Photochemical production of sulfate from dissolved organic matter and atmospheric aqueous phases: Is there something in common?

2020 ◽  
Author(s):  
Rachele Ossola ◽  
Baptiste Clerc ◽  
Julie Tolu ◽  
Lenny H. E. Winkel ◽  
Kristopher McNeill
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Aqueous Phase ◽  
Atmospheric Chemistry ◽  
Degradation Products ◽  
Chemical Mechanism ◽  
Phase Reaction ◽  
Molecular Events ◽  
Wide Range ◽  
Terrestrial Environments

<p>In a recent study, we showed that photodegradation of dissolved organic sulfur (DOS) from a wide range of natural terrestrial environments releases sulfate (SO<sub>4</sub><sup>2–</sup>) and other small and highly oxidized S-containing compounds as degradation products, similar to what had already been reported for dissolved organic carbon, nitrogen and phosphorous. However, the underlying chemical mechanism of photoproduction of sulfate is still unknown.</p><p>To fill this knowledge gap, we selected cysteine as a DOS model compound and we investigated its photodegradation to sulfate using model sensitizers as the source of singlet oxygen (<sup>1</sup>O<sub>2</sub>) and triplet excited states (<sup>3</sup>Sens*), two photochemically produced reactive species ubiquitous in sunlit surface waters. Using a combination of steady-state photochemistry experiments, kinetic modeling and mechanistic knowledge from the biochemistry literature, we reconstructed the molecular events that likely lead to the release of sulfate. We found that the release of SO<sub>2</sub> via triplet-sensitized fragmentation of cysteine sulfinic acid, a <sup>1</sup>O<sub>2</sub> degradation product of cysteine, is a key step in the reaction mechanism. In the presence of oxygen and a photosensitizer, SO<sub>2</sub> is then rapidly oxidized to SO<sub>4</sub><sup>2–</sup>.</p><p>Interestingly, nowadays there is great interest in the atmospheric chemistry community on the same transformation (i.e., aqueous phase oxidation of SO<sub>2</sub> to SO<sub>4</sub><sup>2–</sup>) in the context of extreme haze events. Triplet-induced SO<sub>2</sub> oxidation has already been proposed as a potential aqueous phase reaction that might explain the mismatch between measured and modelled sulfate concentrations, but the mechanism of this process is still not established. Our work provides an example of how mechanistic knowledge gained on the (photo)chemical behaviour of dissolved organic matter in aquatic systems can offer insights on processes occurring in atmospheric aqueous phases.</p>

scholarly journals Explicit modeling of volatile organic compounds partitioning in the atmospheric aqueous phase

2013 ◽  
Vol 13 (2) ◽  
pp. 1023-1037 ◽  
Author(s):  
C. Mouchel-Vallon ◽  
P. Bräuer ◽  
M. Camredon ◽  
R. Valorso ◽  
S. Madronich ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Water Content ◽  
Gas Phase ◽  
Aqueous Phase ◽  
Water Soluble ◽  
Chemical Mechanism ◽  
Organic Species ◽  
Cloud Water Content ◽  
Isoprene Oxidation

Abstract. The gas phase oxidation of organic species is a multigenerational process involving a large number of secondary compounds. Most secondary organic species are water-soluble multifunctional oxygenated molecules. The fully explicit chemical mechanism GECKO-A (Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere) is used to describe the oxidation of organics in the gas phase and their mass transfer to the aqueous phase. The oxidation of three hydrocarbons of atmospheric interest (isoprene, octane and α-pinene) is investigated for various NOx conditions. The simulated oxidative trajectories are examined in a new two dimensional space defined by the mean oxidation state and the solubility. The amount of dissolved organic matter was found to be very low (yield less than 2% on carbon atom basis) under a water content typical of deliquescent aerosols. For cloud water content, 50% (isoprene oxidation) to 70% (octane oxidation) of the carbon atoms are found in the aqueous phase after the removal of the parent hydrocarbons for low NOx conditions. For high NOx conditions, this ratio is only 5% in the isoprene oxidation case, but remains large for α-pinene and octane oxidation cases (40% and 60%, respectively). Although the model does not yet include chemical reactions in the aqueous phase, much of this dissolved organic matter should be processed in cloud drops and modify both oxidation rates and the speciation of organic species.

Degradation of nanoplastics in aquatic environments: reactivity and impact on dissolved organic carbon

2020 ◽  
Author(s):  
Angelica Bianco ◽  
Fabrizio Sordello ◽  
Mikael Ehn ◽  
Davide Vione ◽  
Monica Passananti
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Aqueous Phase ◽  
Surface Waters ◽  
High Resolution Mass Spectrometry ◽  
Degradation Products ◽  
Plastic Material ◽  
Environmental Models ◽  
Reactivity Constant ◽  
The Impact

<p>The large production of plastic material (PlasticsEurope, 2019), together with the mishandling of plastic waste, has resulted in ubiquitous plastic pollution, which now reaches even the most remote areas of the Earth (Allen et al., 2019; Bergmann et al., 2019). Plastics undergo a slow process of erosion in the environment that decreases their size: microplastics (MPs) and nanoplastics (NPs) have diameters between 1 µm and 5 mm and lower than 1 µm, respectively (Frias and Nash, 2019).</p><p>The occurrence, transformation and fate of MPs and NPs in the environment are still unclear. Therefore, the objective of this work is to better understand the reactivity of NPs using an aqueous suspension of polystyrene NPs (PS-NPs) as a proxy, in the presence of sunlight and chemicals oxidants. The results obtained are relevant to both the atmospheric aqueous phase, such as cloud and fog droplets, and surface waters. We investigated the reactivity of PS-NPs with light and with two important oxidants in the environment: ozone (O<sub>3</sub>) and hydroxyl radicals (<sup>•</sup>OH). The adsorption of ozone (O<sub>3</sub>) on PS-NPs is investigated, showing a significant O<sub>3</sub> uptake. Moreover, for the first time, a reactivity constant with <sup>•</sup>OH is determined. We found a linear correlation between the kinetic constants measured for three different sizes of PS-NPs and the surface exposed by the particles. Degradation products (short chain carboxylic acids and aromatic compounds), obtained by direct and <sup>•</sup>OH-mediated photolysis of PS-NPs suspensions, are identified by high-resolution mass spectrometry. Irradiation of a PS-NPs suspension under natural sunlight for 1 year has shown the formation of formic acid and organic compounds similar to those found in riverine and cloud dissolved organic matter.</p><p>This work is crucial to assess the impact of NPs abiotic degradation in atmospheric and surface waters; indeed, the reactivity constant and the degradation products can be implemented in environmental models to estimate the contribution of NPs degradation to the natural dissolved organic matter in the aqueous phase. A preliminary simulation using APEX (Aqueous Photochemistry of Environmentally occurring Xenobiotics) (Bodrato and Vione, 2014) model shows that in NPs-polluted environments (10<sup>9</sup> particles mL<sup>-1</sup>) there is potential for NPs to significantly scavenge <sup>•</sup>OH, if the content of natural organic matter is not too high, as observed for surface and cloud water.</p><p>Allen, S., et al., 2019.  Nat. Geosci. 12, 339–344. https://doi.org/10.1038/s41561-019-0335-5<br>Bergmann, et al., 2019.  Sci. Adv. 5, eaax1157. https://doi.org/10.1126/sciadv.aax1157<br>Bodrato, M., Vione, D., 2014. Environ. Sci.: Processes Impacts 16, 732–740. https://doi.org/10.1039/C3EM00541K<br>Frias, J., Nash, R., 2019. Mar. Pollut. Bull. 138, 145–147. https://doi.org/10.1016/j.marpolbul.2018.11.022</p>

scholarly journals Explicit modeling of volatile organic compounds partitioning in the atmospheric aqueous phase

2012 ◽  
Vol 12 (9) ◽  
pp. 24095-24130
Author(s):  
C. Mouchel-Vallon ◽  
P. Bräuer ◽  
M. Camredon ◽  
R. Valorso ◽  
S. Madronich ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Water Content ◽  
Gas Phase ◽  
Aqueous Phase ◽  
Water Soluble ◽  
Chemical Mechanism ◽  
Organic Species ◽  
Cloud Water Content ◽  
Isoprene Oxidation

Abstract. The gas phase oxidation of organic species is a multigenerational process involving a large number of secondary compounds. Most secondary organic species are water-soluble multifunctional oxygenated molecules. The fully explicit chemical mechanism GECKO-A (Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere) is used to describe the oxidation of organics in the gas phase and their mass transfer to the aqueous phase. The oxidation of three hydrocarbons of atmospheric interest (isoprene, octane and α-pinene) is investigated for various NOx conditions. The simulated oxidative trajectories are examined in a new two dimensional space defined by the mean oxidation state and the solubility. The amount of dissolved organic matter was found to be very low (<2%) under a water content typical of deliquescent aerosols. For cloud water content, 50% (isoprene oxidation) to 70% (octane oxidation) of the carbon atoms are found in the aqueous phase after the removal of the parent hydrocarbons for low NOx conditions. For high NOx conditions, this ratio is only 5% in the isoprene oxidation case, but remains large for α-pinene and octane oxidation cases (40% and 60%, respectively). Although the model does not yet include chemical reactions in the aqueous phase, much of this dissolved organic matter should be processed in cloud drops and modify both oxidation rates and the speciation of organic species.

scholarly journals Excitation-Dependent Fluorescence Quantum Yield for Freshwater Chromophoric Dissolved Organic Matter from Northern Russian Lakes

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Svetlana Patsaeva ◽  
Daria Khundzhua ◽  
Oleg A. Trubetskoj ◽  
Olga E. Trubetskaya
Keyword(s):  
Organic Matter ◽  
Quantum Yield ◽  
Dissolved Organic Matter ◽  
Fluorescence Quantum Yield ◽  
Molecular Size ◽  
Reversed Phase ◽  
Chromophoric Dissolved Organic Matter ◽  
Excitation Wavelength ◽  
Fluorescence Detector ◽  
Wide Range

Advanced fluorescence analysis within the wide range of excitation wavelengths from 230 to 510 nm accompanied with chromatography was used to study natural chromophoric dissolved organic matter (CDOM) from three freshwater Karelian lakes. The influence of excitation wavelength (λex) on fluorescence quantum yield and emission maximum position was determined. The CDOM fluorescence quantum yield has reached a minimum at λex∼270–280 nm and a maximum at λex∼340–360 nm. It was monotonously decreasing after 370 nm towards longer excitation wavelengths. Analytical reversed-phase high-performance liquid chromatography with multiwavelength fluorescence detector characterized distribution of fluorophores between hydrophilic/hydrophobic CDOM parts. This technique revealed “hidden” protein-like fluorophores for some CDOM fractions, in spite of the absence of protein-like fluorescence in the initial CDOM samples. The humic-like fluorescence was documented for all hydrophilic and hydrophobic CDOM chromatographic peaks, and its intensity was decreasing along with peaks’ hydrophobicity. On contrary, the protein-like fluorescence was found only in the hydrophobic peaks, and its intensity was increasing along with peaks’ hydrophobicity. This work provides new data on the CDOM optical properties consistent with the formation of supramolecular assemblies controlled by association of low-molecular size components. In addition, these data are very useful for understanding the CDOM function in the environment.

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.

Measuring dissolved organic matter in estuarine and marine waters: size-exclusion chromatography with various detection methods

2018 ◽  
Vol 15 (7) ◽  
pp. 436 ◽  
Author(s):  
Gabriel Dulaquais ◽  
Johann Breitenstein ◽  
Matthieu Waeles ◽  
Rémi Marsac ◽  
Ricardo Riso
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Humic Substances ◽  
Size Exclusion Chromatography ◽  
Size Exclusion ◽  
Marine Waters ◽  
Wide Range ◽  
Exclusion Chromatography

Environmental contextDissolved organic matter (DOM), a key parameter in aquatic biogeochemistry, is difficult to characterise owing to its variable composition and structure. We report a chromatographic method with carbon, nitrogen and absorbance detection able to record the size distribution of DOM and changes in its composition. The method could be used to identify additional sources to river or coastal waters as well as monitoring the DOM size/reactivity continuum in open oceans. AbstractWe studied the performance and limitations of size-exclusion chromatography with organic carbon, ultraviolet and organic nitrogen detectors (SEC-OCD-UVD-OND) for characterising dissolved organic matter (DOM) in estuarine and marine waters. We identified a strong salt effect on dissolved organic carbon (DOC) determination; however, calibration gave good results at salinity levels close to those of the sample analysed (ΔS ± 2 psu (practical salinity units)), with limited matrix effects, enabling an accurate measurement of DOC, as demonstrated by an intercalibration exercise. The repeatability, reproducibility and limit of detection (3 ppb for both carbon and nitrogen) for the three detectors demonstrated the robustness of the method for a wide range of natural waters, including carbon-rich freshwaters and deep seawaters with low carbon content (6000 ppb-C to 300 ppb-C). Deeper analysis of the SEC demonstrated that proteins and polysaccharides are partly fractionated within the column, and that terrestrial humic substances, isolated on a XAD-8 resin, can also be eluted in both fractions associated with biopolymers and low-molecular-weight neutrals. Application of the method to the study of DOM along a macrotidal estuary that was influenced by agricultural activities revealed significant changes in its composition despite a conservative DOC distribution. Distinct origins and qualities of high-molecular-weight (>500 kDa) organic compounds were identified for riverine and marine end-members. A new diagram to track changes in DOM lability is proposed to complete the humic-substances diagram.

scholarly journals Effects of dissolved organic matter derived from forest leaf litter on biodegradation of phenanthrene in aqueous phase

2017 ◽  
Vol 324 ◽  
pp. 516-525 ◽  
Author(s):  
Dan Cai ◽  
Xiuhong Yang ◽  
Shizhong Wang ◽  
Yuanqing Chao ◽  
J.L. Morel ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Leaf Litter ◽  
Aqueous Phase ◽  
Forest Leaf Litter

Inversion of Chromophoric Dissolved Organic Matter From EO-1 Hyperion Imagery for Turbid Estuarine and Coastal Waters

2013 ◽  
Vol 51 (6) ◽  
pp. 3286-3298 ◽  
Author(s):  
Weining Zhu ◽  
Qian Yu
Keyword(s):  
Organic Matter ◽  
High Resolution ◽  
Dissolved Organic Matter ◽  
Coastal Waters ◽  
Ocean Color ◽  
Chromophoric Dissolved Organic Matter ◽  
Significant Implication ◽  
Coastal Regions ◽  
Data Set ◽  
Wide Range

The significant implication of chromophoric dissolved organic matter (CDOM) for water quality and biogeochemical cycle leads to an increasing need of CDOM monitoring in coastal regions. Current ocean-color algorithms are mostly limited to open-sea water and have high uncertainty when directly applied to turbid coastal waters. This paper presents a semianalytical algorithm, quasi-analytical CDOM algorithm (QAA-CDOM), to invert CDOM absorption from Earth Observing-1 (EO-1) Hyperion satellite images. This algorithm was developed from a widely used ocean-color algorithm QAA and our earlier extension of QAA. The main goal is to improve the algorithm performance for a wide range of water conditions, particularly turbid waters in estuarine and coastal regions. The algorithm development, calibration, and validation were based on our intensive high-resolution underwater measurements, International Ocean Color Coordinating Group synthetic data, and global National Aeronautics and Space Administration Bio-Optical Marine Algorithm Data Set data. The result shows that retrieved CDOM absorption achieved accuracy (root mean square error (RMSE) = 0.115 m-1andR2= 0.73) in the Atchafalaya River plume area. QAA-CDOM is also evaluated for scenarios in three additional study sites, namely, the Mississippi River, Amazon River, and Moreton Bay, whereag(440) was in the wide range of 0.01-15 m-1. It resulted in expected CDOM distribution patterns along the river salinity gradient. This study improves the high-resolution observation of CDOM dynamics in river-dominated coastal margins and other coastal environments for the study of land-ocean interactive processes.

Chemical insights into the ice nucleating ability of macromolecules in immersion freezing

2020 ◽  
Author(s):  
Nadine Borduas-Dedekind ◽  
Anna Miller ◽  
Sophie Bogler ◽  
Jon Went
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Matrix Effects ◽  
Complex Mixture ◽  
Ice Nucleation ◽  
Heating Process ◽  
Biological Macromolecules ◽  
Top Down ◽  
Wide Range ◽  
Immersion Freezing

&lt;p&gt;Cloud glaciation is an atmospheric process with important implications for climate and weather. Indeed, clouds made of liquid water and of ice crystals impact the global radiative balance of the atmosphere by reflecting incoming solar radiation and by absorbing outgoing terrestrial radiation. The relevance of ice nucleating particles (INPs) to the atmosphere depends on three main factors, namely on (1) their atmospheric concentration, (2) their freezing temperature and relative humidity, and (3) their freezing mechanism (Cziczo et al., 2013). Research on characterizing ice nucleating organic matter often takes a &amp;#8220;top-down&amp;#8221; approach where a whole sample of a complex mixture of organic, often biological, macromolecules is subjected to separation techniques and heat treatments to identify IN active sub-components. Studies have used this approach for characterizing bulk soil organic matter, volcanic ash and biological macromolecules from pollen, fungi, and bacteria.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;We and others have recently found that dissolved organic matter collected from rivers and swamps surprisingly contain active INP (Borduas-Dedekind et al., 2019; Knackstedt et al., 2018; Moffett et al., 2018). Yet, all three studies state that it is unclear which sub-component of the dissolved organic matter is responsible for the ice nucleating ability. There are clear challenges in attributing the ice nucleating ability when starting with a complex mixture of organic and/or biological material, including matrix effects, impurities accumulated through the separation and/or heating process and lack of molecule identity.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;We present here a &amp;#8220;bottom-up&amp;#8221; approach to compliment the top-down approach for atmospheric ice nucleation research of macromolecules. Using our home-built drop Freezing Ice Nuclei Counter (FINC) with automated imaging, a range of macromolecules were investigated. Indeed, we have analysed a wide range of dissolved organic matter subcomponents including proteins and fulvic acids. We find a range of ice nucleating ability. We find that lignin, the second most abundant biopolymer in plants, is ice active with 50% frozen fraction temperatures (T&lt;sub&gt;50&lt;/sub&gt;) at &amp;#8211;18 &amp;#176;C at a concentration of 100 mg C/L. Furthermore, we have investigated the ice nucleation ability of common diatom exudates and found that at atmospherically relevant concentration they are likely not ice active in immersion freezing within the detection of our FINC instrument. We are currently investigating the effect of atmospheric processing on these macromolecules with the goal of understanding how macromolecules&amp;#8217; ice activity evolves over their one-week lifetime in the atmosphere.&lt;/p&gt;

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