DDE Remediation and Degradation - Reviews of Environmental Contamination and Toxicology - page 57

Table 2 The five most effective plants assessed in phytoremediation studies and their associated
reductions in DDE
Cultivar Genus, species, Percent uptake Soil

variety subspecies of DDE amendment Reference

Connecticut Field Cucurbita pepo 6.0 Mycorrhizal White et al.

(pumpkin) ssp. pepo inoculant 2006b

Howden (pumpkin) C. pepo ssp. pepo 2.4 None White 2002

Goldrush (zucchini) C. pepo ssp. pepo 2.1 0.01 M citric White et al.

acid 2003b

Raven (zucchini) C. pepo ssp. pepo 1.4 Mycorrhizal White et al.

inoculant 2006b

Costata Romanesco C. pepo ssp. pepo 1.1 Mycorrhizal White et al.

(zucchini) inoculant 2006b

specific based on the data. Not only does phytoremediation potential vary among spe-
cies, but it also varies with the variety of any one species (Table 2). Significant differ-
ences were found between varieties of Cucurbita sp. (squash and pumpkin) with up to
an order magnitude difference in root:soil concentrations and two orders of magnitude
for total plant uptake of p , p '-DDE (White 2002; White et al. 2003a). For two varieties
of Cucurbita pepo , the translocation of DDE from soil to plant ranged from 0.4% to
2.4%, which approaches the values cited for “hyperaccumulating” plants used for
heavy metal phytoremediation (White 2002). The success of Cucurbita pepo species
(zucchini and pumpkin) in translocating DDT, DDD, and DDE is thought to result
from high transpiration volumes, large aboveground biomass, and composition of root
exudates (Lunney et al. 2004). Soil moisture and plant density also influence the
uptake of p , p '-DDE from soil by Cucurbita pepo (Kelsey et al. 2006). Soil amend-
ments such as biosurfactants (rhamnolipids produced by Pseudomonas aeruginosa )
and mycorrhizal inoculation have both been shown to increase the translocation of
p , p '-DDE in Cucurbita pepo (White et al. 2006a,b). Seven low molecular weight
organic acids [succinic, tartaric, malic, malonic, oxalic, citric, and ethylenediamine-
tetraacetic acid (EDTA)] were tested for abiotic desorption of p , p '-DDE from soil with
oxalic and citric acids being selected for use in conjunction with zucchini for phytore-
mediation. Both citric and oxalic acid had a positive influence on the translocation of
p , p '-DDE from soil to shoot system, with the second crop showing even more of an
increase in uptake than the first crop without further addition of the organic acids. It
was suggested that the addition of low molecular weight organic acids disrupted the
soil structure through chelation of inorganic ions, which enhanced the bioavailability
of p , p '-DDE to Cucurbita pepo (White et al. 2003b).
Although much research has gone into phytoremediation by Cucurbita pepo,
other species have shown potential as well. Suresh et al. (2005) found that hairy root
cultures of Chicorium intybus (chicory) and Brassica juncea (brown mustard) took
up ~87% of the 14 C-DDT within 24 hrs, with the transformation products being
DDD, DDE, and DDMU (1-chloro-2,2-bis(4'-chlorophenyl)ethene), which suggests
that these plants could be used for phytoremediation of DDT- and DDE-contaminated