A quasi-steady-state pollutant flux methodology for determining sediment quality criteria

A methodology for estimating quasi-steady-state flux of pollutants from bed sediments to water and air is presented. This is illustrated using the example case of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in a sediment bed. The rate of transport from the bed sediment was found to be important in determining the concentration of TCDD along its pathway from sediment to air. The concentration in the water column that leads to exposure to aquatic species was found to scale in proportion to the flux from the sediment and not to the pollutant concentration in the sediment. The sediment-side processes were found to provide the dominant resistance to mass transfer of pollutant. Both transport (rates) and thermodynamics (equilibrium partition constants) are shown to be important in setting sediment quality criteria. These should be incorporated in the next generation of sediment quality criteria.