Phytoremediation of Soil Polluted by Nickel Using Agricultural Crops

Abstract

Soil pollution due to heavy metals is widespread; on the world scale, it involves about 235 million hectares. The objectives of this research were to establish the uptake efficiency of nickel by some agricultural crops. In addition, we wanted to establish also in which part of plants the metal is stored for an eventual use of biomass or for recycling the metal. The experiments included seven herbaceous crops such as: barley (Hordeum vulgaris), cabbage (Brassica juncea), spinach (Spinacea oleracea), sorghum (Sorgum vulgare), bean (Phaseolus vulgaris), tomato (Solanum lycopersicum), and ricinus (Ricinus communis). We used three levels of treatment (150, 300, and 600 ppm) and one control. At the end of the biological cycle of the crops, the different parts of plants, i.e., roots, stems, leaves, fruits, or seeds, were separately collected, oven dried, weighed, milled, and separately analysed. The leaves and stems of spinach showed a very good nickel storage capacity. The ricinus too proved to be a very good nickel storer. The ability of spinach and ricinus to store nickel was observed also in the leaves of cabbage, even if with a lower storage capacity. The bean, barley, and tomato, in decreasing order of uptake and storage capacity, showed a high concentration of nickel in leaves and stems, whereas the sorghum evidenced a lesser capacity to uptake and store nickel in leaves and stems. The bean was the most efficient in storing nickel in fruits or grains. Tomato, sorghum, and barley have shown a storage capacity notably less than bean. The bean appeared to be the most efficient in accumulating nickel in the roots, followed in decreasing order by sorghum, ricinus, and tomato. With regard to the removal of nickel, spinach was the most efficient as it contains the highest level of this metal per gram of dry matter. The ricinus, cabbage, bean, sorghum, barley, and tomato evidenced a progressively decreasing efficiency in the removal of nickel.

Nickel bioaccumulation by the chosen plant species

“…In their research on various crops abilities for nickel accumulation, Giordani et al (2005) indicated a higher potential of spinach for this metal uptake (65 g Ni ton -1 ) in comparison with cabbage, barley, sorghum or beans. In authors' own research, field bean and lettuce revealed almost twice higher efficiency in nickel removal in comparison with maize.…”

Use of non-hyperaccumulator plant species for the phytoextraction of heavy metals using chelating agents

“…In addition, the toxicity effect on plants, such as growth reduction, is not observed when citric acid is applied, in contrast to EDTA (Evangelou et al, 2006). The excellent reports from do Nascimento et al (2006a) and Freitas et al (2009) showed the efficiency of the application of organic acids as phytoextraction assistants for a wide range of heavy metals, recomPlant species such as sunflower (Helianthus annuus L.), jack bean (Canavalia ensiformis L.), velvet bean (Stizolobium aterrimum L.), castor bean (Ricinus communis L.) and others have been extensively exploited for their heavy metal tolerance and phytoremediation potential (Adhikari and Kumar, 2012;de Andrade et al, 2005;de Andrade et al, 2008;de Souza et al, 2011;Giordani et al, 2005;Ullah et al, 2011). Studies with these plant species have been carried out in hydroponic systems under greenhouse conditions to better understand the patterns of response, distribution and accumulation of heavy metals.…”

Concentrations of Heavy Metals and Pesticide Residues in Leafy Vegetables and Implications for Peri-urban Farming in Nairobi, Kenya

“…Brassicas olaracea (kale) has very high hyperaccumulation and tolerance for Ni (Giordani, Cecchi, & Zanchi, 2005;Kabata-Pendias & Mukherjee, 2007). Based on the nitrate levels in sampled kale, it was estimated that 0.381.32 mg nitrates were consumed daily based on the consumption of 7 ounces (200 g) of kale as estimated by Onyango (2008) (figure 7).…”