Download or read book Relating Dissolved Organic Matter Composition and Photochemistry with High Resolution Mass Spectrometry written by Andrew Chapin Maizel and published by . This book was released on 2017 with total page 301 pages. Available in PDF, EPUB and Kindle. Book excerpt: The irradiation of dissolved organic matter (DOM) produces reactive intermediates, such as excited triplet states of dissolved organic matter (3DOM), which contribute to the degradation of environmental contaminants. An understanding of how DOM composition determines the production of reactive intermediates is useful for predictions of contaminant fate and for relating the environmental processing of DOM to its photochemistry. To compare the reactivity of common 3DOM probe compounds, the photoreactivity of diverse, environmentally relevant waters was quantified with trans,trans-hexadienoic acid, 2,4,6-trimethylphenol, and furfuryl alcohol under ambient and standardized conditions. Measurements with each probe, including apparent quantum yields and pseudo-steady state concentrations, were found to exhibit unique sensitivities to variation in solution conditions. Comparisons of apparent quantum yields under standardized conditions suggest that the probe compounds each react with different 3DOM populations. 3DOM photoreactivity varies with molecular weight, but the underlying mechanisms are unclear. Therefore, the photochemistry and composition of ultrafiltration-fractionated fulvic acid isolates were compared with reactive intermediate probes compounds and Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). Terrestrially derived DOM was increasingly aromatic with molecular weight, while microbially derived DOM was invariant. 3DOM pseudo-steady state concentrations decreased with molecular weight due to increased 3DOM quenching, rather than variation in 3DOM formation rates. In order to relate DOM processing in natural systems to altered composition and photoreactivity, DOM from related lakes of different trophic status was evaluated with FT-ICR MS and reactive intermediate probe compounds. The presence of highly aromatic formulas, similar to lignin and tannin, correlated with 3DOM formation and light absorbance. Conversely, aliphatic formulas correlated with enhanced 3DOM quantum yields and environmental persistence. To investigate the unique composition and photochemistry of DOM from aquatic microbial sources, DOM from a wastewater treatment plant was evaluated by FT-ICR MS and UV-visible spectroscopy. Wastewater DOM contained molecular formulas that were compositionally similar to lipids, proteins, carbohydrates, and lignin, and were enriched in heteroatoms such as N, S, P, and Cl. Secondary treatment increased highly aromatic formulas and increased the number of identified heteroatom containing formulas, while other treatment stages produced smaller changes in DOM composition.

Download or read book Biogeochemistry of Marine Dissolved Organic Matter written by Dennis A. Hansell and published by Academic Press. This book was released on 2014-10-02 with total page 712 pages. Available in PDF, EPUB and Kindle. Book excerpt: Marine dissolved organic matter (DOM) is a complex mixture of molecules found throughout the world's oceans. It plays a key role in the export, distribution, and sequestration of carbon in the oceanic water column, posited to be a source of atmospheric climate regulation. Biogeochemistry of Marine Dissolved Organic Matter, Second Edition, focuses on the chemical constituents of DOM and its biogeochemical, biological, and ecological significance in the global ocean, and provides a single, unique source for the references, information, and informed judgments of the community of marine biogeochemists. Presented by some of the world's leading scientists, this revised edition reports on the major advances in this area and includes new chapters covering the role of DOM in ancient ocean carbon cycles, the long term stability of marine DOM, the biophysical dynamics of DOM, fluvial DOM qualities and fate, and the Mediterranean Sea. Biogeochemistry of Marine Dissolved Organic Matter, Second Edition, is an extremely useful resource that helps people interested in the largest pool of active carbon on the planet (DOC) get a firm grounding on the general paradigms and many of the relevant references on this topic. Features up-to-date knowledge of DOM, including five new chapters The only published work to synthesize recent research on dissolved organic carbon in the Mediterranean Sea Includes chapters that address inputs from freshwater terrestrial DOM

Download or read book Linking Optical and Chemical Properties of Dissolved Organic Matter in Natural Waters written by Christopher L. Osburn and published by Frontiers Media SA. This book was released on 2017-01-17 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: A substantial increase in the number of studies using the optical properties (absorbance and fluorescence) of dissolved organic matter (DOM) as a proxy for its chemical properties in estuaries and the coastal and open ocean has occurred during the last decade. We are making progress on finding the actual chemical compounds or phenomena responsible for DOM’s optical properties. Ultrahigh resolution mass spectrometry, in particular, has made important progress in making the key connections between optics and chemistry. But serious questions remain and the last major special issue on DOM optics and chemistry occurred nearly 10 years ago. Controversies remain from the non-specific optical properties of DOM that are not linked to discrete sources, and sometimes provide conflicting information. The use of optics, which is relatively easier to employ in synoptic and high resolution sampling to determine chemistry, is a critical connection to make and can lead to major advances in our understanding of organic matter cycling in all aquatic ecosystems. The contentions and controversies raised by our poor understanding of the linkages between optics and chemistry of DOM are bottlenecks that need to be addressed and overcome.

Download or read book The Influence of Dissolved Organic Matter Composition on Its Reactivity in Natural and Engineered Systems written by Reid Milstead and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dissolved organic matter (DOM) is a complex heterogeneous mixture of organic compounds that is found in all water systems. DOM is derived from both terrestrial and microbial sources. The composition of DOM can vary greatly depending on a number of variables, including time of year, surrounding groundcover type, and water column depth. The characterization of DOM composition is increasingly performed using high-resolution mass spectrometry, although different instrumentation and techniques may yield different results. Importantly, DOM plays a key role in a number of chemical processes in both natural and engineered systems, such as the generation of carbon dioxide (CO2) from surface waters, the degradation of aquatic contaminants, and the formation of disinfection byproducts (DBPs) during drinking water treatment. The composition of DOM determines its reactivity in all of these processes. Using both bulk and high-resolution analytical techniques, the photooxidation of DOM can be explored. DOM compounds that are more oxidized and aromatic tend to be associated with the consumption of oxygen and the production of CO2. Bulk scale measurements show that DOM becomes less aromatic and lower in molecular weight as a result of partial photooxidation. High-resolution mass spectrometry also provides evidence of oxygen addition and the loss of CO2 from DOM during irradiation experiments. However, the chemical formulas that are most photolabile vary depending on the initial composition of DOM. Using light exposure experiments the kinetics of degradation of four contaminants were quantified for a large set of diverse waters. Using this information, we evaluated the relationships between indirect photolysis rate constants and the formation of photochemically produced reactive intermediates (PPRI) using linear regression analysis. Additionally, quencher experiments were performed to identify the PPRI associated with the degradation of each contaminant in all waters. Triplet state DOM (3DOM) and singlet oxygen (1O2) were identified as critical for atorvastatin, carbamazepine, and sulfadiazine, while hydroxyl radical (•OH) is important for benzotriazole. Our results suggest that quenching experiments should be used with caution due to the non-targeted nature of quenching compounds and the interconnection of PPRI. All of these factors result in probe compounds possibly overstating the importance of PPRI in the indirect photolysis of common contaminants. The characterization of DOM in drinking waters reveals a high degree of variability in DOM composition and reactivity with chlorine, particularly in groundwater samples. Despite the variability in DOM composition, novel DBPs with up to three halogen substituents are compositionally similar among all waters. These novel DBPs are positively correlated with trihalomethane and, to a lesser extent, the formation of haloacetonitriles. This suggests that some low molecular weight DBPs and novel DBPs detected via high-resolution mass spectrometry share similar aromatic precursors, providing evidence that low molecular weight DBPs are useful proxies for the formation of unknown, unidentified high molecular weight DBPs. Compared to Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS), Orbitrap MS yields significantly fewer formula matches and appears to have a bias towards sulfur-containing formulas and against nitrogen-containing formulas. Additionally, the choice of calibration method is particularly important for the less powerful Orbitrap MS. The matched formulas yielded from Orbitrap MS tend to be more oxidized and less highly saturated than those yielded by FT-ICR MS. Despite these differences, the formulas produced by both instruments tend to yield similar relative differences between samples, suggesting that Orbitrap MS is an acceptable replacement for FT-ICR MS in some cases.

Download or read book The Influence of Dissolved Organic Matter Composition on Its Reactivity in Natural and Engineered Systems written by Reid Milstead and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dissolved organic matter (DOM) is a complex heterogeneous mixture of organic compounds that is found in all water systems. DOM is derived from both terrestrial and microbial sources. The composition of DOM can vary greatly depending on a number of variables, including time of year, surrounding groundcover type, and water column depth. The characterization of DOM composition is increasingly performed using high-resolution mass spectrometry, although different instrumentation and techniques may yield different results. Importantly, DOM plays a key role in a number of chemical processes in both natural and engineered systems, such as the generation of carbon dioxide (CO2) from surface waters, the degradation of aquatic contaminants, and the formation of disinfection byproducts (DBPs) during drinking water treatment. The composition of DOM determines its reactivity in all of these processes. Using both bulk and high-resolution analytical techniques, the photooxidation of DOM can be explored. DOM compounds that are more oxidized and aromatic tend to be associated with the consumption of oxygen and the production of CO2. Bulk scale measurements show that DOM becomes less aromatic and lower in molecular weight as a result of partial photooxidation. High-resolution mass spectrometry also provides evidence of oxygen addition and the loss of CO2 from DOM during irradiation experiments. However, the chemical formulas that are most photolabile vary depending on the initial composition of DOM. Using light exposure experiments the kinetics of degradation of four contaminants were quantified for a large set of diverse waters. Using this information, we evaluated the relationships between indirect photolysis rate constants and the formation of photochemically produced reactive intermediates (PPRI) using linear regression analysis. Additionally, quencher experiments were performed to identify the PPRI associated with the degradation of each contaminant in all waters. Triplet state DOM (3DOM) and singlet oxygen (1O2) were identified as critical for atorvastatin, carbamazepine, and sulfadiazine, while hydroxyl radical (•OH) is important for benzotriazole. Our results suggest that quenching experiments should be used with caution due to the non-targeted nature of quenching compounds and the interconnection of PPRI. All of these factors result in probe compounds possibly overstating the importance of PPRI in the indirect photolysis of common contaminants. The characterization of DOM in drinking waters reveals a high degree of variability in DOM composition and reactivity with chlorine, particularly in groundwater samples. Despite the variability in DOM composition, novel DBPs with up to three halogen substituents are compositionally similar among all waters. These novel DBPs are positively correlated with trihalomethane and, to a lesser extent, the formation of haloacetonitriles. This suggests that some low molecular weight DBPs and novel DBPs detected via high-resolution mass spectrometry share similar aromatic precursors, providing evidence that low molecular weight DBPs are useful proxies for the formation of unknown, unidentified high molecular weight DBPs. Compared to Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS), Orbitrap MS yields significantly fewer formula matches and appears to have a bias towards sulfur-containing formulas and against nitrogen-containing formulas. Additionally, the choice of calibration method is particularly important for the less powerful Orbitrap MS. The matched formulas yielded from Orbitrap MS tend to be more oxidized and less highly saturated than those yielded by FT-ICR MS. Despite these differences, the formulas produced by both instruments tend to yield similar relative differences between samples, suggesting that Orbitrap MS is an acceptable replacement for FT-ICR MS in some cases.

Download or read book Photochemistry of Dissolved Organic Matter written by Stephen Andrew Timko and published by . This book was released on 2014 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt: Constructed wetlands have the potential to provide low-energy treatment of pharmaceuticals and other micropollutants via photolysis. Natural dissolved organic matter (DOM) reacts with sunlight to produce reactive species such as singlet oxygen and excited triplet states of DOM that react quickly and efficiently with contaminants. To study the photo-chemistry of DOM, a unique solar-simulation system was developed, allowing for semi-continuous monitoring of absorbance and fluorescence spectra throughout the irradiation. This system was utilized to investigate the effect of solution pH on the fluorescence properties and degradation of DOM. For the first time, parallel factor (PARAFAC) analysis was utilized to deconvolute photo-labile, photo-stable, and pH- dependent fluorescent components during irradiation. Fluorescence is highly pH dependent, and as pH increases, the total amount of fluorescence loss, and the rate at which it is lost, increases significantly. This has important implications in treatment systems, as the photo-reactivity of DOM will change when pH gradients or fluctuations are observed. The photo-degradation of organic matter collected from a depth profile (0-4,500 m) the Sargasso Sea showed increased reactivity with increasing depth. Ultra-high resolution mass spectrometry (FT-MS) was used to characterize the samples, and correlation analyses between the fluorescence data and mass spectra revealed that high molecular weight, aromatic, and possibly polyphenolic compounds are contributing the most to the fluorescence properties that show the most reactivity in marine samples.Production of singlet oxygen, hydroxyl radical, and triplet excited states of DOM along two riverine transects in the Everglades were measured. The abundance of fluorescence PARAFAC components was compared to the reactive species production, and suggested that terrestrial organic matter may be more efficient producers of reactive species than microbial- or seagrass- derived organic matter.Finally, the relationship between optical properties of DOM samples collected around the world and their reactivity were investigated. Photo-irradiations and pH titrations were performed on all samples, and mass spectra collected via FT-MS. Humification indices, the biological index (BIX), and spectral slope from 275-295 nm were found to be most closely tied to changes in the mass spectra of the samples, and showed strong relationship to DOM source.

Download or read book High Resolution Molecular Characterization of Photochemical and Microbial Transformation of Dissolved Organic Matter in Temperate Streams of Different Watershed Land Use written by Xiaping Li and published by . This book was released on 2014 with total page 73 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of the present study was to provide better understanding of the effects of watershed land use on molecular composition of streamwater DOM and molecular transformations associated with photochemical and microbial processing of DOM. We compared DOM from headwater streams draining forest-dominated watersheds (FW) and pasture-dominated watersheds (PW) in the lower Chesapeake Bay region (Virginia, USA). Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry analysis was conducted on streamwater DOM prior to and after laboratory incubations: 1) bacteria-only incubations; 2) light-only incubations; and 3) combined light+bacterial incubations. Results showed that DOM in FW streams and PW streams differed in molecular characteristics--the former was characterized by greater structural complexity and aromaticity, higher proportions of condensed aromatic molecules and black carbon-like components, while the latter was higher in the proportions of lipid-like components, protein-like components and aliphatic compounds. Relative to DOM from FW streams, DOM from PW streams was more reactive to bacterial transformation. Protein-like components, lipid-like components and unsaturated hydrocarbon-like components are primarily responsible for the changes associated with bacterial transformation of DOM. However, similar behavior was also observed for DOM in FW streams and PW streams under the influence of bacterial and photochemical processes. Bacterial transformation reduced the proportions of lipid-like components but increased the proportions of lignin-like components and carboxyl-rich alicyclic molecule-like components, indicating that lipid-like components was a bioreactive class while lignin-like components and carboxyl-rich alicyclic were resistant to bacterial processing. Photochemical processes, alone or combined with microbial alterations, increased the proportions of protein-like components, which may be due to the light stimulation of autochthonous production of protein-like components, and increased the relative abundance of carboxyl-rich alicyclic molecule-like components, which indicates the refractory nature of these molecules. Photochemical processes also significantly reduced the amount of dissolved black carbon-like components, which suggests dissolved black carbon was a photoreactive class, countering the conventional view that black carbon was an inter group in carbon cycle. Collectively, these findings suggest that human land use in upstream watersheds may lead to alterations to the molecular composition of streamwater DOM as well as to its behavior to photochemical and microbial processing.

Download or read book Structure and Reactivity of Dissolved Organic Matter as Determined by Ultra high Resulution i e Resolution Electrospray Ionization Mass Spectrometry written by Sunghwan Kim and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: There is currently little molecular level information available for dissolved organic matter (DOM). In this study, electrospray ionization mass spectrometry (ESI-MS) with ultra-high resolution has been used to study DOM at a molecular level. High resolution mass spectra of DOM routinely contains several thousand peaks with a multitude of peaks in each nominal mass region. To study the spectra at the molecular level, the individual peaks need to be examined, a process that is arduous and time consuming. In this study, use of the van Krevelen diagram is demonstrated as an innovative graphical interpretation tool for ultra-high resolution mass spectrometric data of DOM. Plotting of ESI-FT ICR-MS data from DOM indicates that lignin or tannin type molecules compose the main portion of readily ionizable DOM molecules. In addition, many peaks corresponding to hydrogen deficient molecules are observed. These hydrogen deficient molecules found in DOM samples can be related to black carbon derived material. The process of consumption and utilization of DOM by microorganisms is investigated by employing plug-flow thin film bioreactors and ultra-high resolution mass spectrometry of DOM from inflow and outflow water samples. It is shown that the DOM molecules are subject to modifications to lower molecular weight molecules by micro-organisms. Applying van Krevelen analyses for mass spectral data reveals that relative importance of the peaks with low H/C ratios (especially the peaks in the region that has been assigned to black carbon molecules) are generally increased from inflow to outflow water samples. This is consistent in two sets of bioreactor samples collected from two different locations. The current study clearly demonstrates that the method employed in a significant breakthrough in the ability to recognize such a biologically refractory form of DOM.

Download or read book Towards an Understanding of Dissolved Organic Matter Molecular Composition and Reactivity in the Environment written by Barbara Cottrell and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Characterization of Dissolved Organic Matter in Wastewater Using Liquid Chromatography high Resolution Mass Spectrometry written by Yaroslav Verkh and published by . This book was released on 2019 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: Individual hazardous chemicals and substance mixtures with synergistic toxicity ef-fects occur in the dissolved organic matter (DOM) of wastewater and negatively im-pact human health. Yet a large number of chemicals and their treatment by-products in wastewater makes the tracking of individual compounds nearly impossible and de-mands new analytical strategies. The thesis describes the development and evaluation of non-targeted and suspect anal-ysis methods aimed at the transformation of DOM and micro-contaminants of interest during wastewater treatment using liquid chromatography-high-resolution mass spec-trometry (LC-HRMS) data. On one hand, a non-targeted method to track transformations of DOM in a multiphase wastewater treatment using LC-HRMS data was developed. LC-MS signals were ex-tracted, aligned, and had their isotopologues clustered and elemental composition pre-dicted using open license software MZmine 2 in a way that conceptually prioritized the detection of anthropogenic compounds.

Download or read book Molecular Composition of Dissolved Organic Matter Controls Metal Speciation and Microbial Uptake written by Vaughn Mangal and published by . This book was released on 2019 with total page 596 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aquatic contaminant mobility and biological availability is strongly governed by the complexation oforganic and inorganic ligands. Dissolved organic matter (DOM) is a complex, heterogeneous mixture of organic acids, amino acids, lipids, carbohydrates and polyphenols that varyin composition and cancomplex to dissolved metalsthereby altering their fate in aquatic systems. The research conductedin this doctoral dissertation addresses1) how DOM compositiondiffers betweenphytoplanktontaxa and 2) how DOM composition affectsmetal speciation and its subsequent microbial bioavailabilityin laboratory and field conditions.To accomplish this, a series of analytical methods were developed and applied toquantifythiols, sulphur containing DOM moieties,and the molecular composition of DOM.The works presented in this thesisrepresentsone of the first comprehensiveand multipronged analyses of the impact of phytoplankton metabolite exudates on microbial metalbioavailability.This dissertationdemonstratedthe analytical versatility of high-resolution mass spectrometry as a tool for compound specific information, as well as having the capabilities to obtain speciation information of organometallic complexes. Thework presentedin this PhDstrengthens the understanding compositional differences of both autochthonous and allochthonous DOM andtheir effects on metal biogeochemistry. Keywords:Dissolved organic matter, Mercury, Cadmium, High Resolution Mass Spectrometry, Phytoplankton, Churchill, Metal Bioavailability.

Download or read book A Highly Resolved Molecular level Interrogation of Dissolved Organic Matter DOM Complexity and Composition in a Snowmelt affected System written by Gregory Ian Ball and published by . This book was released on 2013 with total page 303 pages. Available in PDF, EPUB and Kindle. Book excerpt: To better constrain the chemical composition and molecular diversity of dissolved organic matter (DOM) in natural waters, comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GCxGC-TOF-MS) was applied for the first time as a novel technique towards its characterization. This technique chromatographically resolved thousands of peaks per sample and yielded a level of chromatographic resolution that approached the effective mass resolving capabilities of Fourier transform ion cyclotron resonance mass spectrometers (FT-ICR-MS). As with peaks resolved by FT-ICR-MS, the chemical identities of peaks resolved by GCxGC-TOF-MS (> 90 %) remained largely unknown, however GCxGC-TOF-MS provided an independent means by which peaks could be tied to known compounds, which included (1) electron-impact mass spectra accompanying each peak and (2) the separation of structurally related compounds along predictable trajectories in two-dimensional GCxGC space. The development and implementation of this methodology (Chapter II) identified 451 compounds across diverse CuO-oxidized, TMS-derivatized samples and provided a basis for identifying 313 compounds (6.5 % of peaks) within a solid phase extracted (SPE) DOM sample isolated from the Upper Truckee River, Lake Tahoe, California, USA. This represented the most comprehensive compound-specific characterization of a DOM sample to date and an approximate three-folding of compounds previously identified within this oxidation product mixture, a subject of three decades of extensive study. Novel compounds were discovered, isothermal retention in the second dimension was predicted using molecular mechanics modeling, and evidence for a previously unexplored isomeric diversity within DOM was presented. Thousands (> 90 %) of GCxGC-resolvable peaks, however, resisted facile structural elucidation and motivated the development and implementation of a methodology (Chapter III) by which the chemical distance between specific peak populations (defined by chromatographic localization and peak intensity) of two samples could be quantified. Performed pair-wise across a sample set of Lake Tahoe Basin SPE-DOM samples, distance matrices amenable to linkage analysis were constructed, hierarchical relationships of similarity between peak populations were exposed, and cluster analysis identified sample groupings that were subsequently corroborated by high resolution proton nuclear magnetic resonance spectroscopy (1H-NMR) of CuO-oxidized DOM. Interpretively revealing results were obtained, including the likely identification of peak populations specific to degraded terrestrial OM. In Chapter IV, a 13,500-year organic geochemical record ([delta]13C, [delta15N, TOC, TN, C:N) spanning the Holocene was created for Fallen Leaf Lake (FLL), California Sierra Nevada, USA. This was complemented by a 4,500-year lignin phenol record which spanned the Pleistocene-Holocene transition. These records were interpreted within the context of Holocene climate and seismicity and a post-glacial history of flora succession was proposed. In Chapter V a newly developed, high resolution, two-dimensional, heart-cutting preparative capillary gas chromatograph (PCGC) was developed, applied, and successfully evaluated as a tool for the enrichment of &mug quantities of material destined for natural abundance radiocarbon (14C) analysis by accelerator mass spectrometry (AMS).

Download or read book Aquatic Organic Matter Fluorescence written by Paula G. Coble and published by Cambridge University Press. This book was released on 2014-07-14 with total page 407 pages. Available in PDF, EPUB and Kindle. Book excerpt: A core text on principles, laboratory/field methodologies, and data interpretation for fluorescence applications in aquatic science, for advanced students and researchers.

Download or read book Surface Water Photochemistry written by Paola Calza and published by Royal Society of Chemistry. This book was released on 2015-11-20 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt: Borne out of the current widespread interest in the pollution of water bodies, this book explores the latest research concerning the photochemical fate of organic pollutants in surface water. The main objective is to give insight into both the functioning of ecosystems and the behaviour of emerging pollutants in those ecosystems. Particular importance is dedicated to techniques that can be used in the field and in the laboratory for the detection of pollutants and of their transformation intermediates. The inclusion of photochemical processes that have not gained previous coverage will afford the reader novel insights, whilst the focus on modelling and transformation intermediates will ensure the title's relevance to academics, the chemical manufacturing industries and environmental assessment experts alike.

Download or read book Molecular and Optical Characterization of Dissolved Organic Matter in the Central Arctic Ocean written by Xianyu Kong and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dissolved organic matter (DOM) in the ocean is a complex mixture of molecules derived from autochthonous (marine) or allochthonous (terrestrial) origins. DOM plays an important role in marine biogeochemical cycles by attenuating light available for primary production, serving as an energy and nutrient source for heterotrophic communities, regulating the ultraviolet and visible light absorption, undergoing photochemical processing, and acting as a trace metal ligand. DOM in the Central Arctic Ocean (CAO) is influenced by increased freshwater input and associated terrestrial materials in recent decades due to rapid climate change. The quantification of DOM sources (terrestrial versus marine) in the water column of the CAO is not well constrained. Few studies have systematically investigated the seasonality and spatial variability of DOM by combining optical and molecular-level analytical techniques in the CAO, especially during winter. State of the art chemical characterization of DOM is subject to major challenges: Solid phase extraction (SPE) that is often used to desalt and pre-concentrate marine DOM introduces chemical fractionation effects, which limits the comparability between analytical results for original samples and those carried out for SPE-DOM. There is no specific method to quantify fractionation effects, nor specific guidelines to avoid fractionation. Using mass spectrometry, quantitative DOM analyses is challenged by selective ionization of molecules and the large number of unresolved structural isomers that prevent classical external calibration. In the first part of this thesis, a method was developed to quantitatively track optical or chemical fractionation during SPE and investigate the potential mechanisms. We found a decrease in extraction efficiency of dissolved organic carbon (DOC), fluorescence and absorbance, and polar organic substances with increasing carbon loading on the SPE column. As the surface loading of the solid-phase increased, the dominant extraction mechanism shifted from PPL physisorption to increased DOM self-assembly, resulting in optical and chemical fractionation. The relative DOC loading (DOCload) was used to assess the carbon loading during SPE, and a double sigmoid model was applied to our online permeate fluorescence data as a function of DOCload, which allowed us to assess the degree of variability induced by DOCload. This finding has ample implications for the future processing and previous interpretation of chemical characteristics in SPE-DOM of aquatic organic matter. For the second part of the thesis, original water samples were acquired from the “Multidisciplinary Drifting Observatory for the Study of Arctic Climate” (MOSAiC) expedition. The water column samples covered a full year (2019 / 2020) and included the regions Amundsen Basin, western Nansen Basin and Yermak Plateau and Fram Strait. Samples were analyzed using optical spectroscopy to determine chromophoric DOM (CDOM) and fluorescent DOM (FDOM). In addition, a new method was applied that used Fourier transform ion cyclotron resonance mass spectrometry hyphenated to high performance liquid chromatography (LC-FTMS). The method allowed DOM analysis in original filtered water and thus avoided the chemical fractionation introduced by SPE. During the MOSAiC expedition, DOC concentrations and CDOM characteristics in the water column were primarily influenced by regional differences. These differences were largely dependent on terrestrially-derived DOM (tDOM) input by the transpolar drift (TPD) as indicative of average 136% and 45% higher aCDOM(350) and DOC concentration, respectively, in the Amundsen compared to the western Nansen Basin and Yermak Plateau, and slightly modified by seasonal changes. Despite the convenient identification of tDOM, optical spectroscopy was not suitable to quantify the contribution of tDOM to bulk DOC or to track sea ice derived DOM in the water column. In contrast, using LC-FTMS, we found quantitative linear correlation between the summed mass peak magnitudes for each sample (intsum) and DOC concentration. By combing LC-FTMS and source identification with optical parameters, we were able to quantify DOM sources (terrestrial versus marine) in the water column: 83% of the summed peak magnitude of all samples could be related to marine or terrestrial sources. tDOM contributed ∼17% (or 8 μmol kg-1) to deep DOC (~2000 m) in the CAO and was more refractory and had a higher state of unsaturation compared to marine DOM. The quantitative characterization of DOM in original seawater from different origin is a major step in the field of research. It provides a unique and new insight into the molecular changes in marine DOM composition and an improved understanding of the terrestrial DOM distribution in the CAO.

Download or read book Wunderli Karl 1881 1961 written by and published by . This book was released on 1901 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Zeitungsausschnitte.

Download or read book Linking Optical and Chemical Properties of Dissolved Organic Matter in Natural Waters written by and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A substantial increase in the number of studies using the optical properties (absorbance and fluorescence) of dissolved organic matter (DOM) as a proxy for its chemical properties in estuaries and the coastal and open ocean has occurred during the last decade. We are making progress on finding the actual chemical compounds or phenomena responsible for DOM's optical properties. Ultrahigh resolution mass spectrometry, in particular, has made important progress in making the key connections between optics and chemistry. But serious questions remain and the last major special issue on DOM optics and chemistry occurred nearly 10 years ago. Controversies remain from the non-specific optical properties of DOM that are not linked to discrete sources, and sometimes provide conflicting information. The use of optics, which is relatively easier to employ in synoptic and high resolution sampling to determine chemistry, is a critical connection to make and can lead to major advances in our understanding of organic matter cycling in all aquatic ecosystems. The contentions and controversies raised by our poor understanding of the linkages between optics and chemistry of DOM are bottlenecks that need to be addressed and overcome.