Ultrahigh Resolution Electrospray Ionization Research Articles

Compositional and structural characteristics of dissolved organic matter in overlying water of the Chaobai River and its environment significance.

The composition and structure of dissolved organic matter (DOM) play vital roles in the material cycle of river ecosystems. Based on ultraviolet-visible absorption spectroscopy, excitation-emission matrix fluorescence spectroscopy, and ultrahigh-resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry technology, this study comprehensively characterized the composition and structure of DOM in the overlying water of the Chaobai River in order to determine the potential environmental impact of DOM on the water quality. The results showed that the DOM content of the overlying water in the Chaobai River was between 10.94 and 28.13 mg/L. The main DOM component of the overlying water was humus (70.94%). The relative abundance of CHOS compounds in the Chaobai River was lower than Maozhou River (urbanized river) and significantly higher than Xiangxi Bay (suburban river). In addition, the DOM composition and structure of the overlying water were closely related to anthropogenic input, microbial activity, and phytoplankton. In particular, chlorophyll a can indirectly reflect fresh autochthonous DOM content and composition in the overlying water. The results of this study further reveal the characteristics of suburban rivers and provide theoretical basis and guidance for the water quality evaluation and pollution control of the Chaobai River and other suburban rivers worldwide.

Biotransformation of quercetin, kaempferol and apigenin to monoglycosylated derivatives by in vitro suspension cultures of Astragalus vesicarius ssp. carniolicus

Biotransformation of exogenous substrates quercetin, kaempferol and apigenin by suspension cultures of Astragalus vesicarius ssp. carniolicus to their monoglycosylated derivatives was performed. The maximal enzymatic potential of cells of A. vesicarius ssp. carniolicus was evaluated by different concentrations of substrate exposure. According to quantitative ultra-high performance liquid chromatography-high resolution electrospray ionization mass spectrometry (UHPLC-HR-ESI-MS) analysis, the highest concentration of kaempferol O-glycoside (14.88 nmol/g dry weight, DW), apigenin O-glycoside (10.55 nmol/g DW) and quercetin O-glycoside (150.83 nmol/g DW) was achieved, when suspension cultures were treated with 4 mg/mL kaempferol, 4 mg/mL apigenin and 3 mg/mL quercetin, respectively. The glycosidic products of biotransformation were not detected in the untreated control.

Ionic Strength Effect Triggers Brown Carbon Formation through Heterogeneous Ozone Processing of Ortho-Vanillin.

Methoxyphenols are an important class of compounds emerging from biomass combustion, and their reactions with ozone can generate secondary organic aerosols in the atmosphere. Here, we use a vertical wetted wall flow tube reactor to evaluate the effect of ionic strength on the heterogeneous reaction of gas-phase ozone (O3) with a liquid film of o-vanillin (o-VL) (2-hydroxy-3-methoxybenzaldehyde), as a proxy for methoxyphenols. Typical for moderately acidic aerosols, at fixed pH = 5.6, the uptake coefficients (γ) of O3 on o-VL ([o-VL] = 1 × 10-5 mol L-1) increase from γ = (1.9 ± 0.1) × 10-7 in the absence of Na2SO4 to γ = (6.8 ± 0.3) × 10-7 at I = 0.2 mol L-1, and then, it decreases again. The addition of NO3- ions only slightly decreases the uptakes of O3. Ultrahigh-resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) reveals that the formation of multicore aromatic compounds is favored upon heterogeneous O3 reaction with o-VL, in the presence of SO42- and NO3- ions. The addition of NO3- ions favors the formation of nitrooxy (-ONO2) or oxygenated nitrooxy group of organonitrates, which are components of brown carbon that can affect both climate and air quality.

Organic compounds in Weiyuan shale gas produced water: Identification, detection and rejection by ultrafiltration-reverse osmosis processes

Quantification of organic pollutants in flowback and produced water is essential to design appropriate treatment strategy and predict the potential environmental toxicity associated with unconventional energy production. Herein, we firstly characterized the important range chemicals of produced water (PW) collected from Weiyuan shale gas play, China. Ultra-high resolution (>10 M) electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry was used to gain insights into molecular compositions of mass range 170–1,000 Da. Oxygen-containing organic compounds (CHO) was the dominant type of compounds in the PW, and classes of O8 and O9 had the highest relative abundance. Highly unsaturated phenolic and aliphatic compounds were identified as the main compounds. Three low molecular weight (LMW, <170 Da) compounds, dimethylbenzylamine (DMBA), indoline, and 6-methyl-quinoline, were firstly revealed in the PW, with their concentrations of 137.11 μg/L, 5.48 μg/L, and 0.9 μg/L, respectively, as determined by liquid chromatography coupled to tandem mass spectrometry. An integrated process of ultrafiltration coupled with reverse osmosis was employed to treat the PW and achieved 78.3%, 96.3%, and 100% removal for these three chemicals. The concentration of DMBA in the effluent is 29.75 μg/L, which potentially cause environmental risks even after advanced membrane treatment, suggesting that LMW chemicals such as DMBA in PW deserves special attention.

Comprehensive Mass Spectrometric Mapping of Chemical Compounds for the Development of Algorithms for Machine Learning and Artificial Intelligence

The influence of the accuracy of mass measurements on the number of possible structural compositions and the computation time of computer-aided interpretation of mass spectrometric data has been evaluated. Experimental measurements have been performed for two model objects in the range of small and medium masses using high, ultrahigh, and extreme high resolution electrospray ionization mass spectrometers. The number of possible solutions have been examined and prospects of using machine learning in combination with mass spectrometry for predicting new data on reaction mechanisms and searching for hidden relationships in the chemical space have been demonstrated. It has been shown that there are two types of relationships between the molecular formula and the mass determination error depending on the ion mass: a nonlinear curve is observed for small molecules and a linear relationship is observed for large molecules.

Dereplication of Aporphine Alkaloids by UHPLC-HR-ESI-MS/MS and NMR from Duguetia lanceolata St.-Hil (Annonaceae) and Antiparasitic Activity Evaluation

Although the genus Duguetia is well known for producing alkaloids as chemical constituents, there are no reports of alkaloids identified in the species D. lanceolata. Thus, aiming to identify the chemical composition of this species, the dereplication of alkaloidic phase was performed by use of ultra-high performance liquid chromatography high resolution electrospray ionization tandem mass spectrometry (UHPLC-HR-ESI-MS/MS) and 1H nuclear magnetic resonance (NMR). The chromatographic fractionation of the alkaloid extract from Duguetia lanceolata (Annonaceae) leaves afforded four fractions (I-IV) that were shown to be composed of aporphine alkaloids. 1H NMR analysis and UHPLC-HR-ESI-MS/MS based dereplication allowed the identification of eight alkaloids: glaucine (1), norglaucine (2), isocorydine (3), N-methyllaurotetanine (4), oxoglaucine (5), liriodenine (6), lanuginosine (7), dehydroglaucine (8). Compounds 2,3, 4,6 and 7 were described for the first time in this species, while alkaloids 1,5 and 8 are newly discovered in the genus Duguetia. Additionally, the antiparasitic activity of the four fractions was evaluated in vitro against Leishmania infantum and Trypanosoma cruzi. Fraction I, composed exclusively by 1, displayed activity against Leishmania infantum and Trypanosoma cruzi intracellular amastigotes, with half maximal inhibitory concentration (IC50) values of 7.5 and 28.6 µg mL-1, respectively. Fraction IV (constituted by 2,3 and 4) showed activity against promastigotes of Leishmania infantum with IC50 value of 50.0 µg mL-1, while fraction II (constituted by 5 and 6) showed activity against trypomastigotes of Trypanosoma cruzi, with IC50 values of 83.0 µg mL-1. This work showed that fragmentation in UHPLC-HR-ESI-MS/MS combined with 1H NMR analysis of fractions is useful for identifying alkaloids in mixtures. Additionally, it was also demonstrated the potential of aporphine alkaloids from Duguetia lanceolata St. -Hil (Annonaceae) in the search for new drug candidates for neglected diseases.

Molecular Characterization of Water- and Methanol-Soluble Organic Compounds Emitted from Residential Coal Combustion Using Ultrahigh-Resolution Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry.

Water-soluble organic compounds (WSOC) and methanol-soluble organic compounds (MSOC) in smoke particles emitted from residential coal combustion were characterized by ultrahigh-resolution mass spectrometry. The results showed that the molecular compositions of WSOC and MSOC are different. S-containing compounds (CHOS and CHONS) are found to be the dominant components (65-87%) of the WSOC, whereas CHO and CHON compounds make a great contribution (79-96%) to the MSOC samples. It is worth noting that greater abundance of S-containing compounds was found in smoke produced from coal combustion compared to biomass burning and atmospheric samples. The molecular compositions of WSOC and MSOC also varied significantly depending on the maturity of the coal. The WSOC and MSOC derived from the combustion of low-maturity coal contained a higher proportion of oxidized functional groups but with a lower degree of aromaticity than the compounds derived from the combustion of high-maturity coal. Our findings suggest that organic molecules with a high modified aromaticity index, low O/C ratio, and low polarity showed stronger light absorption. This study also suggests that CHO and CHON compounds significantly contributed to the light absorption of WSOC and MSOC and that the contribution of CHON may be stronger.

Characterization of defatted cottonseed meal-derived pyrolysis bio-oil by ultrahigh resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

Defatted cottonseed meal is a N-rich biomass that deserves valorized recycling. In this work, slow pyrolysis was applied to produce pyrolytic bio-oil from this biomass. Both the upper oily and lower aqueous fractions were characterized by elemental analysis, Fourier transform infrared (FT-IR) spectroscopy, and ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) with both negative and positive electrospray ionization modes. The contents of C and S were much higher in the oily fraction than in the aqueous fraction. Furthermore, the composition and molecular formulas of the organic compounds in the oily fraction were much more complex and diverse. From the mass spectral analysis, 9 and 14 different oxygen heteroatom classes were detected in the aqueous and oily fractions, respectively. While CHON compounds were found in both fractions, CHONS compounds were detected only in the oily fraction. The van Krevelen diagrams from the FT-ICR-MS data showed the presence of lipid-, peptide-, and lignin-like components in both fractions. However, carbohydrate-like components were found only in the oily fraction. Furthermore, the diagrams revealed more N species in the oily fraction that mostly clustered with O/C < 0.2 in the unsaturated hydrocarbon-like region. On the other hand, there were less N species in the aqueous fraction, and they were present mostly in the lipid-like region. This information is useful for both chemical fingerprinting of cottonseed meal/cake-based bio-oils and guiding the effective uses of these N-rich types of products as a bioenergy resource and as an industrial feedstock.

Molecular Characterization of Water-Soluble Humic like Substances in Smoke Particles Emitted from Combustion of Biomass Materials and Coal Using Ultrahigh-Resolution Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry.

Water-soluble humic like substances (HULIS) in smoke particles emitted from combustion of biomass materials and coal were characterized by ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry. The formulas identified were classified into four main groups: CHO, CHON, CHOS, and CHONS. The average H/C and O/C ratios are 1.13-1.33, 1.01-1.13, 1.26-1.48, 1.09-1.24 and 0.21-0.41, 0.27-0.45, 0.41-0.46, 0.44-0.61 for the CHO, CHON, CHOS, and CHONS groups, respectively. The CHO compound was the predominant component (43%-72%) of the smoke HULIS from biomass burning (BB) and coal combustion, followed by the CHON group for BB-smoke HULIS and the S-containing groups (i.e., CHOS and CHONS) for coal-smoke HULIS. These results indicate that the primary HULIS emitted from biomass burning contain a high abundance of CHON species, which appear to be made up mainly of oxidized nitrogen functional groups such as nitro compounds and/or organonitrates. The coal-smoke HULIS contained more compounds with relatively low molecular weight and high aromaticity index (AImod). They were significantly enriched in S-containing compounds with high double bond equivalent (≥4), and O/S ratios suggest that they are most likely made up of aromatic organosulfates and nitrooxy organosulfates that are usually found in polluted atmospheres. These findings imply that the primary emissions from combustion of biomass and coal fuels are potential sources of water-soluble HULIS in an atmospheric matrix and that coal combustion is an especially important source of sulfate compounds.

Molecular signatures of dissolved organic matter in a tropical karst system

Karst areas are widespread landforms present on all continents, formed by the dissolution of carbonate or evaporite host rock. Little is known about the composition and nature of dissolved organic matter (DOM) as it moves through karst systems, although karst DOM has been recognized as important for a range of natural processes. Microbial communities living in karst systems are some of the most diverse and intriguing on the planet, and their metabolism and life cycle can give clues related to the development of a host of different life forms. Karst areas are also of interest due to their mostly subterranean hydrology, and the repercussions of these processes on local carbon cycles.We illustrate some of the processes acting on DOM in karst waters through the analysis of soil, drip and cave pool waters at the tropical site of Yok Balum Cave, in southern Belize. Water samples were analyzed using ultra-high resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS), a technique that enables the resolution of single molecular formulae within a DOM spectrum. We perform multivariate statistics to detect trends in the data and identify provenance of detected molecular components. In addition to karst waters, four aliquots of a powdered stalagmite sample from the same cave system are analyzed. Our results show a clear gradient between the soil and the cave system. We hypothesize that both sorption on mineral surfaces and microbial reworking are responsible for the observed trend in DOM composition. The stalagmite extracts show an anomalous DOM pattern, which may be due to a variety of factors, including microbial activity on the stalagmite surface and different affinities of compounds to incorporation in the carbonate. The goal of this study was to follow the molecular transformations of DOM on its journey from the surface to the cave, and to provide a molecular basis for the establishment of stalagmite DOM proxies in karst systems.

Higher Molecular Mass Organic Matter Molecules Compete with Orthophosphate for Adsorption to Iron (Oxy)hydroxide.

The competition between orthophosphate and water-extractable organic matter (WEOM) for adsorption to iron (oxy)hydroxide mineral surfaces is an important factor in determining the plant bioavailability of P in soils. Chemical force spectroscopy was used to determine the binding force between orthophosphate and iron (oxy)hydroxide that was coated onto atomic force microscopy (AFM) tips and adsorbed with WEOM. The force measurements were conducted at pH 4.65 and 0.02 M ionic strength which are representative of typical acid soil solutions. The chemical composition of the WEOM was determined by ultrahigh resolution electrospray ionization Fourier transform ion cyclotron mass spectrometry. The results indicate a correlation between aromatic WEOM molecules that are greater than 600 Da and the reduced binding force of orthophosphate to WEOM-adsorbed iron (oxy)hydroxide AFM tips suggesting that the molecular mass of aromatic WEOM molecules plays a critical role in regulating the WEOM-P interactions with surface functional groups of minerals. Based on the results of this study, we show the importance of obtaining a detailed, molecular-scale understanding of soil processes that can help develop better management strategies to reduce waste of limited P resources and adverse environmental impacts. Specifically, soil amendments with greater content of high molecular mass aromatic components may positively affect dissolved P use efficiency in soils by maintaining P in soil solution.

Depth-dependent variations of sedimentary dissolved organic matter composition in a eutrophic lake: Implications for lake restoration.

Dissolved organic matter (DOM) plays a significant role in regulating nutrients and carbon cycling and the reactivity of trace metals and other contaminants in the environment. However, the environmental/ecological role of sedimentary DOM is highly dependent on organic composition. In this study, fluorescence excitation emission matrix-parallel factor (EEM-PARAFAC) analysis, two dimensional correlation spectroscopy (2D-COS), and ultrahigh resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) were applied to investigate the depth-dependent variations of sediment-leached DOM components in a eutrophic lake. Results of EEM-PARAFAC and 2D-COS showed that fluorescent humic-like component was preferentially degraded microbially over fulvic-like component at greater sediment depths, and the relative abundance of non-fluorescent components decreased with increasing depth, leaving the removal rate of carbohydrates > lignins. The predominant sedimentary DOM components derived from FT-ICR-MS were lipids (>50%), followed by lignins (∼15%) and proteins (∼15%). The relative abundance of carbohydrates, lignins, and condensed aromatics decreased significantly at greater depths, whereas that of lipids increased in general with depth. There existed a significant negative correlation between the short-range ordered (SRO) minerals and the total dissolved organic carbon concentration or the relative contents of lignins and condensed aromatics (p < 0.05), suggesting that SRO mineral sorption plays a significant role in controlling the composition heterogeneity and releasing of DOM in lake sediments. Higher metal binding potential observed for DOM at deeper sediment depth (e.g., 25-30 cm) supported the ecological safety of sediment dredging technique from the viewpoint of heavy metal de-toxicity.

Tracking changes in the optical properties and molecular composition of dissolved organic matter during drinking water production

Absorbance, 3D fluorescence and ultrahigh resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS) were used to explain patterns in the removal of chromophoric and fluorescent dissolved organic matter (CDOM and FDOM) at the molecular level during drinking water production at four large drinking water treatment plants in Sweden. When dissolved organic carbon (DOC) removal was low, shifts in the dissolved organic matter (DOM) composition could not be detected with commonly used DOC-normalized parameters (e.g. specific UV254 absorbance – SUVA), but was clearly observed by using differential absorbance and fluorescence or ESI-FT-ICR-MS. In addition, we took a novel approach by identifying how optical parameters were correlated to the elemental composition of DOM by using rank correlation to connect optical properties to chemical formulas assigned to mass peaks from FT-ICR-MS analyses. Coagulation treatment selectively removed FDOM at longer emission wavelengths (450–600 nm), which significantly correlated with chemical formulas containing oxidized carbon (average carbon oxidation state ≥0), low hydrogen to carbon ratios (H/C: average ± SD = 0.83 ± 0.13), and abundant oxygen-containing functional groups (O/C = 0.62 ± 0.10). Slow sand filtration was less efficient in removing DOM, yet selectively targeted FDOM at shorter emission wavelengths (between 300 and 450 nm), which commonly represents algal rather than terrestrial sources. This shorter wavelength FDOM correlated with chemical formulas containing reduced carbon (average carbon oxidation state ≤0), with relatively few carbon-carbon double bonds (H/C = 1.32 ± 0.16) and less oxygen per carbon (O/C = 0.43 ± 0.10) than those removed during coagulation. By coupling optical approaches with FT-ICR-MS to characterize DOM, we were for the first time able to confirm the molecular composition of absorbing and fluorescing DOM selectively targeted during drinking water treatment.

Illuminating the deep: Molecular signatures of photochemical alteration of dissolved organic matter from North Atlantic Deep Water

Duplicate, filtered samples of North Atlantic Deep Water (NADW) were irradiated for 28days in a solar simulator. Duplicate dark controls were placed alongside the irradiated samples. After 28days, samples were extensively photo-degraded based upon colored dissolved organic matter (CDOM) photo-bleaching (>95%). Samples were solid phase extracted using PPL resin to isolate, concentrate and desalt the dissolved organic matter (DOM) in the samples. Ultrahigh resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) enabled 3024 molecular formulas to be identified in the dark control. Photo-degradation decreased molecular diversity, with 2402 formulas assigned post-irradiation. Molecular formulas were classified based upon their photo-lability as 1) photo-resistant; 2) photo-labile; and, 3) photo-produced. Photo-resistant DOM made up 73% of all formulas and was dominated by highly unsaturated molecular signatures consistent with carboxylic-rich alicyclic molecules, suggesting that these apparently bio-refractory compounds may also survive multiple passages through sunlit surface waters and thus accumulate for timeframes exceeding ocean ventilation. Photo-labile DOM was enriched in low molecular weight formulas, aromatic molecular formulas, and sulfur and phosphorous containing formulas. Compounds containing both sulfur and nitrogen were particularly photo-labile and may represent an underappreciated component of the photo-reactive CDOM pool. Photo-produced DOM was enriched in higher molecular weight formulas, as well as aliphatic and peptide formulas. Molecular formulas are indexed by their photo-lability classification in the supplementary information.

Molecular characterization of free tropospheric aerosol collected at the Pico Mountain Observatory: a case study with a long-range transported biomass burning plume

Abstract. Free tropospheric aerosol was sampled at the Pico Mountain Observatory located at 2225 m above mean sea level on Pico Island of the Azores archipelago in the North Atlantic. The observatory is located ~ 3900 km east and downwind of North America, which enables studies of free tropospheric air transported over long distances. Aerosol samples collected on filters from June to October 2012 were analyzed to characterize organic carbon, elemental carbon, and inorganic ions. The average ambient concentration of aerosol was 0.9 ± 0.7 μg m−3. On average, organic aerosol components represent the largest mass fraction of the total measured aerosol (60 ± 51%), followed by sulfate (23 ± 28%), nitrate (13 ± 10%), chloride (2 ± 3%), and elemental carbon (2 ± 2%). Water-soluble organic matter (WSOM) extracted from two aerosol samples (9/24 and 9/25) collected consecutively during a pollution event were analyzed using ultrahigh-resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. Approximately 4000 molecular formulas were assigned to each of the mass spectra in the range of m/z 100–1000. The majority of the assigned molecular formulas had unsaturated structures with CHO and CHNO elemental compositions. FLEXPART retroplume analyses showed the sampled air masses were very aged (average plume age &gt; 12 days). These aged aerosol WSOM compounds had an average O/C ratio of ~ 0.45, which is relatively low compared to O/C ratios of other aged aerosol. The increase in aerosol loading during the measurement period of 9/24 was linked to biomass burning emissions from North America by FLEXPART retroplume analysis and Moderate Resolution Imaging Spectroradiometer (MODIS) fire counts. This was confirmed with biomass burning markers detected in the WSOM and with the morphology and mixing state of particles as determined by scanning electron microscopy. The presence of markers characteristic of aqueous-phase reactions of phenolic species suggests that the aerosol collected at the Pico Mountain Observatory had undergone cloud processing before reaching the site. Finally, the air masses of 9/25 were more aged and influenced by marine emissions, as indicated by the presence of organosulfates and other species characteristic of marine aerosol. The change in the air masses for the two samples was corroborated by the changes in ethane, propane, and ozone, morphology of particles, as well as by the FLEXPART retroplume simulations. This paper presents the first detailed molecular characterization of free tropospheric aged aerosol intercepted at a lower free troposphere remote location and provides evidence of low oxygenation after long-range transport. We hypothesize this is a result of the selective removal of highly aged and polar species during long-range transport, because the aerosol underwent a combination of atmospheric processes during transport facilitating aqueous-phase removal (e.g., clouds processing) and fragmentation (e.g., photolysis) of components.

Chemical Changes in Fossil and Biogenic Heating Oils on Long-Term Storage

The formation of sediments in biogenic and fossil heating oils as well as in their blends is a well-known problem. These deposits can plug filters and nozzles in heating systems and, consequently, cause economic losses. Polymerization and the formation of corrosive acids are possible explanations for these incidents. To study the influence of long-term storage on different heating oils (biogenic, fossil, and a 10% blend) and to investigate the changes in their composition, the oils were stored for a period of 12–24 months at nearly ambient (40 °C) and analyzed with different techniques every 6 weeks. The formation of several kinds of oxidation products was demonstrated, including ketones, epoxides, aldehydes, carboxylic acids, and furans. Size-exclusion chromatography was used to demonstrate the formation of oligomeric products of the fatty acid methyl esters (FAMEs) (up to pentamers). Short-chain (C1–C6) carboxylic acids were quantified with ion chromatography, and larger carboxylic acids were indicated by mass spectrometry. The first recorded experimental evidence for a coupling reaction between a FAME and components of the fossil oil, namely, such containing the nitrogen heterocycle indols, is described. Cross-coupling products between biogenic and fossil compounds were detected using Orbitrap ultrahigh-resolution electrospray ionization mass spectrometry.

Oil Spill Source Identification by Principal Component Analysis of Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectra

One fundamental challenge with either acute or chronic oil spills is to identify the source, especially in highly polluted areas, near natural oil seeps, when the source contains more than one petroleum product or when extensive weathering has occurred. Here we focus on heavy fuel oil that spilled (~200,000 L) from two suspected fuel tanks that were ruptured on the motor vessel (M/V) Cosco Busan when it struck the San Francisco-Oakland Bay Bridge in November 2007. We highlight the utility of principal component analysis (PCA) of elemental composition data obtained by high resolution FT-ICR mass spectrometry to correctly identify the source of environmental contamination caused by the unintended release of heavy fuel oil (HFO). Using ultrahigh resolution electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry, we uniquely assigned thousands of elemental compositions of heteroatom-containing species in neat samples from both tanks and then applied principal component analysis. The components were based on double bond equivalents for constituents of elemental composition, CcHhN1S1. To determine if the fidelity of our source identification was affected by weathering, field samples were collected at various intervals up to two years after the spill. We are able to identify a suite of polar petroleum markers that are environmentally persistent, enabling us to confidently identify that only one tank was the source of the spilled oil: in fact, a single principal component could account for 98% of the variance. Although identification is unaffected by the presence of higher polarity, petrogenic oxidation (weathering) products, future studies may require removal of such species by anion exchange chromatography prior to mass spectral analysis due to their preferential ionization by ESI.

Molecular Characteristics and Differences of Effluent Organic Matter from Parallel Activated Sludge and Integrated Fixed-Film Activated Sludge (IFAS) Processes

A direct comparison between parallel activated sludge and integrated fixed-film activated sludge (IFAS) processes was performed in this study because both treatments received the same primary effluent, although differences may still remain due to different return flow rates. Modern ultrahigh resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry was applied to characterize the complexity of effluent organic matter (EfOM) and to evaluate both processes in their abilities to change the EfOM molecular composition. At different stages during the two processes a direct comparison of the performance and changes in molecular composition of the IFAS with those of the activated sludge was undertaken. Large differences in the molecular composition between both processes were only apparent in the early stage of the aeration cells and the first cell of the IFAS possibly due to the higher flow rate and a delay in aerobic bacterial degradation. Despite the double flow rate (0.263 m(3) s(-1)) in the IFAS reactors compared to the activated sludge, by the end of the treatment the EfOM composition of both processes were undistinguishable from each other. However, a much more complex EfOM was generated in both processes, suggesting that bacteria are responsible for an increase in molecular diversity in the effluent.

Selective Mass Labeling for Linking the Optical Properties of Chromophoric Dissolved Organic Matter to Structure and Composition via Ultrahigh Resolution Electrospray Ionization Mass Spectrometry

The mass spectra acquired by ESI FT-ICR MS of untreated, borohydride-reduced, and borodeuteride-reduced samples of Suwannee River fulvic acid (SRFA) and a C18 extract from the upper Delaware Bay were compared to one another. Treatment of these samples with sodium borodeuteride was shown to produce unique mass labels for species which contain one or two ketone/aldehyde moieties. Approximately 30% of all identified peaks in the two samples were shown to comprise ketone/aldehyde-containing species. The molecular formulas of the majority of these species had O/C and H/C molar ratios typically attributed to lignin-derived compounds and/or carboxylic rich alicyclic molecules (CRAM). However, the significant loss of UV-vis absorption following reduction supports a lignin-based origin for the optical (and photochemical) properties of these samples. The mass-labeling method described and tested herein shows great promise as a means to further characterize the structure and composition of complex natural samples, especially in terms of identifying specific subsets of chemical species that contribute significantly to the optical and photochemical properties of such samples.

Molecular characterization of water soluble organic nitrogen in marine rainwater by ultra-high resolution electrospray ionization mass spectrometry

Abstract. Atmospheric water soluble organic nitrogen (WSON) is a subset of the complex organic matter in aerosols and rainwater, which impacts cloud condensation processes and aerosol chemical and optical properties and may play a significant role in the biogeochemical cycle of N. However, its sources, composition, connections to inorganic N, and variability are largely unknown. Rainwater samples were collected on the island of Bermuda (32.27° N, 64.87° W), which experiences both anthropogenic and marine influenced air masses. Samples were analyzed by ultra-high resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry to chemically characterize the WSON. Elemental compositions of 2281 N containing compounds were determined over the mass range m/z+ 50 to 500. The five compound classes with the largest number of elemental formulas identified, in order from the highest number of formulas to the lowest, contained carbon, hydrogen, oxygen, and nitrogen (CHON+), CHON compounds that contained sulfur (CHONS+), CHON compounds that contained phosphorus (CHONP+), CHON compounds that contained both sulfur and phosphorus (CHONSP+), and compounds that contained only carbon, hydrogen, and nitrogen (CHN+). Compared to rainwater collected in the continental USA, average O:C ratios of all N containing compound classes were lower in the marine samples whereas double bond equivalent values were higher, suggesting a reduced role of secondary formation mechanisms. Despite their prevalence in continental rainwater, no organonitrates or nitrooxy-organosulfates were detected, but there was an increased presence of organic S and organic P containing compounds in the marine rainwater. Cluster analysis showed a clear chemical distinction between samples collected during the cold season (October to March) which have anthropogenic air mass origins and samples collected during the warm season (April to September) with remote marine air mass origins. This, in conjunction with patterns identified in van Krevelen diagrams, suggests that the cold season WSON is a mixture of organic matter with both marine and anthropogenic sources while in the warm season the WSON appears to be dominated by marine sources. These findings indicate that, although the concentrations and percent contribution of WSON to total N is fairly consistent across diverse geographic regions, the chemical composition of WSON varies strongly as a function of source region and atmospheric environment.