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1.
IP 25 is a highly branched isoprenoid and an organic geochemical biomarker that is produced by some Arctic sea ice diatoms. IP 25 has previously been used in Arctic palaeo sea ice reconstruction studies and as a tracer for studying Arctic food webs. Here,
the molecular structure of IP 25 has been confirmed by 1H and 13C NMR spectroscopy following large-scale extraction from marine sediments obtained from the Canadian Arctic and purification
using a combination of open-column and HPLC chromatographic methods. The structure of IP 25 was consistent between the three different sampling locations and was identical to that found previously for this biomarker
following synthesis from a closely related highly branched isoprenoid diene. Since this study represents the first structural
characterisation of IP 25 in sediments, future analysis of sedimentary IP 25 for palaeo Arctic sea ice reconstructions can be carried out with much greater confidence. 相似文献
2.
Both laboratory and commercial preparations of humic substances (HSs) such as fulvic acids and humic acids along with HC1‐HF preparation of Manitoba peat soil organic matter were characterized using Fourier Transformation (FT) proton ( 1H) and carbon‐13 ( 13C) nuclear magnetic resonance (NMR) spectroscopy. All the samples were dissolved in a solution of 0.4 N NaOD in D 2O. In the case of ‘H‐NMR spectroscopy, all the investigated humic samples displayed resonance absorption peaks in the region of 1–4 ppm indicating the likely presence of aliphatic protons in the preparations. However, with the exception of one fulvic acid preparation (extracted from Manitoba Carrol clay‐loam soil with 0.5 N NaOH), 1H‐NMR spectra of all other samples provided evidence for strong aromatic character. The aliphatic and aromatic characteristics of such samples of HSs were further confirmed with the aid of 13C‐NMR spectra. 相似文献
3.
Heavy metals are common marine and soil pollutants that are mainly the result of industrial activity, and are a threat to the environment and human health. In this study, 1H nuclear magnetic resonance (NMR)-based metabolomics was applied to adult Danio rerio to monitor the metabolic change as a response to ZnCl 2 and CdCl 2 exposure at different concentrations for 72?h. NMR spectroscopy was used to identify and quantify the metabolites extracted from D. rerio. The metabolite profiles of the control and heavy metal exposed group were classified by partial least squares – discriminant analysis (PLS-DA) analysis, and potential contaminant-specific biomarkers were suggested. For the ZnCl 2-exposed zebrafish, the levels of ATP, aspartate and NAD + were increased, whereas the levels of formate, inosine, hypoxanthine and succinate decreased. In addition, the CdCl 2-exposed zebrafish showed an increase in the levels of ATP and formate and a decrease in the levels of glutamate, inosine and glutathione. Overall, Zn and Cd may lead to neurotoxicity, disturbances in the energy metabolism and oxidative stress. Our finding demonstrated that the application of NMR-based metabolomics might be useful for detecting the toxicity caused by sub-lethal concentrations of heavy metal contaminants in the environment. 相似文献
4.
Solid-state 15N NMR was applied to the aqueous extracts of a 13C-enriched plant slurry ( Lolium perenne), anaerobically incubated with 15N 3-trinitrotoluene (TNT). Almost all 15N 3-TNT transformation products became covalently bound to the plant-derived organic material extractable with water. DCPMAS
15N 13C NMR revealed a three-step reaction scheme. After reduction of TNT, the aryl amines are acetylated. Subsequent alkylation
of the resulting amides strengthens the incorporation of TNT-transformation products into humic material. Comparable results
have been recently obtained under aerobic conditions, which indicates that this pathway is a common process during biological
TNT transformation. 相似文献
5.
Advanced oxidation processes, such as photocatalysed oxidation, provide an important route for degradation of wastes. In this
study, the lowest excited state ( 3MLCT) of Ru(bpy) 32+ is used to break down chlorophenol pollutant molecules to harmless products. This has the advantage of using visible light
and a short-lived catalytically active species. Photolysis of deaerated aqueous solutions of a variety of mono- and poly-substituted
chlorophenols has been followed in the presence of Ru(bpy) 32+/S 2O 82− with near visible light (λ > 350 nm) by UV/visible absorption spectroscopy, luminescence, potentiometry, NMR and HPLC techniques.
Upon irradiation, a decrease is observed in the chlorophenol concentration, accompanied by the formation of Cl −, H + and SO 42− ions as the main inorganic products. Benzoquinone, phenol, dihydroxybenzenes and chlorinated compounds were the dominant
organic products. As the ruthenium(II) complex is regenerated in the reaction, the scheme corresponds to an overall catalytic
process. The kinetics of the rapid chlorophenol photodechlorination has been studied, and are described quite well by pseudo-first
order behaviour. Further studies on this were made by following Cl − release with respect to the initial Ru(bpy) 32+ and S 2O 82− concentrations. A comparison is presented of the photodechlorination reactivity of the mono and polychlorophenols studied
at acidic and alkaline pH. 相似文献
6.
In order to investigate the characteristics of pure Nano-Al 13, Nano-Al 13 was separated and purified from a series of poly-aluminum chloride (PAC) solutions which had the same Al 13 percentage but different total Al concentrations, by using column chromatography, ethanol-acetone resolving and SO 2? 4/Ba 2+ displacement. The Al 13 species yield was characterized by Al-ferron timed complexation spectrophotometry and 27Al-NMR (nuclear magnetic resonance). The coagulation efficiency of Nano-Al 13, PAC and AlCl 3 in synthetic water was also investigated by Jar tests. The dynamic process and aggregation state of kaolin suspensions coagulating with Nano-Al 13, PAC and AlCl 3 were similarly investigated using a photometric dispersion analyzer 2000 (PDA2000). The experimental results indicated that the ethanol-acetone resolving method was simple and could separate the PAC solution at different concentrations, while column chromatography could separate PAC solutions at low concentrations. The SO 4 2?/Ba 2+ displacement method could separate PAC solutions at high concentrations. However, extra inorganic cation and anion could be added in the solution during separation. The coagulation efficiency and dynamic experimental results showed that Nano-Al 13 with high positive-charged species was effective in removing turbidity and color. The dynamic process results showed that Nano-Al 13 also had the best recovery capability after shearing compared with PAC and AlCl 3 because the Nano-Al 13 conformation is more effective in charge neutralization. 相似文献
7.
Urea synthesis, currently the largest use of carbon dioxide in organic synthesis, is conventionally operated at high pressure and high temperature. Here, we report for the first time that urea forms at atmosphere and ambient temperatures by negative corona discharge in gas phase. The conversion of CO 2 and yields of a solid mixture of urea and ammonium carbamate, which was identified by the 13C NMR spectrum, rise with reducing temperatures and increasing molar ratios of NH 3/CO 2 and discharge frequencies. The conversion of carbon dioxide was found to be 82.16?% at 20?°C and 1?atm with a molar flow ratio of n(NH 3)/ n(CO 2) of 2.5. High pressure and high temperature as energy inputs are not necessary. 相似文献
8.
Insoluble porous solid functionalized ligand system bearing 2-aminophenylaminopropyl chelating ligand of the general formula
P–(CH 2) 3NH–(C 6H 4)–NH 2 was prepared via the sol–gel process, where P represents [Si–O]
n
polysiloxane network. First, the 2-aminophenylaminopropylsilane agent was prepared by substitution reaction between 3-chloropropyltrimethoxysilane
and 1,2-phenylenediamine, followed by hydrolytic polycondensation between 2-aminophenylaminopropylsilane agent and tetraethylorthosilicate(TEOS).
The immobilized 2-aminophenylaminopropylpolysiloxane P–(CH 2) 3NH–(C 6H 4)–NH 2(P–AphA) was characterized by 13C NMR, XPS, and FTIR. The results showed that 1,2-phenylenediamine groups were introduced onto polysiloxane network. The functionalized
ligand system exhibits 90–100% metal uptake capacity for all metal ions except Cd 2+. The elemental analysis data and the metal uptake capacities of the immobilized ligand system suggest that over than 90%
ligand sites were involved in coordination with metal ions except that of cadmium forming 1:1 metal to ligand ratio complexes. 相似文献
9.
We studied the hydrolysis and TiO 2 photocatalysis of the pesticide dichlorvos at pH 2.6–9 using phosphorus-31 nuclear magnetic resonance ( 31P NMR). We found that the hydrolysis of dichlorvos led to the formation of dimethyl phosphate at pH 5.6–9. On the other hand, TiO 2 photocatalysis decomposed dichlorvos into dimethyl phosphate, which further reacted to form monomethyl phosphate at pH 2.6 and 9. Monomethylphosphate was hydrolysed into phosphate at pH 2.6. 31P NMR is therefore a promising tool to study the degradation of organophosphorus pesticides. 相似文献
10.
Diesel engine railway traffic causes atmosphere pollution due to the exhaust emission which may be harmful to the passengers as well as workers. In this study, the air quality and PM10 concentrations were evaluated around a railway station in Northeast India where trains are operated with diesel engines. The gaseous pollutant (e.g. SO2, NO2, and NH3) was collected and measured by using ultraviolet–visible spectroscopy. The advanced level characterizations of the PM10 samples were carried out by using ion chromatography, Fourier-transform infrared, X-ray diffraction, inductively coupled plasma optical emission spectrometry , X-ray photoelectron spectroscopy, field-emission scanning electron microscopy with energy-dispersive spectroscopy, and high-resolution transmission electron microscopy with energy-dispersive spectroscopy techniques to know their possible environmental contaminants. High-performance liquid chromatography technique was used to determine the concentration of polycyclic aromatic hydrocarbons to estimate the possible atmospheric pollution level caused by the rail traffic in the enclosure. The average PM10 concentration was found to be 262.11 µg m−3 (maximum 24 hour) which indicates poor air quality (AQI category) around the rail traffic. The statistical and air mass trajectory analysis was also done to know their mutual correlation and source apportionment. This study will modify traditional studies where only models are used to simulate the origins. 相似文献
11.
Stable carbon isotopic composition (δ 13C) in tree rings is a widely recognized tool for climate reconstruction, and several works suggest that seasonal information can be extracted from intra-ring δ 13C variations. In this study, we explored the link between climate and intra-seasonal oak ring δ 13C using a process-based modelling approach. The ISOCASTANEA model was developed to compute the seasonal dynamics of tree-ring δ 13C for deciduous species from half-hourly climatic data by accounting for photosynthetic discrimination and carbon translocation and allocation at the tree scale and in tree rings.The model was applied from March 2005 to December 2007 in a 150-year-old deciduous oak forest. Canopy photosynthesis and stomatal conductance were calibrated using H 2O and CO 2 fluxes measured by the eddy flux technique, and simulated δ 13C values were compared to seasonal patterns of total organic matter δ 13C measured in tree rings for 2006 and 2007 at the same site. With the inclusion of carbon translocation and with regard to 13C enrichment of starch compared to soluble sugars, the model can reasonably simulate the intra-seasonal and inter-annual variability of tree-ring δ 13C using the same parameter values for 2006 and 2007. The amplitude of the seasonal carbon isotope pattern in tree rings was influenced by both photosynthetic and post-photosynthetic processes (starch enrichment and reserve use). The δ 13C variations in the early part of the ring, i.e., mainly in the earlywood, were related mostly to carbohydrate metabolism, although diluted information about environmental conditions during the previous year could also be found. The last part of the ring, consisting mainly of latewood, was found to be a good recorder of current-year environmental conditions, in particular relative humidity, at a fine temporal resolution when the growth rate was high. The sensitivity of the δ 13C in the early part of the ring to carbohydrate metabolism suggests that intra-ring δ 13C could be used to explore the relationship between tree decline or mortality and carbohydrate deficiency. 相似文献
12.
We show the potentiality of coupling together different compound-specific isotopic analyses in a laboratory experiment, where 13C-depleted leaf litter was incubated on a 13C-enriched soil. The aim of our study was to identify the soil compounds where the C derived from three different litter species is retained. Three 13C-depleted leaf litter ( Liquidambar styraciflua L., Cercis canadensis L. and Pinus taeda L., δ 13C vsPDB ≈ ?43‰), differing in their degradability, were incubated on a C4 soil (δ 13C vsPDB ≈ ?18‰) under laboratory-controlled conditions for 8 months. At harvest, compound-specific isotope analyses were performed on different classes of soil compounds [i.e. phospholipids fatty acids (PLFAs), n-alkanes and soil pyrolysis products]. Linoleic acid (PLFA 18:2ω6,9) was found to be very depleted in 13C (δ 13C vsPDB ≈ from ?38 to ?42‰) compared to all other PLFAs (δ 13C vsPDB ≈ from ?14 to ?35‰). Because of this, fungi were identified as the first among microbes to use the litter as source of C. Among n-alkanes, long-chain (C27–C31) n-alkanes were the only to have a depleted δ 13C. This is an indication that not all of the C derived from litter in the soil was transformed by microbes. The depletion in 13C was also found in different classes of pyrolysis products, suggesting that the litter-derived C is incorporated in less or more chemically stable compounds, even only after 8 months decomposition. 相似文献
13.
Microbial oxidation of organic compounds (including methane), in freshwater sediments, may result in precipitation of carbonates,
which may become an important geochemical archive of paleoenvironmental variations. Most probably low δ 13C value in calcite in eutrophic systems results from an advanced oxidation of organic compounds in turbulent or/and sulphate-rich
conditions. Likewise, high δ 13C value in calcite from organic-rich sediments may evidence low redox potential of the freshwater system. Oxidation of methane
and organic matter results in significant isotope effects in sulphates dissolved in water. Therefore, to better understand
the origin of carbon isotope signal in carbonates, concentration and stable isotope measurements in dissolved sulphate (water
column), bubble methane and calcite (freshwater sediments) have been carried out in 24 lakes, 2 ponds and 4 rivers in Poland.
The highest concentration of sulphate has been detected in rivers (85.47 SO 4
2− mg/l) and an artificial lake (70.30 SO 4
2− mg/l) located in the extremely SO 4
2−-polluted region called the “Black Triangle”. The lowest concentration of sulphate is found in dystrophic and mountain lakes
(from 0.5 SO 4
2− to about 3 mg/l). The lowest δ 34S(SO 4
2−) and δ 18O(SO 4
2−) values occur in unpolluted lakes in eastern Poland (−0.94 and 1.38‰, respectively). The highest S and O isotopic ratios
are found in a polluted lake in western Poland (δ 14S(SO 4
2)=12.95‰) and in a dystrophic lake in eastern Poland (δ 18O(SO 4
2) = 16.15‰) respectively. It is proposed that δ 34SO 4
2− and ( 18O(SO 4
2−) values in lakes represent a good tool to assess and quantify anthropogenic impact by acid precipitation and to monitor variations
in the trophic state and redox processes controlled by biodegradation of organic compounds in sediments and water column.
In general, increasing depth (up to 12 m) of the water column is associated with decreasing trend the δ 13C(CH 4) value from about –35 to about –78‰. However, δ 13C value in sedimentary calcite (δ 13C vary from –10 to 0.5‰) shows opposite trends as compared to the corresponding methane. This is probably due to redox processes
and distribution of heavy isotopes between methane and calcite. Likewise, turbulent water (river) show high δ 13C value in methane and low δ 13C value in calcite—this is probably due to an enhanced oxidation of methane producing 13C-depleted CO 2. In contrast to clean lakes, it is observed that an increase of the δ 13C(CH 4) value occurs with increasing depth of the water column in a strongly SO 4
2−-contaminated lake. This is probably due to a loss of biological buffering potential of the lake accompanied by an active
oxidation of methane precursors. 相似文献
14.
在B3LYP/6-311+G(d,p)基组水平下采用密度泛函理论方法系统开展了以下工作:(1)优化得到1∶1、1∶2和1∶3铝-麦芽酚配合物10种可能构型的静态结构、NPA电荷以及能量参数,计算得到Al(ma)3配合物4种异构体的核磁共振、紫外和红外等光谱学数据并与文献实验值比较,证明本文采用的计算方法和模型适用于铝-麦芽酚体系的研究;(2)模拟1∶1和1∶2铝-麦芽酚配合物9种可能位点的水交换反应,其中3个位点计算得到的水交换反应速率对数log kex(s-1)分别为2.4(Al(ma)(H2O)2+4(cis to ma))、2.6(cis-Al(ma)2(H2O)+2(I))和3.0(trans-Al(ma)2(H2O)+2(I)),与实验值2.5(Al(ma)2+)和3.3(Al(ma)+2)相符,说明相应位点为反应活性位点;(3)探讨铝-麦芽酚配合物毒性与其形态结构之间的相关机制。 相似文献
15.
Metal pollution produces damage to marine organisms at the cellular level possibly leading to ecological imbalance. The present investigation focused on the acute and chronic toxicity of lead (Pb) and zinc (Zn) by examining the effects of biomarker enzymes in post-larvae of Penaeus monodon (Tiger prawn). Antioxidant biomarker responses such as lipid peroxidation (LPO) and catalase (CAT) activity for Pb and Zn were determined following chronic exposure. Acute Lethal Concentration 50 (LC 50) values observed in the study at 96?h for Pb and Zn at 5.77?±?0.32?mg?L ?1 and 3.02?±?0.82?mg?L ?1, respectively. The estimated No Observed Effect Concentration and Lowest Observed Effect Concentration values for Pb were 0.014 and 0.029?mg?L ?1 and that recorded for Zn was 0.011 and 0.022?mg?L ?1, respectively. Among the two metals studied, toxicity of Zn was found to be greater to P. monodon than Pb. The activities of antioxidant defense enzymes and total protein content differed significantly from control following exposure to both metals. Overall, the biomarker studies demonstrated that alterations in antioxidant enzymes and induction of LPO reflect the consequences of heavy metal exposure in P. monodon. 相似文献
16.
Measuring the amount of fossil fuel carbon stored in the vegetation is now crucial to understand the mechanisms ruling climate
changes. In this respect, highly polluted areas such as major towns represent “natural” laboratories because fossil fuel CO 2 ( 14C-free) is isotopically distinct from mean atmospheric CO 2 ( 14C-labeled). Here, a 14C study of urban grasses near a major highway in Paris, France, shows that plants store up to 13% of fossil fuel carbon. The
14C composition of urban grasses is thus a novel parameter to assess the fossil fuel CO 2 pollution. 相似文献
17.
The relative distribution of Al between its various organic and inorganic complexes dictates its mobility in the environment, bioavailability, and toxicity. In recent years, there has been significant progress made in understanding the differential bioavailability and toxicity of various chemical species of Al to plants and certain aquatic organisms. Far less information concerning chemical speciation and differential uptake and transport of Al in humans is available. Among the important inorganic complexes of interest are the hydrolyzed-Al species, particularly the nonequilibrium, metastable polynuclear complexes, which form readily, have a fairly wide stability range, and have been demonstrated toxic to plants and fish. In recent years 27Al NMR spectroscopy has provided significant direct information on the polynuclear complexes existing in a wide range of aqueous solutions. The [Al 12O 4(OH) 24+n(H 2O) 12–n] (7–n)+ polynuclear complex is often found to be the predominant species in partially neutralized Al solutions and has recently been demonstrated to be more toxic to certain plants than the hexaaqua Al cation. It is also the principal component of Al-chlorohydrate, a highly soluble antiperspirant, present in many hydrolyzed Al solutions utilized in water and waste water treatment, and, as hypothesized herein, a primary constituent of many hydroxide gels utilized as antacids. This polynuclear has a wide pH stability range, reportedly forms copolynuclears with Si, and contains tetrahedrally coordinated Al within its structure, all features that may be relevant to the recently reported properties of Al associated with neuritic plaque cores. 相似文献
18.
Poly(vinylidene fluoride) (PVDF)/titanium dioxide (TiO 2) hybrid membranes were prepared using nano-TiO 2 as the modifier, and characterized by Transmission Electron Microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), atomic force microscope (AFM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The characterization results demonstrated that nano-sized TiO 2 particles dispersed homogeneously within the PVDF matrix, contributing to more hydroxyls and smoother surfaces. Moreover, permeate flux, retention factor, porosity, contact angle and anti-fouling tests were carried out to evaluate the effect of TiO 2 concentration on the performance of PVDF membranes. Among all the prepared membranes, PVDF/TiO 2 membrane containing 10 vol.% TiO 2 exhibited the best hydrophilicity with an average pure water flux up to 237 L·m ?2·h ?1, higher than that of unmodified PVDF membranes (155 L·m ?2·h ?1). Besides, the bovine serum albumin rejection of the hybrid membrane was improved evidently from 52.3% to 70.6%, and the contact angle was significantly lowered from 83° to 60°, while the average pore size and its distribution became smaller and narrower. 相似文献
19.
Analysis of the isotope composition of calcareous structures of marine organisms has proved useful in providing biological
data. The present study constitutes the first detailed work undertaken on the isotope composition of coleoid cephalopods.
We analysed the carbon- and oxygen-isotope composition [δ 13C (CO 2−
3) and δ 18O (CO 2−
3), respectively] of the cuttlebone aragonite of wild and cultivated specimens of Sepia officinalis Linnaeus, 1758. δ 13C (CO 2−
3) ranged from −2.94 to 1.00‰, δ 18O (CO 2−
3) from −0.18 to 2.08‰. The carbon-isotope composition is not in equilibrium with the carbon species of the ambient seawater,
and does not reflect the deposition of CaCO 3 in seawater. The potential influence of environmental factors and biological processes on the carbon-isotope composition
of the cuttlebone is discussed. In contrast to δ 13C, the oxygen-isotope composition of cuttlebone aragonite appears to be in isotopic equilibrium with the ambient seawater.
Seasonal changes in isotopic temperature revealed by our analyses agreed with changes in the temperature of the ambient seawater.
CaCO 3 was deposited all year round. A maximum life span of 2 yr, a year-round spawning season, and variable growth rates among and
within individuals have been inferred from the isotopic temperatures.
Received: 14 April 1998 / Accepted: 26 November 1998 相似文献
20.
This article presents a short overview of selected recent papers using nuclear magnetic resonance (NMR) to investigate interactions between organic pollutants and soil components such as organic matter, clays, whole soils, and sediments. First, we describe solid state cross polarisation magic angle spinning (CP-MAS) experiments as the main tools to investigate covalent bonds. Second, we report NMR approaches allowing us to assess molecule mobility and to characterise non-covalent interactions. Those approaches include correlations between K
oc
values and soil organic matter functions determined by CP-MAS, 2H NMR fingerprints, relaxation time measurements, 19F and 1H high resolution (HR)-MAS experiments. 相似文献
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