Throughout the world, urban agriculture supplies fresh local vegetables to city populations. However, the increasing anthropogenic uses of metal-containing nanoparticles (NPs) such as CuO-NPs in urban areas may contaminate vegetables through foliar uptake. This study focused on the CuO-NP transfer processes in leafy edible vegetables (i.e., lettuce and cabbage) to assess their potential phytotoxicity. Vegetables were exposed via leaves for 5, 10, or 15 days to various concentrations of CuO-NPs (0, 10, or 250 mg per plant). Biomass and gas exchange values were determined in relation to the Cu uptake rate, localization, and Cu speciation within the plant tissues. High foliar Cu uptake occurred after exposure for 15 days for lettuce [3773 mg (kg of dry weight)] and cabbage [4448 mg (kg of dry weight)], along with (i) decreased plant weight, net photosynthesis level, and water content and (ii) necrotic Cu-rich areas near deformed stomata containing CuO-NPs observed by scanning electron microscopy and energy dispersive X-ray microanalysis. Analysis of the CuO-NP transfer rate (7.8-242 μg day), translocation of Cu from leaves to roots and Cu speciation biotransformation in leaf tissues using electron paramagnetic resonance, suggests the involvement of plant Cu regulation processes. Finally, a potential health risk associated with consumption of vegetables contaminated with CuO-NPs was highlighted.
At the global scale, high concentrations of particulate matter (PM) enriched with metal(loid)s are currently observed in the atmosphere of urban areas. Foliar lead uptake was demonstrated for vegetables exposed to airborne PM. Our main objective here was to highlight the health risk associated with the consumption of vegetables exposed to foliar deposits of PM enriched with the various metal(loid)s frequently observed in the atmosphere of urban areas (Cd, Sb, Zn and Pb). Leaves of mature cabbage and spinach were exposed to manufactured mono-metallic oxide particles (CdO, Sb2O3 and ZnO) or to complex process PM mainly enriched with lead. Total and bioaccessible metal(loid) concentrations were then measured for polluted vegetables and the various PM used as sources. Finally, scanning electronic microscopy coupled with energy dispersive X-ray microanalysis was used to study PM-phyllosphere interactions. High quantities of Cd, Sb, Zn and Pb were taken up by the plant leaves. These levels depended on both the plant species and nature of the PM, highlighting the interest of acquiring data for different plants and sources of exposure in order to better identify and manage health risks. A maximum of 2% of the leaf surfaces were covered with the PM. However, particles appeared to be enriched in stomatal openings, with up to 12% of their area occupied. Metal(loid) bioaccessibility was significantly higher for vegetables compared to PM sources, certainly due to chemical speciation changes. Taken together, these results confirm the importance of taking atmospheric PM into account when assessing the health risks associated with ingestion of vegetables grown in urban vegetable crops or kitchen gardens.
In urban areas with high fallout of airborne particles, metal uptake by plants mainly occurs by foliar pathways and can strongly impact crop quality. However, there is a lack of knowledge on metal localization and speciation in plants after pollution exposure, especially in the case of foliar uptake. In this study, two contrasting crops, lettuce (Lactuca sativa L.) and rye-grass (Lolium perenne L.), were exposed to Pb-rich particles emitted by a Pb-recycling factory via either atmospheric or soil application. Pb accumulation in plant leaves was observed for both ways of exposure. The mechanisms involved in Pb uptake were investigated using a combination of microscopic and spectroscopic techniques (electron microscopy, laser ablation, Raman microspectroscopy, and X-ray absorption spectroscopy). The results show that Pb localization and speciation are strongly influenced by the type of exposure (root or shoot pathway) and the plant species. Foliar exposure is the main pathway of uptake, involving the highest concentrations in plant tissues. Under atmospheric fallouts, Pb-rich particles were strongly adsorbed on the leaf surface of both plant species. In lettuce, stomata contained Pb-rich particles in their apertures, with some deformations of guard cells. In addition to PbO and PbSO4, chemical forms that were also observed in pristine particles, new species were identified: organic compounds (minimum 20%) and hexagonal platy crystals of PbCO3. In rye-grass, the changes in Pb speciation were even more egregious: Pb-cell wall and Pb-organic acid complexes were the major species observed. For root exposure, identified here as a minor pathway of Pb transfer compared to foliar uptake, another secondary species, pyromorphite, was identified in rye-grass leaves. Finally, combining bulk and spatially resolved spectroscopic techniques permitted both the overall speciation and the minor but possibly highly reactive lead species to be determined in order to better assess the health risks involved.
The uptake, translocation, and human bioaccessibility of metals originating from atmospheric fine particulate matters (PM) after foliar exposure is not well understood. Lettuce (Lactuca sativa L.) plants were exposed to micronic PbO, CuO, and CdO particulate matters (PMs) by the foliar pathway and mature plants (6 weeks old) were analyzed in terms of: (1) metal accumulation and localization on plant leaf surface, and metal translocation factor (TF) and global enrichment factor (GEF) in the plants; (2) shoot growth, plant dry weight (DW), net photosynthesis (Pn), stomatal conductance (Gs), and fatty acid ratio; (3) metal bioaccessibility in the plants and soil; and (4) the hazard quotient (HQ) associated with consumption of contaminated plants. Substantial levels of metals were observed in the directly exposed edible leaves and newly formed leaves of lettuce, highlighting both the possible metal transfers throughout the plant and the potential for human exposure after plant ingestion. No significant changes were observed in plant biomass after exposure to PbO, CuO, and CdO-PMs. The Gs and fatty acid ratio were increased in leaves after metal exposure. A dilution effect after foliar uptake was suggested which could alleviate metal phytotoxicity to some degree. However, plant shoot growth and Pn were inhibited when the plants are exposed to PbO, and necrosis enriched with Cd was observed on the leaf surface. Gastric bioaccessibility of plant leaves is ranked: Cd > Cu > Pb. Our results highlight a serious health risk of PbO, CuO, and CdO-PMs associated with consumption of vegetables exposed to these metals, even in newly formed leaves in the case of PbO and CdO exposure. Finally, the study highlights the fate and toxicity of metal rich-PMs, especially in the highly populated urban areas which are increasingly cultivated to promote local food.
The behavior and the structural properties of organic radical species (ORs) in their native hydrocarbon environment as a function of temperature were investigated by electron paramagnetic resonance (EPR) spectroscopy. Five petroleum fractions derived from the same initial crude oil were studied in the temperature range of 293–673 K. The results from continuous wave (CW) and pulsed EPR spectroscopy show that petroleum fractions behave differently under thermal activation. The inverse of the normalized area versus temperature gave us different slope changes in accordance with the generation and the recombination of ORs. The EPR experimental parameters (line shape, line width) highlighted that during the thermal treatment, no conformational change occurred, but it impacts the organic matter maturity with the breaking of sulfur chains.
La part des particules nes et très nes (PM2.5 et PM1) émises dans l'atmosphère a augmenté de manière signi cative dans les zones industrielles, en lien avec la mise en place, en sortie d'échappement des usines, de ltres de plus en plus efficaces vis-à-vis des fractions granulométriques plus grossières. Ces particules nes et très nes sont très réactives et présentent donc un risque élevé à la fois pour la santé humaine et les milieux environnants (air, sol, eau, végétal). Ces particules microniques et submicroniques sont en effet capables de pénétrer profondément dans l'appareil respiratoire et d'atteindre les alvéoles pulmonaires. L'ingestion est également une voie d'exposition importante, notamment par la consommation de végétaux contaminés en zones urbaines (où la densité de population est particulièrement élevée) et/ou aux abords des zones industrielles. L'étude de l'accumulation et du transfert de particules par voie foliaire chez des végétaux cultivés en proximité d'usines émettant des particules riches en métaux est donc d'un intérêt majeur. Nos travaux concernent l'étude de l'accumulation foliaire de particules émises par une usine de recyclage de batteries au plomb et de leur transfert dans les tissus des feuilles. Dans un premier temps, nous avons caractérisé des particules à l'échelle individuelle grâce au couplage de techniques spectroscopiques et d'imageries. Les résultats montrent que le plomb se retrouve majoritairement dans les fractions les plus nes (PM1), essentiellement sous forme de sulfates. Nous avons mis en évidence la formation de composés de plomb solubles, en surface des particules. Dans un second temps, des choux ont été exposés aux particules dans l'enceinte de l'usine pour une durée de 6 semaines. Les résultats montrent une accumulation assez importante de particules contenant du plomb dans les feuilles, s'accompagnant parfois de la formation de nécroses enrichies en métaux. Dans certaines de ces nécroses, la spéciation du plomb se trouve modi ée. A n de mieux comprendre ces phénomènes bio-physico-chimiques identi és sur le terrain, des tests d'exposition à différents types de particules monométalliques ont été effectués en conditions contrôlées au laboratoire. Les résultats, complétés par des tests biologiques, montrent des différences signi catives d'un métal à un autre, notamment en termes de génotoxicité liée aux métaux..
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