Impact of single reagent extraction using NH4OAc-EDTA on the solid phase distribution of metals in a contaminated dredged sediment

The solid phase distribution of metals in a contaminated dredged sediment as affected by a single reagent extraction (0.5 mol/1 NH4OAc + 0.02 mol/1 EDTA) was studied. A sediment was dried and portions were heated at 250 and 450°C. From each treatment, a portion was extracted with NH4OAc-EDTA. Both the extracted and the unextracted portions were then subjected to a sequential fractionation. NH4OAc-EDTA extraction decreased both the acid extractable and the reducible fractions. The oxidizable and residual fractions were not significantly affected. Larger portions of the acid extractable and reducible fractions were extracted with NH4OAc-EDTA when the sediment was previously heated at 250°C. After heating the sediment at 450°C the NH4OAc-EDTA extractable portions decreased. Fractionation procedures can provide reliable information on the chemical associations of pollutants in sediments. To estimate short and medium term metal availability, single reagent leaching tests appear more appropriate.