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1.
J Agric Food Chem ; 2020 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-32614578

RESUMO

The increased use of the emerging per- and polyfluoroalkyl substances (PFASs) has led to extensive concerns around the world. Effective detection methods to trace their pollution characteristics and environmental behaviors in complex soil-crop systems are urgently needed. In this study, a reliable and matrix effect-free method was developed for simultaneous determination of fourteen legacy and emerging PFASs, including perfluorooctanoic acid, perfluorooctane sulfonate, six hydrogenous PFASs, three chlorinated PFASs, and three hexafluoropropylene oxide (HFPO) homologues in six crop (the edible parts) and five soil matrices, using ultrasonic combining solid-phase extraction and UPLC-MS/MS. The varieties of extractants and cleanup cartridges, the dosage of ammonia hydroxide, and matrix effect (ME) were studied to obtain an optimal pretreatment procedure. The developed method had high sensitivity and accuracy with satisfactory method detection limits (MDLs, 2.40-83.03 pg/g dry weight) and recoveries (72%-117%) of all target analytes in matrices at five concentrations, i.e. 0.1, 1, 10, 100, and 1000 ng/g. In addition, the ME of this method (0.82-1.15) was negligible for all PFASs even considering 11 different matrices. The successful application of the matrix effect-free method to simultaneously determine the legacy and emerging PFASs in crop and soil samples has demonstrated its excellent practicability for monitoring emerging PFASs in soil-crop systems.

2.
Metallomics ; 2020 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-32558867

RESUMO

Hyperaccumulator plants have the ability to efficiently concentrate metallic elements, e.g. nickel, from low-grade sources into their living biomass. Although the majority of nickel hyperaccumulator plant species restrict cobalt uptake, some species are able to co-accumulate cobalt when growing in ultramafic soils. The asteraceous perennial herb Berkheya coddii from South Africa is one of the most promising agromining crops known globally. It may accumulate nickel in excess of 30 000 µg g-1 in dry leaves, while co-accumulating up to 600 µg g-1 cobalt. This study aimed to elucidate the interactions between nickel and cobalt for uptake by and translocation into B. coddii through a pot experiment including various cobalt/nickel treatment combinations in soil, after which uptake and localisation were recorded. Cobalt in the substrate limits nickel uptake by B. coddii plants and is mainly retained in the basal leaves in contrast to Ni that is rapidly transferred to the top of the plant. B. coddii was more tolerant to high Ni concentration, whether in the substrate or internally but remains a promising crop which could be used, with suitable agronomic measures and practices, for cobalt agromining in areas with high soil cobalt but low soil nickel. A yield of 77 kg ha-1 nickel and 16.5 kg ha-1 cobalt may be attainable under optimum conditions.

3.
Sheng Wu Gong Cheng Xue Bao ; 36(3): 436-449, 2020 Mar 25.
Artigo em Chinês | MEDLINE | ID: mdl-32237538

RESUMO

Phytomining technology cultivates hyperaccumulator plants on heavy metal contaminated soils, followed by biomass harvesting and incineration to recover valuable metals, offering an opportunity for resource recycling and soil remediation. Large areas of ultramafic soils, naturally rich in nickel (Ni), are present in numerous places around the world. As an environmentally friendly and cost-effective soil remediation technology, phytomining has a broad application prospect in such areas and thus has attracted great attention from global researchers. The key processes of phytomining include: (1) high-selectivity response of hyperaccumulator plants to Ni the underlying mechanisms involved in the rhizosphere; (2) underlying mechanisms of high-efficiency uptake and translocation of Ni in hyperaccumulators; and (3) resource recycling of high-added value Ni products from the Ni-rich bio-ore of hyperaccumulators. In recent 30 years, phytomining practices have successfully carried out in United States, Albania and Malaysia. However, the research and application of this technology in China are still in the fledging stage. This paper reviews the key processes and research progress of phytomining, and points out the bottleneck, to provide theoretical basis and technical guidance for phytomining.


Assuntos
Biodegradação Ambiental , Níquel , Poluentes do Solo , China , Níquel/metabolismo , Solo , Poluentes do Solo/metabolismo
4.
Environ Microbiol ; 22(4): 1649-1665, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32128926

RESUMO

The Island of Borneo is a major biodiversity hotspot, and in the Malaysian state of Sabah, ultramafic soils are extensive and home to more than 31 endemic nickel hyperaccumulator plants. The aim of this study was to characterize the structure and the diversity of the rhizosphere bacterial communities of several of these nickel hyperaccumulator plants and factors that affect these bacterial communities in Sabah. The most abundant phyla were Proteobacteria, Acidobacteria and Actinobacteria. At family level, Burkholderiaceae and Xanthobacteraceae (Proteobacteria phylum) were the most abundant families in the hyperaccumulator rhizospheres. Redundancy analysis based on soil chemical analyses and relative abundances of the major bacterial phyla showed that abiotic factors of the studied sites drove the bacterial diversity. For all R. aff. bengalensis rhizosphere soil samples, irrespective of studied site, the bacterial diversity was similar. Moreover, the Saprospiraceae family showed a high representativeness in the R. aff. bengalensis rhizosphere soils and was linked with the nickel availability in soils. The ability of R. aff. bengalensis to concentrate nickel in its rhizosphere appears to be the major factor driving the rhizobacterial community diversity unlike for other hyperaccumulator species.

5.
J Environ Manage ; 263: 110323, 2020 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-32174515

RESUMO

Metal tailings are potential sources of strong environmental pollution. In situ remediation involves the installation of a plant cover to stabilize materials and pollutants. Whether metal(loid)s are effectively immobilized in remediated tailing ponds submitted to heavy rainfall remains uncertain. In this study, tailing materials were collected from bare tailings (control), grass-planted (G) and grass-shrub planted (GS) areas on a former Pb/Zn mine site. Batch column experiments were performed with three rainfall intensities of 0.36, 0.48, and 0.50 mL min-1 for 18 d in the lab. The pH, Eh, Cd, Pb, Zn and As concentration in leachate were recorded. Selected leached tailing materials were finally characterized. Results showed that leachates from control were strongly acidic (pH 3.11-4.65), and that Cd, Pb, Zn and As were quickly released at high rate (e.g., 945 mg L-1 Zn). During the experiment up to 4% Cd present in the material was released and almost 1% Zn. With material collected from the G area, leachates were even more acidic (2.16-2.84) with a rainfall intensity of 0.50 mL min-1 and exhibited a high redox potential (588-639 mV). However, concentrations of metals in leachates were much lower than that in the control, except for Zn (e.g., 433 mg L-1), and they tended to decrease with time. Cumulative leaching rate was still relatively high (e.g., 0.68% Cd; 0.75% Zn) during the first eight days (stage I). However, with the GS treatment, leachate pH gradually raised from acid to alkaline values (3.9-8.2) during stage I, then remained high until the end of the experiment (stage II). Also, amounts of elements released during the 18 d were low in general. The releasing ratios of Cd (R2 > 0.95), Pb (R2 > 0.95), As (R2 > 0.87), and Zn (R2 > 0.90) fitted well with a two-constant model. In conclusion, under subtropical climate with heavy rainfall, phytostabilization is effective but immobilization of metals is higher with a combination of grass and shrub than with only grass to reduce leaching of As and Zn.

6.
Environ Sci Technol ; 54(4): 2287-2294, 2020 02 18.
Artigo em Inglês | MEDLINE | ID: mdl-31951400

RESUMO

The fern Dicranopteris linearis (Gleicheniaceae) from China is a hyperaccumulator of rare earth element (REE), but little is known about the ecophysiology of REE in this species. This study aimed to clarify tissue-level and organ-level distribution of REEs via synchrotron-based X-ray fluorescence microscopy (XFM). The results show that REEs (La + Ce) are mainly colocalized with Mn in the pinnae and pinnules, with the highest concentrations in necrotic lesions and lower concentrations in veins. In the cross sections of the pinnules, midveins, rachis, and stolons, La + Ce and Mn are enriched in the epidermis, vascular bundles, and pericycle (midvein). In these tissues, Mn is localized mainly in the cortex and mesophyll. We hypothesize that the movement of REEs in the transpiration flow in the veins is initially restricted in the veins by the pericycle between vascular bundle and cortex, while excess REEs are transported by evaporation and cocompartmentalized with Mn in the necrotic lesions and epidermis in an immobile form, possibly a Si-coprecipitate. The results presented here provide insights on how D. linearis regulates high concentrations of REEs in vivo, and this knowledge is useful for developing phytotechnological applications (such as REE agromining) using this fern in REE-contaminated sites in China.


Assuntos
Cério , Gleiquênias , Metais Terras Raras , China , Lantânio
7.
Sci Total Environ ; 707: 135654, 2020 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-31784181

RESUMO

Amendments of biochar, the residual solid of biomass pyrolysis, have been shown to enhance metal phytoextraction from contaminated soils with hyperaccumulating plants in specific situations. In order to investigate this phenomenon over successive harvests in field conditions, two identical undisturbed soil cylinders (1-m2 section × 1.85-m height) were excavated from a contaminated agricultural plot and monitored with instrumented lysimeters. Wood-derived biochar was added at a rate of 5% (w/w) in the first 30 cm of one of the two lysimeters. The Cd/Zn-hyperaccumulator Noccaea caerulescens was then grown for the next four years on both lysimeters. Our results showed that the hyperaccumulating plant was able to remove about 2 g m-2 of Cd and 12-16 g m-2 of Zn within four years, representing about 40% and 4% of the initial Cd and Zn soil contamination, respectively. Biochar amendment improved plant germination and survival and increased root surface density. However, no significant effect of biochar on shoot metal content of N. caerulescens was observed. Mass balances suggested that up to 10% the metal contamination moved from the disturbed Ap horizon to the deeper horizons, particularly in the biochar-amended soil profile. Furthermore, shoot Cd and Zn concentration generally decreased over the successive harvests, together with soil metal availability. Depending on the way to account for this progressive decrease in efficiency, our estimations of the time necessary to remove the excess of metals in the topsoil in these conditions ranged from 11 to 111 years for Cd and from 97 years to an infinite time for Zn. In conclusion, the simultaneous use of N. caerulescens and biochar amendment can lead to a significant removal of specific metallic elements from the topsoil, but the risk of metal movement down the soil profile and the observed decrease in phytoextraction efficiency over time deserve further investigations.


Assuntos
Carvão Vegetal , Biodegradação Ambiental , Cádmio , Solo , Poluentes do Solo , Zinco
8.
Environ Sci Pollut Res Int ; 26(25): 25985-25999, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31273661

RESUMO

The large-scale use of quaternary ammonium compounds (QACs) in medicines or disinfectants can lead to their release into the environment, posing a potential risk to organisms. This study examined the effects of three typical QACs, dodecyltrimethylammonium chloride (DTAC), dodecyldimethylbenzylammonium chloride (DBAC), and didodecyldimethylammonium chloride (DDAC), on hydroponically cultured wheat seedlings. After 14 days of exposure, both hormesis and phytotoxicity were observed in the wheat seedlings. The shoot and root fresh weight gradually increased as QAC concentrations rose from 0.05 to 0.8 mg L-1. However, higher QAC concentrations severely inhibited plant growth by decreasing shoot and root fresh weight, total root length, and photosynthetic pigment content. Moreover, the increase in malondialdehyde and O2.- contents, as well as root membrane permeability, reflected an oxidative burst and membrane lipid peroxidation caused by QACs. However, the effects of QACs on the levels of these oxidative stress markers were compound-specific, and the changes in superoxide dismutase, peroxidases, and catalase activity were partly related to reactive oxygen species levels. Considering the order of median effective concentration values (EC50) and the levels of oxidative stress induced by the three tested QACs, their phytotoxicities in wheat seedlings increased in the following order: DDAC < DTAC < DBAC, which mainly depended on their characteristics and applied concentrations. These results, which illustrated the complexity of QAC toxicity to plants, could potentially be used to assess the risk posed by these compounds in the environment.


Assuntos
Malondialdeído/química , Estresse Oxidativo/efeitos dos fármacos , Peroxidases/metabolismo , Peróxidos/química , Compostos de Amônio Quaternário/química , Compostos de Amônio Quaternário/farmacologia , Espécies Reativas de Oxigênio/química , Plântula/efeitos dos fármacos , Superóxido Dismutase/metabolismo , Triticum/crescimento & desenvolvimento , Malondialdeído/farmacologia , Peroxidases/química , Fotossíntese/efeitos dos fármacos , Espécies Reativas de Oxigênio/farmacologia , Superóxido Dismutase/química
9.
Environ Pollut ; 250: 464-474, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31026693

RESUMO

A novel FeSiCa rich material (IS), chicken manure (CM) and its biochar were investigated for their efficiency in simultaneous remediation of Cd and As uptake by the vegetable Brassica chinensis L. Wet chemistry analysis and X-ray powder diffraction, scanning electron microscopy/energy dispersive X-ray spectroscopy as well as Fourier transform infrared spectroscopy were used to reveal the mechanisms responsible for Cd and As fixation in the amended soils. The IS treatment performed best in reducing Cd uptake, while the combination of IS and CM was the optimal one for As fixation. The precipitation/co-precipitation (in cadmium silicate/phosphate/phosphate hydroxide, cadmium iron and manganese oxides under alkaline conditions, and calcium/magnesium/ferric arsenates) and specific chemisorption (by amorphous iron/manganese oxides) were proved to be more efficient in simultaneously lowering As and Cd phytoavailability than was organic complexation. These findings demonstrate that FeSiCa and FeSiCaC amendments are highly efficient and promising in-situ remediation systems for safe crop production on soils contaminated with Cd and As.


Assuntos
Arsênico/metabolismo , Cádmio/metabolismo , Recuperação e Remediação Ambiental/métodos , Poluentes do Solo/metabolismo , Arsênico/análise , Brassica/química , Cádmio/análise , Carvão Vegetal , Ferro , Compostos de Manganês , Esterco , Óxidos , Fosfatos/química , Solo/química , Poluentes do Solo/análise , Verduras
10.
J Hazard Mater ; 369: 621-631, 2019 05 05.
Artigo em Inglês | MEDLINE | ID: mdl-30825808

RESUMO

The efficiency of zero-valent iron (Fe0) for the degradation of contaminants in water or soil can be highly reduced by side reactions with oxygen or water. This work was conducted to test whether this drawback can be effectively suppressed by the carbonation of Fe0 with pyrolyzed biomass, which forms a Fe3C composite. The composite Fe3C was characterized and its reactivity and stability were assessed in batch tests with methyl orange (MO) as a model pollutant. The results indicated that the removal rate of MO on Fe3C composite was higher than that of Fe0 (7.587 mg/(g·min) vs. 4.306 mg/(g·min)) at pH 4, where the degradation mechanism was confirmed by high-performance liquid chromatography-mass spectrometry. More importantly, the produced iron oxide in the Fe3C composite was highly suppressed. Regeneration studies showed that after three times of cycling, the removal efficiency of MO on Fe3C composite was kept to 99.42%, but Fe0 almost lost its reactivity. In situ chemical reduction of a colorimetric redox probe (indigo-5, 5'-disulfonate, I2S) quantitatively demonstrated that Fe3C composite has the reduction kinetics of I2S obviously slower than Fe0, indicating that Fe3C composite improved the stability of incorporated Fe0 to resist the side oxidation.

11.
Sci Total Environ ; 667: 475-484, 2019 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-30833246

RESUMO

The world human population is more and more urban and cities have a strong impact on the biosphere. This explains the development of urban ecology. In this context, the goal of our work is fourfold: to describe the diversity of scientific questions in urban ecology, show how these questions are organized, to assess how these questions can be built in close interactions with stakeholders, to better understand the role urban ecology can play within ecological sciences. A workshop with scientists from all relevant fields (from ecology to sociology) and stakeholders was organized by the Foundation for Research on Biodiversity (FRB). Three types of scientific issues were outlined about (1) the biodiversity of organisms living in urban areas, (2) the functioning of urban organisms and ecosystems, (3) interactions between human societies and urban ecological systems. For all types of issues we outlined it was possible to distinguish both fundamental and applied scientific questions. This allowed building a unique research agenda encompassing all possible types of scientific issues in urban ecology. As all types of ecological and evolutionary questions can be asked in urban areas, urban ecology will likely be more and more influential in the development of ecology. Taken together, the future of towns, their biodiversity and the life of city dwellers is at stake. Increasing the space for ecosystems and biodiversity within towns is more and more viewed as crucial for the well-being of town dwellers. Depending on research and the way its results are taken into account, very different towns could emerge. Urban areas can be viewed as a test and a laboratory for the future of the interactions between human and ecological systems.


Assuntos
Ecologia , Biodiversidade , Evolução Biológica , Cidades , Ecossistema , Monitoramento Ambiental , Humanos , Pesquisa , Urbanização
12.
Chemosphere ; 216: 75-83, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30359919

RESUMO

Due to their specific properties, ion-adsorption rare earth mine sites may be a threat for adjacent environments. This work was undertaken to assess whether former mining operations on ion-adsorption rare earth mine sites have a significant impact on water bodies and soils of the surrounding environments. Tailing soil materials, stream waters and sediments, and farmland soils were collected from one of the largest ion-adsorption rare earth mine sites worldwide (Southern China). Total concentrations of rare earth elements (REEs), Fe, Al, etc., and pH were measured. Results revealed high concentrations of REEs in tailing soils (392 mg kg-1), stream waters (4460 µg L-1), sediments (462 mg kg-1) and farmland soils (928 mg kg-1) in comparison with control sites. In the tailing profiles, light REEs (LREEs) were preferentially leached compared to middle REEs (MREEs) and heavy REEs (HREEs). Anomalies in tailings and stream water indicated strong soil weathering (Eu) and leaching activities (Ce) within the tailings. The MREE enriched pattern in stream water was more related to water parameters such as Al and Fe oxides, and ligands, than to the source of REEs. Anomalies also indicated that REEs contamination in the farmland soils was mainly originated from the stream water contaminated by the leaching from the tailings. In conclusion, a heavy REEs pollution was recorded in the surrounding environment of ion-adsorption rare earth mine. REEs fractionation, Ce and Eu anomalies provided an insight to the understanding of REEs leaching and soil weathering processes, and REEs environmental fate in rare earth mining area.


Assuntos
Monitoramento Ambiental/métodos , Metais Terras Raras/análise , Mineração , Adsorção , Agricultura , China , Poluição Ambiental/análise , Rios , Poluentes do Solo/análise , Poluentes Químicos da Água/análise
13.
Sci Total Environ ; 654: 237-249, 2019 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-30445325

RESUMO

Ultramafic (i.e. serpentine) soils are widespread in the Balkans and particularly in Albania. They account for a large part of plant endemism in that region and host several hyperaccumulator species, which are characterized by leaf nickel concentrations frequently above 1%. This rich nickel hyperaccumulating flora could serve as candidate to be used in phytoextraction and agromining. Despite recent interest in metal hyperaccumulating plants and agromining, very few studies have investigated the bacterial diversity and the influence of environmental factors on microbial gene profiles in the rhizosphere of hyperaccumulator plants growing on ultramafic soils. Because rhizospheric bacteria could be crucial to the success of phytoremediation, we studied a total of 48 nickel-hyperaccumulating plants which were sampled from four species that are widespread in Albania: Noccaea ochroleuca, Odontarrhena smolikana, O. rigida and O. chalcidica. All samples were taken from the ultramafic regions of Librazhd and Pogradec in eastern Albania in October 2015. Our study shows that Proteobacteria, Actinobacteria and Acidobacteria dominated the soil bacterial communities. Of these three phyla, only Proteobacteria was relatively abundant. This study underlines the influence of soil Cation Exchange Capacity on the bacterial community's diversity and structure. Based on the predicted metagenomes, the genes belonging to amino acid, lipid and carbohydrate metabolisms were identified as major gene families. Our study sheds some light on our understanding of how bacterial communities are structured within and affect the rhizosphere of hyperaccumulator plants from ultramafic soils in Albania.


Assuntos
Brassicaceae/crescimento & desenvolvimento , Monitoramento Ambiental/métodos , Níquel/análise , Proteobactérias/isolamento & purificação , Rizosfera , Poluentes do Solo/análise , Albânia , Biodegradação Ambiental , Biodiversidade , Brassicaceae/metabolismo , Níquel/metabolismo , Proteobactérias/classificação , Proteobactérias/genética , Solo/química , Microbiologia do Solo , Poluentes do Solo/metabolismo
14.
Sci Total Environ ; 646: 696-703, 2019 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-30059929

RESUMO

The pollution of natural waters and sediments with metals derived from acid mine drainage (AMD) is a global environmental problem. However, the processes governing the transportation and transformation of AMD metals such as Cd in mountainous areas are poorly understood. In this study, the Cd isotopic composition and Cd concentration of river water and sediments (16 sampling sites) from an AMD-affected river in southern China were determined. Cd concentration in river water declined from its source at a tailings dam (304 µg L-1) to a point 14 km downstream (0.32 µg L-1). Sediment Cd concentration ranged from 0.18 to 39.9 µg g-1, suggesting that anthropogenic Cd is derived primarily from the tailing dam and easily enters the solid phase of the river. Isotopic data showed that the dissolved Cd in rivers was characterized by δ114/110Cd values ranging from 0.21‰ to 1.03‰, with a mean of 0.48‰. The greatest Cd isotope difference was observed between the water and sediments in the LW dam (Δ114/110Cdriver-sediment = 1.61‰, site 1), likely due to a rapid weathering dissolution of the ore tailings. In the river's upper reach (sites 2-3), isotope difference between river and sediment (Δ114/110Cdriver-sediment) ranged from 1.0‰ to 0.91‰. This suggests that a host of secondary processes might have impacted Cd isotope fractionation, including adsorption, ternary complexation and/or (co)precipitation of Cd on secondary oxides and hydroxides. In the middle and lower reaches, an abruptly elevated δ114/110Cd value near farmland (site 10) suggests the existence of a second Cd source. Based on the chemical properties of water samples we can attribute this heavy isotope signature to agricultural fertilizer and drainage from agricultural fields. Our results suggest that Cd isotope is a tracer for identifying and tracking Cd sources and attenuation mechanisms (adsorption/(co)precipitation) in a complex mountain watershed.

15.
Int J Phytoremediation ; 20(5): 415-423, 2018 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-29608375

RESUMO

The widespread use of rare earth elements (REEs) has resulted in problems for soil and human health. Phytolacca americana L. is a herbaceous plant widely distributed in Dingnan county of Jiangxi province, China, which is a REE mining region (ion absorption rare earth mine) and the soil has high levels of REEs. An investigation of REE content of P. americana growing naturally in Dingnan county was conducted. REE concentrations in the roots, stems, and leaves of P. americana and in their rhizospheric soils were determined. Results showed that plant REEs concentrations varied among the sampling sites and can reach 1040 mg/kg in the leaves. Plant REEs concentrations decreased in the order of leaf > root > stem and all tissues were characterized by a light REE enrichment and a heavy REE depletion. However, P. americana exhibited preferential accumulation of light REEs during the absorption process (from soil to root) and preferential accumulation of heavy REEs during the translocation process (from stem to leaf). The ability of P. americana to accumulate high REEs in the shoot makes it a potential candidate for understanding the absorption mechanisms of REEs and for the phytoremediation of REEs contaminated soil.


Assuntos
Metais Terras Raras , Phytolacca americana , Biodegradação Ambiental , China , Humanos , Solo
16.
J Environ Qual ; 46(4): 845-854, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28783796

RESUMO

Metals can be immobilized on biochars by precipitation with carbonate. The distribution of metal-carbonate phases at the surface of biochars and the conditions of their formation, however, are unknown. Electron microscopy and X-photon spectroscopy were used to characterize carbonate phases in various morphological groups of particles of a wood-derived biochar, both before and after a metal-sorption experiment. Our results showed that the distribution of metals at the surface of biochar particles depended on the corresponding wood tissues and the presence of carbonate phases. Metals were particularly concentrated (i) within calcium carbonate crystals in bark-derived particles, which originated from calcium oxalate crystals formed prior to pyrolysis, and (ii) as new phases formed by the reprecipitation of carbonate on specific tissues of biochar. The formation of biochar carbonate phases and their redistribution by dissolution-precipitation mechanisms may primarily control the localization of metals on biochar particles and the durability of metals immobilization.


Assuntos
Carbonatos/química , Carvão Vegetal , Metais/química , Adsorção , Madeira
17.
Environ Sci Pollut Res Int ; 24(36): 27634-27641, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28078519

RESUMO

Biochar amendments, i.e., the solid product of biomass pyrolysis, reduce soil metal availability, which may lower the toxicity of metal-contaminated soils. A direct link between the decrease in soil metal availability and improved plant development is however often difficult to establish, as biochar may induce undesirable side effects on plant growth, e.g., a modification to plant nutrition. In order to investigate toxicity processes at a cellular level, roots of Vicia faba were exposed for 7 days to three metal-contaminated substrates and one control soil, amended with a 0 or 5% (w/w) addition of a wood-derived biochar. Exposure to pure biochar was also tested. Root tip cells were then observed to count the number of micronuclei as an estimation of DNA damage and the number of cells at mitosis stage. Results showed that biochar amendments led to a significant decrease in soil metal availability (Cd, Cu, Ni, Pb, and Zn) and to enhance root development on acidic substrates. The micronucleus frequency in root tip cells was positively correlated and the number of mitotic cells negatively, to the extractability of Zn in soils and to the concentration of Zn in secondary roots. Exposure to pure biochar caused a lower production of roots than most soil substrates, but led to the lowest number of observed micronuclei. In conclusion, biochar amendments can reduce the genotoxicity associated with the presence of metallic contaminants in soils, thereby potentially improving plant growth.


Assuntos
Carvão Vegetal , Metais Pesados/toxicidade , Poluentes do Solo/toxicidade , Solo/química , Vicia faba/efeitos dos fármacos , Biomassa , Metais Pesados/metabolismo , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/crescimento & desenvolvimento , Poluentes do Solo/análise , Vicia faba/metabolismo , Madeira/química
18.
Chemosphere ; 161: 438-445, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27454898

RESUMO

Biochar is being widely considered as a promising amendment agent for immobilizing heavy metals in contaminated acidic soils, where plenty of soluble Al(III) ions exist. In view of uncertain significance of the effects of coexisting Al(III) on Pb(II) sorption by biochars, this study used kenaf core biochar (KB550; high carbon, low ash) and sewage sludge biochar (SB550; low carbon, high ash) pyrolyzed at 550 °C to elucidate the influence of coexisting Al(III) species and biochars' mineral components on Pb(II) immobilization conducted in aqueous solution with initial pHs of 3.0-4.5. Results showed that Al(III) reduced Pb(II) sorption on KB550 primarily via pH buffering against biochar alkalinity, thus inhibiting lead carbonate formation. In contrast, the reduction on SB550 mainly resulted from direct competition for sorption sites, especially on Fe-rich phengite 2M1 and metakaolinite. Because of Pb-P precipitation and Pb-K interlayer exchange, the residual Pb(II) adsorption capacity resistant to coexisting Al(III) was 3-5 times higher on SB550 than on KB550. The Pb-K interlayer exchange was enhanced by lower pH and coexisting Al(III), while Pb-P precipitation was the dominant Pb(II) sorption mechanism on SB550 resistant to Al(III) buffering and competition at higher pH. Application of these two biochars as amendments confirmed that the mineral-rich SB550 was more suitable for Pb(II) immobilization in acidic soils with high levels of extractable Al(III).


Assuntos
Alumínio/química , Carbonatos/análise , Carvão Vegetal/química , Chumbo/análise , Poluentes do Solo/análise , Solo/química , Adsorção , Tampões (Química) , Carbonatos/química , Concentração de Íons de Hidrogênio , Íons , Chumbo/química , Modelos Teóricos , Esgotos/química , Poluentes do Solo/química
19.
Environ Sci Technol ; 50(15): 8020-7, 2016 08 02.
Artigo em Inglês | MEDLINE | ID: mdl-27359107

RESUMO

On the basis of our previous field survey, we postulate that the pattern and degree of zinc (Zn) isotope fractionation in the Zn hyperaccumulator Noccaea caerulescens (J. & C. Presl) F. K. Mey may reflect a relationship between Zn bioavailability and plant uptake strategies. Here, we investigated Zn isotope discrimination during Zn uptake and translocation in N. caerulescens and in a nonaccumulator Thlaspi arvense L. with a contrasting Zn accumulation ability in response to low (Zn-L) and high (Zn-H) Zn supplies. The average isotope fractionations of the N. caerulescens plant as a whole, relative to solution (Δ(66)Znplant-solution), were -0.06 and -0.12‰ at Zn-L-C and Zn-H-C, respectively, indicative of the predominance of a high-affinity (e.g., ZIP transporter proteins) transport across the root cell membrane. For T. arvense, plants were more enriched in light isotopes under Zn-H-A (Δ(66)Znplant-solution = -0.26‰) than under Zn-L-A and N. caerulescens plants, implying that a low-affinity (e.g., ion channel) transport might begin to function in the nonaccumulating plants when external Zn supply increases. Within the root tissues of both species, the apoplast fractions retained up to 30% of Zn mass under Zn-H. Moreover, the highest δ(66)Zn (0.75‰-0.86‰) was found in tightly bound apoplastic Zn, pointing to the strong sequestration in roots (e.g., binding to high-affinity ligands/precipitation with phosphate) when plants suffer from high Zn stress. During translocation, the magnitude of isotope fractionation was significantly greater at Zn-H (Δ(66)Znroot-shoot = 0.79‰) than at Zn-L, indicating that fractionation mechanisms associated with root-shoot translocation might be identical to the two plant species. Hence, we clearly demonstrated that Zn isotope fractionation could provide insight into the internal sequestration mechanisms of roots when plants respond to low and high Zn supplies.


Assuntos
Thlaspi/metabolismo , Zinco/metabolismo , Brassicaceae/metabolismo , Raízes de Plantas/metabolismo , Isótopos de Zinco/metabolismo
20.
Chemosphere ; 142: 48-55, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-25912633

RESUMO

Biochar may be used as an amendment in contaminated soils in phytoremediation processes. The mechanisms controlling plant metal uptake in biochar-amended soils remain however unclear. This work aimed at evaluating the influence of biochar on root development and its consequence on plant metal uptake, for two non-hyperaccumulating plants (Zea mays and Lolium perenne) and one hyperaccumulator of Cd and Zn (Noccaea caerulescens). We conducted rhizobox experiments using one acidic and one alkaline soil contaminated with Cd, Pb and Zn. Biochar was present either homogeneously in the whole soil profile or localized in specific zones. A phenomenon of root proliferation specific to biochar-amended zones was seen on the heterogeneous profiles of the acidic soil and interpreted by a decrease of soil phytotoxicity in these zones. Biochar amendments also favored root growth in the alkaline soil as a result of the lower availability of certain nutrients in the amended soil. This increase of root surface led to a higher accumulation of metals in roots of Z.mays in the acidic soil and in shoots of N. caerulescens in the alkaline soil. In conclusion, biochar can have antagonist effects on plant metal uptake by decreasing metal availability, on one hand, and by increasing root surface and inducing root proliferation, on the other hand.


Assuntos
Carvão Vegetal/química , Magnoliopsida/crescimento & desenvolvimento , Magnoliopsida/metabolismo , Metais/metabolismo , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Solo/química , Biodegradação Ambiental , Magnoliopsida/efeitos dos fármacos , Metais/isolamento & purificação , Metais/toxicidade , Raízes de Plantas/efeitos dos fármacos , Poluentes do Solo/isolamento & purificação , Poluentes do Solo/metabolismo , Poluentes do Solo/toxicidade
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