The performance of Cytisus striatus in association with different microbial inoculant treatments on the dissipation of the insecticide hexachlorocyclohexane (HCH) was studied. Two soils with different organic matter (A and B soil) content were spiked with 0 or 65 mg HCH kg−1. Plants were either not inoculated (NI), or inoculated with the endophyte Rhodococcus erythropolis ET54b and the HCH-degrader Sphingomonas sp. D4 separately or in combination (ET, D4 and ETD4). Unplanted pots were also established. HCH phytotoxicity was more pronounced in the B soil. Soil HCH concentrations in unplanted pots were similar to initial concentrations, whereas concentrations were reduced after plant growth: by 20% and 8% in A and B soil, respectively. Microbial inoculants also modified HCH dissipation, although effects were soil-dependent. Inoculation with the combination of strains (ETD4) led to a significant enhancement in HCH dissipation: up to 53% in the A soil and 43% in the B soil.

Many urban areas are polluted by industrial activities and waste disposal in landfills. Since conventional soil remediation techniques are costly and unsustainable, phytoremediation might offer an alternative. In this article, we explore how phytoremediation can be integrated into the transformation of urban post-industrial areas, while improving public space. Buiksloterham, a polluted and deprived industrial area in Amsterdam, serves as case study. Buiksloterham is polluted with heavy metals, with Zinc (Zn) concentrations being the highest. A regression-model for Alpine Pennycress (Thlaspi caerulescens) is used to estimate the time needed to remediate the site. This reveals a conflict in time between remediation and urban development. A research by design experiment shows how to overcome this conflict by dealing with polluted soil innovatively while emphasizing spatial and aesthetic qualities of the phytoremediation plant species. The resulting landscape framework integrates phytoremediation with biomass production and gives new ecological, economic and social value to Buiksloterham.

Salix caprea is well suited for phytoextraction strategies. In a previous survey we showed that genetically distinct S. caprea plants isolated from metal-polluted and unpolluted sites differed in their zinc (Zn) and cadmium (Cd) tolerance and accumulation abilities. To determine the molecular basis of this difference we examined putative homologues of genes involved in heavy metal responses and identified over 200 new candidates with a suppression subtractive hybridization (SSH) screen. Quantitative expression analyses of 20 genes in leaves revealed that some metallothioneins and cell wall modifying genes were induced irrespective of the genotype's origin and metal uptake capacity while a cysteine biosynthesis gene was expressed constitutively higher in the metallicolous genotype. The third and largest group of genes was only induced in the metallicolous genotype. These data demonstrate that naturally adapted woody non-model species can help to discover potential novel molecular mechanisms for metal accumulation and tolerance.

Production of food crops on trace element-contaminated agricultural lands in the Campine region (Belgium) can be problematic as legal threshold values for safe use of these crops can be exceeded. Conventional sanitation of vast areas is too expensive and alternatives need to be investigated. Zea mays on a trace element-contaminated soil in the region showed an average yield of 53 ± 10 Mg fresh or 20 ± 3 Mg dry biomass ha−1. Whole plant Cd concentrations complied with legal threshold values for animal feed. Moreover, threshold values for use in anaerobic digestion were met. Biogas production potential did not differ between maize grown on contaminated and non-contaminated soils. Results suggested favorable perspectives for farmers to generate non-food crops profitably, although effective soil cleaning would be very slow. This demonstrates that a valuable and sustainable alternative use can be generated for moderately contaminated soils on which conventional agriculture is impaired.

Oxides and their precursors have been extensively studied, either singly or in combination with other amendments promoting sorption, for in situ stabilization of metals and As in contaminated soils. This remediation option aims at reducing the available fraction of metal(loid)s, notably in the root zone, and thus lowering the risks associated with their leaching, ecotoxicity, plant uptake and human exposure. This review summarizes literature data on mechanisms involved in the immobilization process and presents results from laboratory and field experiments, including the subsequent influence on higher plants and aided phytostabilization. Despite the partial successes in the field, recent knowledge highlights the importance of long-term and large-scale field studies evaluating the stability of the oxide-based amendments in the treated soils and their efficiency in the long-term.

Phytomanagement in terms of phytostabilisation is considered a suitable method to decrease environmental risks of metal(loid) enriched mine tailings. The goal of this study was to identify plant-favourable edaphic niches in mine tailings from a semiarid area, in order to obtain relevant information for further phytostabilisation procedures. For this purpose, a transect-designed sampling from non-disturbed soils to two mine tailings was performed, including the description of soil and plant ecology gradients. Plant ecological indicators showed several stages in plant succession: from weeds to stable patches of late successional plant species. PCA results revealed that plant distribution at the tailings was driven mainly by salinity while metal(loid) concentrations played a minor role. The presence of soil desiccation cracks generated low salinity patches which facilitated favourable niches for plant establishment. Edaphic-patch distribution may condition phytostabilisation since ploughing or the employment of certain amendments should take into account favourable niches for plant growth.

Organic matter removal by cultured Sesuvium portulacastrum in constructed floating beds was studied during a 20day greenhouse experiment and an 8month field campaign in the polluted Yundang Lagoon (southeastern China). Experiments were traced via dissolved organic carbon (DOC) concentration, fluorescence excitation–emission matrix and absorption spectroscopy. Two ‘terrestrial’ humic-like, one ‘marine’ humic-like and one protein-like components were identified by parallel factor analysis. The ‘terrestrial’ humic-like and protein-like components, DOC and absorption coefficient (a280) decreased during the greenhouse experiment. The intensities of four fluorescence components were all reduced during the field experiment. These results demonstrate the clear potential of floating bed phytoremediation techniques for reducing organic pollution degree in brackish environments. The rhizosphere may play an important role during phytoremediation. Our results show that spectrophotometric measurements such as fluorescence provide a useful tool for examining the removal of different organic moieties during various bioremediation processes.

The halophytic shrub Halimione portulacoides demonstrates a high tolerance to heavy metal contamination and a capacity for accumulating metals within its tissues. On the Iberian Peninsula, this species has colonized habitats with high levels of metal pollution. The aim of this study is to analyze the response of H. portulacoides stem cuttings to this pollution. Growth, photosynthesis and metal uptake were examined in H. portulacoides through an experiment in which stem cuttings were replanted in metal-contaminated soil. This condition decreased growth and lowered both photosynthetic rate and stomatal conductance. Reduced photosynthetic performance was largely due to the reduced concentration of photosynthetic pigments. Despite these responses, there was some important evidence suggesting the phytoremediatory potential of Halimione stem cuttings. The results of our study indicate that this salt-marsh shrub may represent a biotool of value in the restoration of polluted areas.

This study evaluated the efficiency of Avicennia schaueriana in the implementation of phytoremediation compared with intrinsic bioremediation in mangrove sediments contaminated by total petroleum hydrocarbons (TPHs). The experiment was conducted for 3months at a pilot scale under conditions similar to a mangrove: the dynamics of the tides were simulated, and physical, chemical, microbiological and biogeochemical parameters were monitored. After the 90days, it was found that the phytoremediation was more efficient in the degradation of the TPHs compared to bioremediation, reducing the initial concentration of 32.2–4.2mg/g. A. schaueriana was also more efficient in mediating the degradation of different fractions of hydrocarbons, achieving a removal efficiency of 87%. The microbiological results consisted of a higher growth in the model with the plants, demonstrating the phytostimulation ability of the plants. Finally, the experiment showed that phytoremediation is a promising alternative in mangrove impacted by oil.

Some Pseudomonas fluorescens strains, consistently isolated from the rhizosphere of wild plants grown in a soil that was highly polluted with illegal waste of smelter residues, were utilised for Mirabilis jalapa seed bioinoculation to verify their effects on seed germination and on promoting a higher heavy metal accumulation in the plant rhizosphere and/or uptake in the leaves. The high content of heavy metals in the soil induced a decrease in either the leaf dry weight or photosynthetic pigment concentration during all vegetative phase of M. jalapa. Bioinoculation with P. fluorescens strains significantly increased the germination of seeds and the root length in the contaminated soil. In some bacterial strain/seed combination, bioinoculation significantly increased the accumulation of heavy metals in M. jalapa rhizosphere. For Cd, the concentration of this metal in the rhizospheres of bioinoculated plants ranged from 270 to 910 μg g-1 of dry weight compared with 200 μg g-1 of dry weight for the non-coated plants. Two P. fluorescens strains, AA27 and MO49, which were isolated from Artemisia annua and Melilotus officinalis, respectively, induced a significantly higher rhizosphere availability also for Cr, Cu, Ni and Zn. However, despite the relevant accumulation of the heavy metals in the plant rhizosphere, generally the metal uptake into the leaves was rather low. Both analysis of variance and principal component analysis confirmed this finding. However, one P. fluorescens strain, CD1, which was isolated from the multi-metal accumulator Cynodon dactylon, significantly promoted the M. jalapa leaf uptake for Cr, Cu and Zn. The plant metal uptake assessment, confirmed the per se capability of M. jalapa to effectively uptake Cd (30 %) and Cu (12.72 %) from the rhizosphere to the leaves, whereas the uptake for the other metals was low: Ni (2.66 %), Zn (2.46 %), Cr (1.75 %), Pb (0.73 %). © 2013 Springer Science+Business Media Dordrecht.