Phthalates and Nonylphenols in Roskilde Fjord

The extraction process can be described by a pseudo 1 st order removal ofdissolved and colloid matter from the water phasedCdtw⋅ θ=- k1ext⋅Cw⋅θ⎡ mg ⎤⎢ ⎥⎣litre⋅ sec. ⎦(4)wherek1extv=hext0.5 - 23 mmday= 0.17 - 0.671daysis the extraction constant and v ext is the extraction velocity (Harremoës etal., 1990).The overall vertical transport can be expressed asdCdtw⋅( θ + X ⋅ K ) = - C ⋅ ( k ⋅θ+ k ⋅ X ⋅ K ) ⇒wdww1ext1sedwdwdCdtw⋅ ( θ + X ⋅ K )=wdwmg⎢⎣liter⋅sec.⎡ ⎤( θ + X ⋅ K ) = - C ⋅ k ⋅ R⎥ ⎦- C w ⋅ k1vert⋅w dww 1vert wThe retention factor R w will be close to unity, i.e. low particulate concentrationsprevail in the water, and therefore k 1vert is approximatelyequal to k 1ext .The extraction process is defined for organic matter that is present inabundant concentrations in the water compartment such as proteins, sugarsand other easily degradable and hydrophilic compounds. For thesecompounds the predominant removal mechanism in the sediment is 1 storder microbial degradation and accordingly this can be related to a 1 storder transfer from the water to the sediment (cf. Equation 4).In this work xenobiotics that appear in very low concentrations and thatare practically insoluble are investigated. The degradation rates are lowand the governing removal/transport mechanism in the sediment is diffusion,which in turn is related to a similar removal rate from the waterphase. The approach is therefore to define the vertical transport of nonsedimentarysubstance in terms of a “suction” caused by molecular concentration-gradientconditioned diffusion in the sediment (cf. Equation19).The transport of sedimentary adsorbed substance can be derived fromEquation 3, where the sedimentation of particles isdXdtw=- k1sed⋅Xw⎡ mg ⎤⎢ ⎥⎣liter⋅ sec. ⎦(5)60