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453 results on '"Nelson, Robert K."'

6. Production of Two Highly Abundant 2‑Methyl-Branched Fatty Acids by Blooms of the Globally Significant Marine Cyanobacteria Trichodesmium erythraeum

Author

Gosselin, Kelsey M, Nelson, Robert K, Spivak, Amanda C, Sylva, Sean P, Van Mooy, Benjamin AS, Aeppli, Christoph, Sharpless, Charles M, O’Neil, Gregory W, Arrington, Eleanor C, Reddy, Christopher M, and Valentine, David L

Subjects
Chemical Engineering, Materials Engineering
Abstract

The bloom-forming cyanobacteria Trichodesmium contribute up to 30% to the total fixed nitrogen in the global oceans and thereby drive substantial productivity. On an expedition in the Gulf of Mexico, we observed and sampled surface slicks, some of which included dense blooms of Trichodesmium erythraeum. These bloom samples contained abundant and atypical free fatty acids, identified here as 2-methyldecanoic acid and 2-methyldodecanoic acid. The high abundance and unusual branching pattern of these compounds suggest that they may play a specific role in this globally important organism.

Published
2021

18. Influence of anthropogenic activities and risk assessment on protected mangrove forest using traditional and emerging molecular markers (Ceará coast, northeastern Brazil)

Author

Santos, Felipe R., Martins, Davi A., Morais, Pollyana C.V., Oliveira, André H.B., Gama, Allyne F., Nascimento, Ronaldo F., Choi-Lima, Katherine F., Moreira, Lucas Buruaem, Abessa, Denis M.S., Nelson, Robert K., Reddy, Christopher M., Swarthout, Robert F., and Cavalcante, Rivelino M.

Published
2019
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20. Fallout plume of submerged oil from Deepwater Horizon

Author

Valentine, David L, Fisher, G Burch, Bagby, Sarah C, Nelson, Robert K, Reddy, Christopher M, Sylva, Sean P, and Woo, Mary A

Subjects
Life Below Water, Macondo Well blowout, Gulf of Mexico, ocean pollution, petroleum spill, deep plumes
Abstract

The sinking of the Deepwater Horizon in the Gulf of Mexico led to uncontrolled emission of oil to the ocean, with an official government estimate of ∼ 5.0 million barrels released. Among the pressing uncertainties surrounding this event is the fate of ∼ 2 million barrels of submerged oil thought to have been trapped in deep-ocean intrusion layers at depths of ∼ 1,000-1,300 m. Here we use chemical distributions of hydrocarbons in >3,000 sediment samples from 534 locations to describe a footprint of oil deposited on the deep-ocean floor. Using a recalcitrant biomarker of crude oil, 17α(H),21β(H)-hopane (hopane), we have identified a 3,200-km(2) region around the Macondo Well contaminated by ∼ 1.8 ± 1.0 × 10(6) g of excess hopane. Based on spatial, chemical, oceanographic, and mass balance considerations, we calculate that this contamination represents 4-31% of the oil sequestered in the deep ocean. The pattern of contamination points to deep-ocean intrusion layers as the source and is most consistent with dual modes of deposition: a "bathtub ring" formed from an oil-rich layer of water impinging laterally upon the continental slope (at a depth of ∼ 900-1,300 m) and a higher-flux "fallout plume" where suspended oil particles sank to underlying sediment (at a depth of ∼ 1,300-1,700 m). We also suggest that a significant quantity of oil was deposited on the ocean floor outside this area but so far has evaded detection because of its heterogeneous spatial distribution.

Published
2014

24. Integrating comprehensive two-dimensional gas chromatography and downhole fluid analysis to validate a spill-fill sequence of reservoirs with variations of biodegradation, water washing and thermal maturity

Author

Forsythe, Jerimiah C., Martin, Robin, De Santo, Ilaria, Tyndall, Richard, Arman, Kate, Pye, Jonathan, De Nicolais, Nelly, Nelson, Robert K., Pomerantz, Andrew E., Kenyon-Roberts, Stephen, Zuo, Julian Y., Betancourt, Soraya S., Reddy, Christopher, Peters, Kenneth E., and Mullins, Oliver C.

Published
2017
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32. Hydroxyapatite catalyzed hydrothermal liquefaction transforms food waste from an environmental liability to renewable fuel

Author

LeClerc, Heather O., Tompsett, Geoffrey A., Paulsen, Alex D., McKenna, Amy M., Niles, Sydney F., Reddy, Christopher M., Nelson, Robert K., Cheng, Feng, Teixeira, Andrew R., Timko, Michael T., LeClerc, Heather O., Tompsett, Geoffrey A., Paulsen, Alex D., McKenna, Amy M., Niles, Sydney F., Reddy, Christopher M., Nelson, Robert K., Cheng, Feng, Teixeira, Andrew R., and Timko, Michael T.

Abstract

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in LeClerc, H., Tompsett, G., Paulsen, A., McKenna, A., Niles, S., Reddy, C., Nelson, R., Cheng, F., Teixeira, A., & Timko, M. Hydroxyapatite catalyzed hydrothermal liquefaction transforms food waste from an environmental liability to renewable fuel. IScience, 25(9), (2022): 104916, https://doi.org/10.1016/j.isci.2022.104916., 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., This work was funded by the DOE Bioenergy Technology Office (DE-EE0008513), a DOE DBIR (DE-SC0015784) and the MassCEC. The authors thank WenWen Yao, Department of Environmental Science at WPI, for TOC analysis, Mainstream Engineering for heating value characterization of the oil and solid samples, Wei Fan for assistance in obtaining SEM images and, Julia Martin and Ronald Grimm for their assistance in collecting XPS data, and Jeffrey R. Page for his assistance with oil upgrading and analysis. HOL was partially funded for this work by NSF Graduate Research Fellowship award number 2038257. A portion of this work was performed at the National High Magnetic Field Laboratory Ion Cyclotron Resonance user facility, which is supported by the NSF Division of Materials Research and Division of Chemistry through DMR 16-44779 and the State of Florida.

Published
2023

33. Advances in Chemical Analysis of Oil Spills Since the Deepwater Horizon Disaster.

Author

Wise, Stephen A., Rodgers, Ryan P., Reddy, Christopher M., Nelson, Robert K., Kujawinski, Elizabeth B., Wade, Terry L., Campiglia, Andres D., and Liu, Zhanfei

Subjects
BP Deepwater Horizon Explosion & Oil Spill, 2010, ANALYTICAL chemistry, GAS chromatography/Mass spectrometry (GC-MS), CHEMICAL weathering, POLYCYCLIC aromatic hydrocarbons, GAS chromatography, OIL spills
Abstract

Analytical techniques for chemical analysis of oil, oil photochemical and biological transformation products, and dispersants and their biodegradation products benefited significantly from research following the 2010 Deepwater Horizon (DWH) disaster. Crude oil and weathered-oil matrix reference materials were developed based on the Macondo well oil and characterized for polycyclic aromatic hydrocarbons, hopanes, and steranes for use to assure and improve the quality of analytical measurements in oil spill research. Advanced gas chromatography (GC) techniques such as comprehensive two-dimensional GC (GC × GC), pyrolysis GC with mass spectrometry (MS), and GC with tandem MS (GC-MS/MS) provide a greater understanding at the molecular level of composition and complexity of oil and weathering changes. The capabilities of high-resolution MS (HRMS) were utilized to extend the analytical characterization window beyond conventional GC-based methods to include polar and high molecular mass components (>400 Da) and to provide new opportunities for discovery, characterization, and investigation of photooxidation and biotransformation products. Novel separation approaches to reduce the complexity of the oil and weathered oil prior to high-resolution MS and advanced fluorescence spectrometry have increased the information available on spilled oil and transformation products. HRMS methods were developed to achieve the required precision and sensitivity for detection of dispersants and to provide molecular-level characterization of the complex surfactants. Overall, research funding following the DWH oil spill significantly advanced and expanded the use of analytical techniques for chemical analysis to support petroleum and dispersant characterization and investigations of fate and effects of not only the DWH oil spill but future spills. [ABSTRACT FROM AUTHOR]

Published
2023
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37. Is there a similarity between the 2019 and 2022 oil spills that occurred on the coast of Ceará (Northeast Brazil)? An analysis based on forensic environmental geochemistry

Author

Azevedo, Rufino N.A., primary, Bezerra, Kamylla M.M., additional, Nascimento, Ronaldo F., additional, Nelson, Robert K., additional, Reddy, Christopher M., additional, Nascimento, Adriana P., additional, Oliveira, André H.B., additional, Martins, Laercio L., additional, and Cavalcante, Rivelino M., additional

Published
2022
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40. Mapping inequality

Author

Connolly, N. D. B., primary, Winling, LaDale, additional, Nelson, Robert K., additional, and Marciano, Richard, additional

Published
2018
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