2-STAGE DESORPTION-KINETICS AND IN-SITU PARTITIONING OF HEXACHLOROBENZENE AND DICHLOROBENZENES IN A CONTAMINATED SEDIMENT

The desorption kinetics of in situ hexachlorobenzene (HCB), 1,3-dichlo robenzene (1,3-DCB) and 1,4-dichlorobenzene (1,4-DCB) from a sediment were determined by a method in which the aqueous phase was kept solute -free with Tenax TA beads. Slowly desorbing fractions were 47-98% for HCB, 58-76% for 1,3-DCB and 36-63% for 1,4-DCB. Also, in situ partitio n coefficients (K-OC(in situ)) were measured; they were 0.24-1.4 log-u nit higher than literature K-OC-values measured using short-term labor atory incubations. K-OC values for the rapid fractions (K-OC(rap)), ca lculated with K-OC(in situ) and the rapidly desorbing fraction, were s imilar to literature K-OC values. From this, it is concluded that the slowly desorbing contaminant fractions and the fractions not available for rapid equilibrium partitioning are the same. (C) 1997 Elsevier Sc ience Ltd.