Desorption of tetrachloroethene and 1,2-dibromo-3-chloropropane from aquifer sediments



Desorption of tetrachloroethene (TeCE) or 1,2-dibromo-3-chloropropane (DBCP) from aquifer sediment (0.19% organic carbon) was monitored following sorption for 6 or 30 d in 100 μM aqueous solutions. The compounds were desorbed by a previously developed purge technique in which a third phase of Tenax GC® polymeric adsorbent beads provided a sink for desorbed chemical, thereby simulating desorption to infinite dilution. Sorbed concentrations in the sediments were quantified by hot acetone extraction of sacrificed replicates. More than 95% of the initial sorbed compound was desorbed within the first 4 d, but a persistent fraction (8–15 μg/kg, 0.4 to 1%) remained associated with the sediments for at least 35 d. The desorption curves were little affected by the prepurge sorption time. The results may rationalize the unexpectedly high sediment-associated concentrations of a similar compound (1,2-dibromoethane) in a long-contaminated aquifer.