scholarly journals Laboratory Investigations Coupled to VIR/Dawn Observations to Quantify the Large Concentrations of Organic Matter on Ceres

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 719
Author(s):  
Vassilissa Vinogradoff ◽  
Giovanni Poggiali ◽  
Andrea Raponi ◽  
Mauro Ciarniello ◽  
Simone De Angelis ◽  
...  
Keyword(s):  
Organic Matter ◽  
Amorphous Carbon ◽  
Surface Characterization ◽  
Global Scale ◽  
Absorption Bands ◽  
Planetary Body ◽  
Dawn Mission ◽  
Optical Effects ◽  
Aliphatic Carbon ◽  
Laboratory Investigations

Organic matter directly observed at the surface of an inner planetary body is quite infrequent due to the usual low abundance of such matter and the limitation of the infrared technique. Fortuitously, the Dawn mission has revealed, thanks to the Visible and InfraRed mapping spectrometer (VIR), large areas rich in organic matter at the surface of Ceres, near Ernutet crater. The origin of the organic matter and its abundance in association with minerals, as indicated by the low altitude VIR data, remains unclear, but multiple lines of evidence support an endogenous origin. Here, we report an experimental investigation to determine the abundance of the aliphatic carbon signature observed on Ceres. We produced relevant analogues containing ammoniated-phyllosilicates, carbonates, aliphatic carbons (coals), and magnetite or amorphous carbon as darkening agents, and measured their reflectance by infrared spectroscopy. Measurements of these organic-rich analogues were directly compared to the VIR spectra taken from different locations around Ernutet crater. We found that the absolute reflectance of our analogues is at least two orders of magnitude higher than Ceres, but the depths of absorption bands match nicely the ones of the organic-rich Ceres spectra. The choices of the different components are discussed in comparison with VIR data. Relative abundances of the components are extrapolated from the spectra and mixture composition, considering that the differences in reflectance level is mainly due to optical effects. Absorption bands of Ceres’ organic-rich spectra are best reproduced by around 20 wt.% of carbon (a third being aliphatic carbons), in association with around 20 wt.% of carbonates, 15 wt.% of ammoniated-phyllosilicate, 20 wt.% of Mg-phyllosilicates, and 25 wt.% of darkening agent. Results also highlight the pertinence to use laboratory analogues in addition to models for planetary surface characterization. Such large quantities of organic materials near Ernutet crater, in addition to the amorphous carbon suspected on a global scale, requires a concentration mechanism whose nature is still unknown but that could potentially be relevant to other large volatile-rich bodies.

scholarly journals Towards a representation of priming on soil carbon decomposition in the global land biosphere model ORCHIDEE (version 1.9.5.2)

2016 ◽  
Vol 9 (2) ◽  
pp. 841-855 ◽  
Author(s):  
Bertrand Guenet ◽  
Fernando Esteban Moyano ◽  
Philippe Peylin ◽  
Philippe Ciais ◽  
Ivan A Janssens
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Soil Carbon ◽  
Global Scale ◽  
Soil Incubation ◽  
First Order ◽  
Carbon Decomposition ◽  
Litter Manipulation ◽  
Global Land ◽  
Biosphere Model

Abstract. Priming of soil carbon decomposition encompasses different processes through which the decomposition of native (already present) soil organic matter is amplified through the addition of new organic matter, with new inputs typically being more labile than the native soil organic matter. Evidence for priming comes from laboratory and field experiments, but to date there is no estimate of its impact at global scale and under the current anthropogenic perturbation of the carbon cycle. Current soil carbon decomposition models do not include priming mechanisms, thereby introducing uncertainty when extrapolating short-term local observations to ecosystem and regional to global scale. In this study we present a simple conceptual model of decomposition priming, called PRIM, able to reproduce laboratory (incubation) and field (litter manipulation) priming experiments. Parameters for this model were first optimized against data from 20 soil incubation experiments using a Bayesian framework. The optimized parameter values were evaluated against another set of soil incubation data independent from the ones used for calibration and the PRIM model reproduced the soil incubations data better than the original, CENTURY-type soil decomposition model, whose decomposition equations are based only on first-order kinetics. We then compared the PRIM model and the standard first-order decay model incorporated into the global land biosphere model ORCHIDEE (Organising Carbon and Hydrology In Dynamic Ecosystems). A test of both models was performed at ecosystem scale using litter manipulation experiments from five sites. Although both versions were equally able to reproduce observed decay rates of litter, only ORCHIDEE–PRIM could simulate the observed priming (R2  =  0.54) in cases where litter was added or removed. This result suggests that a conceptually simple and numerically tractable representation of priming adapted to global models is able to capture the sign and magnitude of the priming of litter and soil organic matter.

Magneto-optical properties of defect centres in alkali halide crystals

1967 ◽  
Vol 300 (1460) ◽  
pp. 78-93 ◽  
Keyword(s):  
Optical Absorption ◽  
Silver Atom ◽  
Alkali Halides ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Coupling Constant ◽  
Absorption Bands ◽  
Optical Effects ◽  
Alkali Halide Crystals ◽  
Defect Centres

Zeeman spectroscopy is not practicable for the investigation of the structure of electronic conventional states which give rise to broad optical absorption bands in solids. We have investigated the application of Faraday rotation and circular dichroism techniques to absorption bands of neutral silver atoms and F centres in alkali halides. These centres give rise to optical absorption bands due to transitions of the type 2 S → 2 P which are 2000 to 6000 cm -1 in width because, in part, of strong coupling to lattice phonons. A discussion is given of information which may be obtained concerning the electonic states involved in the 2 S → 2 P transition by analysis of the magneto-optical effects by the method of moments. It is shown, for example, that the spin-orbit coupling constant of the 2 P state of the silver atom is reduced from 613 cm -1 in the free state to 365 cm -1 in KCl, to 102 cm -1 in KBr and to an unmeasurably small value in KI. This cancellation of spin-orbit interaction of the silver atom is assigned to symmetry allowed admixtures of lattice ion wavefunctions into the 2 P state.

scholarly journals Analysis of functional groups in atmospheric aerosols by infrared spectroscopy: method development for probabilistic modeling of organic carbon and organic matter concentrations

2020 ◽  
Vol 13 (3) ◽  
pp. 1517-1538
Author(s):  
Charlotte Bürki ◽  
Matteo Reggente ◽  
Ann M. Dillner ◽  
Jenny L. Hand ◽  
Stephanie L. Shaw ◽  
...  
Keyword(s):  
Cluster Analysis ◽  
Organic Matter ◽  
Organic Carbon ◽  
Functional Groups ◽  
Method Development ◽  
Estimation Method ◽  
Chemical Species ◽  
Monitoring Network ◽  
Ftir Spectra ◽  
Absorption Bands

Abstract. The Fourier transform infrared (FTIR) spectra of fine particulate matter (PM2.5) contain many important absorption bands relevant for characterizing organic matter (OM) and obtaining organic matter to organic carbon (OM∕OC) ratios. However, extracting this information quantitatively – accounting for overlapping absorption bands and relating absorption to molar abundance – and furthermore relating abundances of functional groups to that of carbon atoms poses several challenges. In this work, we define a set of parameters that model these relationships and apply a probabilistic framework to identify values consistent with collocated field measurements of thermal–optical reflectance organic carbon (TOR OC). Parameter values are characterized for various sample types identified by cluster analysis of sample FTIR spectra, which are available for 17 sites in the Interagency Monitoring of Protected Visual Environments (IMPROVE) monitoring network (7 sites in 2011 and 10 additional sites in 2013). The cluster analysis appears to separate samples according to predominant influence by dust, residential wood burning, wildfire, urban sources, and biogenic aerosols. Functional groups calibrations of aliphatic CH, alcohol COH, carboxylic acid COOH, carboxylate COO, and amine NH2 combined together reproduce TOR OC concentrations with reasonable agreement (r=0.96 for 2474 samples) and provide OM∕OC values generally consistent with our current best estimate of ambient OC. The mean OM∕OC ratios corresponding to sample types determined from cluster analysis range between 1.4 and 2.0, though ratios for individual samples exhibit a larger range. Trends in OM∕OC for sites aggregated by region or year are compared with another regression approach for estimating OM∕OC ratios from a mass closure equation of the major chemical species contributing to PM fine mass. Differences in OM∕OC estimates are observed according to estimation method and are explained through the sample types determined from spectral profiles of the PM.

Carbon monoxide emissions by phytoplankton: evidence from laboratory experiments

2009 ◽  
Vol 6 (5) ◽  
pp. 369 ◽  
Author(s):  
Valérie Gros ◽  
Ilka Peeken ◽  
Katrin Bluhm ◽  
Eckart Zöllner ◽  
Roland Sarda-Esteve ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Atmospheric Chemistry ◽  
Laboratory Experiments ◽  
Euphotic Zone ◽  
Global Scale ◽  
Emission Rates ◽  
Direct Production ◽  
Diurnal Cycles

Environmental context. Carbon monoxide (CO) is a key component for atmospheric chemistry and its production in the ocean, although minor at the global scale, could play a significant role in the remote marine atmosphere. Up to now, CO production in the ocean was considered to mainly originate from the photo-production of dissolved organic matter (mainly under UV radiation). In this paper, we show evidence for direct production of CO by phytoplankton and we suggest it as a significant mechanism for CO production in the ocean. Abstract. In order to investigate carbon monoxide (CO) emissions by phytoplankton organisms, a series of laboratory experiments was conducted in Kiel (Germany). Nine monocultures, including diatoms, coccolithophorids, chlorophytes and cyanobacteria have been characterised. This was done by following the CO variations from monoculture aliquots exposed to photosynthetically active radiation during one or two complete diurnal cycles. All the studied cultures have shown significant CO production when illuminated. Emission rates have been estimated to range from 1.4 × 10–5 to 8.7 × 10–4 μg of CO μg chlorophyll–1 h–1 depending on the species. When considering the magnitude of the emission rates from the largest CO emitters (cyanobacteria and diatoms), this biotic source could represent up to 20% of the CO produced in oceanic waters. As global models currently mainly consider CO production from the photo-degradation of dissolved organic matter, this study suggests that biotic CO production should also be taken into account. Whether this biological production might also contribute to some degree to the previous observed non-zero CO production below the euphotic zone (dark CO production) cannot be deduced here and needs to be further investigated.

Thickness-Dependent Optical Effects in Infrared Reflection-Absorption Spectra of a Fairly Thick Polymer Layer

2002 ◽  
Vol 56 (1) ◽  
pp. 24-30 ◽  
Author(s):  
Marta KlanjšEk Gunde ◽  
Zorica Crnjak Orel
Keyword(s):  
Absorption Spectra ◽  
Normal Incidence ◽  
Peak Position ◽  
Mean Value ◽  
Absorption Bands ◽  
Medium Thickness ◽  
Peak Intensity ◽  
Infrared Reflection ◽  
Optical Effects ◽  
The Mean

Thickness-dependent intensities and positions of absorption lines in infrared reflection-absorption spectra of thin films on reflective substrates at near-normal incidence are investigated. Two types of absorption bands in a polymer, the weak and the strong, were examined. Their optical properties were determined by the dielectric response function. The optical path of the beam was described by the coherent sum of all successively reflected beams. The thickness-dependent properties of absorption bands were examined in three typical thickness regions. At small thickness, the peak intensity oscillates around the mean value defined by the simple internal absorptance of the beam crossing the double layer. For medium thickness, the peak position swings around the original frequency and its intensity oscillations move above the simple internal absorptance. In layers within the high-thickness region, optical distortions cause large changes in line shape due to approaching the bulk reflectance. A simple analytical interpretation is possible only within the low-thickness region. The width of these thickness regions depends on the absorptivity of the considered band; for strong bands they are considerably narrower than for weak bands. The theoretically predicted effects compare well with those measured in RAS spectra of variously thick silicon resin layers on aluminium substrates.

On the nature and origin of "muck" deposits in the Klondike area, Yukon Territory

1997 ◽  
Vol 34 (10) ◽  
pp. 1333-1344 ◽  
Author(s):  
T. A. Fraser ◽  
C. R. Burn
Keyword(s):  
Organic Matter ◽  
Fine Sand ◽  
Yukon Territory ◽  
Low Flow ◽  
Radiocarbon Dates ◽  
The Holocene ◽  
Yukon River ◽  
Laboratory Investigations ◽  
Late Wisconsinan ◽  
Kluane Lake

Organic-rich "muck" deposits, which blanket auriferous gravels in the Klondike area, Yukon Territory, comprise two principal stratigraphic units: (i) a silty Late Pleistocene deposit, and (ii) Holocene organics lying unconformably on the silt. The deposits are found predominantly in valley bottoms and, if undisturbed, are normally perennially frozen. Field and laboratory investigations of particle size, mineralogy, and morphology, as well as organic matter and sedimentary structures, indicate that the silt is both primary (massive) and redeposited (bedded) loess (by weight 87% medium and coarse silt and fine sand). Radiocarbon dates indicate that the loess was deposited during Late Wisconsinan McConnell glaciation, beginning after 27 000 14C years BP. The loess was likely derived from the floodplain of the Yukon River during periods of low flow. Turf in growth position and organic matter in the silt similar to that of loessal grasslands near Kluane Lake suggest a grassland environment for the area during McConnell glaciation. A mummified carcass in the silts indicates that some of these sediments have been frozen since shortly after deposition. Ice wedges are commonly found in the upper portion of the silt, but these wedges rarely extend into the overlying organic material. Separate, smaller ice wedges are found in the Holocene unit. Radiocarbon dates indicate that peat growth began at the start of the Holocene, as in other unglaciated portions of Yukon, when the climate became abruptly wetter.

scholarly journals A network perspective reveals decreasing material diversity in studies on nanoparticle interactions with dissolved organic matter

2017 ◽  
Vol 114 (10) ◽  
pp. E1756-E1765 ◽  
Author(s):  
Nicole Sani-Kast ◽  
Jérôme Labille ◽  
Patrick Ollivier ◽  
Danielle Slomberg ◽  
Konrad Hungerbühler ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Engineered Nanoparticles ◽  
Experimental Results ◽  
Aquatic Environments ◽  
Particle Coating ◽  
Nanoparticle Interactions ◽  
Aliphatic Carbon ◽  
Extensive Body ◽  
Micrometer Scale

Dissolved organic matter (DOM) strongly influences the properties and fate of engineered nanoparticles (ENPs) in aquatic environments. There is an extensive body of experiments on interactions between DOM and ENPs and also larger particles. [We denote particles on the nano- and micrometer scale as particulate matter (PM).] However, the experimental results are very heterogeneous, and a general mechanistic understanding of DOM–PM interactions is still missing. In this situation, recent reviews have called to expand the range of DOM and ENPs studied. Therefore, our work focuses on the diversity of the DOM and PM types investigated. Because the experimental results reported in the literature are highly disparate and difficult to structure, a new format of organizing, visualizing, and interpreting the results is needed. To this end, we perform a network analysis of 951 experimental results on DOM–PM interactions, which enabled us to analyze and quantify the diversity of the materials investigated. The diversity of the DOM–PM combinations studied has mostly been decreasing over the last 25 y, which is driven by an increasing focus on several frequently investigated materials, such as DOM isolated from fresh water, DOM in whole-water samples, and TiO2and silver PM. Furthermore, there is an underrepresentation of studies into the effect of particle coating on PM–DOM interactions. Finally, it is of great importance that the properties of DOM used in experiments with PM, in particular the molecular weight and the content of aromatic and aliphatic carbon, are reported more comprehensively and systematically.

scholarly journals Characterization of Dissolved Organic Matter in Landfill Leachate during Two–Stage Membrane Bioreactor Treatment

2017 ◽  
Vol 15 (1) ◽  
Author(s):  
S. Sanguanpak ◽  
C. Chiemchaisri ◽  
W. Chiemchaisri ◽  
K. Yamamoto
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Landfill Leachate ◽  
Membrane Bioreactor ◽  
Disposal Site ◽  
Solid Waste Disposal ◽  
High Concentration ◽  
Absorption Bands ◽  
Two Stage

Landfill leachate is a complex wastewater containing high concentration of dissolved organic matter (DOM). In this study, DOM in raw leachate and treated water from pilot–scale two–stage membrane bioreactor (MBR) installed at solid waste disposal site were investigated by using fractionation method, fluorescence excitation–emission matrix spectroscopy (FEEM) and fourier transform infrared (FTIR). The fractionation results showed hydrophilic (Hyl) compound was the most abundant fraction in DOM of raw leachate, whereas the dominant fraction of DOM in mixed liquor inside MBR and its effluent was fulvic acid (FA). The fluorescent peaks of protein-like, humic and fulvic–like substances were detected in influent DOM, while the fluorescence peaks of MBR and effluent DOM were humic and fulvic-like substances. From the FTIR results, absorption bands that could be related to humic acid (HA) and FA were found in both MBR and effluent DOM. The characterization of DOM indicated that the most of Hyl and protein–like substances could be significantly removed by microbial process in MBR. Furthermore, a part of humic substance (HA and FA) could be eliminated by microbial and filtration processes.

scholarly journals Swept under the carpet: the effect of organic matter burial in global biogeochemical ocean models

2013 ◽  
Vol 10 (7) ◽  
pp. 10859-10911 ◽  
Author(s):  
I. Kriest ◽  
A. Oschlies
Keyword(s):  
Organic Matter ◽  
Numerical Models ◽  
Global Scale ◽  
Benthic Fluxes ◽  
Biogeochemical Fluxes ◽  
Biogeochemical Models ◽  
Wide Range ◽  
Potential Impact ◽  
Bathypelagic Zone ◽  
Global Carbon

Abstract. Although of substantial importance for marine tracer distributions and eventually global carbon, oxygen, and nitrogen fluxes, the interaction between sinking and remineralization of organic matter, benthic fluxes and burial is not always represented consistently in global biogeochemical models. We here aim to investigate the relationships between these processes with a suite of global biogeochemical models, each simulated over millennia, and compared against observed distributions of pelagic tracers and benthic and pelagic fluxes. We concentrate on the representation of sediment-water interactions in common numerical models, and investigate their potential impact on simulated global sediment-water fluxes and nutrient and oxygen distributions. We find that model configurations with benthic burial simulate global oxygen well over a wide range of possible sinking flux parameterizations, making the model more robust with regard to uncertainties about the remineralization length scale. On a global scale, burial mostly affects oxygen in the meso- to bathypelagic zone. While all model types show an almost identical fit to observed pelagic particle flux, and the same sensitivity to particle sinking speed, comparison to observational estimates of benthic fluxes reveals a more complex pattern and may be influenced by the data distribution and methodology. Still, evaluating model results against observed pelagic and benthic fluxes of organic matter can complement model assessments based on more traditional tracers such as nutrients or oxygen. Based on a combined metric of dissolved tracers and biogeochemical fluxes, we here identify two model descriptions of burial as suitable candidates for further experiments and eventual model refinements.

scholarly journals Towards a representation of priming on soil carbon decomposition in the global land biosphere model ORCHIDEE (version 1.9.5.2)

2015 ◽  
Vol 8 (10) ◽  
pp. 9193-9227
Author(s):  
B. Guenet ◽  
F. E. Moyano ◽  
P. Peylin ◽  
P. Ciais ◽  
I. A. Janssens
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Soil Carbon ◽  
Global Scale ◽  
Soil Incubation ◽  
First Order ◽  
Carbon Decomposition ◽  
Litter Manipulation ◽  
Global Land ◽  
Biosphere Model

Abstract. Priming of soil carbon decomposition encompasses different processes through which the decomposition of native (already present) soil organic matter is amplified through the addition of new organic matter, with new inputs typically being more labile than the native soil organic matter. Evidence for priming comes from laboratory and field experiments, but to date there is no estimate of its impact at global scale and under the current anthropogenic perturbation of the carbon cycle. Current soil carbon decomposition models do not include priming mechanisms, thereby introducing uncertainty when extrapolating short-term local observations to ecosystem and regional to global scale. In this study we present a simple conceptual model of decomposition priming, called PRIM, able to reproduce laboratory (incubation) and field (litter manipulation) priming experiments. Parameters for this model were first optimized against data from 20 soil incubation experiments using a Bayesian framework. The optimized parameter values were evaluated against another set of soil incubation data independent from the ones used for calibration and the PRIM model reproduced the soil incubations data better than the original, CENTURY-type soil decomposition model, whose decomposition equations are based only on first order kinetics. We then compared the PRIM model and the standard first order decay model incorporated into the global land biosphere model ORCHIDEE. A test of both models was performed at ecosystem scale using litter manipulation experiments from 5 sites. Although both versions were equally able to reproduce observed decay rates of litter, only ORCHIDEE-PRIM could simulate the observed priming (R2 = 0.54) in cases where litter was added or removed. This result suggests that a conceptually simple and numerically tractable representation of priming adapted to global models is able to capture the sign and magnitude of the priming of litter and soil organic matter.

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