A QUASI-STEADY-STATE POLLUTANT FLUX METHODOLOGY FOR DETERMINING SEDIMENT QUALITY CRITERIA

A methodology for estimating quasi-steady-state flux of pollutants fro m bed sediments to water and air is presented. This is illustrated usi ng 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 t o be important in determining the concentration of TCDD along its path way from sediment to air. The concentration in the water column that l eads to exposure to aquatic species was found to scale in proportion t o the flux from the sediment and not to the pollutant concentration in the sediment. The sediment-side processes were found to provide the d ominant resistance to mass transfer of pollutant. Both transport (rate s) and thermodynamics (equilibrium partition constants) are shown to b e important in setting sediment quality criteria. These should be inco rporated in the next generation of sediment quality criteria.