Phytoremediation Potential of Vetiver Grass (Vetiveria Zizanioides) in Two Mixed Heavy Metal Contaminated Soils from the Zoundweogo and Boulkiemde Regions of Burkina Faso (West Africa)

In the agricultural regions of Burkina Faso, urban solid waste fertilizers were usually applied. This activity is likely to contaminate the soils and expose populations to serious diseases. This study aims to assess rate of heavy metal (Cd, Cu, Mn, Pb, Zn, Ni, Cr) contamination in both agricultural lixisol and vertisol and to evaluate the removal efficiency of heavy metals using Vetiver grass on different two mixed heavy metal contaminated soils. A pot experiment was conducted to compare the metal accumulation and overall efficiency of metal uptake by different plant parts (roots and shoots) on both tropical soils. After 3 and 6 months growing on laboratory conditions, Vetiver grass plants were harvested and heavy metal concentrations in shoot and root parts determined by Inductively Coupled Plasma - Atomic Emission Spectroscopy. The results indicate that at 3 and 6 moths, the shoot and root concentrations of heavy metals in Vetiver grass harvested in lixisol were higher than vertisol. For different plant parts, all metal concentrations were higher in root than in shoot, except Cu and Pb. At the 3 and 6 months, the BCF values > 1 for Cd, Cu and Zn in both soils showed Vetiver grass as an effective phyto-stabilizer for these metals. However, the TF values > 1 for Cd (lixisol), Mn, Zn Ni and Cr (vertisol) indicated the efficiency of Vetiver for phytoextraction. The results of this study showed that Vetiver is more effective in lixisol, but it can be used for remediation of both studied tropical soils from agricultural region of Burkina Faso. Nevertheless, considering the special limitations of the experimental conditions, further field monitoring is necessary to demonstrate the phytoremediation efficiency of Vetiver in agricultural soils under the climatic conditions of Burkina Faso.

Patterns of climber distribution in temperate forests of the Americas

Aims and Methods We propose a standard protocol at the landscape to continental scale for examining to what extent the range of ecological conditions found in temperate latitudes explains the variations in climber species richness and traits.The protocol was tested in forests of the two Americas.The data set included 151 climber species.We selected four categorical traits and grouped these species into six clusters with regard to these traits.Floristic records of American forests were first gathered into alliances,second combined with bioclimatic indices(rainfall,temperature,continentality).We obtained a total of 59 vegetational units in which we calculated values of climber species richness and proportion of clusters.Vegetational units were ultimately gathered into five forest formations(characterized by leaf longevity).Wetlands and uplands were considered separately.Important Findings Our results emphasize clear trends in large-scale patterns of climber distribution,independently of taxonomy.Climber species richness(in particular woody climbers)peaks in moist and warm upland forests with oceanic climates,and where conifers are rare.In flooded areas,climber richness is also very high and peaks in seasonally flooded large floodplains.In ecological conditions of frost,dryness or lack of nutrients,climber species richness,abundance and trait diversity decline,resulting in the dominance of small,twining and deciduous life traits.