64 research outputs found
Bromine and iodine in plant-soil systems
Brom und Jod kommen in von Folge sowohl natĂŒrlichen als auch anthropogenen Prozessen (z.B.Verdunstung von Meerwasser, Verbrennung von Biomasse) als Spurenelemente in der BiosphĂ€re vor. Obwohl das Verhalten von Halogenen in der Umwelt intensiv untersucht worden ist, bestehen nach wie vor groĂe LĂŒcken im VerstĂ€ndnis ihres Verhaltens, ihrer Verteilung und ihrer Bindungsformen in terrestrischen Milieu. Ziel dieser Arbeit war die Untersuchung natĂŒrlicher Anreicherungsprozesse von Halogenen in terrestrischen Milieu, sowie der Wechselbeziehungen zwischen Halogenen, Boden, Streu und Pflanzen. Sowohl terrestrische Pflanzen als auch Böden vermögen den natĂŒrlichen Halogen-Kreislauf entscheidend zu beeinflussen, indem sie sowohl als Speichermedium (Senke) als auch als Emittent (Quelle) einer vielzahl von Halogen-Spezies dienen. Das Verhalten von Brom und Jod wurde wĂ€hrend des einjĂ€hrigen Lebenszyklus (vom Samen bis zur Zersetzung) von Weidelgras (Lolium multiflorum) untersucht. DarĂŒber hinaus wurden BlĂ€tter von Buchen (Fagus Sylvatica) unter aborbedingungen zersetzt, um diese Ergebnisse mit denen von Abbauprozessen unter natĂŒrlichen Umweltbedingungen zu vergleichen. Die Verteilung von Brom und Jod in Boden, Bodenlösung, Ausgangsgestein, Niederschlag, BlĂ€ttern und Streu wurde in zwei Wald-Gebieten in der Umgebung von Heidelberg (Deutschland) untersucht. Zur Quantifizierung der Halogene kamen verschiedene Methoden zum Einsatz, unter ihnen INAA, XRF, ICP-MS und IC/ICP-MS. WĂ€hrend der Weidelgras-Zersetzung werden die beiden Halogene sowohl in organischer, als auch anorganischer Form freigesetzt Brom in ĂŒberwiegend flĂŒchtiger Form (bis zu ~80%), wĂ€hrend kleine Mengen im Detritus verbleiben (bis zu ~2,6%) und die restliche Menge ausgewaschen wird. Das Verhalten von Jod wĂ€hrend der Zersetzung ist weniger schlĂŒssig und bedarf weiterer Untersuchungen. Bei der Verrottung von Buchen-BlĂ€ttern zeigt sich fĂŒr die Freisetzung von Brom ein anderes Muster als bei der Weidelgras-Verrottung, was auf die Bedeutung der Eigenschaften des jeweiligen Streus hinweist. Brom- und Jod-Konzentrationen in den untersuchten Bodenprofilen reichen von 0,6 ÎŒg/g bis 15 ÎŒg/g und die in den Bodenlösungen von 0,5ÎŒg/l bis 43ÎŒg/l. Dabei ist eine AbhĂ€ngigkeit vom jeweiligen Bodenhorizont zu beobachten. Im Oberboden (reich an organischem Material) sind die Halogene bevorzugt in organischen Bindungsformen zu finden (zwischen 60 und 100%), wĂ€hrend deren Anteil im Verlauf des Bodenprofils nach unten hin abnimmt. Bei einem der untersuchten Waldgebiete stellt die atmospĂ€rische Deposition die Quelle fĂŒr Brom und Jod dar, wĂ€hrend im zweiten Waldgebiet eine zusĂ€tzliche Beeinflussung durch das Ausgangsgestein festzustellen ist. Bei der Verrottung von BuchenblĂ€ttern im Labor war die Bildung flĂŒchtiger Bromver-bindungen geringer (12,9% ± 6.1) als es Berechnungen aus dem gleichen ProzeĂ unter natĂŒrlichen Bedingungen ergaben (24,4%). Man kann daher das Streu selbst als Quelle fĂŒr Bromverbindungen ansehen. Die vorliegende Arbeit zeigt das Vorhandensein von Halogenen in den Komponenten terrestrischer Ăkosysteme, sowie deren Austausch und die Beeinflussung der Halogenverteilung und Bindungsphase durch biologische Prozesse (z.B. Wachstum, Zerfall)
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Emission of volatile halogenated organic compounds over various Dead Sea landscapes
Volatile halogenated organic compounds (VHOCs), such as methyl halides (CH3X; X is Br, Cl and I) and very short-lived halogenated substances (VSLSs; bromoform-CHBr3, dibromomethane-CH2Br2, bromodichloromethane-CHBrCl2, trichloroethylene-C2HCl3, chloroform-CHCl3- A nd dibromochloromethane-CHBr2Cl) are well known for their significant influence on ozone concentrations and oxidation capacity of the troposphere and stratosphere and for their key role in aerosol formation. Insufficient characterization of the sources and the emission rate of VHOCs limits our ability to understand and assess their impact in both the troposphere and stratosphere. Over the last two decades, several natural terrestrial sources for VHOCs, including soil and vegetation, have been identified, but our knowledge of emission rates from these sources and their responses to changes in ambient conditions remains limited. Here we report measurements of the mixing ratios and fluxes of several chlorinated and brominated VHOCs from different landscapes and natural and agricultural vegetated sites at the Dead Sea during different seasons. Fluxes were generally positive (emission into the atmosphere), corresponding to elevated mixing ratios, but were highly variable. Fluxes (and mixing ratios) for the investigated VHOCs ranged as follows: CHBr3 from 79 to 187 nmolm2 d1 (1.9 to 22.6 pptv), CH2Br2 from 55 to 71 nmolm2 d1 (0.7 to 19 pptv), CHBr2Cl from 408 to 768 nmolm2 d1 (0.4 to 11 pptv), CHBrCl2 from 29 to 45 nmolm2 d1 (0.5 to 9.6 pptv), CHCl3 from 577 to 883 nmolm2 d1 (15 to 57 pptv), C2HCl3 from 74 to 884 nmolm2 d1 (0.4 to 11 pptv), methyl chloride (CH3Cl) from-5300 to 10,800 nmolm2 d1 (530 to 730 pptv), methyl bromide (CH3Br) from 111 to 118 nmolm2 d1 (7.5 to 14 pptv) and methyl iodide (CH3I) from 25 to 17 nmolm2 d1 (0.4 to 2.8 pptv). Taking into account statistical uncertainties, the coastal sites (particularly those where soil is mixed with salt deposits) were identified as sources of all VHOCs, but this was not statistically significant for CHCl3. Further away from the coastal area, the bare soil sites were sources for CHBrCl2, CHBr2Cl, CHCl3, and probably also for CH2Br2 and CH3I, and the agricultural sites were sources for CHBr3, CHBr2Cl and CHBrCl2. In contrast to previous reports, we also observed emissions of brominated trihalomethanes, with net molar fluxes ordered as follows: CHBr2Cl > CHCl3 > CHBr3 > CHBrCl2 and lowest positive flux incidence for CHCl3 among all trihalomethanes; this finding can be explained by the soil's enrichment with Br. Correlation analysis, in agreement with recent studies, indicated common controls for the emission of CHBr2Cl and CHBrCl2 and likely also for CHBr3. There were no indications for correlation of the brominated trihalomethanes with CHCl3. Also in line with previous reports, we observed elevated emissions of CHCl3 and C2HCl3 from mixtures of soil and different salt-deposited structures; the flux correlations between these compounds and methyl halides (particularly CH3I) suggested that at least CH3I is also emitted via similar mechanisms or is subjected to similar controls. Overall, our results indicate elevated emission of VHOCs from bare soil under semiarid conditions. Along with other recent studies, our findings point to the strong emission potential of a suite of VHOCs from saline soils and salt lakes and call for additional studies of emission rates and mechanisms of VHOCs from saline soils and salt lakes
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Emission of volatile halogenated organic compounds over various landforms at the Dead Sea
Abstract. Volatile halogenated organic compounds (VHOCs), such as methyl halides (CH3X; Xâ=âBr, Cl and I) and very short-lived halogenated substances (VSLS; CHBr3, CH2Br2, CHBrCl2, C2HCl3, CHCl3 and CHBr2Cl) are well known for their significant influence on ozone concentrations and oxidation capacity of the troposphere and stratosphere, and for their key role in aerosol formation. Insufficient characterization of the sources and emission rate of VHOCs limits our present ability to understand and assess their impact in both the troposphere and the stratosphere. Over the last two decades several natural terrestrial sources for VHOCs, including soil and vegetation, have been identified, but our knowledge about emission rates from these sources and their responses to changes in ambient conditions remains limited. Here we report measurements of the mixing ratios and the fluxes of several chlorinated and brominated VHOCs from different landforms and vegetated sites at the Dead Sea during different seasons. Fluxes were highly variable but were generally positive (emissive), corresponding with elevated mixing ratios for all of the VHOCs investigated in the four investigated site types â bare soil, coastal, cultivated and natural vegetated sites â except for fluxes of CH3I and C2HCl3 over the vegetated sites. In contrast to previous reports, we also observed emissions of brominated trihalomethanes, with net molar fluxes ordered as follows: CHBr2Clâ>âCHBr3â>âCHBrCl2â>âCHCl3. This finding can be explained by the enrichment of soil with Br. Correlation analysis, in agreement with recent studies, indicated common controls for the formation and emission of all the above trihalomethanes but also for CH2Br2. Also in line with previous reports, we observed elevated emissions of CHCl3 and C2HCl3 from mixtures of soil and different salt-deposited structures; the high correlations of flux with methyl halides, and particularly with CH3I, suggested that at least CH3I is also emitted via similar mechanisms or is subjected to similar controls. Overall, our results indicate elevate emission of VHOCs from bare soil under semi-arid conditions. Along with other recent studies, our findings point to the strong emission potential of a suite of VHOCs from saline soils and salt lakes, and call for additional studies of emission rates and mechanisms of VHOCs from saline soils and salt lakes
Cyanomethanaminium tetraÂfluoroÂborate
In the title compound, C2H5N2
+·BF4
â, the cations and anions are connected via interÂmolecular NâHâŻF and CâHâŻF hydrogen bonds, forming a three-dimensional network
Direct and indirect effects of soil fauna, fungi and plants on greenhouse gas fluxes
Soils harbour diverse soil fauna and a wide range of soil microorganisms. These fauna and microorganisms directly contribute to soil greenhouse gas (GHG) fluxes via their respiratory and metabolic activities and indirectly by changing the physical, chemical and biological properties of soils through bioturbation, fragmentation and redistribution of plant residues, defecation, soil aggregate formation, herbivory, and grazing on microorganisms and fungi. Based on recent results, the methods and results found in relation to fauna as well as from fungi and plants are presented. The approaches are outlined, and the significance of these hitherto ignored fluxes is discussed
Bromine soil/sediment enrichment in tidal salt marshes as a potential indicator of climate changes driven by solar activity: New insights from W coast Portuguese estuaries
This paper aims at providing insight about bromine (Br) cycle in four Portuguese estuaries: Minho, Lima (in the NW coast) and Sado, Mira (in the SW coast). The focus is on their tidal marsh environments, quite distinct with regard to key biophysicochemical attributes. Regardless of the primary bromide (Br-) common natural source, i.e., seawater, the NW marshes present relatively higher surface soil/sediment Br concentrations than the ones from SW coast. This happens in close connection with organic matter (OM) content, and is controlled by their main climatic contexts. Yet, the anthropogenic impact on Br concentrations cannot be discarded. Regarding [Br] spatial patterns across the marshes, the results show a general increase from tidal flat toward high marsh. Maxima [Br] occur in the upper driftline zone, at transition from highest low marsh to high marsh, recognized as a privileged setting for OM accumulation. Based on the discovery of OM ubiquitous bromination in marine and transitional environments, it is assumed that this Br occurs mainly as organobromine. Analysis of two dated sediment cores indicates that, despite having the same age (AD ~1300), the Caminha salt marsh (Minho estuary) evidences higher Br enrichment than the Casa Branca salt marsh (Mira estuary). This is related to a greater Br storage ability, which is linked to OM build-up and rate dynamics under different climate scenarios. Both cores evidence a fairly similar temporal Br enrichment pattern, and may be interpreted in light of the sun-climate coupling. Thereby, most of the well-known Grand Solar Minima during the Little Ice Age appear to have left an imprint on these marshes, supported by higher [Br] in soils/sediments. Besides climate changes driven by solar activity and impacting marsh Br biogeodynamics, those Br enrichment peaks might also reflect inputs of enhanced volcanic activity covarying with Grand Solar Minima.This work was partly supported by IDL through the UID/GEO/50019/2013 program, by C2
TN through the UID/Multi/04349/2013 program, and is a contribution of the project WestLog (PTDC/CTE/105370/2008), funded by the Fundação para a CiĂȘncia e a Tecnologia (FCT). JoĂŁo
Moreno benefits from a FCT PhD grant (SFRH/BD/87995/2012). J.J. GĂłmez-Navarro acknowledges the funding provided through the contract for the return of experienced researches, resolution R-735/2015 of the University of Murcia.info:eu-repo/semantics/publishedVersio
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DiaCurv: a value-based curvature analysis application in diatom taxonomy
<p>DiaCurv is a software application that uses a simple approach to calculating curvature by identifying the chord (length) and the sagitta (length) from a mid-point of an object or part of an object. This software application and associated R scripts provide the users with the possibilities to identify and apply curvature analysis in diatom taxonomy. Different taxa from the genera <i>Cymbella</i> and <i>Luticola</i>, with good size diminution series, were selected to validate curvature metrics for shape evaluations in taxonomy. The dorsal ventral curvature of <i>Cymbella</i> makes species within this genus a natural choice for comparison. In contrast, the lanceolate, elliptic-lanceolate to rhombic forms of species within <i>Luticola</i> are more problematic. Machine-learning techniques (principal component analysis and linear discriminant analysis (LDA)) were used to evaluate the curvature metrics for distinguishing diatom taxa. Selected taxa (<i>C. aspera</i>, <i>C. cymbiformis</i>, <i>C. diversa</i>, <i>C. excisa</i>, <i>C. japonica</i>, <i>C. neogena</i>, <i>C. neuquina</i>, <i>C. parva</i>, <i>C. saxoicola</i>, <i>C. tumidula</i>) were identified by valve curvature, except when valve shape was not a distinguishing character for the species. With the lanceolate, elliptic-lanceolate shapes of <i>Luticola</i>, curvature was effective in separating the linear-lanceolate forms (e.g., <i>L. australomutica</i>, <i>L. goeppertiana</i>, <i>L. murrayi</i>, <i>L. saprophila</i>), and some broadly lanceolate forms (<i>L. crozetensis</i>, <i>L. subcrozetensis</i>) but not elliptic-lanceolate forms within the same size range (e.g., <i>L. katkae</i>, <i>L. pseudocharcotii</i>, <i>L. yellowstonensis</i>). The experimental results indicated that LDA was more suitable for distinguishing taxa. Valve shapes which are circular, or centrally constricted or with polar differentiation or 3D in complexity may not be appropriate for curvature analysis unless specific parts of the valve are selected. The merits of this approach, or any other type of shape analysis, are that the subjective interpretation of shape differences between taxa is removed or reduced.</p
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