Figure 2: Removal of perchlorate from three 20 L soil bioreactors planted with one willow (Salix nigra) tree each and dosed with 300 mg L-1 DOC derived from chicken litter extract or acetate. DOC was added to the bioreactors during the first and fourth perchlorate dosing events to biostimulate and sustains rhizodegradation. Peaks correspond to the initial perchlorate concentrations measured in the rhizosphere immediately after the reactors were dosed with perchlorate. The slow rate of removal of the third dose of perchlorate is attributed to the low concentration of DOC remaining in the pore water.