Publications by authors named "Michael Gonsior"

41 Publications

Correspondence between DOM molecules and microbial community in a subtropical coastal estuary on a spatiotemporal scale.

Environ Int 2021 Apr 23;154:106558. Epub 2021 Apr 23.

State Key Laboratory for Marine Environmental Science, Institute of Marine Microbes and Ecospheres, College of Ocean and Earth Sciences, Xiamen University, Xiang'an Campus, Xiang'an South Road, Xiamen 361102, China; Fujian Key Laboratory of Marine Carbon Sequestration, Xiamen University, Xiang'an Campus, Xiang'an South Road, Xiamen 361102, China. Electronic address:

Dissolved organic matter (DOM) changes in quantity and quality over time and space, especially in highly dynamic coastal estuaries. Bacterioplankton usually display seasonal and spatial variations in abundance and composition in the coastal regions, and influence the DOM pool via assimilation, transformation and release of organic molecules. The change in DOM can also affect the composition of bacterial community. However, little is known on the correspondence between DOM molecules and bacterial composition, particularly through a systematic field survey. In this study, the spatiotemporal signatures of microbial communities and DOM composition in the subtropical coastal estuary of Xiamen are investigated over one and half years. The co-occurrence analysis between bacteria and DOM suggested microorganisms likely transformed the DOM from a relatively high (>400 Da) to a low (<400 Da) molecular weight, corresponding to an apparent increase in overall aromaticity. This might be the reason why microbial transformation renders "dark" organic matter visible in mass spectrometry due to more efficient ionization of microbial metabolites, as well as photodegradation processes. K- and r-strategists exhibited different correlations with two-size categories of DOM molecules owing to their different lifestyles and responses to environmental nutrient conditions. A comparison of the environmental variables and DOM composition with the microbial communities showed that the environmental/DOM variations played a more important role in shaping the microbial communities than vice versa. This study sheds light on the interactions between microbial populations and DOM molecules at the spatiotemporal scale, improving our understanding of microbial roles in marine biogeochemical cycles.
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http://dx.doi.org/10.1016/j.envint.2021.106558DOI Listing
April 2021

Combined fluorescent measurements, parallel factor analysis and GC-mass spectrometry in evaluating the photodegradation of PAHS in freshwater systems.

Chemosphere 2021 Apr 21;269:129386. Epub 2020 Dec 21.

University of Maryland Center for Environmental Science, Chesapeake Biological Laboratory, Solomons, MD, USA.

To better understand the transformation and photochemical fate of PAHs in aquatic environments, a custom-designed closed-circuit recirculation photodegradation system, combined with inline semi-continuous fluorescence and absorbance measurements, as well as modelling of excitation-emission (EEM) measurements with parallel factor analysis (PARAFAC), and GC-MS analysis, were combined to create a robust tool for holistically assessing the photodegradation of individual PAHs, their mixtures and photoproduct formation. Selected compounds included in the US EPA priority list, representing 2- to 6-ring compounds, were monitored individually and in mixtures, during 24 h photodegradation experiments. Experiments were conducted in solutions simulating ideal (ultrapure water) and environmentally relevant conditions (1.00 mg L Suwannee River Natural Organic Matter (SRNOM)). The fluorescence, primary PARAFAC components and quantification data obtained by GC-MS, indicated that the decline in parent molecule concentration occurred rapidly within 200 min. The degradation rates of parent PAHs increased with aromaticity (6-ring ≫ 2-ring PAHs) and followed pseudo-first order degradation kinetics. The presence and transformation of degradation products, were captured by PARAFAC. NOM influenced the diversity of photoproducts. From the GC-MS results, photoproducts were only detected in Ant, BAnt and the PAH mixture solutions, but optical property analyses indicated that diverse changes occurred with all PAHs. Spectrometric and chromatographic data demonstrated that parent PAHs and photoproducts co-existed at various stages, which is significant for freshwater systems contaminated with these compounds if photoproducts have higher-toxic potential. These results may be used to model the hazard-potential associated with PAHs present in freshwater systems and understanding the mechanisms that govern their environmental fate.
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http://dx.doi.org/10.1016/j.chemosphere.2020.129386DOI Listing
April 2021

Influence of the UV/HO Advanced Oxidation Process on Dissolved Organic Matter and the Connection between Elemental Composition and Disinfection Byproduct Formation.

Environ Sci Technol 2020 12 12;54(23):14964-14973. Epub 2020 Nov 12.

Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon 000, Hong Kong SAR.

The UV/HO process is a promising advanced oxidation process (AOP) for micropollutant abatement in drinking water treatment and water reuse plants. However, during micropollutant degradation by the AOP, dissolved organic matter (DOM) and the disinfection byproduct (DBP) formation potential may also be altered. This study investigated the influence of the UV/HO AOP on the elemental composition and DBP formation potential of two DOM isolates by using ultrahigh-resolution mass spectrometry (UHRMS). After the AOP, 629 new chemical formulas with an increased degree of oxidation and decreased aromaticity were obtained. Such alterations led to the formation of 226 unknown DBPs with decreased aromaticity indices (AI) in the subsequent 3-day chlorination. Links between the unknown DBPs and the corresponding precursors in DOM were visualized by network computational analysis. The analysis gave three zones in the van Krevelen diagram based on the possibility of the CHO formulas located in each zone to link to the corresponding DBPs. A further investigation with two model compounds reconfirmed the hydroxylation and ring cleavage of DOM by HO attack during the AOP and the influence on DBP formation. These results obtained from UHRMS build the connection between the elemental composition of DOM and the formation potential of DBPs.
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http://dx.doi.org/10.1021/acs.est.0c03220DOI Listing
December 2020

Unraveling the chemodiversity of halogenated disinfection by-products formed during drinking water treatment using target and non-target screening tools.

J Hazard Mater 2021 01 15;401:123681. Epub 2020 Aug 15.

Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences (SLU), Box 7050, SE-750 07, Uppsala, Sweden.

To date, there is no analytical approach available that allows the full identification and characterization of highly complex disinfection by-product (DBP) mixtures. This study aimed at investigating the chemodiversity of drinking water halogenated DBPs using diverse analytical tools: measurement of adsorbable organic halogen (AOX) and mass spectrometry (MS)-based target and non-target analytical workflows. Water was sampled before and after chemical disinfection (chlorine or chloramine) at four drinking water treatment plants in Sweden. The target analysis had the highest sensitivity, although it could only partially explain the AOX formed in the disinfected waters. Non-target Fourier transform ion cyclotron resonance (FT-ICR) MS analysis indicated that only up to 19 Cl and/or Br-CHO formulae were common to all disinfected waters. Unexpectedly, a high diversity of halogenated DBPs (presumed halogenated polyphenolic and highly unsaturated compounds) was found in chloraminated surface water, comparable to that found in chlorinated surface water. Overall, up to 86 DBPs (including isobaric species) were tentatively identified using liquid chromatography (LC)-Orbitrap MS. Although further work is needed to confirm their identity and assess their relevance in terms of toxicity, they can be used to design suspect lists to improve the characterization of disinfected water halogenated mixtures.
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http://dx.doi.org/10.1016/j.jhazmat.2020.123681DOI Listing
January 2021

A Glacier Bacterium Produces High Yield of Cryoprotective Exopolysaccharide.

Front Microbiol 2019 11;10:3096. Epub 2020 Feb 11.

Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, Baltimore, MD, United States.

sp. BGI-2 is a psychrotrophic bacterium isolated from the ice sample collected from Batura glacier, Pakistan. This strain produces highly viscous colonies on agar media supplemented with glucose. In this study, we have optimized growth and production of exopolysaccharide (EPS) by the cold-adapted sp. BGI-2 using different nutritional and environmental conditions. sp. BGI-2 is able to grow in a wide range of temperatures (4-35°C), pH (5-11), and salt concentrations (1-5%). Carbon utilization for growth and EPS production was extensively studied and we found that glucose, galactose, mannose, mannitol, and glycerol are the preferable carbon sources. The strain is also able to use sugar waste molasses as a growth substrate, an alternative for the relatively expensive sugars for large scale EPS production. Maximum EPS production was observed at 15°C, pH 6, NaCl (10 g L), glucose as carbon source (100 g L), yeast extract as nitrogen source (10 g L), and glucose/yeast extract ratio (10/1). Under optimized conditions, EPS production was 2.01 g L, which is relatively high for a species compared to previous studies using the same method for quantification. High-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) analysis of EPS revealed glucose, galactose, and glucosamine as the main sugar monomers. Membrane protection assay using human RBCs revealed significant reduction in cell lysis (∼50%) in the presence of EPS, suggesting its role in membrane protection. The EPS (5%) also conferred significant cryoprotection for a mesophilic k12 which was comparable to glycerol (20%). Also, improvement in lipid peroxidation inhibition () resulted when lipids from the was pretreated with EPS. Increased EPS production at low temperatures, freeze thaw tolerance of the EPS producing strain, and increased survivability of in the presence of EPS as cryoprotective agent supports the hypothesis that EPS production is a strategy for survival in extremely cold environments such as the glacier ice.
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http://dx.doi.org/10.3389/fmicb.2019.03096DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7026135PMC
February 2020

Advanced identification of global bioactivity hotspots via screening of the metabolic fingerprint of entire ecosystems.

Sci Rep 2020 Jan 28;10(1):1319. Epub 2020 Jan 28.

Research Unit Analytical BioGeoChemistry, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, D-85764, Germany.

Natural products (NP) are a valuable drug resource. However, NP-inspired drug leads are declining, among other reasons due to high re-discovery rates. We developed a conceptual framework using the metabolic fingerprint of entire ecosystems (MeE) to facilitate the discovery of global bioactivity hotspots. We assessed the MeE of 305 sites of diverse aquatic ecosystems, worldwide. All samples were tested for antiviral effects against the human immunodeficiency virus (HIV), followed by a comprehensive screening for cell-modulatory activity by High-Content Screening (HCS). We discovered a very strong HIV-1 inhibition mainly in samples taken from fjords with a strong terrestrial input. Multivariate data integration demonstrated an association of a set of polyphenols with specific biological alterations (endoplasmic reticulum, lysosomes, and NFkB) caused by these samples. Moreover, we found strong HIV-1 inhibition in one unrelated oceanic sample closely matching to HIV-1-inhibitory drugs on a cytological and a chemical level. Taken together, we demonstrate that even without physical purification, a sophisticated strategy of differential filtering, correlation analysis, and multivariate statistics can be employed to guide chemical analysis, to improve de-replication, and to identify ecosystems with promising characteristics as sources for NP discovery.
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http://dx.doi.org/10.1038/s41598-020-57709-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6987164PMC
January 2020

Contribution of ketone/aldehyde-containing compounds to the composition and optical properties of Suwannee River fulvic acid revealed by ultrahigh resolution mass spectrometry and deuterium labeling.

Anal Bioanal Chem 2020 Feb 16;412(6):1441-1451. Epub 2020 Jan 16.

Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, 20742, USA.

A prior method of mass labeling ketone-/aldehyde-containing species in natural dissolved organic matter (DOM) is further developed and applied. This application involved the treatment of Suwannee River fulvic acid (SRFA) with increasing concentrations of sodium borodeuteride (NaBD), followed by detection of reduced species via negative mode electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FTICR MS). The extent of reduction, as determined by ESI FTICR MS, resulting from increasing concentrations of NaBD correlated well with changes in the absorption and emission spectra of the corresponding untreated and borodeuteride-reduced samples, providing evidence that ketone/aldehyde functional groups contribute substantially to the bulk optical properties of SRFA. Furthermore, the differences in the reactivity and abundance of ketone-/aldehyde-containing species for various regions in Van Krevelen plots were revealed, thus showing how this mass labeling method can be used to provide more detailed structural information about components within complex DOM samples than that provided by the determination and analysis of molecular formulae alone. Graphical abstract.
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http://dx.doi.org/10.1007/s00216-019-02377-xDOI Listing
February 2020

Molecular differences between water column and sediment pore water SPE-DOM in ten Swedish boreal lakes.

Water Res 2020 Mar 22;170:115320. Epub 2019 Nov 22.

Helmholtz Zentrum Munich, German Research Center for Environmental Health, Research Unit Analytical Biogeochemistry (BGC), Ingolstädter Landstraße 1, P. O. Box 1129, D-85758, Neuherberg, Germany. Electronic address:

Boreal lakes are considered hot spots of dissolved organic matter (DOM) processing within the global carbon cycle. This study has used FT-ICR mass spectrometry and comprehensive data evaluation to assess the molecular differences of SPE-DOM between lake column water SPE-DOM and sedimentary pore water SPE-DOM in 10 Swedish boreal lakes of the Malingsbo area, which were selected for their large diversity of physicochemical and morphological characteristics. While lake column water is well mixed and fairly oxygenated, sedimentary pore water is subject to depletion of oxygen and to confinement of molecules. Robust trends were deduced from molecular compositions present in all compartments and in all 10 lakes ("common compositions") with recognition of relative abundance. Sedimentary pore water SPE-DOM featured higher proportions of heteroatoms N and S, higher average H/C ratios in presence of higher DBE/C ratios, and higher average oxygenation than lake column water SPE-DOM. These trends were observed in all lakes except Ljustjärn, which is a ground water fed kettle lake with an unique lake biogeochemistry. Analogous trends were also observed in case of single or a few lakes and operated also for compounds present solely in either lake column water or sedimentary pore water. Unique compounds detected in either compartments and/or in a few lakes showed higher molecular diversity than the "common compositions". Processing of DOM molecules in sediments included selective preservation for polyphenolic compounds and microbial resynthesis of selected molecules of considerable diversity.
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http://dx.doi.org/10.1016/j.watres.2019.115320DOI Listing
March 2020

Simulated Sunlight Selectively Modifies Maillard Reaction Products in a Wide Array of Chemical Reactions.

Chemistry 2019 Oct 13;25(57):13208-13217. Epub 2019 Sep 13.

Comprehensive Foodomics Platform, Analytical Food Chemistry, Technical University Munich, Maximus-von-Imhof-Forum 2, 85354, Freising, Germany.

The photochemical transformation of Maillard reaction products (MRPs) under simulated sunlight into mostly unexplored photoproducts is reported herein. Non-enzymatic glycation of amino acids leads to a heterogeneous class of intermediates with extreme chemical diversity, which is of particular relevance in processed and stored food products as well as in diabetic and age-related protein damage. Here, three amino acids (lysine, arginine, and histidine) were reacted with ribose at 100 °C in water for ten hours. Exposing these model systems to simulated sunlight led to a fast decay of MRPs. The photodegradation of MRPs and the formation of new compounds have been studied by fluorescence spectroscopy and nontargeted (ultra)high-resolution mass spectrometry. Photoreactions showed strong selectivity towards the degradation of electron-rich aromatic heterocycles, such as pyrroles and pyrimidines. The data show that oxidative cleavage mechanisms dominate the formation of photoproducts. The photochemical transformations differed fundamentally from "traditional" thermal Maillard reactions and indicated a high amino acid specificity.
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http://dx.doi.org/10.1002/chem.201902804DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6856810PMC
October 2019

Microbial transformation of virus-induced dissolved organic matter from picocyanobacteria: coupling of bacterial diversity and DOM chemodiversity.

ISME J 2019 10 21;13(10):2551-2565. Epub 2019 Jun 21.

Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, Cambridge, USA.

Picocyanobacteria make up half of the ocean's primary production, and they are subjected to frequent viral infection. Viral lysis of picocyanobacteria is a major driving force converting biologically fixed carbon into dissolved organic carbon (DOC). Viral-induced dissolved organic matter (vDOM) released from picocyanobacteria provides complex organic matter to bacterioplankton in the marine ecosystem. In order to understand how picocyanobacterial vDOM are transformed by bacteria and the impact of this process on bacterial community structure, viral lysate of picocyanobacteria was incubated with coastal seawater for 90 days. The transformation of vDOM was analyzed by ultrahigh-resolution mass spectrometry and the shift of bacterial populations analyzed using high-throughput sequencing technology. Addition of picocyanobacterial vDOM introduced abundant nitrogen components into the coastal water, which were largely degraded during the 90 days' incubation period. However, some DOM signatures were accumulated and the total assigned formulae number increased over time. In contrast to the control (no addition of vDOM), bacterial community enriched with vDOM changed markedly with increased biodiversity indices. The network analysis showed that key bacterial species formed complex relationship with vDOM components, suggesting the potential correspondence between bacterial populations and DOM molecules. We demonstrate that coastal bacterioplankton are able to quickly utilize and transform lysis products of picocyanobacteria, meanwhile, bacterial community varies with changing chemodiverisity of DOM. vDOM released from picocyanobacteria generated a complex labile DOM pool, which was converted to a rather stable DOM pool after microbial processing in the time frame of days to weeks.
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http://dx.doi.org/10.1038/s41396-019-0449-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6776026PMC
October 2019

Formation of Brominated Organic Compounds and Molecular Transformations in Dissolved Organic Matter (DOM) after Ballast Water Treatment with Sodium Dichloroisocyanurate Dihydrate (DICD).

Environ Sci Technol 2019 Jul 26;53(14):8006-8016. Epub 2019 Jun 26.

University of Maryland Center for Environmental Science , Chesapeake Biological Laboratory , Solomons , Maryland 20688 , United States.

Estuarine water treated with a ballast water management system (BWMS) using a solution of dissolved dichloroisocyanurate dihydrate (DICD) resulted in the formation of newly described brominated disinfection byproducts (Br-DBPs). Analysis of dissolved organic matter (DOM) in untreated water with ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) identified 3897 / ions and their exact molecular formulas. After DICD treatment, a total of 213 halogenated molecular ions with relative abundance of at least 1% were assigned and confirmed using isotope simulation. Halogenated ions were assigned in four DBP elemental groups including CHOBr (180), CHONBr (13), CHOCl (16), and CHOBrCl (4). Forty-nine of the 197 brominated formulas have not been previously reported. We also were able to tentatively assign possible structures to the formula CHBrN due to very limited isomeric possibilities. The tentatively assigned compound found at 6.4% relative abundance was identified as either tribromoimidazole or tribromopyrazole. Our results show the formation of complex halogenated DBPs that are formed in the treatment of water with a novel BWMS that employs granular DICD as a biocide. The toxicological and mutagenic properties as well as the fate of these newly identified brominated DBPs are unknown.
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http://dx.doi.org/10.1021/acs.est.9b01064DOI Listing
July 2019

Occurrence and distribution of UV-filters and other anthropogenic contaminants in coastal surface water, sediment, and coral tissue from Hawaii.

Sci Total Environ 2019 Jun 13;670:398-410. Epub 2019 Mar 13.

University of Maryland Baltimore County, Department of Chemical, Biochemical, and Environmental Engineering, 1000 Hilltop Circle, Engineering 314, Baltimore, MD 21250, USA.

The occurrence of UV-filters in the environment has raised concerns over potentially adverse impacts on corals. In this study, the concentrations of 13 UV-filters and 11 hormones were measured in surface seawater, sediment, and coral tissue from 19 sites in Oahu, Hawaii. At least eight UV-filters were detected in seawater, sediment, and coral tissue and total mass concentrations of all UV-filters were <750 ng L, <70 ng g dry weight (dw), and <995 ng g dw, respectively. Four UV-filters were detected in water, sediment, and coral tissue at detection frequencies of 63-100%, 56-91%, and 82-100%, respectively. These UV-filter concentrations generally varied as follows: water, homosalate (HMS) > octisalate (OS) > benzophenone-3 (BP-3, also known as oxybenzone) > octocrylene (OC); sediment, HMS > OS > OC > BP-3; coral, OS ≈ HMS > OC ≈ BP-3. BP-3 concentrations in surface seawater were <10 ng L at 12 of 19 sites and highest at Waikiki beach (e.g., 10.9-136 ng L). While BP-3 levels were minimal in sediment (e.g., <1 ng g dw at 18 of 19 sites), and ranged from 6.6 to 241 ng g dw in coral tissue. No quantifiable levels of 2-ethylhexyl 4-methoxycinnamate (also known as octinoxate) were recorded in surface seawater or coral tissues, but 5-12.7 ng g dw was measured for sediment at 5 of 19 sites. No hormones were detected in seawater or sediment, but 17α-ethinylestradiol was present in three corals from Kaneohe Bay. Surfactant degradation products were present in seawater, especially at Waikiki beach. These results demonstrate ubiquitous parts-per-trillion concentrations of UV-filters in surface seawater and is the first report of UV-filters in coral tissue from U.S.A. coastal waters. These data inform the range of environmentally-relevant concentrations for future risk assessments on the potential impacts of UV-filters on coral reefs in Oahu, Hawaii.
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http://dx.doi.org/10.1016/j.scitotenv.2019.03.034DOI Listing
June 2019

The chemodiversity of algal dissolved organic matter from lysed Microcystis aeruginosa cells and its ability to form disinfection by-products during chlorination.

Water Res 2019 May 27;155:300-309. Epub 2019 Feb 27.

Helmholtz Zentrum Muenchen, Research Unit Analytical BioGeoChemistry, Neuherberg, Germany; Technische Universität München, Chair of Analytical Food Chemistry, Freising-Weihenstephan, Germany.

Algal-derived dissolved organic matter (ADOM) originating from lysed Microcystis aeruginosa cells was investigated as precursor material to form disinfection by-products upon disinfection with free chlorine. Non-targeted ultrahigh resolution 12 T negative mode electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) revealed high molecular diversity in solid-phase extracted and ionizable components of Microcystis aeruginosa ADOM. The toxin microcystin LR was effectively degraded by free chlorine, which was expected. However, we found a high diversity of disinfection by-products associated with the addition of free chlorine to the water-soluble and solid-phase extractable fraction of ADOM and of double-bond moieties in abundant and known unsaturated fatty acids. Aromatic DOM precursors were absent from known metabolites of Microcystis aeruginosa and no evidence for aromatic disinfection by-products (DBPs) was found, despite N-containing compounds. A large diversification of N-containing molecular formulas was observed after chlorination, which seems indicative for the breakdown and oxidation of larger peptides. Additionally, a diverse group of N-compounds with presumed chloramine functional groups was observed. This study highlights the importance to evaluate ADOM and its ability to form different DBPs when compared to allochthonous or terrestrially-derived DOM.
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http://dx.doi.org/10.1016/j.watres.2019.02.030DOI Listing
May 2019

Organic sulfur fingerprint indicates continued injection fluid signature 10 months after hydraulic fracturing.

Environ Sci Process Impacts 2019 Feb;21(2):206-213

University of New Hampshire, Department of Civil and Environmental Engineering, Durham, NH 03825, USA.

Hydraulic fracturing requires the injection of large volumes of fluid to extract oil and gas from low permeability unconventional resources (e.g., shale, coalbed methane), resulting in the production of large volumes of highly complex and variable waste fluids. Shale gas fluid samples were collected from two hydraulically fractured wells in Morgantown, WV, USA at the Marcellus Shale Energy and Environment Laboratory (MSEEL) and analyzed using ultrahigh resolution mass spectrometry to investigate the dissolved organic sulfur (DOS) pool. Using a non-targeted approach, ions assigned DOS formulas were analyzed to identify dominant DOS classes, describe their temporal trends and their implications, and describe the molecular characteristics of the larger DOS pool. The average molecular weight of organic sulfur compounds in flowback decreased and was lowest in produced waters. The dominant DOS classes were putatively assigned to alcohol sulfate and alcohol ethoxysulfate surfactants, likely injected as fracturing fluid additives, on the basis of exact mass and homolog distribution matching. This DOS signature was identifiable 10 months after the initial injection of hydraulic fracturing fluid, and an absence of genes that code for alcohol ethoxysulfate degrading proteins (e.g., sulfatases) in the shale well genomes and metagenomes support that these additives are not readily degraded biologically and may continue to act as a chemical signature of the injected fluid. Understanding the diversity, lability, and fate of organic sulfur compounds in shale wells is important for engineering productive wells and preventing gas souring as well as understanding the consequences of unintended fluid release to the environment. The diversity of DOS, particularly more polar compounds, needs further investigation to determine if the identified characteristics and temporal patterns are unique to the analyzed wells or represent broader patterns found in other formations and under other operating conditions.
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http://dx.doi.org/10.1039/c8em00331aDOI Listing
February 2019

Yellowstone Hot Springs are Organic Chemodiversity Hot Spots.

Sci Rep 2018 09 20;8(1):14155. Epub 2018 Sep 20.

Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany.

Yellowstone National Park hydrothermal springs were investigated according to their organic geochemistry with a special focus on the Yellowstone hot spring dissolved organic matter (YDOM) that was solid-phase extracted. Here we show that YDOM has a unique chemodiversity that has not yet been observed anywhere else in aquatic surface environments and that Yellowstone hot springs are organic chemodiversity hot spots. Four main geochemically classified hot spring types (alkaline-chloride, mixed alkaline-chloride, acid-chloride-sulfate and travertine-precipitating) exhibited distinct organic molecular signatures that correlated remarkably well with the known inorganic geochemistry and manifested themselves in excitation emission matrix fluorescence, nuclear magnetic resonance, and ultrahigh resolution mass spectra. YDOM contained thousands of molecular formulas unique to Yellowstone of which 80% contained sulfur, even in low hydrogen sulfide containing alkaline-chloride springs. This unique YDOM reflects the extreme organic geochemistry present in the hydrothermal features of Yellowstone National Park.
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http://dx.doi.org/10.1038/s41598-018-32593-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6147864PMC
September 2018

Author Correction: Sulfate Reduction in Sediments Produces High Levels of Chromophoric Dissolved Organic Matter.

Sci Rep 2018 May 1;8(1):7086. Epub 2018 May 1.

University of Maryland Center for Environmental Science, Chesapeake Biological Laboratory, 146 Williams Street, Solomons, MD, 20688, USA.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
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http://dx.doi.org/10.1038/s41598-018-25424-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5928040PMC
May 2018

Temporal dynamics of halogenated organic compounds in Marcellus Shale flowback.

Water Res 2018 06 2;136:200-206. Epub 2018 Mar 2.

University of Maryland Center for Environmental Science, Chesapeake Biological Laboratory, USA.

The chemistry of hydraulic fracturing fluids and wastewaters is complex and is known to vary by operator, geologic formation, and fluid age. A time series of hydraulic fracturing fluids, flowback fluids, and produced waters was collected from two adjacent Marcellus Shale gas wells for organic chemical composition analyses using ultrahigh resolution mass spectrometry. Hierarchical clustering was used to compare and extract ions related to different fluid ages and many halogenated organic molecular ions were identified in flowback fluids and early produced waters based on exact mass. Iodinated organic compounds were the dominant halogen class in these clusters and were nearly undetectable in hydraulic fracturing fluid prior to injection. The iodinated ions increased in flowback and remained elevated after ten months of well production. We suggest that these trends are mainly driven by dissolved organic matter reacting with reactive halogen species formed abiotically through oxidizing chemical additives applied to the well and biotically via iodide-oxidizing bacteria. Understanding the implications of these identified halogenated organic compounds will require future investigation in to their structures and environmental fate.
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http://dx.doi.org/10.1016/j.watres.2018.02.055DOI Listing
June 2018

Extensive processing of sediment pore water dissolved organic matter during anoxic incubation as observed by high-field mass spectrometry (FTICR-MS).

Water Res 2018 02 7;129:252-263. Epub 2017 Nov 7.

Helmholtz Zentrum Munich, German Research Center for Environmental Health, Neuherberg, Germany. Electronic address:

Dissolved organic matter (DOM) contained in lake sediments is a carbon source for many microbial degradation processes, including aerobic and anaerobic mineralization. During anaerobic degradation, DOM is partially consumed and transformed into new molecules while the greenhouse gases methane (CH) and carbon dioxide (CO) are produced. In this study, we used ultrahigh resolution mass spectrometry to trace differences in the composition of solid-phase extractable (PPL resin) pore water DOM (SPE-DOM) isolated from surface sediments of three boreal lakes before and after 40 days of anoxic incubation, with concomitant determination of CH and CO evolution. CH and CO production detected by gas chromatography varied considerably among replicates and accounted for fractions of ∼2-4 × 10 of sedimentary organic carbon for CO and ∼0.8-2.4 × 10 for CH. In contrast, the relative changes of key bulk parameters during incubation, such as relative proportions of molecular series, elemental ratios, average mass and unsaturation, were regularly in the percent range (1-3% for compounds decreasing and 4-10% for compounds increasing), i.e. several orders of magnitude higher than mineralization alone. Computation of the average carbon oxidation state in CHO molecules of lake pore water DOM revealed rather non-selective large scale transformations of organic matter during incubation, with depletion of highly oxidized and highly reduced CHO molecules, and formation of rather non-labile fulvic acid type molecules. In general, proportions of CHO compounds slightly decreased. Nearly saturated CHO and CHOS lipid-like substances declined during incubation: these rather commonplace molecules were less specific indicators of lake sediment alteration than the particular compounds, such as certain oxygenated aromatics and carboxyl-rich alicyclic acids (CRAM) found more abundant after incubation. There was a remarkable general increase in many CHNO compounds during incubation across all lakes. Differences in DOM transformation between lakes corresponded with lake size and water residence time. While in the small lake Svarttjärn, CRAM increased during incubation, lignin-and tannin-like compounds were enriched in the large lake Bisen, suggesting selective preservation of these rather non-labile aromatic compounds rather than recent synthesis. SPE-DOM after incubation may represent freshly synthesized compounds, leftover bulk DOM which is primarily composed of intrinsically refractory molecules and/or microbial metabolites which were not consumed in our experiments. In spite of a low fraction of the total DOM being mineralized to CO and CH, the more pronounced change in molecular DOM composition during the incubation indicates that diagenetic modification of organic matter can be substantial compared to complete mineralization.
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http://dx.doi.org/10.1016/j.watres.2017.11.015DOI Listing
February 2018

Sulfate Reduction in Sediments Produces High Levels of Chromophoric Dissolved Organic Matter.

Sci Rep 2017 08 18;7(1):8829. Epub 2017 Aug 18.

University of Maryland Center for Environmental Science, Chesapeake Biological Laboratory, 146 Williams Street, Solomons, MD, 20688, USA.

Sulfate reduction plays an important role in altering dissolved organic matter (DOM) in estuarine and coastal sediments, although its role in the production of optically active chromophoric DOM (CDOM) and a subset of fluorescent DOM (FDOM) has not been previously investigated in detail. Freshwater sediment slurries were incubated anaerobically with added sulfate and acetate to promote sulfate-reducing bacteria. Ultraviolet visible (UV-Vis) absorbance and 3-dimensional excitation emission matrix (EEM) fluorescence spectra were measured over a five weeks anaerobic dark incubation period. Parallel Factor Analysis (PARAFAC) of FDOM determined components that increased significantly during dark and anaerobic incubation matching three components previously considered of terrestrially-derived or humic-like origin published in the OpenFluor database. The observed FDOM increase was strongly correlated (R = 0.96) with the reduction of sulfate. These results show a direct experimental link between sulfate reduction and FDOM production, which impacts our understanding of coastal FDOM sources and early sediment diagenesis. As 3D fluorescence techniques are commonly applied to diverse systems, these results provide increasing support that FDOM can have many diverse sources not consistently captured by common classifications such as "humic-like" fluorescence.
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http://dx.doi.org/10.1038/s41598-017-09223-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5562794PMC
August 2017

Sulfites and the wine metabolome.

Food Chem 2017 Dec 8;237:106-113. Epub 2017 May 8.

Analytical Food Chemistry, Technische Universität München, Alte Akademie 10, 85354 Freising-Weihenstephan, Germany; Research Unit Analytical BioGeoChemistry, Department of Environmental Sciences, Helmholtz Zentrum München, Ingolstaedter Landstrasse 1, 85764 Neuherberg, Germany. Electronic address:

In a context of societal concern about food preservation, the reduction of sulfite input plays a major role in the wine industry. To improve the understanding of the chemistry involved in the SO protection, a series of bottle aged Chardonnay wines made from the same must, but with different concentrations of SO added at pressing were analyzed by ultrahigh resolution mass spectrometry (FT-ICR-MS) and excitation emission matrix fluorescence (EEMF). Metabolic fingerprints from FT-ICR-MS data could discriminate wines according to the added concentration to the must but they also revealed chemistry-related differences according to the type of stopper, providing a wine metabolomics picture of the impact of distinct stopping strategies. Spearman rank correlation was applied to link the statistically modeled EEMF components (parallel factor analysis (PARAFAC)) and the exact mass information from FT-ICR-MS, and thus revealing the extent of sulfur-containing compounds which could show some correlation with fluorescence fingerprints.
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http://dx.doi.org/10.1016/j.foodchem.2017.05.039DOI Listing
December 2017

Organic compounds in hydraulic fracturing fluids and wastewaters: A review.

Water Res 2017 10 5;123:536-548. Epub 2017 Jul 5.

University of Maryland Center for Environmental Science, Chesapeake Biological Laboratory, Solomons, MD 20688, USA.

High volume hydraulic fracturing (HVHF) of shale to stimulate the release of natural gas produces a large quantity of wastewater in the form of flowback fluids and produced water. These wastewaters are highly variable in their composition and contain a mixture of fracturing fluid additives, geogenic inorganic and organic substances, and transformation products. The qualitative and quantitative analyses of organic compounds identified in HVHF fluids, flowback fluids, and produced waters are reviewed here to communicate knowledge gaps that exist in the composition of HVHF wastewaters. In general, analyses of organic compounds have focused on those amenable to gas chromatography, focusing on volatile and semi-volatile oil and gas compounds. Studies of more polar and non-volatile organic compounds have been limited by a lack of knowledge of what compounds may be present as well as quantitative methods and standards available for analyzing these complex mixtures. Liquid chromatography paired with high-resolution mass spectrometry has been used to investigate a number of additives and will be a key tool to further research on transformation products that are increasingly solubilized through physical, chemical, and biological processes in situ and during environmental contamination events. Diverse treatments have been tested and applied to HVHF wastewaters but limited information has been published on the quantitative removal of individual organic compounds. This review focuses on recently published information on organic compounds identified in flowback fluids and produced waters from HVHF.
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http://dx.doi.org/10.1016/j.watres.2017.07.012DOI Listing
October 2017

PARAFAC Modeling of Irradiation- and Oxidation-Induced Changes in Fluorescent Dissolved Organic Matter Extracted from Poultry Litter.

Environ Sci Technol 2017 Jul 27;51(14):8036-8047. Epub 2017 Jun 27.

University of Maryland Baltimore County Department of Chemical, Biochemical and Environmental Engineering 1000 Hilltop Circle, ECS 314 Baltimore, Maryland 21250 United States.

Parallel factor analysis (PARAFAC) applied to fluorescence excitation emission matrices (EEMs) allows quantitative assessment of the composition of fluorescent dissolved organic matter (DOM). In this study, we fit a four-component EEM-PARAFAC model to characterize DOM extracted from poultry litter. The data set included fluorescence EEMs from 291 untreated, irradiated (253.7 nm, 310-410 nm), and oxidized (UV-HO, ozone) poultry litter extracts. The four components were identified as microbial humic-, terrestrial humic-, tyrosine-, and tryptophan-like fluorescent signatures. The Tucker's congruence coefficients for components from the global (i.e., aggregated sample set) model and local (i.e., single poultry litter source) models were greater than 0.99, suggesting that the global EEM-PARAFAC model may be suitable to study poultry litter DOM from individual sources. In general, the transformation trends of the four fluorescence components were comparable for all poultry litter sources tested. For irradiation at 253.7 nm, ozonation, and UV-HO advanced oxidation, transformation of the humic-like components was slower than that of the tryptophan-like component. The opposite trend was observed for irradiation at 310-410 nm, due to differences in UV absorbance properties of components. Compared to the other EEM-PARAFAC components, the tyrosine-like component was fairly recalcitrant in irradiation and oxidation processes. This novel application of EEM-PARAFAC modeling provides insight into the composition and fate of agricultural DOM in natural and engineered systems.
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http://dx.doi.org/10.1021/acs.est.6b06589DOI Listing
July 2017

Picocyanobacteria and deep-ocean fluorescent dissolved organic matter share similar optical properties.

Nat Commun 2017 05 17;8:15284. Epub 2017 May 17.

Institute of Marine and Science Technology, Shandong University, Joint Lab of Microbial Oceanography at QNLMST, Wenhai Road, Qingdao 266237, China.

Marine chromophoric dissolved organic matter (CDOM) and its related fluorescent components (FDOM), which are widely distributed but highly photobleached in the surface ocean, are critical in regulating light attenuation in the ocean. However, the origins of marine FDOM are still under investigation. Here we show that cultured picocyanobacteria, Synechococcus and Prochlorococcus, release FDOM that closely match the typical fluorescent signals found in oceanic environments. Picocyanobacterial FDOM also shows comparable apparent fluorescent quantum yields and undergoes similar photo-degradation behaviour when compared with deep-ocean FDOM, further strengthening the similarity between them. Ultrahigh-resolution mass spectrometry (MS) and nuclear magnetic resonance spectroscopy reveal abundant nitrogen-containing compounds in Synechococcus DOM, which may originate from degradation products of the fluorescent phycobilin pigments. Given the importance of picocyanobacteria in the global carbon cycle, our results indicate that picocyanobacteria are likely to be important sources of marine autochthonous FDOM, which may accumulate in the deep ocean.
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http://dx.doi.org/10.1038/ncomms15284DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5442323PMC
May 2017

Halogenated Organic Compounds Identified in Hydraulic Fracturing Wastewaters Using Ultrahigh Resolution Mass Spectrometry.

Environ Sci Technol 2017 May 26;51(10):5377-5385. Epub 2017 Apr 26.

University of Maryland Center for Environmental Science , Chesapeake Biological Laboratory, Solomons, Maryland United States.

Large volumes of water return to the surface following hydraulic fracturing of deep shale formations to retrieve oil and natural gas. Current understanding of the specific organic constituents in these hydraulic fracturing wastewaters is limited to hydrocarbons and a fraction of known chemical additives. In this study, we analyzed hydraulic fracturing wastewater samples using ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) as a nontargeted technique to assign unambiguous molecular formulas to singly charged molecular ions. Halogenated molecular formulas were identified and confirmed using isotopic simulation and MS-MS fragmentation spectra. The abundance of halogenated organic compounds in flowback fluids rather than older wastewaters suggested that the observed molecular ions might have been related to hydraulic fracturing additives and related subsurface reactions, such as through the reaction of shale-extracted chloride, bromide, and iodide with strong oxidant additives (e.g., hypochlorite, persulfate, hydrogen peroxide) and subsequently with diverse dissolved organic matter. Some molecular ions matched the exact masses of known disinfection byproducts including diiodoacetic acid, dibromobenzoic acid, and diiodobenzoic acid. The identified halogenated organic compounds, particularly iodinated organic molecules, are absent from inland natural systems and these compounds could therefore play an important role as environmental tracers.
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http://dx.doi.org/10.1021/acs.est.6b06213DOI Listing
May 2017

Previously unknown class of metalorganic compounds revealed in meteorites.

Proc Natl Acad Sci U S A 2017 03 27;114(11):2819-2824. Epub 2017 Feb 27.

Research Unit Analytical BioGeoChemistry, Helmholtz Zentrum München, 85764 Neuherberg, Germany;

The rich diversity and complexity of organic matter found in meteorites is rapidly expanding our knowledge and understanding of extreme environments from which the early solar system emerged and evolved. Here, we report the discovery of a hitherto unknown chemical class, dihydroxymagnesium carboxylates [(OH)MgOCR], in meteoritic soluble organic matter. High collision energies, which are required for fragmentation, suggest substantial thermal stability of these Mg-metalorganics (CHOMg compounds). This was corroborated by their higher abundance in thermally processed meteorites. CHOMg compounds were found to be present in a set of 61 meteorites of diverse petrological classes. The appearance of this CHOMg chemical class extends the previously investigated, diverse set of CHNOS molecules. A connection between the evolution of organic compounds and minerals is made, as Mg released from minerals gets trapped into organic compounds. These CHOMg metalorganic compounds and their relation to thermal processing in meteorites might shed new light on our understanding of carbon speciation at a molecular level in meteorite parent bodies.
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http://dx.doi.org/10.1073/pnas.1616019114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5358384PMC
March 2017

Asymmetrical flow field-flow fractionation of white wine chromophoric colloidal matter.

Anal Bioanal Chem 2017 Apr 8;409(10):2757-2766. Epub 2017 Feb 8.

UMR PAM Université de Bourgogne/AgroSupDijon, Institut Universitaire de la Vigne et du Vin, Jules Guyot, 21004, Dijon, France.

Two analytical separation methods-size-exclusion chromatography and asymmetrical flow field-flow fractionation-were implemented to evaluate the integrity of the colloidal composition of Chardonnay white wine and the impact of pressing and fermentations on the final macromolecular composition. Wine chromophoric colloidal matter, representing UV-visible-absorbing wine macromolecules, was evaluated by optical and structural measurements combined with the description of elution profiles obtained by both separative techniques. The objective of this study was to apply these two types of fractionation on a typical Chardonnay white wine produced in Burgundy and to evaluate how each of them impacted the determination of the macromolecular chromophoric content of wine. UV-visible and fluorescence measurements of collected fractions were successfully applied. An additional proteomic study revealed that grape and microorganism proteins largely impacted the composition of chromophoric colloidal matter of Chardonnay wines. Asymmetrical flow field-flow fractionation appeared to be more reliable and less invasive with respect to the native chemical environment of chromophoric wine macromolecules, and hence is recommended as a tool to fractionate chromophoric colloidal matter in white wines. Graphical Abstract An innovative macromolecular separation method based on Asymmetrical Flow Field-Flow Fractionation was developed to better control colloidal dynamics across Chardonnay white winemaking.
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http://dx.doi.org/10.1007/s00216-017-0221-1DOI Listing
April 2017

Comprehensive structure-selective characterization of dissolved organic matter by reducing molecular complexity and increasing analytical dimensions.

Water Res 2016 Dec 14;106:477-487. Epub 2016 Oct 14.

Helmholtz Zentrum München, German Research Center for Environmental Health, Research Unit Analytical Biogeochemistry (BGC), Ingolstaedter Landstrasse 1, 85764, Neuherberg, Germany. Electronic address:

Deciphering the molecular codes of dissolved organic matter (DOM) improves our understanding of its role in the global element cycles and its active involvement in ecosystem services. This study demonstrates comprehensive characterization of DOM by an initial polarity-based stepwise solid phase extraction (SPE) with single methanol elution of the cartridges, but separate collection of equal aliquots of eluate. The reduction of molecular complexity in the individual DOM fractions attenuates intermolecular interactions and substantially increases the disposable resolution of any structure selective characterization. Suwannee River DOM (SR DOM) was used to collect five distinct SPE fractions with overall 91% DOC recovery. Optical spectroscopy (UV and fluorescence spectroscopy), high-field Fourier transform ion cyclotron mass spectrometry (FTICR MS) and nuclear magnetic resonance (NMR) spectroscopy showed analogous hierarchical clustering among the five eluates corroborating the robustness of this approach. Two abundant moderately hydrophobic fractions contained most of the SR DOM compounds, with substantial proportions of aliphatics, carboxylic-rich alicyclic molecules, carbohydrates and aromatics. A minor early eluting hydrophilic fraction was highly aliphatic and presented a large diversity of alicyclic carboxylic acids, whereas the two late eluting, minor hydrophobic fractions appeared as a largely defunctionalized mixture of aliphatic molecules. Comparative mass analysis showed that fractionation of SR DOM was governed by multiple molecular interactions depending on O/C ratio, molecular weight and aromaticity. The traditional optical indices SUVA and fluorescence index (FI) indicated the relative aromaticity in agreement with FTICR mass and NMR spectra; the classical fluorescent peaks A and C were observed in all four latter eluates. This versatile approach can be easily expanded to preparative scale under field conditions, and transferred to different DOM sources and SPE conditions.
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http://dx.doi.org/10.1016/j.watres.2016.10.034DOI Listing
December 2016

The completely fused medial clavicular epiphysis in high-frequency ultrasound scans as a diagnostic criterion for forensic age estimations in the living.

Int J Legal Med 2016 Nov 21;130(6):1603-1613. Epub 2016 Aug 21.

Department of Legal Medicine, University Hospital of Frankfurt, Goethe University, Kennedyallee 104, D-60596, Frankfurt am Main, Germany.

The assessment of ossification of the medial clavicular epiphysis plays a decisive role in the forensic age estimation of living subjects. Primarily for reasons of minimizing the radiation exposure currently associated with such evaluations, non-ionizing methods would be an advance.This study pursued the question whether full union of the medial clavicular epiphysis, visualized by high-frequency sonography, is a reliable criterion for age-threshold determinations. The ossification stage of the medial clavicular epiphysis of 215 female and 195 male volunteers, aged between 14 and 26 years, was evaluated in bilateral sonograms. Stage 4, defined as complete fusion by Schulz et al. (Int J Legal Med 122:163-167, 2008), was observed on at least one body side in 48 of 334 individuals younger than 21 years (14.4 %) and in 32 of 264 individuals younger than 18 years (12.1 %).With the high-frequency ultrasound used in this study, even the smallest convexities of the medial clavicular ending can be visualized. This may have led to overestimation of the ossification stage. It is not clear whether any observed roundings in the sonograms should actually be interpreted in terms of stages 3 and 4 as defined by Schulz. Also, due to the low penetration depth of high-frequency ultrasound waves, epiphyseal plate residues and ossification centers may have remained undetected. Reliable differentiation of the stages 1-4 with high-frequency sonography is thus difficult, and the results suggest that this method is not a radiation-free alternative to computed tomography, the current gold standard for determining age thresholds.
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http://dx.doi.org/10.1007/s00414-016-1435-zDOI Listing
November 2016

Geochemistry of Dissolved Organic Matter in a Spatially Highly Resolved Groundwater Petroleum Hydrocarbon Plume Cross-Section.

Environ Sci Technol 2016 06 17;50(11):5536-46. Epub 2016 May 17.

Helmholtz Zentrum München-German Research Center for Environmental Health , Research Unit Analytical BioGeoChemistry, D-85764 Neuherberg, Germany.

At numerous groundwater sites worldwide, natural dissolved organic matter (DOM) is quantitatively complemented with petroleum hydrocarbons. To date, research has been focused almost exclusively on the contaminants, but detailed insights of the interaction of contaminant biodegradation, dominant redox processes, and interactions with natural DOM are missing. This study linked on-site high resolution spatial sampling of groundwater with high resolution molecular characterization of DOM and its relation to groundwater geochemistry across a petroleum hydrocarbon plume cross-section. Electrospray- and atmospheric pressure photoionization (ESI, APPI) ultrahigh resolution mass spectrometry (FT-ICR-MS) revealed a strong interaction between DOM and reactive sulfur species linked to microbial sulfate reduction, i.e., the key redox process involved in contaminant biodegradation. Excitation emission matrix (EEM) fluorescence spectroscopy in combination with Parallel Factor Analysis (PARAFAC) modeling attributed DOM samples to specific contamination traits. Nuclear magnetic resonance (NMR) spectroscopy evaluated the aromatic compounds and their degradation products in samples influenced by the petroleum contamination and its biodegradation. Our orthogonal high resolution analytical approach enabled a comprehensive molecular level understanding of the DOM with respect to in situ petroleum hydrocarbon biodegradation and microbial sulfate reduction. The role of natural DOM as potential cosubstrate and detoxification reactant may improve future bioremediation strategies.
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http://dx.doi.org/10.1021/acs.est.6b00849DOI Listing
June 2016

Influence of pH on fluorescent dissolved organic matter photo-degradation.

Water Res 2015 Nov 28;85:266-74. Epub 2015 Aug 28.

Department of Civil and Environmental Engineering, University of California, Irvine, Irvine, CA 92697-2175, USA. Electronic address:

A novel semi-continuous excitation emission matrix (EEM) fluorescence and absorbance monitoring system has been developed. Full EEMs were collected simultaneously with absorbance spectra every 20 min during 24 h solar-simulated irradiation experiments, and the kinetic change of fluorescence of Suwannee River natural organic matter IHSS standard material (SRNOM) at various pH values was investigated. Parallel factor analysis (PARAFAC) was then used to isolate the photo-labile and pH-influenced fluorescent components of SRNOM. Kinetic analysis showed increasing rates of fluorescence loss with increasing pH. This has significant implications for the photo-degradation of dissolved natural organic matter during estuarine mixing, when large increases of pH are common. The influence of pH on fluorescence and photo-degradation kinetics emphasizes the need for pH to be monitored and accurately controlled during laboratory experiments. It is also highly recommended that when constructing PARAFAC models or monitoring changes in fluorescence data between samples of different origins, that the pH be held constant to remove any potential artifacts or misinterpretation of data.
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http://dx.doi.org/10.1016/j.watres.2015.08.047DOI Listing
November 2015