Effect of fulvic acids on lead-induced oxidative stress to metal sensitive Vicia faba L. plant

Lead (Pb) is a ubiquitous environmental pollutant capable to induce various morphological, physiological, and biochemical functions in plants. Only few publications focus on the influence of Pb speciation both on its phytoavailability and phytotoxicity. Therefore, Pb toxicity (in terms of lipid peroxidation, hydrogen peroxide induction, and photosynthetic pigments contents) was studied in Vicia faba plants in relation with Pb uptake and speciation. V. faba seedlings were exposed to Pb supplied as Pb(NO3)2 or complexed by two fulvic acids (FAs), i.e. Suwannee River fulvic acid (SRFA) and Elliott Soil fulvic acid (ESFA), for 1, 12, and 24 h under controlled hydroponic conditions. For both FAs, Pb uptake and translocation by Vicia faba increased at low level (5 mg l−1), whereas decreased at high level of application (25 mg l−1). Despite the increased Pb uptake with FAs at low concentrations, there was no influence on the Pb toxicity to the plants. However, at high concentrations, FAs reduced Pb toxicity by reducing its uptake. These results highlighted the role of the dilution factor for FAs reactivity in relation with structure; SRFA was more effective than ESFA in reducing Pb uptake and alleviating Pb toxicity to V. faba due to comparatively strong binding affinity for the heavy metal

Long-term field metal extraction by pelargonium:phytoextraction efficiency in relation to plant maturity

The long length of periods required for effective soil remediation via phytoextraction constitutes a weak point that reduces its industrial use. However, these calculated periods are mainly based on short-term and/or hydroponic controlled experiments. Moreover, only a few studies concern more than one metal, although soils are scarcely polluted by only one element.In this scientific context, the phytoextraction of metals and metalloids (Pb, Cd, Zn, Cu,and As) by Pelargonium was measured after a long-term field experiment. Both bulk and rhizosphere soils were analyzed in order to determine the mechanisms involved in soil-root transfer. First, a strong increase in lead phytoextraction was observed with plant maturity, significantly reducing the length of the period required for remediation. Rhizosphere Pb, Zn, Cu, Cd, and As accumulation was observed (compared to bulk soil), indicating metal mobilization by the plant, perhaps in relation to root activity. Moreover, metal phytoextraction and translocation were found to be a function of the metals’ nature. These results, taken altogether, suggest that Pelargonium could be used as a multi-metal hyperaccumulator under multi-metal soil contamination conditions, and they also provide an interesting insight for improving field phytoextraction remediation in terms of the length of time required, promoting this biological technique

Foliar lead uptake by lettuce exposed to atmospheric fallouts

Metal uptake by plants occurs by soil−root transfer but also by direct transfer of contaminants from the atmosphere to the shoots. This second pathway may be particularly important in kitchen gardens near industrial plants. The mechanisms of foliar uptake of lead by lettuce (Lactuca sativa) exposed to the atmospheric fallouts of a lead-recycling plant were studied. After 43 days of exposure, the thoroughly washed leaves contained 335 ± 50 mg Pb kg−1 (dry weight). Micro-X-ray fluorescence mappings evidenced Pb-rich spots of a few hundreds of micrometers in diameter located in necrotic zones. These spots were more abundant at the base of the central nervure. Environmental scanning electron microscopy coupled with energy dispersive X-ray microanalysis showed that smaller particles (a few micrometers in diameter) were also present in other regions of the leaves, often located beneath the leaf surface. In addition, submicrometric particles were observed inside stomatal openings. Raman microspectrometry analyses of the leaves identified smelter-originated Pb minerals but also secondary phases likely resulting from the weathering of original particles. On the basis of these observations, several pathways for foliar lead uptake are discussed. A better understanding of these mechanisms may be of interest for risk assessment of population exposure to atmospheric metal contamination

Ecological changes in historically polluted soils: Metal(loid) bioaccumulation in microarthropods and their impact on community structure

International audienceSoil pollution by persistent metal(loid)s present environmental and sanitary risks. While the effects of metal(loid)s on vegetation and macrofauna have been widely studied, their impact on microarthropods (millimetre scale) and their bioaccumulation capacity have been less investigated. However, microarthropods provide important ecosystem services, contributing in particular to soil organic matter dynamics. This study focussed on the impact of metal(loid) pollution on the structure and distribution of microarthropod communities and their potential to bioaccumulate lead (Pb). Soil samples were collected from a contaminated historical site with a strong horizontal and vertical gradient of Pb concentrations. Microarthropods were extracted using the Berlese method. The field experiments showed that microarthropods were present even in extremely polluted soils (30,000 mg Pb kg− 1). However, while microarthropod abundance increased with increasing soil C/N content (R2 = 0.79), richness decreased with increasing pollution. A shift in the community structure from an oribatid-to a springtail-dominated community was observed in less polluted soils (R2 = 0.68). In addition, Pb bioamplification occurred in microarthropods, with higher Pb concentrations in predators than in detritivorous microarthropods. Finally, the importance of feeding and reproductive ecological traits as potentially relevant descriptors of springtail community structures was highlighted. This study demonstrates the interest of microarthropod communities with different trophic levels and ecological features for evaluating the global environmental impact of metal(loid) pollution on soil biological quality

Behavior and Impact of Zirconium in the Soil–Plant System: Plant Uptake and Phytotoxicity

Because of the large number of sites they pollute, toxic metals that contaminate terrestrial ecosystems are increasingly of environmental and sanitary concern (Uzu et al. 2010, 2011; Shahid et al. 2011a, b, 2012a). Among such metals is zirconium (Zr), which has the atomic number 40 and is a transition metal that resembles titanium in physical and chemical properties (Zaccone et al. 2008). Zr is widely used in many chemical industry processes and in nuclear reactors (Sandoval et al. 2011; Kamal et al. 2011), owing to its useful properties like hardness, corrosion-resistance and permeable to neutrons (Mushtaq 2012). Hence, the recent increased use of Zr by industry, and the occurrence of the Chernobyl and Fukashima catastrophe have enhanced environmental levels in soil and waters (Yirchenko and Agapkina 1993; Mosulishvili et al. 1994 ; Kruglov et al. 1996)

Bioaccessibility of selenium after human ingestion in relation to its chemical species and compartmentalization in maize

International audienceSelenium is a micronutrient needed by all living organisms including humans, but often present in low concentration in food with possible deficiency. From another side, at higher concentrations in soils as observed in seleniferous regions of the world, and in function of its chemical species, Se can also induce (eco)toxicity. Root Se uptake was therefore studied in function of its initial form for maize (Zea mays L.), a plant widely cultivated for human and animal food over the world. Se phytotoxicity and compartmentalization were studied in different aerial plant tissues. For the first time, Se oral human bioaccessibility after ingestion was assessed for the main Se species (SeIV and SeVI) with the BARGE ex vivo test in maize seeds (consumed by humans), and in stems and leaves consumed by animals. Corn seedlings were cultivated in hydroponic conditions supplemented with 1 mg L−1 of selenium (SeIV, SeVI, Control) for 4 months. Biomass, Se concentration, and bioaccessibility were measured on harvested plants. A reduction in plant biomass was observed under Se treatments compared to control, suggesting its phytotoxicity. This plant biomass reduction was higher for selenite species than selenate, and seed was the main affected compartment compared to control. Selenium compartmentalization study showed that for selenate species, a preferential accumulation was observed in leaves, whereas selenite translocation was very limited toward maize aerial parts, except in the seeds where selenite concentrations are generally high. Selenium oral bioaccessibility after ingestion fluctuated from 49 to 89 % according to the considered plant tissue and Se species. Whatever the tissue, selenate appeared as the most human bioaccessible form. A potential Se toxicity was highlighted for people living in seleniferous regions, this risk being enhanced by the high Se bioaccessibility

Taking Two-Photon Excitation to Exceptional Path-Lengths in Photonic Crystal Fiber

The well-known, defining feature of two-photon excitation (TPE) is the tight, three-dimensional confinement of excitation at the intense focus of a laser beam. The extremely small excitation volume, on the order of 1 μm3 (1 femtoliter), is the basis of far-reaching applications of TPE in fluorescence imaging, photodynamic therapy, nanofabrication, and three-dimensional optical memory. Paradoxically, the difficulty of detecting photochemical events in such a small volume is a barrier to the development of the two-photon-activated molecular systems that are essential to the realization of such applications. We show, using two-photon-excited fluorescence to directly visualize the excitation path, that confinement of both laser beam and sample solution within the 20 μm hollow core of a photonic crystal fiber permits TPE to be sustained over an extraordinary path-length of more than 10 cm, presenting a new experimental paradigm for ultrasensitive studies of two-photon-induced processes in solution. (Figure Presented).We are grateful to the Koerber Foundation (Germany) and the EPSRC (UK) for financial support. G.O.S.W. is a recipient of an EPSRC Prize Postdoctoral Fellowshi

Metal ion geochemistry in smelter impacted soils and soil solutions

As part of an extended project to understand the speciation of metal ions in contaminated lands, we conducted a series of chemical extraction experiments on soil and extracted the soil pore water to determine the speciation of Pb, Cd and Cu in a smelter impacted site. The chemical extractions show that soil organic matter and metal oxides (Fe and Mn) control the speciation of Pb, Cu and Cd in the soil. For Pb, these results are in agreement with previous EXAFS data on the same soils. The soil solution speciation is calculated with the help of the NICA-Donnan modelling approach. The modelling shows that Pb and Cu speciation is dominated by the dissolved organic matter while Cd is mainly in solution as a free aquo-ion. The speciation in the soil is also simulated by a model coupling both the binding to soil organic matter and metal oxides. The simulated partition coefficient (Kd) is in good agreement with the experimentally measured Kd

Gestion agro-environnementale pragmatique des sites industriels pollués : favoriser les services écosystémiques et la dynamique collective

International audience►Introduction : Les activités de recyclage des métaux participent à l’économie circulaire, mais elles ont également engendré des pollutions historiques persistantes des sols. Désormais, les émissions industrielles sont très contrôlées (meilleures techniques disponibles) et les citoyens riverains des sites ICPE sont particulièrement attentifs aux risques environnementaux et sanitaires. Dans ce contexte, certains gestionnaires de sites ICPE, tels que la STCM adoptent une démarche proactive de gestion des pollutions historiques : ils anticipent la réglementation et mettent en œuvre des démarches participatives de gestion du site avec les différents acteurs concernés. L’objectif de cette communication est de présenter un projet de « phytoremédiation pragmatique » mené sur le site de Bazoches (proche Orléans) par l’entreprise STCM en collaboration avec un agriculteur riverain et l’Axe Transition Ecologique du CERTOP. ►Mise en œuvre du projet : Le site STCM de Bazoches a fait l’objet de plusieurs projets de recherche (Leveque, 2015 et Foucault, 2014). Un fort gradient de concentrations en métaux (Pb, Cd) et metalloïdes (As, Sb..) dans les sols de surface (30 cm) existe, depuis le mur d’enceinte de l’usine (40000 mgPb/kg sol) vers le chemin à 140m de distance (100 mgPb/kg sol au correspond au fond géochimique régional naturel) qui sépare la parcelle STCM d’une parcelle cultivée en différentes céréales (blé, orge…). Cette pollution historique des sols de surface a pour origine des retombées atmosphériques de particules riches en métaux et des épandages d’eaux usées pendant plusieurs années puisque l’usine a été implantée en 1967. Une très faible migration des polluants depuis le sol de surface vers les horizons plus profonds est observée (30 cm pour le Pb en 50 ans d’activité de l’usine). Mais, cette pollution historique a un impact sur l’écosystème sol (dynamique des matières organiques et de la faune du sol) et une pollution diffuse aux particules fines riches en polluants peut influencer la qualité des végétaux cultivés aux abords de ce site. Un projet de gestion agro-environnementale du site a démarré en 2016 :A) Le site concerné ne fait pas l’objet d’une pression foncière, il est donc possible dans un premier temps de tester l’efficience une étape de phytoextraction des polluants en exportant de façon systématique dans une « zone de stockage » les tontes de végétaux qui poussent sur le site dans la zone comprise entre 140 et 100m de distance de l’usine. Les observations de terrain ont en effet permis de constater la présence de syllénes, plantes hyperaccumulatrices des métaux bien implantées sur le site. Cette étape pourrait être effectuée pendant 3 ans avec un suivi annuel des concentrations dans les partis des végétaux récoltées et dans les sols à t=0 et t=3 ans. Les résidus de végétaux riches en métaux seront stockés dans une zone de compostage créée aux abords du mur d’enceinte puis le compost serait incorporé au sol de surface de la zone 100m-80m de distance à l’usine. Les objectifs visés par cette méthode à moindre coût et qui utilise des plantes endogènes qui ont démontré leur capacité à pousser sur le site sont :-Réduire progressivement la zone de contamination des sols de surface autour de l’usine par la phytoextraction des métaux.-Partir de la zone la moins polluée et progresser vers la zone la plus polluée permet l’utilisation sur le site du compost riche en métaux issus du compostage des tontes. Le sol de la zone 100-80 enrichi en matières organiques sera aussi plus propice ensuite à la pousse des végétaux et à la vie biologique du sol. Ensuite, selon les résultats il pourrait être décidé :-de cultiver si besoin des plantes plus performantes pour la phytoextraction.-d’utiliser des acides organiques pour favoriser la solubilité des polluants inorganiques dans une démarche de phytoextraction assistée.B) Des haies d’arbres ont été plantées à 140 de distance de l’usine (zone considérée comme non polluée) pour réduire les transferts de particules, rendre visible les limites de la parcelle…. Ces aménagements ont pour objectif de réduire à moindre coût les transferts de particules de sol pollués et d’intercepter les particules. Les arbres et/ou haies doivent être choisis en termes de hauteur, d’adaptation au climat. ►Conclusions & Perspectives : L'étude de la végétation sur les sols fortement pollués apporte des données importantes pour l'amélioration des techniques de phytoremédiation. De nombreux auteurs ont souligné que la prairie métallophyte illustre l’adaptation de l'écosystème aux perturbations anthropiques (Austruy, 2012). Par exemple, l’espèce pseudo métallophyte, Silene vulgaris a été observée sur le site de Bazoches ainsi que sur l'ancien site industriel d’Auzon en Haute-Loire (Auvergne, France) présentant une forte pollution des sols (As, Sb, Cd, Cu et Pb). Le projet scientifique décrit permettra de tester en conditions de terrain l’efficacité de remédiation des plantes endogènes et surtout de créer des synergies avec les acteurs riverains du site. Par ailleurs, la STCM envisage de développer d’autres projets de gestion volontaire de ses environs et effluents. Par exemple sur Toulouse, la mise en place d’une zone pédagogique de phytoextraction est en discussion. Le traitement des eaux usées de l’entreprise est désormais pour partie assuré grâce à un dispositif innovant « le tapis biosorbant » à base d’écorces développé par PearL (Limoges)