Before it was banned in 1972, DDT was used widely as an insecticide. A type of persistant organic pollutant, its hydrophobic, or water-fearing, characteristics make it difficult to remove from soil. Often large swathes of land must be removed and either buried in a specially designed landfill or burned in a high-temperature incinerator. Ken Reimer of the Royal Military College of Canada and his colleagues studied a number of plant species to determine whether they are viable candidates for DDT phytoremediation (the use of vegetation for treating contaminated soils). The researchers grew zucchini, tall fescue, alfalfa, rye grass and pumpkins in a greenhouse using soil imported from the Canadian Artic that had been treated with DDT. The cold temperatures meant that the contamination was virtually identical to the technical grade DDT mixture that had originally been used, Reimer says. We could therefore examine the ability of [the plants] to suck the DDT out of the soil that had been contaminated with DDT for several decades.
The team reports in the November 15 issue of the journal Environmental Science and Technology that pumpkins performed this job the best out of the five species tested. Zucchinis also extracted DDT from the soil well, whereas the rye grass and fescue accumulated the toxin in their roots but did not move the DDT above ground. Alfalfa performed poorly overall, the team reports. "Our research has shown that members of the Cucurbita pepo species, including pumpkins, are particularly effective in this regard," Reimer notes. Using plants to clean contaminated soils is an approach that would work best for smaller sites that do not urgently need to be cleaned up or those in areas that do not have access to more technologically advanced--and more expensive--options.