scholarly journals Atmospheric chemistry of carboxylic acids: microbial implication versus photochemistry

2011 ◽  
Vol 11 (16) ◽  
pp. 8721-8733 ◽  
Author(s):  
M. Vaïtilingom ◽  
T. Charbouillot ◽  
L. Deguillaume ◽  
R. Maisonobe ◽  
M. Parazols ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Microbial Activity ◽  
Carboxylic Acids ◽  
Atmospheric Chemistry ◽  
Temperature Shift ◽  
Cloud Water ◽  
Reaction Rate Constants ◽  
Modelling Studies ◽  
Order Of Magnitude ◽  
Continental Origin

Abstract. The objective of this work was to compare experimentally the contribution of photochemistry vs. microbial activity to the degradation of carboxylic acids present in cloud water. For this, we selected 17 strains representative of the microflora existing in real clouds and worked on two distinct artificial cloud media that reproduce marine and continental cloud chemical composition. Photodegradation experiments with hydrogen peroxide (H2O2) as a source of hydroxyl radicals were performed under the same microcosm conditions using two irradiation systems. Biodegradation and photodegradation rates of acetate, formate, oxalate and succinate were measured on both media at 5 °C and 17 °C and were shown to be on the same order of magnitude (around 10−10–10−11 M s−1). The chemical composition (marine or continental origin) had little influence on photodegradation and biodegradation rates while the temperature shift from 17 °C to 5 °C decreased biodegradation rates of a factor 2 to 5. In order to test other photochemical scenarios, theoretical photodegradation rates were calculated considering hydroxyl (OH) radical concentration values in cloud water estimated by cloud chemistry modelling studies and available reaction rate constants of carboxylic compounds with both hydroxyl and nitrate radicals. Considering high OH concentration ([OH] = 1 × 10−12 M) led to no significant contribution of microbial activity in the destruction of carboxylic acids. On the contrary, for lower OH concentration (at noon, [OH] = 1 × 10−14 M), microorganisms could efficiently compete with photochemistry and in similar contributions than the ones estimated by our experimental approach. Combining these two approaches (experimental and theoretical), our results led to the following conclusions: oxalate was only photodegraded; the photodegradation of formate was usually more efficient than its biodegradation; the biodegradation of acetate and succinate seemed to exceed their photodegradation.

scholarly journals Global modeling of cloud water acidity, precipitation acidity, and acid inputs to ecosystems

2020 ◽  
Vol 20 (20) ◽  
pp. 12223-12245
Author(s):  
Viral Shah ◽  
Daniel J. Jacob ◽  
Jonathan M. Moch ◽  
Xuan Wang ◽  
Shixian Zhai
Keyword(s):  
East Asia ◽  
Carboxylic Acids ◽  
Atmospheric Chemistry ◽  
Wet Deposition ◽  
Cloud Water ◽  
Water Ph ◽  
Precipitation Ph ◽  
Water Acidity ◽  
Global Mean ◽  
Precipitation Acidity

Abstract. Cloud water acidity affects the atmospheric chemistry of sulfate and organic aerosol formation, halogen radical cycling, and trace metal speciation. Precipitation acidity including post-depositional inputs adversely affects soil and freshwater ecosystems. Here, we use the GEOS-Chem model of atmospheric chemistry to simulate the global distributions of cloud water and precipitation acidity as well as the total acid inputs to ecosystems from wet deposition. The model accounts for strong acids (H2SO4, HNO3, and HCl), weak acids (HCOOH, CH3COOH, CO2, and SO2), and weak bases (NH3 as well as dust and sea salt aerosol alkalinity). We compile a global data set of cloud water pH measurements for comparison with the model. The global mean observed cloud water pH is 5.2±0.9, compared to 5.0±0.8 in the model, with a range from 3 to 8 depending on the region. The lowest values are over East Asia, and the highest values are over deserts. Cloud water pH over East Asia is low because of large acid inputs (H2SO4 and HNO3), despite NH3 and dust neutralizing 70 % of these inputs. Cloud water pH is typically 4–5 over the US and Europe. Carboxylic acids account for less than 25 % of cloud water H+ in the Northern Hemisphere on an annual basis but 25 %–50 % in the Southern Hemisphere and over 50 % in the southern tropical continents, where they push the cloud water pH below 4.5. Anthropogenic emissions of SO2 and NOx (precursors of H2SO4 and HNO3) are decreasing at northern midlatitudes, but the effect on cloud water pH is strongly buffered by NH4+ and carboxylic acids. The global mean precipitation pH is 5.5 in GEOS-Chem, which is higher than the cloud water pH because of dilution and below-cloud scavenging of NH3 and dust. GEOS-Chem successfully reproduces the annual mean precipitation pH observations in North America, Europe, and eastern Asia. Carboxylic acids, which are undetected in routine observations due to biodegradation, lower the annual mean precipitation pH in these areas by 0.2 units. The acid wet deposition flux to terrestrial ecosystems taking into account the acidifying potential of NO3- and NH4+ in N-saturated ecosystems exceeds 50 meqm-2a-1 in East Asia and the Americas, which would affect sensitive ecosystems. NH4+ is the dominant acidifying species in wet deposition, contributing 41 % of the global acid flux to continents under N-saturated conditions.

scholarly journals Chemical characteristics of cloud water and the impacts on aerosol properties at a subtropical mountain site in Hong Kong

2019 ◽  
Author(s):  
Tao Li ◽  
Zhe Wang ◽  
Yaru Wang ◽  
Chen Wu ◽  
Yiheng Liang ◽  
...  
Keyword(s):  
Hong Kong ◽  
Chemical Composition ◽  
Gas Phase ◽  
Carboxylic Acids ◽  
Carbonyl Compounds ◽  
Cloud Water ◽  
Water Soluble ◽  
Soluble Ions ◽  
Aerosol Cloud Interactions ◽  
Aerosol Properties

Abstract. To investigate the cloud water chemistry and the effects of cloud processes on aerosol properties, comprehensive field observations of cloud water, aerosols, and gas-phase species were conducted at a mountaintop site in Hong Kong in October and November 2016. The chemical composition of cloud water including water-soluble ions, dissolved organic matter (DOM), carbonyl compounds, carboxylic acids, and trace metals was quantified. The measured cloud water was very acidic with a mean pH of 3.63, as the ammonium (174 μeq L−1) was insufficient for neutralizing the dominant sulfate (230 μeq L−1) and nitrate (160 μeq L−1). Substantial DOM was found in cloud water, with carbonyl compounds and carboxylic acids accounting for 18.2 % and 5.6 %, respectively. Different from previous observations, concentrations of methylglyoxal (19.1 μM) and glyoxal (6.72 μM) were higher than that of formaldehyde (1.59 μM). The partitioning of carbonyls between cloud water and the gas phase was also investigated. The measured aqueous fractions of dicarbonyls were comparable to the theoretical estimations, while significant aqueous-phase supersaturation was found for less soluble monocarbonyls, suggesting complicated effects of both physical and chemical processes. In-cloud oxidation played an important role in increasing DOM and sulfate in the cloud water. Abundant glyoxal is suggested to be the most likely precursor of cloud water organics. The aqueous formation of organics was enhanced by photochemistry and under less-acidic conditions. Moreover, as a result of the cloud processes, DOM mass fractions were found to be significantly elevated in in-cloud aerosols, which was likely to contribute to the increase in droplet-mode mass fraction of cloud processed aerosols. This study demonstrates the significant role of clouds in altering the chemical composition and physical properties of aerosols via scavenging and aqueous processes, and provides valuable information about aerosol–cloud interactions in subtropical and coastal regions.

scholarly journals Atmospheric chemistry of carboxylic acids: microbial implication versus photochemistry

2011 ◽  
Vol 11 (2) ◽  
pp. 4881-4911 ◽  
Author(s):  
M. Vaïtilingom ◽  
T. Charbouillot ◽  
L. Deguillaume ◽  
R. Maisonobe ◽  
M. Parazols ◽  
...  
Keyword(s):  
Carboxylic Acids ◽  
Atmospheric Chemistry ◽  
Chemical Reactivity ◽  
Cloud Water ◽  
Oh Radicals ◽  
Chemical Transformations ◽  
Bacterial Strains ◽  
Active Biomass ◽  
Significant Difference ◽  
Pure Cultures

Abstract. Clouds are multiphasic atmospheric systems in which the dissolved organic compounds, dominated by carboxylic acids, are subject to multiple chemical transformations in the aqueous phase. Among them, solar radiation, by generating hydroxyl radicals (•OH), is considered as the main catalyzer of the reactivity of organic species in clouds. We investigated to which extent the active biomass existing in cloud water represents an alternative route to the chemical reactivity of carboxylic acids. Pure cultures of seventeen bacterial strains (Arthrobacter, Bacillus, Clavibacter, Frigoribacterium, Pseudomonas, Sphingomonas and Rhodococcus), previously isolated from cloud water and representative of the viable community of clouds were first individually incubated in two artificial bulk cloud water solutions at 17 °C and 5 °C. These solutions mimicked the chemical composition of cloud water from "marine" and "continental" air masses, and contained the major carboxylic acids existing in the cloud water (i.e. acetate, formate, succinate and oxalate). The concentrations of these carboxylic compounds were monitored over time and biodegradation rates were determined. In average, they ranged from 2 ×10−19 for succinate to 1 × 10−18 mol cell−1 s−1 for formate at 17 °C and from 4 × 10−20 for succinate to 6 × 10−19 mol cell−1 s−1 for formate at 5 °C, with no significant difference between "marine" and "continental" media. In parallel, irradiation experiments were also conducted in these two artificial media to compare biodegradation and photodegradation of carboxylic compounds. To complete this comparison, the photodegradation rates of carboxylic acids by •OH radicals were calculated from literature data. Inferred estimations suggested a significant participation of microbes to the transformation of carboxylic acids in cloud water, particularly for acetate and succinate (up to 90%). Furthermore, a natural cloud water sample was incubated (including its indigenous microflora); the rates of biodegradation were determined and compared to the photodegradation rates involving •OH radicals. The biodegradation rates in "natural" and "artificial" cloud water were in the same order of magnitude; this confirms the significant role of the active biomass in the aqueous reactivity of clouds.

GC-MS, HPLC, TLC of Dorycnium herbaceum Tincture Species and Synergistic / Antagonist Effect Testing in Combination with Antibiotics

2017 ◽  
Vol 68 (2) ◽  
pp. 228-231 ◽  
Author(s):  
Renata Maria Varut ◽  
Luciana Teodora Rotaru
Keyword(s):  
Chemical Composition ◽  
Clavulanic Acid ◽  
Carboxylic Acids ◽  
Therapeutic Effect ◽  
Antagonistic Effect ◽  
Hydroalcoholic Extract ◽  
Low Concentrations ◽  
Amoxicillin Clavulanic Acid ◽  
Reference Strains ◽  
Antagonist Effect

The study objectives were to determine the chemical composition and the synergistic / antagonistic effect of the association between hydroalcoholic extract from the Dorycnii pentaphylli herba (DPH) and the antibiotics of choice, on five reference strains. The tincture contains flavonoids and polyphenol carboxylic acids in low concentrations. DPH has an antagonistic effect on three of the drugs tested (amoxicillin + clavulanic acid, levofloxacin, amikacin), the therapeutic effect being completely canceled and has no significant effect on two of them (ceftazidime, cefotaxime).

Atmospheric Chemistry of Perfluorinated Carboxylic Acids:  Reaction with OH Radicals and Atmospheric Lifetimes

2004 ◽  
Vol 108 (4) ◽  
pp. 615-620 ◽  
Author(s):  
M. D. Hurley ◽  
M. P. Sulbaek Andersen ◽  
T. J. Wallington ◽  
D. A. Ellis ◽  
J. W. Martin ◽  
...  
Keyword(s):  
Carboxylic Acids ◽  
Atmospheric Chemistry ◽  
Oh Radicals ◽  
Perfluorinated Carboxylic Acids

ADSORPTION LIQUID CHROMATOGRAPHY OF ETHANOL ELUATE OF ETHANOL EXTRACT OF GREEN WALNUTS+LEAVES (LUGLANS REGIA L., NUT FAMILY - LUGLANDACEAC) (Message VI)

2021 ◽  
Vol 7 (2) ◽  
pp. 17-22
Author(s):  
V. Platonov ◽  
Aleksandr Hadarcev ◽  
G. Suhih ◽  
M. Volochaeva ◽  
I. Dunaeva
Keyword(s):  
Mass Spectrometry ◽  
Liquid Chromatography ◽  
Chemical Composition ◽  
Carboxylic Acids ◽  
Phthalic Acid ◽  
Ethanol Extract ◽  
X Ray ◽  
Chromatography Mass Spectrometry ◽  
Column Adsorption ◽  
Structural Formulas

The aim of the study was to perform column adsorption liquid chromatography in order to obtain ethanol eluate, after preliminary sequential elution of ethanol extract with solvents in the order of their polarity: n–hexane, toluene, chloroform, acetone; to study in detail the chemical composition of this eluate by chromatography-mass spectrometry and X-ray fluorescence spectroscopy, with the intensification of compounds determining the composition of eluate, obtaining their masses -spectra, structural formulas, determination of the nature of trace elements. Materials and methods of research. A detailed study of the chemical composition of acetone eluate of ethanol extract of walnuts+ leaves was carried out using column adsorption liquid chromatography, chromato-mass spectrometry and X-ray fluorescence analysis. The results and their discussion. The features of the chemical composition of ethanol eluate of the product of column adsorption liquid chromatography of ethanol extract were studied, the qualitative composition and quantitative content of compounds identified in the first one were established by chromatography-mass spectrometry. Mass spectra and structural formulas were obtained for 31 individual eluate compounds. Ethanol eluate is characterized by the following indicators of structural and group composition (mass. % of eluate): esters of phthalic acid - 52.14, silicon and sulfur-containing compounds, respectively - 20.19 and 6.43, hydrocarbons - 15.38, glycosides - 2.21, alcohols - 1.92, carboxylic acids - 1.07, sterols - 0.89. It is assumed that the pharmacological effect of ethanol eluate is mainly determined by a set of free carboxylic acids, as well as phthalic acid, formed as a result of biochemical and hydrological transesterification of its esters containing compounds, alcohols, glycosides and sterols. Organosilicon compounds during hydrolysis give silica in the size of nanoparticles, which play the role of carriers of the above compounds to various organs of a living organism, as well as drainage of blood vessels from the products of cell metabolism, for example, cholesterol, various fats, etc. A comparative characteristic of the chemical composition of all ethanol extract eluates was carried out, the effectiveness of column adsorption liquid chromatography was shown.

A climatology of cloud chemistry for the eastern United States derived from the mountain cloud chemistry project

1993 ◽  
Vol 1 (1) ◽  
pp. 38-54 ◽  
Author(s):  
Volker A. Mohnen ◽  
Richard J. Vong
Keyword(s):  
United States ◽  
Chemical Composition ◽  
Chemical Analysis ◽  
Cloud Water ◽  
Cloud Base ◽  
Eastern United States ◽  
Cloud Chemistry ◽  
Air Mass ◽  
Ion Concentrations ◽  
Air Mass Trajectories

The chemical composition of clouds collected in the eastern United States has been intensely monitored over a 4-year period as part of the Mountain Cloud Chemistry Project. On the basis of these measurements we prepared a climatology for cloud chemistry, using simple statistical analyses tools and incorporating meteorological and cloud physical and chemical information. Five mountain stations have been established for cloud collection covering the northern and southern Appalachian Mountain range: Whiteface Mountain, New York; Mount Moosilauke, New Hampshire; Shenandoah Mountain, Virginia; Whitetop Mountain, Virginia; and Mount Mitchell, North Carolina. This review presents the major result from this 4-year measurement program. Cloud cover and cloud base over the eastern United States were deduced from the global real-time nephanalysis archives produced by the U.S. Air Force, augmented by local observations. Both active and passive cloud collectors were deployed to sample cloud water on an hourly basis, i.e., with sufficient time resolution to resolve synoptic scale phenomena. Chemical analysis of cloud water was performed by a central analytical laboratory with occasional on-site analysis to satisfy quality control procedures. Reliable methods now exist for collecting cloud-water samples in sufficient quantities for detailed chemical analysis. The chemical composition of cloud water varied significantly between sites. However, the differences in cloud-water ion concentration do not necessarily establish a geographic gradient between the sites but rather reflect differences in air-mass trajectories associated with the synoptic air-flow pattern and differences in sample location above cloud base. The dependence of cloud-water ion concentrations on synoptic weather type and observed differences in relative frequencies of warm sector, marine flow, and post-cold frontal synoptic types between northern and southern sites suggest that the north–south differences in cloud-water ion concentrations are related to cloud climatology at the northern sites. When air-mass trajectories shift from southwest to northwest, the concentrations of H+, SO42−, NO3− and NH4+ normally decrease but the southern sites continue to receive high concentrations under northwest flow. The height of cloud-water sample collection above cloud base was found to be an additional source of variability in both cloud-water chemistry and liquid-water content. Seasonal variation in cloud-water chemical composition was investigated at one site only. Sulfate levels were found to be significantly lower in supercooled clouds (i.e., during the 'cold' season) than in 'warm' clouds, but nitrate levels remained about the same.Key words: cloud chemistry, cloud frequency, air-mass trajectories, ANOVA.

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