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1.
Ecotoxicol Environ Saf ; 210: 111865, 2021 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-33418154

RESUMO

Cd contamination in rice grains has become a topic of great concern because of the high health risks associated with the long-term consumption of Cd-contaminated rice. Identification of Cd sources in rice grains by scientific methods is important for controlling heavy metal pollution and protecting human health. Here, the Cd concentrations and Cd isotopic compositions of rice plants (root, stem, leaf, and grain) and topsoil, and possible pollution sources (agricultural fertilizers, industrial dust, and automobile exhaust) were analyzed using an instrument of inductively coupled plasma mass spectrometry (ICP-MS) and multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The results showed variations in the Cd isotopes of different components of rice plants and the fractionation coefficient of rice grains relative to topsoil (Δ114/110Cdrice grains-topsoil = 0.25‰). The contributions of pollution sources to rice grains were realized by combining the Cd isotopic composition with an isotopic mixing model (Isosource). The analysis showed that all three possible pollution sources contributed to the Cd in the rice grains in the field, the average Cd contribution of industrial dust, agricultural fertilizers and automobile exhaust was 87%, 9%, and 4%, respectively. Our study provides a feasible method for the identification of pollution sources of Cd in rice grains at the field scale and demonstrates that Cd isotopic composition is one of the powerful tools to trace the pollution sources of Cd in crops.


Assuntos
Cádmio/análise , Grão Comestível/química , Oryza , Poluentes do Solo/análise , Cádmio/química , Fracionamento Químico , Poeira , Monitoramento Ambiental , Fertilizantes , Humanos , Indústrias , Isótopos/análise , Emissões de Veículos
2.
Food Chem ; 334: 127599, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-32711278

RESUMO

The research towards the identification of new authenticity markers is crucial to fight against fraudulent activities on honey, one of the top ten most falsified food commodities. This work proposes an association of stable isotopes and elemental content as markers for honey authentication, with respect to its floral and geographical origin. Emerging markers like isotopic signature of honey water alongside with carbon and hydrogen isotopic ratios of ethanol obtained from honey fermentation and Rare Earth Elements, were used to develop new recognition models. Thus, the efficiency of the discrimination potential of these emerging markers was discussed individually and in association. This approach proved its effectiveness for geographical differentiation (>98%) and the role of the emerging markers in these classifications was an essential one, especially of: (D/H)I, δ2H, δ18O, La, Ce and Pr. Floral recognition was realized in a lower percentage revealing the suitability of these markers mainly for geographical classification.


Assuntos
Análise de Alimentos/métodos , Mel/análise , Isótopos/análise , Isótopos de Carbono/análise , Fermentação , França , Espectroscopia de Ressonância Magnética , Metais Terras Raras/análise , Isótopos de Oxigênio/análise , Romênia , Água/análise , Água/química
3.
Sci Total Environ ; 740: 139992, 2020 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-32927536

RESUMO

Mining activities at Duparquet in Western Quebec (Canada) have significantly affected the local environment and left behind significant amounts of metals. Monitoring this contamination is essential to infer its past and present impacts on environmental quality and to evaluate the resulting human exposure. In that context, we measured long time series of Pb concentrations and their corresponding stable isotope ratios in long-lived white cedars (Thuja occidentalis L.) growing at Duparquet Lake in order to evaluate potential time variations of the Pb environmental contamination as well as to identify the responsible source(s). Results show that before 1950, Pb at Duparquet is mostly terrigenous. Lead concentrations rapidly increase afterwards. A simultaneous shift to lower 206Pb/207Pb ratios identifies the smelting of Abitibi ores as the source of contamination. An isotope mass balance model evaluates at roughly 7.5-20%, 5-40%, 5-9% and <3% the Pb contributions from local smelters at distances of 3.6, 3.9, 7 and 9 km, respectively. The dispersion of the Pb contamination plume is possibly driven by the distance from the Beattie smelter. We finally estimated a delay of at least 13 years between atmospheric emissions from the Beattie smelting activities and the time they are recorded by tree rings. Ultimately, this study demonstrates that white cedar tree rings series provide reliable archives of past and present Pb atmospheric contamination.


Assuntos
Chumbo/análise , Thuja , Canadá , Monitoramento Ambiental , Isótopos/análise , Quebeque
4.
Environ Pollut ; 266(Pt 2): 115104, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32650201

RESUMO

Copper export and mobility in acid mine drainage are difficult to understand with conventional approaches. Within this context, Cu isotopes could be a powerful tool and here we have examined the relative abundance of dissolved (<0.22 µm) Cu isotopes (δ65Cu) in the Meca River which is an outlet of the Tharsis mine, one of the largest abandoned mines of the Iberian Pyrite Belt, Spain. We followed the chemical and isotopic composition of the upstream and downstream points of the catchment during a 24-h diel cycle. Additional δ65Cu values were obtained from the tributary stream, suspended matter (>0.22 µm) and bed sediments samples. Our goals were to 1) assess Cu sources variability at the upstream point under contrasted hydrological conditions and 2) investigate the conservative vs. non conservative Cu behavior along a stream. Average δ65Cu values varied from -0.47 to -0.08‰ (n = 9) upstream and from -0.63 to -0.31‰ downstream (n = 7) demonstrating that Cu isotopes are heterogeneous over the diel cycle and along the Meca River. During dry conditions, at the upstream point of the Meca River the Cu isotopic composition was heavier which is in agreement with the preferential release of heavy isotopes during the oxidative dissolution of primary sulfides. The more negative values obtained during high water flow are explained by the contribution of soil and waste deposit weathering. Finally, a comparison of upstream vs. downstream Cu isotope composition is consistent with a conservative behavior of Cu, and isotope mass balance calculations estimate that 87% of dissolved Cu detected downstream originate from the Tharsis mine outlet. These interpretations were supported by thermodynamic modelling and sediment characterization data (X-ray diffraction, Raman Spectroscopy). Overall, based on contrasted hydrological conditions (dry vs flooded), and taking the advantage of isotope insensitivity to dilution, the present work demonstrates the efficiency of using the Cu isotopes approach for tracing sources and processes in the AMD regions.


Assuntos
Monitoramento Ambiental , Poluentes Químicos da Água/análise , Isótopos/análise , Mineração , Rios , Espanha
5.
Isotopes Environ Health Stud ; 56(4): 335-345, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32508160

RESUMO

For many years after the discovery of the two stable isotopes of boron (10B,11B) in 1920 they were not used as tracers in the soil-plant system due to analytical constraints. However, with the advent of inductively coupled plasma mass spectrometry in the early 1980s, it became possible to measure precisely the natural variations of the B isotopes in biological systems. Nevertheless, up to the present time there is very little information in the literature on δ 11B variations in soils, plants, fertilizers and foodstuffs. Therefore, information on the potential of δ 11B as a tracer of B dynamics in natural- and agro-ecosystems remains limited. The relative abundance of the boron isotope (δ 11B) in soils, plants and nutrient sources, and applications of variations in the natural abundance of 11B as a tracer of anthropogenic sources of nitrate contamination of water and the provenance of agricultural products are reviewed.


Assuntos
Boro/análise , Poluentes Ambientais/análise , Isótopos/análise , Nitratos/análise , Produtos Agrícolas/química , Ecossistema , Fertilizantes/análise , Plantas/química , Solo/química
6.
Chemosphere ; 257: 127182, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32534293

RESUMO

The impact of offshore constructions on the marine environment is unknown in many aspects. The application of Al- and Zn-based galvanic anodes as corrosion protection results in the continuous emission of inorganic matter (e.g. >80 kg Al-anode material per monopile foundation and year) into the marine environment. To identify tracers for emissions from offshore wind structures, anode materials (Al-based and Zn-based) were characterized for their elemental and isotopic composition. An acid digestion and analysis method for Al and Zn alloys was adapted and validated using the alloy CRMs ERM®-EB317 (AlZn6CuMgZr) and ERM®-EB602 (ZnAl4Cu1). Digests were measured for their elemental composition by ICP-MS/MS and for their Pb isotope ratios by MC ICP-MS. Ga and In were identified as potential tracers. Moreover, a combined tracer approach of the elements Al, Zn, Ga, Cd, In and Pb together with Pb isotope ratios is suggested for a reliable identification of offshore-wind-farm-induced emissions. In the Al anodes, the mass fractions were found to be >94.4% of Al, >26200 mg kg-1 of Zn, >78.5 mg kg-1 of Ga, >0.255 mg kg-1 of Cd, >143 mg kg-1 of In and >6.7 mg kg-1 of Pb. The Zn anodes showed mass fractions of >2160 mg kg-1 of Al, >94.5% of Zn, >1.31 mg kg-1 of Ga, >254 mg kg-1 of Cd, >0.019 mg kg-1 of In and >14.1 mg kg-1 of Pb. The n(208Pb)/n(206Pb) isotope ratios in Al anodes range from 2.0619 to 2.0723, whereas Zn anodes feature n(208Pb)/n(206Pb) isotope ratios ranging from 2.0927 to 2.1263.


Assuntos
Monitoramento Ambiental , Metais Pesados/análise , Poluentes Químicos da Água/análise , Ligas , Alumínio , Corrosão , Eletrodos , Isótopos/análise , Espectrometria de Massas em Tandem , Vento
7.
Environ Monit Assess ; 192(7): 444, 2020 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-32562061

RESUMO

Rivers play a key role in the water cycle on the earth via integrating all hydrological channels to return terrestrial precipitations back to the oceans. In addition, rivers, together with groundwater, are powerful transformers of the surface lithosphere, responsible for chemical weathering of rocks and the removal of solute into the ocean. Tracing the dynamics of surface water and groundwater versus atmospheric feeding of rivers presents important issues in Arctic regions due to the ongoing change of the structure of hydrological runoff. In this study, stable water isotopes were used to reveal the temporal dynamics of water sources and to predict their possible change under the conditions of ongoing climate warming of the largest European Arctic river, the Severnaya Dvina, and adjacent groundwater. The isotopic composition of the river waters of the studied region is formed by the mixing of atmospheric precipitation with groundwater. The isotopic depletion in the springtime is mainly due to the recharge of thawed snow waters. A less pronounced effect in the autumn-winter period is provided by the discharge of groundwater into rivers, including the meltwater of the Last Glacial Period. This depletion is partially offset due to discharge of isotopically light thawed snow waters and is linked to evaporation in headwater streams, reservoirs, and wetlands. The isotopic composition of groundwater with low mineralization was formed throughout the Holocene and to a large extent depends on paleoclimatic conditions in the study area. In addition to fresh groundwater, brackish groundwater also takes part in the river's recharge. These brackish waters are associated with ancient and modern marine transgressions on the estuarine site and with the dissolution of Ca sulfate rocks in a karst region located in the middle reaches of the river. According to isotope data, the average annual input of the underground source to the total river flow is 25%. The results of this work will serve as the basis for continuing monitoring of the isotopic composition of river waters with an assessment of hydrological processes and observation of short as well as long-term climatic and anthropogenic impacts.


Assuntos
Água Subterrânea , Isótopos , Rios , Regiões Árticas , Monitoramento Ambiental , Isótopos/análise
8.
Food Chem ; 326: 126958, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32416418

RESUMO

This work examines the use of stable isotopes and elemental composition for determining geographical origin and authenticity of cow milk from four geographical regions of Slovenian. Samples (277) were collected during summer and winter (2012-2014). It was possible to discriminate milk samples according to the year, season and production region using discriminant analysis (DA). The overall temporal prediction variability was 84.6% and 56.4% for regional differences. It was also possible to discriminate milk from three geographic regions, although Alpine samples overlap with Dinaric and Pannonian ones. Prediction ability was the highest for the Pannonian (82.1%) and lowest (26.9%) for the Alpine region. Pairwise comparison using OPLS-DA also displaying good regional predictability (≥0.77) with δ13Ccas values and Br content carrying the most variance. A model based on DD-SIMCA was also developed and applied to the control of Slovenian milk. The results revealed the mislabeling of three Slovenian milk products.


Assuntos
Isótopos/análise , Leite/química , Animais , Isótopos de Carbono/análise , Bovinos , Análise Discriminante , Feminino , Geografia , Isótopos de Nitrogênio/análise , Estações do Ano , Eslováquia
10.
J Contam Hydrol ; 232: 103640, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32353562

RESUMO

This study was aimed at identifying and quantifying mixing proportions in surface waters downstream of historical Cu-W-F skarn mine tailings at Yxsjöberg, Sweden, using 18O, 2H, and 87Sr/86Sr isotopes. In addition, a simple mathematical model was developed to evaluate the consistency of the mixing calculations. Hydrochemical and isotopic data from 2 groundwater wells, 6 surface water and 2 rainwater sampling sites, spanning 6 sampling campaigns between May and October were used. Three mixed surface waters downstream of the tailings were identified, namely: C7, C11 and C14. C7 was directly influenced by groundwater from the tailings whereas C11 was also subsequently influenced by C7. C14 on the other hand, had contributions from C11. Sequential mixing calculations indicated that the contribution of the groundwater to C7 ranges from 1 to 17%. The subsequent contribution of C7 to C11 varied from 49 to 91% whereas C14 had contributions of C11 ranging between 16 and 56%. A strong agreement between the model data (MD) and measured raw data (RD) for C11 and C14 indicated the accuracy of the mixing calculations. Variations between the MD and RD at C7, however, was mainly due to sorption and reductive processes underneath the tailings, which tend to attenuate the amount of dissolved ions reaching the surface waters, resulting in a low ionic contribution of the tailings groundwater to the surface water. The low ionic contribution of the groundwater to C7 suggested that although the tailings impoundment is of environmental concern, its impact on the downstream surface waters is small. The results of this study suggest that mixing calculations in surface waters involving a closed system such as groundwater (as an end-member) must be treated with caution. It is recommended that the interpretation of such mixing results must be coupled with detailed knowledge of the potential hydrogeochemical processes along its flow paths.


Assuntos
Água Subterrânea , Poluentes Químicos da Água , Monitoramento Ambiental , Isótopos/análise , Suécia , Poluentes Químicos da Água/análise
11.
Chemosphere ; 255: 126858, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32387726

RESUMO

Lead (Pb) concentration and Pb isotope ratios have been determined in 109 snow pit samples collected at Dome C, on the East Antarctic Plateau, corresponding to the period 1971-2017. The Pb concentration was 8.2 ± 1.0 pg g-1 (mean ± 95%-confidence interval), with a decreasing trend from the early 1990s (the median Pb concentration halved from 9.0 pg g-1 in 1970-1980 to 4.4 pg g-1 in 2010-2017). The 206Pb/207Pb and 208Pb/207Pb ratios were 2.419 ± 0.003 and 1.158 ± 0.003 (mean and 95%-confidence interval), respectively. The temporal variations of Pb isotopic composition from 1970 to mid-1990s reflect the changes in the consumption of Pb-enriched gasoline in the Southern Hemisphere, whereas the subsequent increase of the Pb isotope ratios is ascribed to a shift toward the natural isotopic signature. Accordingly, the anthropogenic Pb contribution decreased from (61 ± 3)% in 1980-1990 to (49 ± 10)% in 2010-2017. The measured ratios suggest that Australia has been a significant source of anthropogenic Pb to Antarctica, even in recent times. Differences and similarities among Pb content and isotopic composition in various sites across Antarctica have been displayed by principal component analysis, indicating that the altitude and the distance from the coast significantly affect the Pb content, while the Pb isotopic signatures are not influenced by these parameters.


Assuntos
Monitoramento Ambiental , Poluição Ambiental/estatística & dados numéricos , Chumbo/análise , Neve/química , Altitude , Regiões Antárticas , Austrália , Gasolina/análise , Isótopos/análise
12.
Meat Sci ; 165: 108129, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32234581

RESUMO

The purpose of this study was to verify that the organic status of pork purchased in the markets from four different regions of China can be authenticated by the combined analysis of stable isotopes and multiple elements. Four stable isotope ratios (δ13C, δ15N, δ2H and δ18O) and the concentrations of seven elements (K, Na, Mg, Ca, Fe, Cu and Se) were determined in organic and conventional pork samples from four locations of China. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were used to analyze stable isotope ratios and multi-element concentrations in pork. Based on the limited database of analytical values, the methodology would be potentially able to confirm whether a sample of pork came from the region and organic status it claimed. These results provide a possibility for authenticity of organic agricultural products from a large scope such as a province even a country.


Assuntos
Alimentos Orgânicos/normas , Isótopos/análise , Carne de Porco/análise , Animais , China , Análise Discriminante , Carne de Porco/normas , Análise de Componente Principal , Suínos
13.
Environ Res ; 185: 109475, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32272290

RESUMO

Lead (Pb) isotopic composition analysis is a useful tool to accurately identify the origin of Pb in environmental media. The existing calculation method of the contribution of Pb sources from Pb isotope ratios greatly restricted the development of Pb contamination source apportionment. In the present study, a new distance model for calculating the mass proportion of Pb sources, which is based on the distance between the samples and the possible Pb sources in the Pb isotope ratios plot, was presented. The inverse distance model was applied to calculate the contribution proportion of two Pb sources in three previous studies. The average absolute differences between the proportions calculated by the conventional binary mixing equation and the inverse distance model were 0.21%, 1% and 1.9%, respectively, indicating that the new model agreeably calculated the contribution of two Pb sources. The anthropogenic sources proportion (52%) calculated by the inverse distance model of three Pb sources to park soil Pb in Shanghai was comparable to the result that was calculated by the conventional ternary mixing equation (53%), which showed the validity of the new model in calculating the contribution proportion of three Pb sources. Rational results were obtained by the inverse distance model in calculating the contribution of four Pb sources, illustrating that the new model has potential use in calculating the apportionment of four or more Pb sources. These results suggest that the inverse distance model is a simple and efficient approach for calculating the contribution proportion of various Pb contamination sources, and provides a prospective in the study of this field.


Assuntos
Monitoramento Ambiental , Poluentes do Solo , China , Isótopos/análise , Chumbo , Estudos Prospectivos , Solo , Poluentes do Solo/análise
14.
Artigo em Inglês | MEDLINE | ID: mdl-32222674

RESUMO

The pyridine nucleotides nicotineamide adenine dinucleotide (NAD) and nicotineamide adenine dinucleotide phosphate (NADP) are conserved coenzymes across all domains of life, and are involved in more than 200 different hydride transfer reactions supporting essential catabolic and anabolic functions. The intracellular levels of these metabolites, and the ratio of their oxidized to reduced forms regulate an extensive network of reactions ranging beyond metabolism. Hence, monitoring their intracellular levels provides information about, but not limited to, the metabolic state of a cell or tissue. Interconversion between oxidized and reduced forms, varying pH liability and varying intracellular concentrations of the different species leaves absolute quantification of the pyridine nucleotides analytically challenging. These polar metabolites are poorly retained on conventional reverseed-phase stationary phases without ion-pair reagents that contaminates the LC-system. Herein we demonstrate that zwitterionic HILIC-tandem mass spectroemtry can be applied to successfully resolve the pyridine nucleotides in biological extracts in a fast, robust and highly sensitive way. The presented method applies isotope dilution to compensate potential loss of these labile metabolites and is validated for low, medium and high biomass samples of two popular biological model systems; Escherichia coli and the human cell line JJN-3. High stability and rapid sample preparation without solvent removal allows for long sequence runs, making this method ideal for high-throughput analysis of biological extracts.


Assuntos
Isótopos/análise , Nucleotídeos/análise , Extratos Vegetais/análise , Piridinas/análise , Nucleotídeos de Adenina/química , Linhagem Celular , Cromatografia Líquida de Alta Pressão , Escherichia coli , Humanos , Limite de Detecção , NAD/metabolismo , Oxirredução , Reprodutibilidade dos Testes , Espectrometria de Massas em Tandem
15.
PLoS One ; 15(3): e0229623, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32187196

RESUMO

The innovation of iron production is often considered one of the greatest technological advances in human history. A reliable provenancing method for iron is instrumental for the reconstruction of economic, social and geo-political aspects of iron production and use in antiquity. Although the potential of osmium isotopes analysis for this purpose has been previously suggested, here we present for the first time the results of osmium isotope analysis of ores, bloom and metal obtained from a set of systematic, bloomery iron-smelting experiments, utilizing selected ores from the Southern Levant. The results show that the 187Os/188Os ratio is preserved from ore to metal, with no isotopic fractionation. In addition, enrichment/depletion of osmium content was observed in the transition from ore to metal and from ore to slag. This observation has potential significance for our ability to differentiate between the various processes and sheds light on the suitability of various production remains for this method, which emerges as a robust and promising tool for the provenancing of archaeological ferrous metals.


Assuntos
Ferro/história , Isótopos/análise , Osmio/análise , Arqueologia , História Antiga , Humanos , Ferro/isolamento & purificação , Israel , Metalurgia/história
16.
Meat Sci ; 165: 108113, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32203812

RESUMO

High-value yak meat from Qinghai-Tibet Plateau was investigated using stable isotopes (δ13C, δ2H, δ18O, δ15N and δ34S) to identify attributes which could verify and protect its geographical origin. Supervised PLS-DA was applied to the isotope data to discriminate four geographical locations. δ13C, δ2H, and δ18O values showed significant differences according to origin while δ15N and δ34S values did not show any change across the different regions. Isotope values of different body tissues from the same animal showed no statistical difference for the five stable isotopes. In addition, the δ2H and δ18O values of defatted yak meat was highly correlated to farm altitude and associated drinking water. This yak meat traceability method is particularly useful to protect the Product of Geographical Indication (PGI) status of Gannan yak meat and verify the farming origin of yak meat sold in markets for food safety purposes, especially when excessive hormones, pesticides or heavy metals are found.


Assuntos
Bovinos , Isótopos/análise , Carne/análise , Altitude , Animais , Água Potável/química , Carne/normas , Tibet , Distribuição Tecidual
17.
Nature ; 579(7798): 240-244, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32161386

RESUMO

The accretion of volatile-rich material from the outer Solar System represents a crucial prerequisite for Earth to develop oceans and become a habitable planet1-4. However, the timing of this accretion remains controversial5-8. It has been proposed that volatile elements were added to Earth by the late accretion of a late veneer consisting of carbonaceous-chondrite-like material after core formation had ceased6,9,10. This view could not be reconciled with the ruthenium (Ru) isotope composition of carbonaceous chondrites5,11, which is distinct from that of the modern mantle12, or of any known meteorite group5. As a possible solution, Earth's pre-late-veneer mantle could already have contained a fraction of Ru that was not fully extracted by core formation13. The presence of such pre-late-veneer Ru can only be established if its isotope composition is distinct from that of the modern mantle. Here we report the first high-precision, mass-independent Ru isotope compositions for Eoarchaean ultramafic rocks from southwest Greenland, which display a relative 100Ru excess of 22 parts per million compared with the modern mantle value. This 100Ru excess indicates that the source of the Eoarchaean rocks already contained a substantial fraction of Ru before the accretion of the late veneer. By 3.7 billion years ago, the mantle beneath southwest Greenland had not yet fully equilibrated with late accreted material. Otherwise, no Ru isotopic difference relative to the modern mantle would be observed. If constraints from other highly siderophile elements besides Ru are also considered14, the composition of the modern mantle can only be reconciled if the late veneer contained substantial amounts of carbonaceous-chondrite-like materials with their characteristic 100Ru deficits. These data therefore relax previous constraints on the late veneer and are consistent with volatile-rich material from the outer Solar System being delivered to Earth during late accretion.


Assuntos
Planeta Terra , Isótopos/análise , Rutênio/análise , Groenlândia
18.
Nat Commun ; 11(1): 1534, 2020 03 24.
Artigo em Inglês | MEDLINE | ID: mdl-32210225

RESUMO

Changes in ocean circulation and the biological carbon pump have been implicated as the drivers behind the rise in atmospheric CO2 across the last deglaciation; however, the processes involved remain uncertain. Previous records have hinted at a partitioning of deep ocean ventilation across the two major intervals of atmospheric CO2 rise, but the consequences of differential ventilation on the Si cycle has not been explored. Here we present three new records of silicon isotopes in diatoms and sponges from the Southern Ocean that together show increased Si supply from deep mixing during the deglaciation with a maximum during the Younger Dryas (YD). We suggest Antarctic sea ice and Atlantic overturning conditions favoured abyssal ocean ventilation at the YD and marked an interval of Si cycle reorganisation. By regulating the strength of the biological pump, the glacial-interglacial shift in the Si cycle may present an important control on Pleistocene CO2 concentrations.


Assuntos
Atmosfera/química , Camada de Gelo/química , Isótopos/metabolismo , Água do Mar/química , Silício/metabolismo , Movimentos da Água , Regiões Antárticas , Oceano Atlântico , Dióxido de Carbono/metabolismo , História Antiga , Isótopos/análise , Oceanografia/métodos , Paleontologia/métodos , Água do Mar/análise , Silício/análise , Temperatura
19.
Environ Pollut ; 259: 113888, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32023786

RESUMO

The contributions of contaminant sources are difficult to resolve in the sediment record using concentration gradients and flux reconstruction alone. In this study, we demonstrate that source partitioning using lead isotopes provide complementary and unique information to concentration gradients to evaluate point-source releases, transport, and recovery of metal mining pollution in the environment. We analyzed eight sediment cores, collected within 24 km of two gold mines, for Pb stable isotopes, Pb concentration, and sediment chronology. Stable Pb isotope ratios (206Pb/207Pb, 208Pb/204Pb) of mining ore were different from those of background (pre-disturbance) sediment, allowing the use of a quantitative mixing model. As previously reported for some Arctic lakes, Pb isotope ratios indicated negligible aerosol inputs to sediment from regional or long-range pollution sources, possibly related to low annual precipitation. Maximum recorded Pb flux at each site reached up to 63 mg m-2 yr-1 in the period corresponding to early years of mining when pollution mitigation measures were at a minimum (1950s-1960s). The maximum contribution of mining-derived Pb to these fluxes declined with distance from the mines from 92 ± 8% to 8 ± 4% at the farthest site. Mining-derived Pb was still present at the sediment surface within 9 km of Giant Mine more than ten years after mine closure (5-26 km, 95% confidence interval) and model estimates suggest it could be present for another ∼50-100 years. These results highlight the persistence of Pb pollution in freshwater sediment and the usefulness of Pb stable isotopes to quantify spatial and temporal trends of contamination from mining pollution, particularly as concentrations approach background.


Assuntos
Baías , Monitoramento Ambiental , Sedimentos Geológicos , Isótopos , Chumbo , Mineração , Regiões Árticas , Baías/química , Poluentes Ambientais/análise , Sedimentos Geológicos/química , Ouro , Isótopos/análise , Chumbo/análise , Territórios do Noroeste
20.
BMC Bioinformatics ; 21(1): 37, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-32000676

RESUMO

BACKGROUND: DNA-stable isotope probing (DNA-SIP) links microorganisms to their in-situ function in diverse environmental samples. Combining DNA-SIP and metagenomics (metagenomic-SIP) allows us to link genomes from complex communities to their specific functions and improves the assembly and binning of these targeted genomes. However, empirical development of metagenomic-SIP methods is hindered by the complexity and cost of these studies. We developed a toolkit, 'MetaSIPSim,' to simulate sequencing read libraries for metagenomic-SIP experiments. MetaSIPSim is intended to generate datasets for method development and testing. To this end, we used MetaSIPSim generated data to demonstrate the advantages of metagenomic-SIP over a conventional shotgun metagenomic sequencing experiment. RESULTS: Through simulation we show that metagenomic-SIP improves the assembly and binning of isotopically labeled genomes relative to a conventional metagenomic approach. Improvements were dependent on experimental parameters and on sequencing depth. Community level G + C content impacted the assembly of labeled genomes and subsequent binning, where high community G + C generally reduced the benefits of metagenomic-SIP. Furthermore, when a high proportion of the community is isotopically labeled, the benefits of metagenomic-SIP decline. Finally, the choice of gradient fractions to sequence greatly influences method performance. CONCLUSIONS: Metagenomic-SIP is a valuable method for recovering isotopically labeled genomes from complex communities. We show that metagenomic-SIP performance depends on optimization of experimental parameters. MetaSIPSim allows for simulation of metagenomic-SIP datasets which facilitates the optimization and development of metagenomic-SIP experiments and analytical approaches for dealing with these data.


Assuntos
DNA/química , DNA/genética , Marcação por Isótopo/métodos , Metagenômica/métodos , Composição de Bases , Bases de Dados Genéticas , Biblioteca Gênica , Isótopos/análise , Metagenoma
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