Phytoremediation could reduce heavy metal bioavailability in soils and obtain renewable energy from lands useless. Some fast-growing, high biomass crop species are known to display a significant heavy metal tolerance, particularly those from the genus Brassica. These species could be phytoremediator candidates for recuperate polluted soils with heavy metals. Brachypodium distachyon has also been recently proposed as a model species to develop bioenergy. However, there are no experiments about the tolerance of this plant to metals. The present work reports data concerning the ability of Brachypodium distachyon and Brassica napus seeds to germinate and grow in media containing different doses of Cd, Cr, As and Zn, in order to evaluate their use as energy crops in polluted sites. Biomass reduction and length decreasing were observed as consequence on increasing metal doses in both species, but the effect was different attending to metal and species. The maximum toxicity level was found in plants treated with Cr (VI). Exposures of 30 mg L−1 of Cd and As (V) reduced the shoot elongation by 50% in both species, while root was affected by lower doses than 30 mg L−1. Concentrations of Zn affected neither length, nor biomass of B. distachyon, but shoot and root elongation of B. napus were reduced from the lowest dose of Zn.
Hyperaccumulation and phytoremediation potentials of arsenic by Pteris vittata and P. ensiformis were investigated and documented mainly for ability to clean arsenic contaminated soil sites by both plants in Nigeria. 5.0 kg of soil was air dried, sieved and analysed for the physical and chemical properties and placed inside four plastic pots labelled CT, A, B and C. They were treated with different concentrations of sodium arsenate. One-month-old fernlets of each species was transplanted into each of the soil treatments and left for 12 weeks. Little quantity of water was added to each of these pots every other day. The results showed that P. vittata hyperaccumulated up to 64,132 mg As kg−1 arsenic in the root and 65,747 mg As kg−1 in the frond in all the treatments, while P. ensiformis hyperaccumulated up to 15,662 mg As kg−1 in the root and 15,120 mg As kg−1 in the frond. The total arsenic accumulation was greater in P. vittata than in P. ensiformis and showed no sign of phytotoxicity. Treatment C was lethal to P. ensiformis after four weeks. P. vittata fulfilled all the criteria for classification as a hyperaccumulator and phytoremediator of arsenic contaminated soil in Nigeria. In contrast, P. ensiformis did not satisfy all the criteria because it could not withstand high concentration of arsenic for a long period of time. This study had provided base-line information on the hyperaccumulation status of the two species in Nigeria.
There are millions of acres of chemically contaminated lands on which biofuel crops can be planted for dual purposes of biomass production and land reclamation. Phytoremediation is a proven technology for environmental cleanup, particularly in tropical and sub-tropical environments. There are advantages in that multiple growing seasons and increased soil temperature accelerate the clean-up processes. Seeds of 13 tropical and temperate plant species were germinated and grown for 10 days in petroleum contaminated soil containing 3148 μg/g of polycyclic aromatic hydrocarbons (PAHs). The results indicate that the presence of PAHs enhanced both emergence and early seedling growth with some of the species tested. Kiawe tree germination rate was 7-fold higher in PAH soils than that in the control media. The potential biofuel grasses sugarcane, banagrass, switch grass, vetiver and miscanthus showed degradation of PAHs in at least one of the amended PAH-contaminated soils in 35 days of growth. Banagrass biomass production in all the treatments was far greater than the other four species. No plant control pots were most effective to reduce PAHs in the un-amended PAH soil. Vetiver degraded all PAHs when planted in the PAH soil amended with 1/3 of the Promix soil (a 2/3 PAH soil volume). Among five biofuel crops tested, banagrass produced a tripled amount or more of biomass than all the other species in the LF-14 un-amended PAH soil or its amended soils. The dry weight (dw) biomass of banagrass averaged ∼3 g/day/3-L pot in all PAH soils and 6 g/day/3-L pot in Promix as harvested at the ground level. Banagrass in 90-cm spacing could produce approximately 30 tons/ha/yr of dry matter in a 70-day crop season. The results warrant further investigation of biofuel crops for phytoremediation and biomass production purposes. Future plantings may be considered using these and other crops in combination with applicable contaminants to help clean up the contaminated environment and reduce petroleum dependency.