Solubility of 2,3,7,8-TCDD (tetrachlorodibenzo-p-dioxin) in contaminated soils

Soils from ten sites contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) were investigated in aqueous batch and intact core leaching studies to determine water/soil partition coefficients (K/sub p/) for TCDD and factors affecting the K/sub p/. TCDD content in soils ranged from 8 to 26,000 ng/g. For the batch extractions, TCDD concentrations in solution ranged from 0.1 to 56 ng/L; 79% of the values were 2.0 ng/L or less. For the intact cores, TCDD concentrations in leachate ranged from 0.1 to 14 ng/L; 81% of the values were 2.0 ng/L or less. The amount of TCDD in the soil and the amount of TCDD in the water extracts were strongly related to the total solvent-extractable organic matter (SEOM) in soil and the halogenated semi-volatiles in the solvent-extractable fraction. These results suggest that co-contaminants in the wastes along with the TCDD were sorbed to the soil and that these materials as a group greatly influence the partitioning of TCDD between soil and water in these contaminated soils.