Abstract
The phytoremediation potential of four crop species cultivated on carbonation lime coming from the sugar industry with water-soluble nickel (Ni) exceeding the Italian legal limit of 10 µg L−1 was assessed. Two autumn–winter species (spinach and canola) were tested with and without the addition of bentonite in a greenhouse experiment in order to overcome prolonged unfavourable weather conditions. Two spring-summer species (sunflower and sorghum) were grown in outdoor boxes. Plant species were selected among crops of interest for phytoremediation and their rotation throughout the year enable to maintain a permanent vegetation cover. Nickel concentration in different plant tissues and the concentrations of soluble and bioavailable Ni in lime were measured. In the greenhouse study, soluble Ni decreased below the legal limit in all the tests, and the combined effect of bentonite and plants reduced Ni in lime mainly in the bioavailable fraction. Spinach and sunflower emerged to be more suitable for phytoextraction than canola and sorghum, because of the higher concentration of the metal in the epigeal portions. The results from the outdoor experiment highlighted that sorghum has a good phytostabilisation potential since its ability to accumulate Ni mainly at the root level and to attract a significant amount of bioavailable Ni in the rhizosphere. This study arose from a real scenario of environmental contamination and investigated the potential of different approaches on the bioremediation of a specific industrial waste product.
Highlights
Environmental pollution by Potentially Toxic Elements (PTE) has become a serious problem since the 1940s, when rapid industrialisation and urbanisation started to cause contamination [1]
The median concentration of Ni after treatments was slightly lower using canola compared to spinach, both in soluble and bioavailable fractions (Figure 1)
The above findings support the use of a combination of sequestrants and plants in a practical case of bioremediation
Summary
Environmental pollution by Potentially Toxic Elements (PTE) has become a serious problem since the 1940s, when rapid industrialisation and urbanisation started to cause contamination [1]. Several physical and chemical methods have been used for removing potentially toxic elements from contaminated matrices [5]; nowadays, these traditional remediation technologies are being replaced by biological ones, usually known as bioremediation technologies [6,7]. Since the nineties [13,14], a growing scientific and commercial interest has developed regarding this promising technology as a more eco-friendly, non-intrusive and cost-effective remediation method for the reclamation of polluted sites [15,16]. Substrate aeration, pH, cation exchange capacity (CEC) and the presence of organic matter, clay components and the elements available affects the bioavailability of potentially toxic element and their accumulation in plant tissues [24,25,26,27]
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