Equilibrium Partitioning Approach to Define Sediment Quality Guideline of Some Metals in Chao Phraya Estuary, Thailand

This study aims to define numerical sediment quality guideline (SQG) based on equilibrium partitioning approach that represents availability of metal in estuarine sediment. The labile-phase metal was used in calculating the partition coefficient caused by remobilization of this fraction in the sediment-interstitial water system as a result of changing physicochemical condition in sediment. In addition, the metal bound with sulphide fraction was taken into account in calculating the SQG since this fraction is potentially available to interstitial water when oxidation process occurs in anoxic sediment. The SQG values for Chao Phraya estuarine sediment for cadmium, copper, lead and zinc were found in the range of 1.2-3.1, 7-105, 23-86 and 16-125 mg/kg dry weight in