Investigating the Chemical Composition of the CIRS-Observed 160 cm-1 Ice Cloud in Titan’s Stratosphere

2020 ◽  
Author(s):  
Melissa Ugelow ◽  
Carrie Anderson
Keyword(s):  
Chemical Composition ◽  
Emission Feature ◽  
Individual Species ◽  
Ice Clouds ◽  
Mixing Ratios ◽  
Ice Cloud ◽  
Near Ir ◽  
Infrared Spectral ◽  
Infrared Spectrometer ◽  
The Individual

<p>Remote sensing observations from Voyager 1’s InfraRed Interferometer Spectrometer (IRIS) and Cassini’s Composite InfraRed Spectrometer (CIRS) confirmed the presence of nitrile ice clouds in Titan’s stratosphere (Samuelson 1985, 1992; Khanna, R.K. et al., 1987; Samuelson et al., 1997, 2007; Coustenis, A. et al., 1999; Mayo and Samuelson, 2005; Anderson, C.M. et al., 2010, 2018a,b; Anderson and Samuelson, 2011). While individual gases in Titan’s stratosphere are expected to condense to form pure ices, some of these gases will enter altitude regions where they undergo simultaneous saturation, or co-condensation, and form a mixed ice. The infrared spectral features resulting from a mixed ice have their own unique spectral signatures that notably diverge from the weighted sum of the individual species, and must therefore be experimentally determined as functions of temperature and mixing ratio (Anderson and Samuelson, 2011; Anderson et al. 2018a,b).</p> <p>The first observation of a co-condensate in Titan’s stratosphere was acquired by CIRS, which revealed a spectrally broad quasi-continuum ice emission feature with a spectral peak near 160 cm<sup>-1</sup>.  Based on the altitude of the observed cloud top, combined with preliminary experimental efforts (Anderson and Samuelson, 2011), the co-condensate was determined to predominately contain cyanoacetylene (HC<sub>3</sub>N) and hydrogen cyanide (HCN). Here we present experimentally-measured absorbance spectra for the far-, mid-, and near-IR spectral regions (1.25 – 200 µm; 8000 – 50 cm<sup>-1</sup>), along with the corresponding optical constants, of HC<sub>3</sub>N-HCN co-condensed ices utilizing the SPECtroscopy of Titan-Related ice AnaLogs (SPECTRAL) Chamber (Anderson et al., 2018a). Various deposition temperatures and mixing ratios of mixed HC<sub>3</sub>N and HCN were systematically studied to quantify the chemical composition of Titan’s CIRS-observed 160 cm<sup>-1</sup> stratospheric ice cloud emission feature.</p>

scholarly journals The Aarhus Chamber Campaign on Highly Oxidized Multifunctional Organic Molecules and Aerosols (ACCHA): Particle Formation and Detailed Chemical Composition at Different Temperatures

2020 ◽  
Author(s):  
Kasper Kristensen ◽  
Louise N. Jensen ◽  
Lauriane L. J. Quéléver ◽  
Sigurd Christiansen ◽  
Bernadette Rosati ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Organic Acids ◽  
Organic Molecules ◽  
Particle Formation ◽  
Effect Of Temperature ◽  
Individual Species ◽  
Chemical Structures ◽  
Heating And Cooling ◽  
The Individual ◽  
Mass Concentrations

Abstract. Little is known about the effects of low temperatures on the formation of SOA from α-pinene. In the current work, ozone-initiated oxidation of α-pinene at initial concentrations of 10 and 50 ppb, respectively, is performed at temperatures of 20, 0 and −15 °C in the Aarhus University Research on Aerosol (AURA) smog chamber during the Aarhus Chamber Campaign on highly oxidized multifunctional organic molecules and Aerosol (ACCHA). Here, we show how temperature influences the formation and chemical composition of α-pinene-derived SOA with a specific focus on the formation of organic acids and dimer esters. With respect to particle formation, results show significant increase in both particle formation rates, particle number concentrations and particle mass concentrations at lower temperatures. In particular, the number concentrations of sub-10 nm particles were significantly enhanced at the lower 0 and -15 °C temperatures. Temperatures also affect chemical composition of the formed SOA. Here, detailed off-line chemical analyses show organic acids contributing from 15 to 30 % by mass, with highest contributions observed at the lower temperatures indicative of enhanced condensation of these semi-volatile species. In comparison, 30 identified dimer esters contribute between 4–11 % to SOA mass. No significant differences in the chemical composition (i.e. organic acids and dimer esters) of the α-pinene-derived SOA particles are observed between experiments performed at 10 and 50 ppb initial α-pinene concentrations, thus suggesting a higher influence of reaction temperature compared to that of α-pinene loading on the SOA chemical composition. Interestingly, the effect of temperature on the formation of dimer esters differs between the individual species. The formation of less oxidized (oxygen-to-carbon ratio (O:C) < 0.4) dimer esters is shown to increase at lower temperatures while the formation of the more oxidized (O:C > 0.4) species is suppressed, consequently resulting in temperature-modulated composition of the α-pinene derived SOA. Temperature ramping experiments exposing α-pinene-derived SOA to changing temperatures (heating and cooling) reveal that the chemical composition of the SOA with respect to dimer esters is governed almost solely by the temperature during the initial oxidization and insusceptible to subsequent changes in temperature. Similarly, the resulting SOA mass concentrations were found to be more influenced by the initial α-pinene oxidation temperatures, thus suggesting that the formation conditions to a large extent govern the type of SOA formed, rather than the conditions to which the SOA is later exposed. For the first time, we discuss the relation between the identified dimer ester and the highly oxidized multifunctional organic molecules (HOMs) measured by Chemical Ionization Atmospheric Pressure interface Time-of-Flight mass spectrometer (CI-APi-TOF) during ACCHA experiments. We propose that, although very different in chemical structures and O:C-ratios, dimer esters and HOMs may be linked through the mechanism of RO2 autoxidation, and that dimer esters and HOMs merely represent two different fates of the RO2 radicals.

scholarly journals A spectral model for turbulence and microphysics dynamics in an ice cloud

1996 ◽  
Vol 3 (1) ◽  
pp. 23-28 ◽  
Author(s):  
A. J. Palmer
Keyword(s):  
Doppler Radar ◽  
Spectral Model ◽  
Velocity Measurements ◽  
Ice Clouds ◽  
One Dimensional ◽  
Mixing Ratios ◽  
Ice Cloud ◽  
Microphysical Properties ◽  
Vertical Scale ◽  
Direct Measurements

Abstract. A one-dimensional, nine-mode spectral model for temperature, velocity, and the mixing ratios of suspended and precipitating ice-particle components is shown to be consistent with ice-cloud observations. The observations include Doppler radar time-series measurements of a single winter ice cloud and direct measurements of mean particle size vs. icewater content for a set of ice clouds. Fitting of the model to the Doppler vertical-velocity measurements allows a prediction to be made of the vertical scale and turbulent Prandtl number active in the ice-cloud vertical motions. The model is then used to explore the question of how turbulence and gravity-wave motions affect the microphysical properties of an ice cloud. The model predicts interesting dynamical effects on the mixing ratios due to these motions, but no significant effects on the time-averaged microphysical quantities.

scholarly journals Gene Sequencing and Phylogenetic Analysis: Powerful Tools for an Improved Diagnosis of Fish Mycobacteriosis Caused by Mycobacterium fortuitum Group Members

2021 ◽  
Vol 9 (4) ◽  
pp. 797
Author(s):  
Davide Mugetti ◽  
Mattia Tomasoni ◽  
Paolo Pastorino ◽  
Giuseppe Esposito ◽  
Vasco Menconi ◽  
...  
Keyword(s):  
Phylogenetic Analysis ◽  
Gene Sequencing ◽  
Diagnostic Techniques ◽  
Individual Species ◽  
Identification System ◽  
Mycobacterium Fortuitum ◽  
Biochemical Tests ◽  
Species Determination ◽  
Gene Encoding ◽  
The Individual

The Mycobacterium fortuitum group (MFG) consists of about 15 species of fast-growing nontuberculous mycobacteria (NTM). These globally distributed microorganisms can cause diseases in humans and animals, especially fish. The increase in the number of species belonging to MFG and the diagnostic techniques panel do not allow to clarify their real clinical significance. In this study, biomolecular techniques were adopted for species determination of 130 isolates derived from fish initially identified through biochemical tests as NTM belonging to MFG. Specifically, gene sequencing and phylogenetic analysis were used based on a fragment of the gene encoding the 65 KDa heat shock protein (hsp65). The analyzes made it possible to confirm that all the isolates belong to MFG, allowing to identify the strains at species level. Phylogenetic analysis substantially confirmed what was obtained by gene sequencing, except for six strains; this is probably due to the sequences present in NCBI database. Although the methodology used cannot represent a univocal identification system, this study has allowed us to evaluate its effectiveness as regards the species of MFG. Future studies will be necessary to apply these methods with other gene fragments and to clarify the real pathogenic significance of the individual species of this group of microorganisms.

scholarly journals Impact of solar radiation and environmental temperature on Art Nouveau glass windows

2019 ◽  
Vol 7 (1) ◽  
Author(s):  
Teresa Palomar ◽  
Miguel Silva ◽  
Marcia Vilarigues ◽  
Isabel Pombo Cardoso ◽  
David Giovannacci
Keyword(s):  
Chemical Composition ◽  
Solar Radiation ◽  
Surface Temperature ◽  
Environmental Temperature ◽  
Summer Solstice ◽  
Art Nouveau ◽  
Ir Thermography ◽  
Hot Air ◽  
Near Ir ◽  
Air Pocket

Abstract This work presents the results of the evaluation of two Art Nouveau glass windows from the Casa-Museu Dr. Anastácio Gonçalves (Lisbon, Portugal) with IR-thermography during the summer solstice. According to the measurements, the surface temperature of glass depended on the outdoor environmental temperature and, mainly, on the direct solar radiation. Colored glasses presented a higher surface temperature due to the absorption of their chromophores at near-IR wavelengths. Enamels and grisailles showed higher surface temperatures than their support glasses due to both their chemical composition and color. The protective glazing, with small slits in one of the window panels, induced a hot-air pocket in its upper part due to the insufficient ventilation.

A Comparison of Aphelion Cloud Belt Phase Functions Before and After the Mars Year 34 Global Dust Storm

2021 ◽  
Author(s):  
Alex Innanen ◽  
Brittney Cooper ◽  
Charissa Campbell ◽  
Scott Guzewich ◽  
Jacob Kloos ◽  
...  
Keyword(s):  
Dust Storm ◽  
Phase Function ◽  
Dust Storms ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Water Ice ◽  
Ice Cloud ◽  
Sky Survey ◽  
Scattering Phase ◽  
Scattering Phase Function

&lt;p&gt;1. INTRODUCTION&lt;/p&gt;&lt;p&gt;The Mars Science Laboratory (MSL) is located in Gale Crater (4.5&amp;#176;S, 137.4&amp;#176;E), and has been performing cloud observations for the entirety of its mission, since its landing in 2012 [eg. 1,2,3]. One such observation is the Phase Function Sky Survey (PFSS), developed by Cooper et al [3] and instituted in Mars Year (MY) 34 to determine the scattering phase function of Martian water-ice clouds. The clouds of interest form during the Aphelion Cloud Belt (ACB) season (L&lt;sub&gt;s&lt;/sub&gt;=50&amp;#176;-150&amp;#176;), a period of time during which there is an increase in the formation of water-ice clouds around the Martian equator [4]. The PFSS observation was also performed during the MY 35 ACB season and the current MY 36 ACB season.&lt;/p&gt;&lt;p&gt;Following the MY 34 ACB season, Mars experienced a global dust storm which lasted from L&lt;sub&gt;s&lt;/sub&gt;~188&amp;#176; to L&lt;sub&gt;s&lt;/sub&gt;~250&amp;#176; of that Mars year [5]. Global dust storms are planet-encircling storms which occur every few Mars years and can significantly impact the atmosphere leading to increased dust aerosol sizes [6], an increase in middle atmosphere water vapour [7], and the formation of unseasonal water-ice clouds [8]. While the decrease in visibility during the global dust storm itself made cloud observation difficult, comparing the scattering phase function prior to and following the global dust storm can help to understand the long-term impacts of global dust storms on water-ice clouds.&lt;/p&gt;&lt;p&gt;2. METHODS&lt;/p&gt;&lt;p&gt;The PFSS consists of 9 cloud movies of three frames each, taken using MSL&amp;#8217;s navigation cameras, at a variety of pointings in order to observe a large range of scattering angles. The goal of the PFSS is to characterise the scattering properties of water-ice clouds and to determine ice crystal geometry.&amp;#160; In each movie, clouds are identified using mean frame subtraction, and the phase function is computed using the formula derived by Cooper et al [3]. An average phase function can then be computed for the entirety of the ACB season.&lt;/p&gt;&lt;p&gt;&lt;img src=&quot;https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.eda718c85da062913791261/sdaolpUECMynit/1202CSPE&amp;app=m&amp;a=0&amp;c=67584351a5c2fde95856e0760f04bbf3&amp;ct=x&amp;pn=gnp.elif&amp;d=1&quot; alt=&quot;Figure 1 &amp;#8211; Temporal Distribution of Phase Function Sky Survey Observations for Mars Years 34 and 35&quot; width=&quot;800&quot; height=&quot;681&quot;&gt;&lt;/p&gt;&lt;p&gt;Figure 1 shows the temporal distributions of PFSS observations taken during MYs 34 and 35. We aim to capture both morning and afternoon observations in order to study any diurnal variability in water-ice clouds.&lt;/p&gt;&lt;p&gt;3. RESULTS AND DISCUSSION&lt;/p&gt;&lt;p&gt;There were a total of 26 PFSS observations taken in MY 35 between L&lt;sub&gt;s&lt;/sub&gt;~50&amp;#176;-160&amp;#176;, evenly distributed between AM and PM observations. Typically, times further from local noon (i.e. earlier in the morning or later in the afternoon) show stronger cloud features, and run less risk of being obscured by the presence of the sun. In all movies in which clouds are detected, a phase function can be calculated, and an average phase function determined for the whole ACB season. &amp;#160;&lt;/p&gt;&lt;p&gt;Future work will look at the water-ice cloud scattering properties for the MY 36 ACB season, allowing us to get more information about the interannual variability of the ACB and to further constrain the ice crystal habit. The PFSS observations will not only assist in our understanding of the long-term atmospheric impacts of global dust storms but also add to a more complete image of time-varying water-ice cloud properties.&lt;/p&gt;

Taxonomic application of macro and micro morphological characters of seeds in Astragalus L. (Galegeae, Fabaceae) in India

Phytotaxa ◽  
2021 ◽  
Vol 502 (2) ◽  
pp. 191-207
Author(s):  
SHIVANI KASHYAP ◽  
CHANDAN KUMAR SAHU ◽  
ROHIT KUMAR VERMA ◽  
LAL BABU CHAUDHARY
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Light Microscopy ◽  
Seed Coat ◽  
Morphological Plasticity ◽  
Morphological Characters ◽  
Individual Species ◽  
Large Size ◽  
The Individual ◽  
Scanning Electron

Due to large size and enormous morphological plasticity, the taxonomy of the genus Astragalus is very complex and challenging. The identification and grouping of species chiefly based on macromorphological characters become sometimes difficult in the genus. In the present study, the micromorphology of the seeds of 30 species belonging to 14 sections of Astragalus from India has been examined applying scanning electron microscopy (SEM) along with light microscopy (LM) to evaluate their role in identification and classification. Attention was paid to colour, shape, size and surface of seeds. The overall size of the seeds ranges from 1.5–3.2 × 0.8–2.2 mm. The shape of the seeds is cordiform, deltoid, mitiform, orbicular, ovoid and reniform. The colour of seeds varies from brown to blackish-brown to black. Papillose, reticulate, ribbed, rugulate and stellate patterns were observed on the seed coat surface (spermoderm) among different species. The study reveals that the seed coat ornamentations have evolved differently among species and do not support the subgeneric and sectional divisions of the genus. However, they add an additional feature to the individual species, which may help in identification in combination with other macro-morphological features.

Investigation of atmospheric hydrogen cyanide: a modelling perspective

2021 ◽  
Author(s):  
Antonio G. Bruno ◽  
Jeremy J. Harrison ◽  
David P. Moore ◽  
Martyn P. Chipperfield ◽  
Richard J. Pope
Keyword(s):  
Biomass Burning ◽  
Atmospheric Chemistry ◽  
Hydrogen Cyanide ◽  
Three Dimensional ◽  
Oxidation Reactions ◽  
Loss Mechanism ◽  
Mixing Ratios ◽  
The Individual ◽  
Atmospheric Loss ◽  
Physical And Chemical

&lt;p&gt;Hydrogen cyanide (HCN) is one of the most abundant cyanides present in the global atmosphere, and is a tracer of biomass burning, especially for peatland fires. The HCN lifetime is 2&amp;#8211;5 months in the troposphere but several years in the stratosphere. Understanding the physical and chemical mechanisms of HCN variability is important due to its non-negligible role in the nitrogen cycle. The main source of tropospheric HCN is biomass burning with minor contributions from industry and transport. The main loss mechanism of atmospheric HCN is the reaction with the hydroxyl radical (OH). Ocean uptake is also important, while in the stratosphere oxidation by reaction with O(&lt;sup&gt;1&lt;/sup&gt;D) needs to be considered.&lt;/p&gt;&lt;p&gt;HCN variability can be investigated using chemical model simulations, such as three-dimensional (3-D) chemical transport models (CTMs). Here we use an adapted version of the TOMCAT 3-D CTM at a 1.2&amp;#176;x1.2&amp;#176; spatial resolution from the surface to ~60 km for 12 idealised HCN tracers which quantify the main loss mechanisms of HCN, including ocean uptake, atmospheric oxidation reactions and their combinations. The TOMCAT output of the HCN distribution in the period 2004-2020 has been compared with HCN profiles measured by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) over an altitude grid from 6 to 42 km. HCN model data have also been compared with ground-based measurements of HCN columns from NDACC FTIR stations and with in-situ volume mixing ratios (VMRs) from NOAA ground-based measurement sites.&lt;/p&gt;&lt;p&gt;The model outputs for the HCN tracer with full treatment of the loss processes generally agree well with ACE-FTS measurements, as long as we use recent laboratory values for the atmospheric loss reactions. Diagnosis of the individual loss terms shows that decay of the HCN profile in the upper stratosphere is due mainly to the O(&lt;sup&gt;1&lt;/sup&gt;D) sink. In order to test the magnitude of the tropospheric OH sink and the magnitude of the ocean sink, we also show the comparisons of the model tracers with surface-based observations. The implications of our results for understanding HCN and its variability are then discussed.&lt;/p&gt;

Larval and post-larval stages of fishes recorded from the plankton of Galway Bay, 1972–73

1976 ◽  
Vol 56 (1) ◽  
pp. 197-211 ◽  
Author(s):  
Julie M. Fives ◽  
F. I. O'Brien
Keyword(s):  
Copepod Species ◽  
Individual Species ◽  
Larval Stages ◽  
Percentage Occurrence ◽  
Bay Area ◽  
The Individual ◽  
Recorded Occurrence

The Galway Bay area was sampled quantitatively for plankton during 1972–3. The larvae and/or post-larvae of 67 species of fish were identified from the plankton. The recorded occurrence per m3 and the percentage occurrence of the individual species is presented and discussed, and reference is made to the concurrent occurrence of various chaetognath species and copepod species. The results of previous investigations of the plankton of the Galway Bay area are mentioned.

scholarly journals Hygroscopicity and composition of Alaskan Arctic CCN during April 2008

2011 ◽  
Vol 11 (8) ◽  
pp. 21789-21834
Author(s):  
R. H. Moore ◽  
R. Bahreini ◽  
C. A. Brock ◽  
K. D. Froyd ◽  
J. Cozic ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Cloud Condensation Nuclei ◽  
Anthropogenic Pollution ◽  
Organic Aerosol ◽  
International Polar Year ◽  
Mass Spectral ◽  
Aerosol Mass ◽  
Alaskan Arctic ◽  
Air Mass Types ◽  
The Individual

Abstract. We present a comprehensive characterization of cloud condensation nuclei (CCN) sampled in the Alaskan Arctic during the 2008 Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) project, a component of the POLARCAT and International Polar Year (IPY) initiatives. Four distinct air mass types were sampled including relatively pristine Arctic background conditions as well as biomass burning and anthropogenic pollution plumes. Despite differences in chemical composition, inferred aerosol hygroscopicities were fairly invariant and ranged from κ = 0.1–0.3 over the atmospherically-relevant range of water vapor supersaturations studied. Analysis of the individual mass spectral m/z 43 and 44 peaks from an aerosol mass spectrometer show the organic aerosols sampled to be well-oxygenated, consistent with with long-range transport and aerosol aging processes. However, inferred hygroscopicities are less than would be predicted based on previous parameterizations of biogenic oxygenated organic aerosol, suggesting an upper limit on organic aerosol hygroscopicity above which κ is less sensitive to the O:C ratio. Most Arctic aerosol act as CCN above 0.1 % supersaturation, although the data suggest the presence of an externally-mixed, non-CCN-active mode comprising approximately 0–20 % of the aerosol number. CCN closure was assessed using measured size distributions, bulk chemical composition measurements, and assumed aerosol mixing states; CCN predictions tended toward overprediction, with the best agreement (± 0–20 %) obtained by assuming the aerosol to be externally-mixed with soluble organics. Closure also varied with CCN concentration, and the best agreement was found for CCN concentrations above 100 cm−3 with a 1.5- to 3-fold overprediction at lower concentrations.

scholarly journals Species interactions in three Lemnaceae species growing along a gradient of zinc pollution

2021 ◽  
Author(s):  
Lorena Lanthemann ◽  
Sofia van Moorsel
Keyword(s):  
Growth Rates ◽  
Species Interactions ◽  
Metal Removal ◽  
Lemna Minor ◽  
Polluted Water ◽  
Future Research ◽  
Individual Species ◽  
High Tolerance ◽  
Species Mixture ◽  
The Individual

Duckweeds (Lemnaceae) are increasingly studied for their potential for phytoremediation of heavy-metal polluted water bodies. A prerequisite for metal removal, however, is the tolerance of the organism to the pollutant, e.g., the metal zinc (Zn). Duckweeds have been shown to differ in their tolerances to Zn, however, despite them most commonly co-occurring with other species, there is a lack of research concerning the effect of species interactions on Zn tolerance. Here we tested whether the presence of a second species influenced the growth rate of the three duckweed species Lemna minor, Lemna gibba, and Lemna turionifera. We used four different Zn concentrations in a replicated microcosm experiment under sterile conditions, either growing the species in isolation or in a 2-species mixture. The response to Zn differed between species, but all three species showed a high tolerance to Zn, with low levels of Zn even increasing the growth rates. The growth rates of the individual species were influenced by the identity of the competing species, but this was independent of the Zn concentration. Our results suggest that species interactions should be considered in future research with duckweeds and that several duckweed species have high tolerance to metal pollution, making them candidates for phytoremediation efforts.

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