sedimentsurface caused by sediment “suction” of substance. The total mass balancefor the water compartment furthermore includes 1 st order degradationand thus becomes( q + q )∂ Cw,narr ∂= Q Cnarr w,narr f,narr p,narr⋅ +⋅ C w,narr +∂ t b ⋅ h ∂ xb ⋅ h2∂ Cw,narrDsz∂ CsD wx ⋅ - ⋅ +2∂ x R w ⋅ h ∂ zz=0CdepR h - S ⋅ R s⋅ C w,narr- k 1⋅ Cw,narrw ⋅ R w ⋅ h R wq f,narrq p,narr⋅ C tot,f +⋅ Ctot,p(18)b ⋅ h ⋅ Rb ⋅ h ⋅ RwBoundary conditions:C w,narr = C w,bred for x = 0C w,narr = C w,sea = 0 for x = L narr + 5 kmwSediment:The horizontal flux is negligible. The vertical flux arises from moleculardiffusion and advection from sediment build-upN = - Dszsz∂ Cs⋅ + S ⋅ R s ⋅ C∂ zw(19)The total mass balance for the sediment compartment is∂ C∂ ts= D Rszs2∂ Cs∂ Cs - S - k 1⋅ ⋅ ⋅ C2s(20)∂ z ∂ z RsIn the upper 5 cm the aerobic degradation rate, k 1N , is used and furtherdown the anoxic degradation rate, k 1D , is used.The two coupled 2 nd order differential Equations 18 and 20 each havingtwo independent variables, x and t for the water model and z and t for thesediment model respectively, can be solved numerically using a grid consistingof discrete nodes for the (x,t) and the (z,t) system respectively,and by employing a forward time central space scheme (cf. Figure 36).70