Abstract
The effectiveness of surfactant formulations to remove aged metals from a field soil and their influence on soil toxicity was investigated. Batch studies were conducted to evaluate the efficacy of cationic (1‐dodecylpyridinium chloride; DPC), nonionic (oleyl dimethyl benzyl ammonium chloride; trade name Ammonyx KP), and anionic (rhamnolipid biosurfactant blend; trade name JBR‐425) surfactants for extracting Zn, Cu, Pb, and Cd from a soil subjected to more than 80 years of metal deposition. All three surfactants enhanced removal of the target metals. The anionic biosurfactant JBR‐425 was most effective, reducing Zn, Cu, Pb, and Cd in the soil by 39, 56, 68, and 43%, respectively, compared with less than 6% removal by water alone. Progressive acidification of the surfactants with citric acid buffer or addition of ethylenediaminetetra‐acetic acid (EDTA) further improved extraction efficiency, with more than 95% extraction of all four metals by surfactants acidified to pH 3.6 and generally greater than 90% removal of all metals with addition of 0.1 M EDTA. In two species of earthworm, Eisenia fetida and Lumbricus terrestris, metal bioaccumulation was reduced by approximately 30 to 80%, total biomass was enhanced by approximately threefold to sixfold, and survival was increased to greater than 75% in surfactant‐remediated soil compared with untreated soil. The data indicate that surfactant washing may be a feasible approach to treat surface soils contaminated with a variety of metals, even if those metals have been present for nearly a century, and that the toxicity and potential for metal accumulation in biota from the treated soils may be significantly reduced. Environ. Toxicol. Chem. 2011;30:112–123. © 2010 SETAC