As plants and associated insects are at the bottom of some terrestrial food webs, they are the primary contributors to mercury (Hg) fluxes in ecosystems. In addition to the trophic position of these ...organisms, factors related to their life traits have been hypothesized to influence their exposure to Hg. This study investigates the transfer of Hg in a soil-nettle-insect system and the insect-related factors affecting their Hg concentrations in a revegetated chlor-alkali landfill. Twenty-three insect species were identified and classified according to their life traits, their relationship with nettle, and their morphological characteristics. We observed low total mercury (THg) concentrations in nettles, with only 1% methylmercury (MeHg) being detected, while concentrations ranged from 5 to 3700 μg/kg dry wt. in insects with a MeHg percentage of up to 75%. The nettle-related insects were primarily exposed to Hg through the food web with significant biomagnification, particularly at the level of secondary predators. Within the nettle-unrelated group, the insect habitat was the most explanatory factor, with the highest enrichment being for the insects that spent part of their cycle in direct contact with Hg sources. Therefore, these insects require special attention because they are an essential vector of Hg transfer for terrestrial top predators.
Dark septate endophytes (DSEs) can improve plant stress tolerance by promoting growth and affecting element accumulation. Due to its ability to accumulate high Cd, Zn, and Ni concentrations in its ...shoots,
Noccaea caerulescens
is considered a promising candidate for phytoextraction in the field. However, the ability of DSEs to improve trace element (TE) phytoextraction with
N. caerulescens
has not yet been studied. The aim of this study was therefore to determine the ability of five DSE strains, previously isolated from poplar roots collected at different TE-contaminated sites, to improve plant development, mineral nutrient status, and metal accumulation by
N. caerulescens
during a pot experiment using two soils differing in their level of TE contamination. Microscopic observations revealed that the tested DSE strains effectively colonised the roots of
N. caerulescens
. In the highly contaminated (HC) soil, a threefold increase in root biomass was found in plants inoculated with the
Leptodontidium
sp. Pr30 strain compared to that in the non-inoculated condition; however, the plant nutrient status was not affected. In contrast, the two strains
Phialophora mustea
Pr27 and
Leptodontidium
sp. Me07 had positive effects on the mineral nutrient status of plants without significantly modifying their biomass. Compared to non-inoculated plants cultivated on HC soil, Pr27- and Pr30-inoculated plants extracted more Zn (+ 30%) and Cd (+ 90%), respectively. In conclusion, we demonstrated that the responses of
N. caerulescens
to DSE inoculation ranged from neutral to beneficial and we identified two strains (i.e.
Leptodontidium
sp. (Pr30) and
Phialophora mustea
(Pr27)) isolated from poplar that appeared promising as they increased the amounts of Zn and Cd extracted by improving plant growth and/or TE accumulation by
N. caerulescens
. These results generate interest in further characterising the DSEs that naturally colonise
N. caerulescens
and testing their ability to improve phytoextraction.
•The use of trace-element contaminated soils is a relevant option to expand the material purposegrown biomass.•Bast fibers from nettle which are growing spontaneously on trace-element contaminated ...soils can be used for composites application.•Industrial extraction of nettle fibers allows to obtain tensile properties comparable to the properties of the best industrial flax fibres.
This work assesses the potential of stinging nettle (Urtica dioica L.) growing on trace element contaminated soils to produce fibres for material applications. The nettles studied in this work grew spontaneously and dominated the vegetation cover in poplar short rotation coppices planted for the phytomanagement of lands contaminated by trace elements. Two sites were studied, contaminated by Hg for the first one and a mix of As, Cd, Pb and Zn for the second one. Results show that, for the considered soils, the contaminant contents in nettle bast fibres were at low levels, comparable to those collected at unpolluted control areas. It makes it possible to consider this biomass for material use. The measured matter yield was lower than those obtained with traditional fibre crops cultivated in Europe on agricultural lands. However, the tensile properties of the bast fibres mechanically extracted without field retting or prior alkaline treatment were equal to or better than those of industrial hemp and flax, making spontaneous nettles an interesting supplement to traditional European fibre crops for material applications.
Phytoextraction using hyperaccumulating plants is a method for the remediation of soils contaminated with trace elements (TEs). As a strategy for improvement, the concept of fungal-assisted ...phytoextraction has emerged in the last decade. However, the role played by fungal endophytes of hyperaccumulating plants in phytoextraction is poorly studied. Here, fungal endophytes isolated from calamine or non-metalliferous populations of the Cd/Zn hyperaccumulator
Noccaea caerulescens
were tested for their growth promotion abilities affecting the host plant. Plants were inoculated with seven different isolates and grown for 2 months in trace element (TE)-contaminated soil. The outcomes of the interactions between
N. caerulescens
and its native strains ranged from neutral to beneficial. Among the strains,
Alternaria thlaspis
and
Metapochonia rubescens
, respectively, isolated from the roots of a non-metallicolous and a calamine population of
N. caerulescens
, respectively, exhibited the most promising abilities to enhance the Zn phytoextraction potential of
N. caerulescens
related to a significant increase of the plant biomass. These strains significantly increased the root elemental composition, particularly in the case of K, P, and S, suggesting an improvement of the plant nutrition. Results obtained in this study provide new insights into the relevance of microbial-assisted phytoextraction approaches in the case of hyperaccumulating plants.
Stinging nettle (Urtica dioica L.) raises growing interest in phytomanagement because it commonly grows under poplar Short Rotation Coppices (SRC) set up at trace-metal (TM) contaminated sites and ...provides high-quality herbaceous fibres. The mycobiome of this non-mycorhizal plant and its capacity to adapt to TM-contaminated environments remains unknown. This study aimed at characterizing the mycobiome associated with nettle and poplar roots co-occurring at a TM-contaminated site. Plant root barcoding using the fungi-specific ITS1F-ITS2 primers and Illumina MiSeq technology revealed that nettle and poplar had distinct root fungal communities. The nettle mycobiome was dominated by Pezizomycetes from known endophytic taxa and from the supposedly saprotrophic genus Kotlabaea (which was the most abundant). Several ectomycorrhizal fungi such as Inocybe (Agaricomycetes) and Tuber (Pezizomycetes) species were associated with the poplar roots. Most of the Pezizomycetes taxa were present in the highly TM-contaminated area whereas Agaricomycetes tended to be reduced. Despite being a known non-mycorrhizal plant, nettle was associated with a significant proportion of ectomycorrhizal OTU (9.7%), suggesting some connexions between the poplar and the nettle root mycobiomes. Finally, our study raised the interest in reconsidering the fungal networking beyond known mycorrhizal interactions.
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•Urtica dioica L. raises growing interest because it easily grows at metal contaminated sites and represents a source of high-quality fibres.•We characterized the mycobiomes associated with nettle and poplar roots co-occuring at a TM-contaminated site.•Nettle was dominated by endophytic and saprotrophic taxa while poplar was associated with ectomycorrhizal fungi.•Pezizomycetes taxa were more represented in the highly TM-contaminated area whereas Agaricomycetes tended to be reduced.•We detected a partial overlap of communities, suggesting some connexions between the poplar and the nettle root mycobiomes.
Growing lignocellulosic crops on marginal lands could compose a substantial proportion of future energy resources. The potential of poplar was explored, by devising a field trial of two hectares in ...2007 in a metal-contaminated site to quantify the genotypic variation in the growth traits of 14 poplar genotypes grown in short-rotation coppice and to assess element transfer and export by individual genotypes. Our data led us to conclusions about the genotypic variations in poplar growth on a moderately contaminated site, with the Vesten genotype being the most productive. This genotype also accumulated the least amounts of trace elements, whereas the Trichobel genotype accumulated up to 170 mg Zn kg−1 DW in the branches, with large variation being exhibited among the genotypes for trace element (TE) accumulation. Soil element depletion occurred for a range of TEs, whereas the soil content of major nutrients and the pH remained unchanged or slightly increased after 10 years of poplar growth. The higher TE content of bark tissues compared with the wood and the higher proportion of bark in branches compared with the wood led us to recommend that only stem wood be harvested, instead of the whole tree, which will enable a reduction in the risks encountered with TE-enriched biomass in the valorization process.
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•We observed genotypic variations in growth of poplar at a moderately contaminated site.•There were large variations between genotypes for trace element accumulation.•Soil depletion occurred for a range of trace element after 10 years of growth.•Branches had accumulated a lot more elements than wood.•We recommend choosing stemwood-only harvesting instead of whole-tree harvesting.
Chlorinated ethenes (CE) are among the most common volatile organic compounds (VOC) that contaminate groundwater, currently representing a major source of pollution worldwide. Phytoscreening has been ...developed and employed through different applications at numerous sites, where it was generally useful for detection of subsurface chlorinated solvents. We aimed at delineating subsurface CE contamination at a chlor-alkali facility using tree core data that we compared with soil data. For this investigation a total of 170 trees from experimental zones was sampled and analyzed for perchloroethene (PCE) and trichloroethene (TCE) concentrations, measured by solid phase microextraction gas chromatography coupled to mass spectrometry. Within the panel of tree genera sampled, Quercus and Ulmus appeared to be efficient biomonitors of subjacent TCE and PCE contamination, in addition to the well known and widely used Populus and Salix genera. Among the 28 trees located above the dense non-aqueous phase liquid (DNAPL) phase zone, 19 tree cores contained detectable amounts of CE, with concentrations ranging from 3 to 3000 μg L−1. Our tree core dataset was found to be well related to soil gas sampling results, although the tree coring data were more informative. Our data further emphasized the need for choosing the relevant tree species and sampling periods, as well as taking into consideration the nature of the soil and its heterogeneity. Overall, this low-invasive screening method appeared useful to delineate contaminants at a small-scale site impacted by multiple sources of chlorinated solvents.
•CE contamination were delineated at a chlor-alkali facility using tree core data.•170 trees were sampled and analyzed for TCE and PCE content using SPME-GC-MS.•Populus, Quercus, Salix and Ulmus species are efficient biomonitors.•Our tree core dataset was well related to soil gas sampling results.
The stinging nettle Urticadioica L. is a perennial crop with low fertilizer and pesticide requirements, well adapted to a wide range of environmental conditions. It has been successfully grown in ...most European climatic zones while also promoting local flora and fauna diversity. The cultivation of nettle could help meet the strong increase in demand for raw materials based on plant fibers as a substitute for artificial fibers in sectors as diverse as the textile and automotive industries. In the present review, we present a historical perspective of selection, harvest, and fiber processing features where the state of the art of nettle varietal selection is detailed. A synthesis of the general knowledge about its biology, adaptability, and genetics constituents, highlighting gaps in our current knowledge on interactions with other organisms, is provided. We further addressed cultivation and processing features, putting a special emphasis on harvesting systems and fiber extraction processes to improve fiber yield and quality. Various uses in industrial processes and notably for the restoration of marginal lands and avenues of future research on this high-value multi-use plant for the global fiber market are described.
Although current Hg emissions from industrial activities may be accurately monitored, evidence of past releases to the atmosphere must rely on one or more environmental proxies. We used Hg ...concentrations in tree cores collected from poplars and willows to investigate the historical changes of Hg emissions from a dredged sediment landfill and compared them to a nearby control location. Our results demonstrated the potential value of using dendrochemistry to record historical Hg emissions from past industrial activities.
•We investigated historical changes of Hg emissions from a dredged sediment landfill.•Tree-ring analysis is a potentially useful technique.•Hg concentrations in poplars peaked at around 35ng/g dry wood in the early sixties.•We showed the potential value of using dendrochemistry to record historical Hg emissions.
This work assesses the potential of nettle (Urtica dioica L.) fibers produced on contaminated lands for composite applications. The nettles studied in this work grew spontaneously and in a prevalent ...manner in poplar short rotation coppice planted for the phytomanagement of a land contaminated by traces of metals. Results show that the contaminant contents in nettle bast fibers are low: only traces were measured. It makes it possible to consider this biomass for material use. The measured matter yield is lower than those obtained with traditional fiber crops cultivated in Europe on agricultural lands but the tensile properties of the bast fibers are equal to or better than those of hemp and flax, making spontaneous nettle an interesting supplement to traditional European fiber crops for composite applications.
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