Phytoremediation: using plants as biopumps to improve degraded environments

Abstract

Plants pump large amounts of water, solutes, and organic matter as part of their normal physiological processes. This pumping action can be exploited to improve degraded environments by stabilising, removing, or breaking-down contaminants in the substrates. In addition, soil amendments such as fertilisers and microbes may also be added to enhance the efficacy of the operation. Basic plant physiology sets limits on the capacity of phytoremediation. However, combining this technology with the production of saleable products may render the extra time needed for clean-up relatively unimportant. Phytoremediation is still poorly developed, particularly the phytoextraction of heavy metals. Continual innovation will greatly expand the scope and efficacy of phytoremediation. The greatest potential use for this technology may be in developing countries that have the highest levels of environmental degradation, and scant funds for remediation. Phytoremediation could provide a low-cost and sustainable way to improve local economies. Here a case study is reported on the phytoremediation of a 3.6 ha sawdust pile that was leaching unacceptable amounts of boron (B) into local waterways. High water-use poplars were used to control leaching and potentially remove B from the site via phytoextraction. Selected trees that are coppiced before leaf-fall could be mulched and used to provide 'organic' B on nearby orchards that are deficient in this element.