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Plants and associated microorganisms are used to remediate anthropogenic metal(loid) contamination of water, soils and sediments. This review focuses on the potential ofArundo donaxL. (Giant reed) for alleviating risks due to soils, water, and sediments contaminated by trace elements (TE), with emphasis on its advantages and limits over macrophytes and perennial grasses used for bioenergy and plant-based feedstock. Arundo donax is relevant to phytomanage TE-contaminated matrices, notably in its native area, as it possesses characteristics of large biomass production even under nutrient and abiotic stresses, fast growth rate, TE tolerance and accumulation mainly in belowground plant parts. Cultivating A. donax on contaminated lands and in constructed wetlands can contribute to increase land availability and limit the food vs. plant-based feedstock controversy. To gain more tools for decision-taking and sustainable management, further researches on A. donax should focus on: interactions between roots, TE exposure, and rhizosphere and endophytic microorganisms; biomass response to (a)biotic factors; sustainable agricultural practices on marginal and contaminated land; integration into local, efficient, energy and biomass conversion chains with concern to biomass quality and production; Life-Cycle Assessment including contaminant behavior, as well as environmental, agricultural and socio-economic benefits and drawbacks. [ABSTRACT FROM PUBLISHER]

We examined whether long-term Cd exposure leads to beneficial changes in the cultivable endophytic bacteria present in the seeds ofAgrostis capillaris. Therefore the cultivable seed endophytes ofAgrostis capillarisgrowing on a long-term Cd/Ni-contaminated plot (Cd/Ni seeds) were compared with those originating from a non-contaminated plot (control seeds). We observed plant- and contaminant-dependent effects on the population composition between control and Cd/Ni seeds. Also differences in phenotypic characteristics were found: endophytes from Cd/Ni seeds exhibited more ACC deaminase activity and production of siderophores and IAA, while endophytes from control seeds, very surprisingly, showed more metal tolerance. Finally, the 3 most promising seed endophytes were selected based on their metal tolerance and plant growth promoting potential, and inoculated inAgrostis capillarisseedlings. In case of non-exposed plants, inoculation resulted in a significantly improved plant growth; after inoculation of Cd-exposed plants an increased Cd uptake was achieved without affecting plant growth. This indicates that inoculation ofAgrostiswith its seed endophytes might be beneficial for its establishment during phytoextraction and phytostabilisation of Cd-contaminated soils. [ABSTRACT FROM AUTHOR]

A comprehensive 2D + 1 multi-phase computational model has been applied to polymer electrolyte fuel cells with a porous metallic flow field to investigate operating strategies which enable high power density operation in dry, elevated temperature environment. Extensive experimental model validation has been completed under a wide range of temperature, pressure, stoichiometry and humidity conditions. Both qualitative and quantitative agreement has been achieved in regard to voltage, area-specific resistance, and net water drag coefficient. Internal water distribution predictions show that modest changes in operating parameters on the cathode side help maintain a hydrated anode stream and thus effectively push the envelope of stable operating temperature 20°C higher, enabling more efficient heat dissipation in coolant system. Results also show that thermo-osmotic water flux across the membrane, as observed and measured experimentally, can be significant compared to electro-osmosis under high current (> 2 A/cm²) hot and dry conditions, even with thin electrolyte membranes. [ABSTRACT FROM AUTHOR]

The purpose of this work is to explore engineered interfacial and structural architecture in fuel cell diffusion media (DM). Perforations were introduced via lasers on samples of virgin DM that contained hydrophobic content. Depending on laser choice, some laser-cut samples displayed a heat affected zone" (HAZ) at the catalyst layer/microporous layer interface, characterized by a region surrounding each perforation where hydrophobic content was removed. At 50% inlet relative humidity, DM with homogeneously dispersed 100-km perforations and a HAZ displayed a 25% power density increase compared to virgin DM. Analyzing the oxygen concentration dependence in the double-Tafel region showed transport resistances were dominated by oxygen at moderate current values. Electrochemical impedance spectroscopy (EIS) and neutron radiography results indicated charge- and mass-transport impedances and liquid water redistribution play an important role, depending on the operating current density. Results suggested two mechanisms for the increased performance of the 100-p.m DM with HAZ: i) liquid water storage and through-plane water redistribution led to rehydration of the catalyst layer and membrane, and ii) in-plane water redistribution led to improved oxygen transport through the DM. The results of this study shed light on the importance of interfacial and structural architecture of fuel cell DM. [ABSTRACT FROM AUTHOR]

SUMMARY Root exudates were collected from maize plants ( Zea mays L.), grown under sterile and hydroponic conditions. Exudates of low molecular weight were isolated by filtration and dialysis (MW 1000) of the nutrient solution and analysed. Metal binding properties of the exudates were investigated at 25°C in 0.1 m NaCIO4 ionic medium, using a potentiometric method. The total acidity of the exudates and the successive stability constants of complexes formed with Cu2+, Pb2+ and Zn2+ were determined. Sugars and organic acids were the major components of the exudates. Measured total acidity was resolved into strong (5.85meq g−1C), weak (2.10meq g−1C) and very weak (2.20 meq g−1 C) acidities. Mono-complexes were formed with Cu, Pb and Zn and bis-complexes with Cu. At pH 5, stability constants followed the order Cu>Pb>Zn. [ABSTRACT FROM AUTHOR]

Discusses the effect of cadmium toxicity on changes in growth parameters and enzyme activities, directly related to cellular free radical scavanging systems as studied in maize plants. Observations on shoot length and leaf dry biomass; Advantages of the measurement of enzyme activities as early biomarkers in plant bioassays for assessment of phytotoxicity of cadmium-contaminated soils on maize plants.

In order to evaluate the possible use of hydroxyapatite (HA) as a soil additive for the in situ remediation of metal contaminated soils, the immobilizing capacity of this product was investigated. Three different concentrations of HA (0.5%, 1%, and 5% by weight (w/w)) were applied to a metal (Zn, Pb, Cu, Cd) and As contaminated soil originating from an old zinc smelter site in Belgium. After a three weeks equilibration period, exchangeable metal concentrations of the soils weredetermined using 0.1 M Ca(NO3)2 extraction. Test plants (Zea mays cv. Volga and Phaseolus vulgaris cv. Limburgse vroege) were grown on all soils. Growth parameters were determined and mineral analysis (Cu, Zn, Pb, Cd, Ni, Mn, Mg, Ca, K, As and P) of plants was performed. Exchangeable metal contents in soil decreased withincreasing HA application. Plant growth was partly restored on the 0.5% and 1% HA treated soils. However, at the 5% HA application rate growth was inhibited again. Plant mineral analysis showed that concentrations of 'toxic' metals in the leaves of the test plants decreased after HA application. However, the uptake of essential trace elementsalso decreased and probably led to Mn-deficiency in maize. In bean, addition of 0.5% and 1% HA resulted in a gradual decrease of metal uptake. At the 5% application level an increase of Zn, Cu, and Ni uptake was observed compared to the 0.5% and 1% application rate. In contrast to metal uptake, As uptake was found to increase after HA treatment. The increased PO42- concentration in the soil may be responsible for this. These results illustrate that HA application for the remediation of metal contaminated soils can be effective, but is not self evident. Strong immobilization of essential nutrients may lead to deficiency problems and mobilization of As may leadto an increased transfer to plants and animals and to an increased percolation of this element to the ground water. (c) 1999 Elsevier Science [ABSTRACT FROM AUTHOR]

The aim of this study was to assess thallium (Tl) uptake into the aerial parts of selected crop species grown on French soils with high Tl content of pedogeochemical origin (0.3-40 mg Tl kg-1 on a dry wt (DW) basis). Husked wheat and maize grains contained less than 4 Mu g Tl kg-1 DW, but rape shoots accumulated Tl with a shoot-soil partition coefficient (PC) > 1, and rape seeds had PC> 3. Tl content of rape seed reached 33 mg Tl kg-1 DW and higher concentrations in soil corresponded to increased concentrations in rape seeds. It is argued that parent material of the soil and pedogenesis have a considerable effect on Tl accumulation in rape seeds. These results show enhanced phytoavailability of Tl of pedogeochemicalorigin and prompt questions on the potential for food chain contamination by Tl in rape cattle cakes. [ABSTRACT FROM AUTHOR]

The thallium (Tl) content of the upper horizons of 244 French soils was determined as the first step towards the creation of a reference data bank for total Tl content of arable soils. Forty soil samples were collected in the vicinity of potential anthropogenic sources of Tl, but the remainder came from rural areas. The distribution of Tl concentrations in soils was characterized by a median value of 0.29 mg Tl kg-1 and a 90th percentile value of 1.54 mg Tl kg-1. Very high pedogeochemical contents were found (up to 55 mg Tlkg-1) but none could be attributed to obvious anthropogenic pollution. Areas of very high Tl concentration belong to an epihercynian transgression zone with a contact between a sedimentary basin and a crystalline massif. This contact is associated with stratified mineralizations (Zn, Pb, F, Sb, Ba, Tl and pyrites). High Tl concentrations were common in limestone, marl or granite derived soils, and the Tl in limestones or marls is probably concentrated in the sulfidescontained in these rocks because Tl has a high affinity to S. In granites, Tl may be in the micas and feldspars because Tl+ can replace K+ in these minerals. Silty or clay-silty soils showed the highest concentrations. These granulometric fractions contain the majority of the minerals, which are supposed to be the major hosts of Tl in soils, i.e. clay minerals, oxides and micas. Tl in thesoils was positively correlated with Ba, V, Pb, Fe, Ni, Cd, Zn, Co, As and especially Mn. A significant proportion of Tl may be in the Mnoxides: in oxidizing conditions, Tl(III) could enter the Mn oxides by sorption, or Tl(I) could replace K(I) in the oxide. [ABSTRACT FROM AUTHOR]

Preliminary results from the French ASPITET programme demonstrated that Cd background levels in agricultural soils can vary greatly (0.02--6.9 mg Cd kg{sup}-1{end}) depending on parent material and pedogenic processes (Baize, 1997). However, the total Cd content in soil is often not significantly related to the Cd concentration in edible plant parts. A field case study was undertaken across the southern part of the Yonne district, Burgundy, France. This area has various soil series with either low or high geochemical Cd content in the topsoil. Cd availability in soils sampled at 16 sites belonging to five soil series was investigated using single extractions. In addition, shoots (at stem elongation) and grains (at harvest) of field-grown wheat werecollected at the same sites and analysed for macronutrients and trace elements. Cd concentrations in grain varied from 0.015 to 0.146 mg Cd kg{sup}- 1{end} DM depending on soil characteristics, soil series,and plant mineral composition. Cd grain concentrations did not reflect total Cd content in the surface soil layer; however, they were correlated with Cd extracted by a 0.1 M calcium nitrate unbuffered solution, and to a lesser extent with either soil pH or CEC. These three parameters may be useful guides to predict Cd in wheat grain harvestedin the Yonne district. An inverse relationship was found between Cd and Cu contents in grain. The highest Cd concentrations in wheat grain occurred in plants grown on Aubues soils which had marginal Cu and Zn deficiencies in shoots. In order of Cd accumulation in wheat grain, soil series may be ranked as follows: Domerien < Carixien, Terres Noires < Sols Marron < Aubues. [ABSTRACT FROM AUTHOR]

The rapid increase of the world population constantly demands more food production from agricultural soils. This causes conflicts, since at the same time strong interest arises on novel bio-based products from agriculture, and new perspectives for rural landscapes with their valuable ecosystem services. Agriculture is in transition to fulfill these demands. In many countries, conventional farming, influenced by post-war food requirements, has largely been transformed into integrated and sustainable farming. However, since it is estimated that agricultural production systems will have to produce food for a global population that might amount to 9.1 billion by 2050 and over 10 billion by the end of the century, we will require an even smarter use of the available land, including fallow and derelict sites. One of the biggest challenges is to reverse non-sustainable management and land degradation. Innovative technologies and principles have to be applied to characterize marginal lands, explore options for remediation and re-establish productivity. With view to the heterogeneity of agricultural lands, it is more than logical to apply specific crop management and production practices according to soil conditions. Cross-fertilizing with conservation agriculture, such a novel approach will provide (1) increased resource use efficiency by producing more with less (ensuring food security), (2) improved product quality, (3) ameliorated nutritional status in food and feed products, (4) increased sustainability, (5) product traceability and (6) minimized negative environmental impacts notably on biodiversity and ecological functions. A sustainable strategy for future agriculture should concentrate on production of food and fodder, before utilizing bulk fractions for emerging bio-based products and convert residual stage products to compost, biochar and bioenergy. The present position paper discusses recent developments to indicate how to unlock the potentials of marginal land. [ABSTRACT FROM AUTHOR]

(Aided) phytostabilisation has been proposed as a suitable technique to decrease the environmental risks associated with metal(loid)-enriched mine tailings. Field scale evaluations are needed for demonstrating their effectiveness in the medium- to long-term. A field trial was implemented in spring 2011 in Cu-rich mine tailings in the NW of Spain. The tailings were amended with composted municipal solid wastes and planted with Salix spp., Populus nigra L. or Agrostis capillaris L. cv. Highland. Plant growth, nutritive status and metal accumulation, and soil physico- and bio-chemical properties, were monitored over three years (four years for plant growth). The total bacterial community, α- and β-Proteobacteria , Actinobacteria and Streptomycetaceae were studied by DGGE of 16s rDNA fragments. Compost amendment improved soil properties such as pH, CEC and fertility, and decreased soil Cu availability, leading to the establishment of a healthy vegetation cover. Both compost-amendment and plant root activity stimulated soil enzyme activities and induced important shifts in the bacterial community structure over time. The woody plant, S. viminalis , and the grassy species, A. capillaris , showed the best results in terms of plant growth and biomass production. The beneficial effects of the phytostabilisation process were maintained at least three years after treatment. [ABSTRACT FROM AUTHOR]