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 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 Structural Characterization of Freshwater Dissolved Organic Matter from Arctic and Temperate Climates Using Novel Analytical Approaches written by Gwen C. Woods and published by . This book was released on 2012 with total page 428 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Chemical Characterization of Refractory Dissolved Organic Matter written by Neal Ken Arakawa and published by . This book was released on 2016 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt: The primary objective of this thesis was to combine a chemical degradation technique together with an analytical framework centered primarily around gas chromatography (GC) to more fully interrogate the composition of aquatic dissolved organic matter (DOM). Previous studies had suggested that aliphatic compounds could represent a significant fraction of refractory organic matter isolated by solid phase extraction (SPE). These studies had also uncovered the vast complexity of DOM. Gas chromatography coupled to mass spectrometry provides superior separation capability and is ideal for examining complex mixtures of lipid-derived molecules. As such I sought to develop a comprehensive GC analysis methods to provide molecular level information for DOM isolated by solid phase extraction (SPE) onto a hydrophobic resin- PPL (Agilent Bond Elut). In Chapter II, a comprehensive chemical reduction procedure was developed and first applied to the environmental DOM standard Suwannee River Fulvic Acid (SRFA) as a proxy for marine DOM. The resulting hydrocarbons were amenable to comprehensive gas chromatography time-of-flight mass spectrometry (GCxGC-TOF-MS), and effectively resolved into multiple series of alicyclic, unsaturated compounds. This was the first direct demonstration of the isomeric complexity of aquatic DOM. Similar alicyclic compounds were recovered from the reduction of terrestrial source material, implicating resin acids and sterols as potential precursors of SRFA. In Chapter III the reduction process was applied to marine surface DOM from the Scripps Institution of Oceanography Pier, and similar alicylic compounds were found. The GCxGC-TOF-MS identified carbon backbones closely resembling carotenoids, implicating these ubiquitous and highly reactive biomolecules as the source of a significant fraction of DOM accumulating in the marine water column. The structural assignment was supported by the identification of carotenoid derived resonances in two dimensional nuclear magnetic resonance (NMR) spectra, which indicated that these molecules were highly oxidized compared to the parent molecules consistent with their present in DOM. Following up on this work in Chapter IV the carotenoid [beta]-carotene was irradiated with natural sunlight to test the hypothesis that photodegradation was one pathway that converted carotenoids into water-soluble degradation products. The first finding was that the reaction produced a series of compounds identical to compounds isolated from marine DOM. The second important result was that the reaction produced a complex mixture of isomers from a single compound that helps to at least partly explain the compositional diversity in marine DOM. Together, the data in Chapters III and IV allowed us to link a large fraction of DOM to a ubiquitous biomolecule that can now serve as a model for studies examining the formation and fate of DOM that accumulates in the ocean on long timescales. Finally, in Chapter V we sought to examine how the composition of DOM -- both the complex alicyclic fraction and small, polar biomolecules, which are considered a "fresher" signal of biological input -- evolved across a salinity gradient. Although core biochemical classes were present in all regions the data supported in situ production of compositionally similar material rather than mixing across the gradients as proposed in some studies. Together, the chapters in my thesis provide new insight in the composition of dissolved organic matter in marine and terrestrial environments. The thesis also represents the most comprehensive molecular level characterization of DOM isolated by this solid phase extraction method, which is the most commonly used isolation method in the field. My findings also provide an important foundation for future lab-based mechanistic studies of DOM cycling in the marine environment.

Download or read book The Role of Dissolved Organic Matter DOM in Biogeochemical and Coastal Waters written by Abida Mahmood and published by . This book was released on 2018 with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dissolved organic matter (DOM) characterization was attained at molecular levels for samples collected from Mersey River estuary and Liverpool Bay using electrospray ionization coupled to Fourier transform ion cyclotron resonance mass spectrometry technique (ESI FT-ICR MS). The complexity of molecular level data was resolved with the aid of advance multivariate statistical tools. The presence of heteroatomic containing molecular formulae in high abundance among total molecular formulae was evident for impact from anthropogenic inputs onto DOM composition.

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 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 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 From Freshly Produced Compounds to Refractory Molecules written by Helena Osterholz and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis includes the results of two field studies and one laboratory incubation experiment focusing on the production and turnover of freshly produced dissolved organic matter (DOM) by microorganisms. High resolution methods were applied to elucidate the DOM molecular composition and the microbial community structure, and the data was analyzed via multivariate statistics to provide novel insights into the relationship between the two key players. Main findings include 1. DOM in high latitude environments is rapidly transformed due to microbial activity, 2. the North Sea is highly impacted by the input of terrigenous DOM and the molecular DOM composition can be connected with the composition of the total and the active microbial community, and 3. refractory deep ocean-like DOM may be biologically produced by microorganisms in the laboratory within several weeks. engl.

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 CHARACTERIZATION AND TRANSFORMATION OF DISSOLVED ORGANIC MATTER DOM IN ENGINEERED ULTRAVIOLET UV PHOTOLYSIS AND UV BASED ADVANCED OXIDATION PROCESSES written by and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract : Dissolved organic matter (DOM) is a complex mixture of heterogeneous surrogate organic compounds and includes natural organic matter (NOM), dissolved organic nitrogen (DON), dissolved organic phosphorous (DOP) and soluble microbial products (SMP). DOM plays a key role in moderating the aquatic biogeochemical cycle in freshwater ecosystems. Shedding light into the composition of freshwater DOM will aid in understanding the biogeochemical dynamics of freshwater ecosystems and consequently the role of DOM as a local climate regulator. An increase in de facto wastewater reuse has made the removal of DOM present in wastewater imperative, as DOM can be potentially toxic to human health. Additionally, wastewater DOM can reduce the efficiency of the treatment performances of advanced treatment techniques such as UV-advanced oxidation processes (UV-AOPs), as DOM can screen UV light and scavenge reactive radical species, thereby reducing the concentrations of reactive radical species that are available to destroy the target trace organic contaminants. Therefore, understanding the molecular composition of DOM present in wastewater as well as in the effluent to surface water is crucial, as this knowledge will aid in upgrading treatment performances and subsequently contribute towards the effective removal of target contaminants. In this regard, ultrahigh resolution mass spectrometry was used to evaluate the molecular composition of DOM present in wastewater as well as in the effluent to surface water. DOM composition is characterized in terms of H/C and O/C elemental ratios and double bond equivalents (DBEs). Effluent DOM was found to comprise of a higher number of unsaturated aromatic species relative to wastewater DOM. Species with nitrogen and sulfur heteroatoms are less common among effluent DOM relative to wastewater DOM. In order to better understand the interference of DOM in the treatment performances of individual UV-AOPs, the transformation of a standard DOM isolate, i.e. Suwannee River Fulvic Acid (SRFA) as well as municipal effluent wastewater DOM (EfOM) were investigated in UV/H2O2, UV/free chlorine and UV/persulfate AOPs using ultrahigh resolution mass spectrometry. The changes in the H/C and O/C elemental ratios, DBEs, and the low-molecular-weight transformation product concentrations reveal that different DOM and EfOM transformation patterns are induced by each UV-AOP. DOM and EfOM transformation routes induced by hydroxyl, chlorine and sulfate radicals were mechanistically elucidated by comparing the known reactivities of each active radical species with specific organic compounds. In the UV/H2O2 system, distinct transformation of aliphatic components of DOM and transformation of olefinic as well as aliphatic components of EfOM was observed. In the UV/free chlorine system, transformation of aliphatic as well as olefinic species of DOM and transformation of aromatic species of EfOM was observed. Transformation of aromatic and olefinic moieties of both DOM as well as EfOM was observed in the UV/persulfate system. Transformation products of DOM such as chlorinated compounds are of concern due to their adverse health impacts. However, only a small portion of these compounds have been well-characterized, thus necessitating the characterization of the unknown compounds. Plausible structural information about chlorinated compounds produced from UV/free chlorine triggered transformation of DOM is provided through the means of tandem mass spectrometry (MS/MS) with ultrahigh resolution mass analysis. The two compounds of interest were hypothesized to be composed of alcohol, carboxylic acid and aldehyde/ketone groups.

Download or read book Insights Into the Molecular Level Composition Sources and Formation Mechanisms of Dissolved Organic Matter in Aerolsols and Precipitation written by Katye Elisabeth Altieri and published by . This book was released on 2009 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atmospheric aerosols scatter and absorb light influencing the global radiation budget and climate, and are associated with adverse effects on human health. Precipitation is an important removal mechanism for atmospheric dissolved organic matter (DOM), and a potentially important input for receiving ecosystems. However, the sources, formation, and composition of atmospheric DOM in aerosols and precipitation are not well understood. This dissertation investigates the composition and formation mechanisms of secondary organic aerosol (SOA) formed through cloud processing reactions, elucidates the composition and sources of DOM in rainwater, and provides links connecting the two. Photochemical batch aqueous-phase reactions of organics with both biogenic and anthropogenic sources (i.e., methylglyoxal, pyruvic acid) and OH radical were performed to simulate cloud processing. The composition of products formed through cloud processing experiments and rainwater collected in New Jersey, USA was investigated using a combination of electrospray ionization mass spectrometry techniques, including ultra-high resolution Fourier transform ion cyclotron resonance mass spectrometry. This dissertation has resulted in the first evidence that oligomers form through cloud processing reactions, the first detailed chemical mechanism of aqueous phase oligomerization, the first identification of oligomers, organosulfates, and nitrooxy organosulfates in precipitation, and the first molecular level chemical characterization of organic nitrogen in precipitation. The formation of oligomers in SOA helps to explain the presence of large multifunctional compounds and humic like substances (HULIS) that dominate particulate organic mass. Oligomers have low vapor pressures and remain in the particle phase after cloud evaporation, enhancing SOA. The chemical properties of the oligomers suggest that they are less hygroscopic than the monomeric reaction products (i.e., organic acids). Their elemental ratios are consistent with the hypothesis that oligomers are a large contributor to aged organic aerosol mass. The majority of the compounds identified in rainwater samples by advanced mass spectrometry appear to be products of atmospheric reactions, including known contributors to SOA formed from gas phase, aerosol phase, and in-cloud reactions in the atmosphere. The similarities between the complex organic matter in rainwater and SOA suggest that the large uncharacterized component of SOA is the main contributor to the large uncharacterized component of rainwater 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 The Evolution of Stream Dissolved Organic Matter Composition Following Glacier Retreat in Coastal Watersheds of Southeast Alaska written by Amy Dehner Holt and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Climate change is melting glaciers and altering watershed biogeochemistry across the globe, particularly in regions dominated by mountain glaciers, such as southeast Alaska. Glacier dominated watersheds exhibit distinct dissolved organic matter (DOM) characteristics compared to forested and vegetated watersheds. However, there is a paucity of information on how stream DOM composition changes as glaciers retreat and terrestrial ecosystem succession ensues. Importantly, it is unclear over what timescales these transformations occur. Here, we used bulk, isotopic and ultrahigh resolution molecular-level techniques to assess how streamwater DOM composition evolves in response to glacier retreat and subsequent terrestrial ecosystem succession. For this, water samples were collected from eleven streams across a chronosequence spanning a temporal gradient 0 to ~1,400 years since glacier retreat in coastal, southeast Alaska. During the first ~200 years since glacier retreat, stream DOM showed marked and consistent changes in bulk, isotopic, and molecular-level composition. In particular, there was a decreased abundance of ancient, energy-rich (e.g., elevated aliphatic contribution), low aromaticity (e.g., low SUVA254 and AImod) DOM and an increased abundance of soil and vegetation derived aromatic DOM (e.g., more depleted d13C, elevated condensed aromatic and polyphenolic contribution) that had a modern radiocarbon age. After ~200 years of ecosystem development, DOM composition was comparable to that observed for other temperate and arctic forested watersheds without permafrost influence. These results underscore the timelines on which glacier retreat may have substantial impacts on watershed biogeochemistry and coastal ecosystems that receive DOM subsidies from these rapidly changing landscapes.

Download or read book Decomposition of Dissolved Organic Matter in Arctic and Boreal Streams written by Audrey Mutschlecner and published by . This book was released on 2017 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: Arctic and boreal rivers connect terrestrial, oceanic, and atmospheric carbon (C) pools by transporting and processing dissolved organic matter (DOM). DOM composition influences its susceptibility to decomposition (biolability), which in turn determines whether the associated C is respired, stored, or exported. High-latitude ecosystems are changing rapidly due to processes such as permafrost thaw, shifts in vegetative communities, and increasing discharge, and each of these processes can influence the composition of DOM reaching rivers. The eventual fate of riverine DOM, whether it is mineralized or exported, shifts the balance of global C pools. Therefore, to understand how changes to high-latitude ecosystems influence the global C cycle, we must be able to connect patterns in DOM composition to its biolability and subsequent fate within the C cycle. The objectives of this study were to describe spatial and temporal patterns in DOM composition and biolability, and to determine links between the composition and biolability of DOM. I sampled DOM from streams along an Arctic-boreal gradient in interior Alaska throughout the year. I measured DOM biolability and nutrient limitation of decomposition in laboratory incubations and characterized DOM composition using optical properties and chemical analysis. I found that temporal patterns in DOM composition corresponded to seasonal trends in the hydrology of high-latitude catchments, linking DOM source to shallow, organic-rich flowpaths in spring and deeper groundwater flows in winter. Biolability was low, indicating that the majority of riverine DOM is recalcitrant to biological decomposition. I observed increased biolability in response to phosphorus (P) addition, particularly during spring, indicating that phosphorus limits DOM decomposition. To further examine the mechanisms driving C processing in streams, I also conducted a series of whole-stream experiments to compare the relative influence of molecular composition and nutrient content of DOM. I added leaf leachate to boreal streams and measured C retention, which represents both biological uptake and sorption. The leachates varied by molecular composition, due to differences in tissue chemistry of plant species, and in nutrient content, because the leaves were collected from plots with different fertilization regimes. Retention was greatest for leachates derived from trees that had been fertilized with P, indicating P-limitation of biological uptake of C or preferential sorption of P-containing organic molecules. Although leachates varied in molecular composition as determined by optical properties, these differences did not correspond to a difference in uptake rates by species. These patterns in DOM retention indicate that nutrient content is a greater constraint on C uptake than molecular composition. Together, the two studies suggest that export is the primary fate of ambient DOM in high-latitude streams, but that C processing is highly sensitive to inputs of bioavailable DOM. The coupling between the P and C cycles observed in both studies highlights the potential for nutrient availability to constrain or promote CO2 emissions from C-rich, high-latitude catchments.