DDE Remediation and Degradation - Reviews of Environmental Contamination and Toxicology - page 62

and the surfactant Brij 30, using aged DDT-contaminated soil that initially contained
DDE, there was no change in the concentration of DDE after 31 wks, although DDT
degradation was accelerated and DDD concentration increased (Walters and Aitken
2001). Similarly, in other microcosm experiments where Na + was added to aged
DDT-contaminated soils in an effort to increase clay dispersal, which leads to more
dissolved organic carbon and greater bioavailability of the sorbed contaminants, it
was reported that the DDT degradation increased, DDD accumulation increased, but
DDE remained relatively the same throughout the experiments. The conditions used
in these experiments gave anoxic levels similar to those found for denitrification
(Kantachote et al. 2004). The only literature located that described a pure culture to
degrade DDE anaerobically involved a denitrifier, Alcaligenes denitrificans (Ahuja
et al. 2001). Degradation was accelerated under glucose but was inhibited by sodium
acetate and sodium succinate. The addition of biphenyl fumes had no effect on the
rate of DDE disappearance. Denitrifying conditions can be easily reached by flood-
ing the soil (Kantachote et al. 2004).

V Abiotic Remediation and Degradation

The effect of soil flooding on the binding of DDT and DDE was examined using
microcosm experiments. Using 14 C -DDT, Boul (1996) found that in nonflooded
conditions 6.7% and 9.7% of DDT and DDE, respectively, were bound to the soil
over a 42-d period. Under flooded conditions, the amounts increased to 24.5%
DDT and 11.5% DDE. It was also reported that <0.7% of the 14 C was emitted as
14 CO 2 under nonflooded conditions and that virtually no 14 CO 2 evolved when the
soil was flooded. Flooding, as a land management practice, along with deep
plowing, were used in a 23-yr experiment to determine the effects on the con-
taminants by these practices (Spencer et al. 1996). It was found that the major
residue was p , p '-DDE, with the greatest amounts being in the nonflooded and
deep-plowed plots; deep plowing possibly reduced the amount of DDT and DDE
volatilization. Irrigation significantly enhanced volatilization of DDT residues,
particularly p , p '-DDE. These findings are consistent with the earlier report that
long-term irrigation with superphosphate fertilizer lowered p , p '-DDE residues
compared to nonirrigated fields. The irrigation did not affect the DDT residue
distribution by depth, which indicated that irrigation did not cause an increase in
the leaching potential (Boul et al. 1994).
To increase the degradation rates of DDT, DDD, and DDE in flooded soils and
sediments, some researchers have used Fe ° , zero-valent iron (Eggen and Majcherczyk
2006; Pirnie at al. 2006; Satapanajaru et al. 2006; Sayles et al. 1997; Yao et al.
2006). Sayles et al. (1997) used a soil-free system and found that the rate of dechlo-
rination of DDT and DDE was independent of the iron powder concentration, but
that the rate was much higher when the surfactant Triton X-114 was used in con-
junction with the iron powder. Various combinations of calcium peroxide, zero-
valent iron, iron sulfide, and hydrogen peroxide were tested in aqueous solutions
with and without the surfactant Triton X-114. Although these systems did degrade