Fourier transform ion-cyclotron resonance mass spectrometry (FT-ICR MS) is the only mass analyzer that can resolve the molecular complexity of natural organic matter at the level of elemental composition assignment. Here, we leverage the high dynamic range, resolving power, resistance to peak coalescence, and maximum ion number and ion trapping duration in a custom built, 21 tesla hybrid linear ion trap /FT-ICR mass spectrometer for a dissolved organic matter standard (Suwanne River Fulvic Acid). We compare the effect of peak-picking threshold (3σ, 4σ, 5σ, and 6σ) on number of elemental composition assignments, mass measurement accuracy, and dynamic range for a 6.3 s transient across the mass range of m/z 200-1200 that comprises the highest achieved resolving power broadband FT-ICR mass spectrum collected to date. More than 36 000 species are assigned with signal magnitude greater than 3σ at root-mean-square mass error of 36 ppb, the most species identified reported to date for dissolved organic matter. We identify 18O and 17O isotopologues and resolve isobaric overlaps on the order of a few electrons across a wide mass range (up to m/z 1000) leveraging mass resolving powers (3 000 000 at m/z 200) only achievable by 21 T FT-ICR MS and increased by ∼30% through absorption mode data processing. Elemental compositions unique to the 3σ span a wide compositional range of aromaticity not detected at higher peak-picking thresholds. Furthermore, we leverage the high dynamic range at 21 T FT-ICR MS to provide a molecular catalogue of a widely utilized reference standard (SRFA) to the analytical community collected on the highest performing mass analyzer for complex mixture analysis to date. This instrument is available free of charge to scientists worldwide.
When oil weathers in the environment, it undergoes oxidative transformations that increase its molecular complexity, influencing the fate, transport, and toxicity of the oil plume. The primary natural processes driving these transformations are photochemical- and microbial-oxidation. However, the relative contributions of each process to the postspill transformation of petroleum remain poorly understood. To address this, we utilized laboratory microcosms to evaluate the products of bio-oxidation and photo-oxidation independently. Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) was employed to characterize the chemical evolution and degradation pathways of Macondo Crude oil (SRM 2779). Bio-oxidation microcosms were monitored for 30 days using live seawater filtered to capture the microbial population and resuspended in sterile artificial seawater. For comparison, a photo-oxidation microcosm and an early field sample collected after the Deepwater Horizon (DWH) spill were included. Results revealed distinct oxidation patterns: bio-oxidation releases a diverse range of oxyhydrocarbons into the water phase, while the oxygenated species in the field samples (oil-soluble) largely resemble photochemically oxidized products. Bio-oxidation does not significantly affect the composition of oil-soluble species but releases oxygenated transformation products into the water, containing 1–14 oxygen atoms. These low oxygen species (Ox) are initially oil-soluble but become water-soluble with increased oxygen incorporation. In contrast, photo-oxidation disproportionately contributes to the DOC pool, showing a 30-fold increase in DOC compared to bio-oxidation. Photo-oxidation nonselectively oxidizes petrogenic compounds, increasing the relative abundances of O1 to O12 classes and generating abundant oil-soluble transformation products similar to those detected in field samples. Toxicity assessments using the Microtox bioassay suggest that the toxicity of photosolubilized carbon increases at early periods, while bacterial transformation products show a sustained decrease. These controlled microcosm experiments provide insights into the distinct oxidative processes affecting the fate and transport of oil components in the Gulf of Mexico.
Eutrophication has been a long-term issue in aquatic environments, where dissolved organic nitrogen (DON) recalcitrance is important. Bioavailable nitrogen qualification and quantification for effluents from stormwater and wastewater are always a challenge. The information in this study deepens the understanding of the interactions between carbon addition and DON decomposition through linear-ditch best management practices for stormwater and groundwater cotreatment. By running a laboratory-scale column study for nitrogen removal using green sorption media, the variation in composition and concentration of DON can be further linked to the population dynamics of microbial species that dominate the nitrification and denitrification processes. With the varying levels of influent total nitrogen concentration, the efficacy of nitrogen removal via biosorption activated media may be realized at the molecular level with ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry.
Abstract Environments where geothermal waters and glacier meltwater mix are common on Earth yet little is known about the biogeochemical processes that occur when hot, reduced geothermal water mixes with cold, oxidized glacial meltwater in natural systems. Mount St. Helens provides an ideal location to study the interaction between geothermal and glacier waters since the water sources, and their mixing environment in Step Creek, are exposed in the volcanic crater. We find that the two water sources contain distinct major ion, trace element, dissolved organic matter (DOM), and biological signatures. The hot spring contains high concentrations of biogeochemically reactive components (e.g., siderophile and chalcophile trace elements and DOM) compared to the glacier discharge but a large fraction of these solutes do not remain in solution after the waters mix. In contrast, glacier discharge contains fewer solutes but most of these solutes remain in solution after the waters mix. The mixing of glacier and hot spring water in Step Creek supports seston and benthic ecosystems that have higher phototrophic and microbial biomass than those in the source waters, suggesting that the mixing environment in this high‐gradient stream provide a more comprehensive suite of soluble and essential nutrients that promote primary production and DOM cycling.
Landfill leachate properties contain important information and can be a unique indicator for the chemical and biochemical activities in landfills. In the recent decade, more landfills are experiencing elevated temperature, causing an imbalance in the decomposition of solid waste and affecting the properties of the landfill leachate. This study analyzes the properties of leachate from two landfills that were experiencing elevated temperature (ETLFs), samples were collected from both elevated temperature impacted and non-impacted areas in each landfill. The accumulation of volatile fatty acids (VFA) in leachates from elevated temperature impacted areas of both landfill sites revealed that methanogenesis was inhibited by the elevated temperature, which was further confirmed by the more acidic pH, higher H/C elemental ratio, and lower degree of aromaticity of the elevated temperature impacted leachates. Also, carbohydrates depletion indicated possible enhancement of hydrolysis and acidogenesis by elevated temperature, which was supported by compositional comparison of isolated acidic species by negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICRMS) at 21 tesla derived from both elevated temperature impacted and non-impacted areas in the same landfill site. Furthermore, leachate organics fractionation showed that leachates not impacted by elevated temperature contain less hydrophilic fraction and more humic fraction than elevated temperature-impacted leachates for both ETLFs.
We present an analytical method for direct analysis of thin-layer chromatography (TLC) separations of petroleum samples by laser desorption ionization (LDI) coupled to Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) imaging. LDI of TLC plates selectively ionizes condensed aromatic hydrocarbons and facilitates two-dimensional imaging of TLC-separated petroleum compounds. Molecular-level characterization available only with ultrahigh-resolution FT-ICR MS provides elemental composition assignment and surpasses conventional TLC readout-based flame ionization detection. Resolution and assignment of migrated molecules targeted by LDI combined with FT-ICR MS provides elemental composition assignment and, therefore, chemical information, i.e., heteroatom class, aromaticity (double bond equivalents), and carbon number. Here, three petroleum samples (a field deposit, a crude oil, and a tar ball) were TLC-separated by their solubility in n-heptane and imaged by LDI FT-ICR MS.
Food waste is an abundant and inexpensive resource for the production of renewable fuels. Biocrude yields obtained from hydrothermal liquefaction (HTL) of food waste can be boosted using hydroxyapatite (HAP) as an inexpensive and abundant catalyst. Combining HAP with an inexpensive homogeneous base increased biocrude yield from 14 ± 1 to 37 ± 3%, resulting in the recovery of 49 ± 2% of the energy contained in the food waste feed. Detailed product analysis revealed the importance of fatty-acid oligomerization during biocrude formation, highlighting the role of acid-base catalysts in promoting condensation reactions. Economic and environmental analysis found that the new technology has the potential to reduce US greenhouse gas emissions by 2.6% while producing renewable diesel with a minimum fuel selling price of $1.06/GGE. HAP can play a role in transforming food waste from a liability to a renewable fuel.
Lithium cationization can significantly extend the compositional range for analysis of petroleum components by positive electrospray ionization [(+) ESI], by accessing species that lack a basic nitrogen atom and, hence, are not seen by conventional (+) ESI that relies on protonation as the primary ionization mechanism. Here, various solvent compositions and lithium salts enabled us to optimize ionization by formation of lithium adducts ([M + Li]+), and the results are compared to production of [M + H]+ by conventional (+) ESI with formic acid. Lithium cationization (+) ESI Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) of Athabasca bitumen heavy vacuum gas oil (475–500 °C) and North and South American crude oils demonstrates considerable improvement over protonation for production of ions from compounds belonging to SxOy (SO, SO2, SO3, SO4, S2O, S2O2, etc.) heteroatom classes. Those compounds exhibit much higher affinity for lithium cation than for proton and yield abundant [M + Li]+ ions. Li+ cationization thus opens a pathway for detection and characterization of SxOy class compounds that preferentially concentrate at the interface in oil/water emulsions.
Traditional tools for routine environmental analysis and forensic chemistry of petroleum have relied almost exclusively on gas chromatography–mass spectrometry (GC-MS), although many compounds in crude oil (and its transformation products) are not chromatographically separated or amenable to GC-MS due to volatility. To enhance current and future studies on the fate, transport, and fingerprinting of the Macondo well oil released from the 2010 Deepwater Horizon disaster, we created an extensive molecular library of the unadulterated petroleum to compare to a tar ball collected on the beach of Louisiana. We apply ultrahigh resolution Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry to identify compositional changes at the molecular level between native and weathered crude oil samples and reveal enrichment in polar compounds inaccessible by GC-based characterization. The outlined approach provides unprecedented detail with the potential to enhance insight into the environmental fate of spilled oil, improved toxicology, molecular modeling of biotic/abiotic weathering, and comprehensive molecular characterization for petroleum-derived releases. Here, we characterize more than 30 000 acidic, basic, and nonpolar unique neutral elemental compositions for the Macondo well crude oil, to provide an archive for future chemical analyses of the environmental consequences of the oil spill.
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