Localisation and mobility of trace metal in silver fir needles

Trace metals (TM: Co, Ni, Cu, Zn, Cd, and Pb) as well as Al, Mn, and Fe content was measured in needles of a remote silver fir stand in the south of France. TM localisation and behaviour in needles was evaluated by measuring total and internal content of needles of different ages. Measured concentrations fell within background values. Al, Fe, Co, and Pb were trapped in wax following atmospheric particulate deposition. Contrasting accumulation and migration behaviours of the different elements studied were observed. The wax contained less than 10% Mn, Al, Ni, Co, and Zn and 15–45% Fe, Cu, and Cd in the young needles. Lead was mostly located in the wax (50–80%), and this proportion decreased with needle age. Only the internal content of Pb and Fe increased significantly with needle age. Finally, due to atmospheric deposition accumulation, higher input fluxes of Fe, Cu, Cd, and Pb can be expected in forest soil

The importance of biomass net uptake for a trace metal budget in a forest stand in north-eastern France

The trace metal (TM: Cd, Cu, Ni, Pb and Zn) budget (stocks and annual fluxes) was evaluated in a forest stand (silver fir, Abies alba Miller) in north-eastern France. Trace metal concentrations were measured in different tree compartments in order to assess TM partitioning and dynamics in the trees. Inputs included bulk deposition, estimated dry deposition and weathering. Outputs were leaching and biomass exportation. Atmospheric deposition was the main input flux. The estimated dry deposition accounted for about 40% of the total trace metal deposition. The relative importance of leaching (estimated by a lumped parameter water balance model, BILJOU) and net biomass uptake (harvesting) for ecosystem exportation depended on the element. Trace metal distribution between tree compartments (stem wood and bark, branches and needles) indicated that Pb was mainly stored in the stem, whereas Zn and Ni, and to a lesser extent Cd and Cu, were translocated to aerial parts of the trees and cycled in the ecosystem. For Zn and Ni, leaching was the main output flux (N95% of the total output) and the plot budget (input–output) was negative, whereas for Pb the biomass net exportation represented 60% of the outputs and the budget was balanced. Cadmium and Cu had intermediate behaviours, with 18% and 30% of the total output relative to biomass exportation, respectively, and the budgets were negative. The net uptake by biomass was particularly important for Pb budgets, less so for Cd and Cu and not very important for Zn and Ni in such forest stands

Toxicity of Pb and of Pb/Cd combination on the springtail Folsomia candida in natural soils: Reproduction, growth and bioaccumulation as indicators

The toxicity of Pb and Cd+Pb was assessed on the Collembola F. candida in two cultivated soils (SV and AU) with low organic matter (OM) content and circumneutral to basic pH, and an acid forested soil (EPC) with high OM content. Collembola reproduction and growth as well as metal content in Collembola body, in soil, exchangeable fraction and soil solutions, pH and DOC were investigated. Pb and Cd+Pb were the highest in exchangeable fraction and soil solution of the acidic soils. Soil solution pH decreased after metal spiking in every soil due to metal adsorption, which was similar for Cd and the highest in AU for Pb. With increasing Pb and Cd+Pb, the most important reproduction decrease was in EPC soil. The LOEC for reproduction after metal addition was 2400 (Pb) and 200/2400 (Cd/Pb), 1200 and 100/1200, 300 and 100/1200 μg g−1 for AU, SV and EPC, respectively. The highest and the lowest Pb toxicity was observed for EPC and AU bulk soil, respectively. The metal in Collembola increased with increasing soil concentration, except in AU, but the decreasing BFsolution with increasing concentrations indicates a limited metal transfer to Collembola or an increased metal removal. Loading high Pb concentrations decreases Cd absorption by the Collembola, but the reverse was not true. The highest Pb toxicity in EPC can be explained by pH and OM content. Because of metal complexation, OM might have a protective role but its ingestion by Collembola lead to higher toxicity. Metal bioavailability in Collembola differs from soil solution indicating that soil solution is not sufficient to evaluate toxicity in soil organisms. The toxicity as a whole decreased when metals were combined, except for Pb in AU, due to adsorption competition between Cd and Pb on clay particles and OM sites in AU and EPC soils, respectively

Determining cadmium critical concentrations in natural soils by assessing Collembola mortality, reproduction and growth

The toxicity of cadmium for the Collembola Folsomia candida was studied by determining the effects of increasing Cd concentrations on growth, survival and reproduction in three cultivated and forested soils with different pH (4.5–8.2) and organic matter content (1.6–16.5%). The Cd concentration in soil CaCl2 exchangeable fraction, in soil solution and in Collembola body was determined. At similar total soil concentrations, the Cd concentration in soil solutions strongly decreased with increasing pH. Reproduction was the most sensitive parameter. Low organic matter content was a limiting factor for reproduction. Effect of Cd on reproduction was better described by soil or body concentrations than by soil solution concentration. Values of EC50-Repro expressed on the basis of nominal soil concentration were 182, 111 and 107 μg g−1, respectively, for a carbonated cultivated soil (AU), an acid forested soil with high organic matter (EPC) and a circumneutral cultivated soil with low organic content (SV). Sensitivity to Cd was enhanced for low OM content and acidic pH. The effect of Cd on reproduction is not directly related to Cd concentration in soil solution for carbonated soil: a very low value is found for EC50-Repro (0.17) based on soil solution for the soil with the highest pH (AU; pH=8.2). Chronic toxicity cannot be predicted on the basis of soluble fractions. Critical concentrations were 8×10−5, 1.1, 0.3 μg mL−1, respectively, for AU, EPC and SV soils

Impact of nitrogenous fertiliser-induced proton release on cultivated soils with contrasting carbonate contents: A column experiment

An experimental study was carried out in order to evaluate the impact of nitrogen fertiliser-induced acidification in carbonated soils. Undisturbed soil columns containing different carbonate content were sampled in the field. Fertiliser spreading was simulated by NH4Cl addition on top of the soil column. Soil solution composition (mainly nitrate and base cations) was studied at the soil column’s base. Nitrification occurred to a different extent depending on soil type. Higher nitrification rates were observed in calcareous soils. In all the soil types, strong correlations between leached base cation and nitrate concentrations were observed. Regression coefficients between base cations, nitrate and chloride were used to determine the dominant processes occurring following NH4Cl spreading. In non-carbonated soils, nitrogen nitrification induced base cation leaching and soil acidification. In carbonated soils, no change of soil pH was observed. However, fertilisers induced a huge cation leaching. Carbonate mineral weathering led to the release of base cations, which replenished the soil exchangeable complex. Carbonated mineral weathering buffered acidification. Since direct weathering might have occurred without atmospheric CO2 consumption, the use of nitrogen fertiliser on carbonated soil induces a change in the cation and carbon budgets. When the results of these experiments are extrapolated on a global scale to the surface of fertilised areas lying on carbonate, carbonated reactions with N fertilisers would imply an additional flux of 5.7 x 1012 mol yr -1 of Ca + Mg. The modifications of weathering reactions in cultivated catchments and the ability of nitrogen fertilisers to significantly modify the CO2 budget should be included in carbon global cycle assessment

Le mobilier du « dolmen de Saint-Père-en-Retz » (Loire-Atlantique) : nouveaux éléments de réflexion

Whilst studying flat axes in the collections of the Dobrée Museum in Nantes and the National Archaeology Museum in Saint-Germain-en-Laye, it was found that one of the axes had the mention “Saint-Père-en-Retz, Loire-Inférieure” written on it. Found in the so-called “dolmen of Saint-Père-en-Retz” along with another axe and two gold artefacts, this material is often considered as typical of the Beaker culture and has thus been covered in a large number of papers and books. The objects were collected by F. Parenteau, the first curator of the local archaeology museum, the study of its private archives kept in the Dobrée Museum provided unpublished documents concerning this find. The objects were not discovered by Parenteau himself as he wrote in a publication that came out much later in 1872 (Musée des Beaux-arts de Nantes, 1872, p. 36), but were bought second-hand from a goldsmith in Nantes. Parenteau’s notes lead us to understand that both the location (Saint-Père-en-Retz) and the context (‘dolmen’) are not verified. The subsequent publications sometimes contained fanciful artefacts. Some previously unpublished drawings from the Parenteau archives do complete the documentation we have while at the same time cast a doubt over the provenance of the Saint-Germain-en-Laye axe. It also provides us with an opportunity to put forth a new hypothesis as to the provenance of one of the axes of the Dobrée Museum. To conclude, the new elements gathered here show that both provenance and context are extremely doubtful, and that therefore the study of the 19th century archives can often be of invaluable assistance when one works on old collections.Die Untersuchung der Flachbeile aus den Sammlungen des Museums Dobrée in Nantes und derjenigen des Musée d’archéologie nationale (MAN) in Saint-Germain-en-Laye haben es gestattet, ein Beil wiederaufzufinden, dass die Bezeichnung „Saint-Père-en-Retz, Loire-Inférieure“ trägt. Das archäologische Fundmaterial (zwei Goldobjekte sowie zwei Flachbeile aus Kupfer bzw. einer Kupferlegierung), das in einem „Dolmen“ in dieser Gemeinde gefunden worden war, gilt allgemein als typisch für die Glockenbecherkultur und wird entsprechend häufig in der Fachliteratur zitiert. Die Funde sind von F. Parenteau, dem ersten Konservator des Musée départemental d’Archéologie des Departments Loire-Atlantique, geborgen worden. Die Überprüfung der sehr reichen Dokumentation zu diesen Funden hat es ermöglicht, einige bisher unveröffentlichte Dokumente zu sichten, die neue Informationen zu diesem Fundensemble liefern. Es hat sich dabei herausgestellt, dass diese Funde nicht von Parenteau selbst entdeckt wurden wie er a posteriori 1872 schreibt (Musée des Beaux-Arts von Nantes, 1872, p. 36), sondern aus zweiter Hand von einem Goldschmied in Nantes erworben wurden. Die Aufzeichnungen von Parenteau erlauben es ferner anzunehmen, dass die Lokalisierung der Funde (Saint-Père-en-Retz) und ihr archäologischer Kontext („Dolmen“) wenig gesichert sind, ebenso wie die Umstände ihrer Entdeckung. In der Folge kommt es in einigen Publikationen zu weiteren, sehr fantasievollen Ausschmückungen der Fundgeschichte. Einige bisher unveröffentlichte Zeichnungen aus dem Konvolut der Aufzeichnungen Parenteaus vervollständigen die bisher bekannte Dokumentation dieser Funde, ziehen jedoch die genannte Herkunft des im MAN verwahrten Flachbeiles in Zweifel und erlauben es, eines der im Musée Dobrée verwahrten Beile dem Fundensemble hinzuzufügen. Zusammenfassend kann gefolgert werden, dass die neuen Erkenntnisse das bekannte und sehr umfangreich zitierte Fundensemble hinsichtlich seiner Lokalisierung sowie seines Fundkontextes als ausgesprochen zweifelhaft erscheinen lassen. Es zeigt sich, dass das Studium der alten Archivunterlagen aus dem 19. Jahrhundert sich häufig als eine unverzichtbare Hilfe bei der Analyse und Überprüfung alter Sammlungsbestände erweist.El estudio de hachas planas de las colecciones del museo Dobrée en Nantes y del Museo Arqueológico Nacional (MAN) en Saint-Germain-en-Laye permitió encontrar un hacha marcada por la inscripción “Saint-Père-en-Retz, Loire-Inférieure”. El material que se habría encontrado en un “dolmen” de este municipio (dos artefactos de oro y dos hachas planas de cobre/aleación de cobre) es a menudo visto como emblemático de la cultura del campaniforme y citado ampliamente en la literatura. Los artefactos fueron recogidos por F. Parenteau, primer conservador del museo departamental de arqueología de Loire-Atlantique. La consultación de la rica documentación de este hombre erudito ha ayudado para recuperar algunos documentos inéditos que aportan nuevos elementos a propósito de este conjunto. Demuestra, entre otros, que los objetos no fueron descubiertos por Parenteau sí mismo como escribió retrospectivamente en 1872 (Museo de Bellas Artes de Nantes, 1872, p. 36) pero que fueron comprados de segunda mano a un orfebre de Nantes. Las notas de Parenteau permiten darse cuenta de que la ubicación (Saint-Père-en-Retz) y el contexto (“Dolmen”) del depósito no son fiables y, esto, en el momento mismo del descubrimiento. Luego, varias publicaciones han añadido materiales, a veces de poca credibilidad. Dibujos inéditos del fondo Parenteau completan la documentación de este conjunto, pero cuestionan también fuertemente el origen de la hacha plana del MAN, mientras que, al mismo tiempo, permiten adjuntar una de las hachas del museo Dobrée a este conjunto. Al final, los nuevos elementos reunidos indican que el conjunto famoso y mencionado con profusión es muy dudoso, tanto desde el punto de vista de la ubicación como él del contexto, y que la consultación de los archivos del siglo XIX aparece a menudo como ayuda inestimable para el estudio de las colecciones antiguas

Use of geochemical signatures, including rare earth elements, in mosses and lichens to assess spatial integration and the influence of forest environment

In order to assess the influence of local environment and spatial integration of Trace Metals (TM) by biomonitors, Al, As, Cd, Cr, Cs, Cu, Fe, Mn, Ni, Pb, Sb, Sn, V and Zn and some rare earth element (REE) concentrations have been measured in lichens and mosses collected in three French forest sites located in three distinct mountainous areas, as well as in the local soil and bedrock, and in both bulk deposition (BD) and throughfall (TF). Similar enrichment factors (EF) were calculated using lichens and mosses and local bedrock for most elements, except for Cs, Mn, Ni, Pb, and Cu which were significantly (KW, p < 0.05) more enriched in mosses. Similar REE ratios were measured in soils, bedrock, lichens and mosses at each study sites, indicating a regional integration of atmospheric deposition by both biomonitors. Both TM signature and REE composition of mosses revealed that this biomonitor is highly influenced by throughfall composition, and reflect atmospheric deposition interaction with the forest canopy. This explained the higher enrichment measured in mosses for elements which concentration in deposition were influenced by the canopy, either due to leaching (Mn), direct uptake (Ni), or dry deposition dissolution (Pb, Cu, Cs)

Anaerobic oxidation of methane and associated microbiome in anoxic water of Northwestern Siberian lakes

Arctic lakes emit methane (CH4) to the atmosphere. The magnitude of this flux could increase with permafrost thaw but might also be mitigated by microbial CH4 oxidation. Methane oxidation in oxic water has been extensively studied, while the contribution of anaerobic oxidation of methane (AOM) to CH4 mitigation is not fully understood. We have investigated four Northern Siberian stratified lakes in an area of discontinuous permafrost nearby Igarka, Russia. Analyses of CH4 concentrations in the water column demonstrated that 60 to 100% of upward diffusing CH4 was oxidized in the anoxic layers of the four lakes. A combination of pmoA and mcrA gene qPCR and 16S rRNA gene metabarcoding showed that the same taxa, all within Methylomonadaceae and including the predominant genus Methylobacter as well as Crenothrix, could be the major methane-oxidizing bacteria (MOB) in the anoxic water of the four lakes. Correlation between Methylomonadaceae and OTUs within Methylotenera, Geothrix and Geobacter genera indicated that AOM might occur in an interaction between MOB, denitrifiers and iron-cycling partners. We conclude that MOB within Methylomonadaceae could have a crucial impact on CH4 cycling in these Siberian Arctic lakes by mitigating the majority of produced CH4 before it leaves the anoxic zone. This finding emphasizes the importance of AOM by Methylomonadaceae and extends our knowledge about CH4 cycle in lakes, a crucial component of the global CH4 cycle

How temporal patterns in rainfall determine the geomorphology and carbon fluxes of tropical peatlands

Tropical peatlands now emit hundreds of megatons of carbon dioxide per year because of human disruption of the feedbacks that link peat accumulation and groundwater hydrology. However, no quantitative theory has existed for how patterns of carbon storage and release accompanying growth and subsidence of tropical peatlands are affected by climate and disturbance. Using comprehensive data from a pristine peatland in Brunei Darussalam, we show how rainfall and groundwater flow determine a shape parameter (the Laplacian of the peat surface elevation) that specifies, under a given rainfall regime, the ultimate, stable morphology, and hence carbon storage, of a tropical peatland within a network of rivers or canals. We find that peatlands reach their ultimate shape first at the edges of peat domes where they are bounded by rivers, so that the rate of carbon uptake accompanying their growth is proportional to the area of the still-growing dome interior. We use this model to study how tropical peatland carbon storage and fluxes are controlled by changes in climate, sea level, and drainage networks. We find that fluctuations in net precipitation on timescales from hours to years can reduce long-term peat accumulation. Our mathematical and numerical models can be used to predict long-term effects of changes in temporal rainfall patterns and drainage networks on tropical peatland geomorphology and carbon storage