Use of Stable Isotopes to Assess Phytoremediation of Soils Contaminated with Cadmium and Zinc PDF Download

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Land contaminated with heavy metals such as Cd and Zn can be remediated using a number of different approaches. Many of these strategies are very expensive (e. g. removal and disposal of the soil, covering the soil with uncontaminated soil, extraction with acids or chelates) whilst others provide only short term solutions (e. g. reduction of metal bioavailability by liming or adding organic matter). An alternative approach is the use of hyperaccumulator plants to remove the heavy metals. Phytoremediation, as this process is known, is an attractive method for remediation of contaminated land since it is relatively inexpensive and has the potential through the appropriate selection of plant species to be effective. However, there are many factors that need to be considered for phytoremediation, perhaps the most important is the bioavailability of metals from different component or functional pools within the soil. The bioavailability of heavy metals has been assessed through a variety of approaches, with extraction using chemicals being the most common. Another approach is the isotopic exchange method which has been regularly used for estimating the bioavailable P in soil. This technique relies on the assumption that isotopically exchangeable P is available to a growing plant and yields the so called E-value for a soil. In past studies, particularly in highly P fixing soils, the E-value has been shown to overestimate the soil available P. To overcome this a second procedure based on the measurement of isotope uptake by a plant growing on a spiked soil has been proposed and yields the so called L-value. As well as P, this method has been applied to Ni and only very recently to Cd and Zn using radioisotopes. In the present work, stable isotopes are used for the first time to measure the Cd and Zn available for plant uptake using isotopic exchange principles based on the E and L-values using a contaminated (Great Billings) and a non-contaminated (Countesswells) soil. The.