Publications by authors named "Stéphanie Gagné"

7 Publications

  • Page 1 of 1

Ash-Decorated and Ash-Painted Soot from Residual and Distillate-Fuel Combustion in Four Marine Engines and One Aviation Engine.

Environ Sci Technol 2021 May 27;55(10):6584-6593. Epub 2021 Apr 27.

Metrology Research Centre, National Research Council Canada, Ottawa K1A 0R6, Canada.

Soot is typically the dominant component of the nonvolatile particles emitted from internal combustion engines. Although soot is primarily composed of carbon, its chemistry, toxicity, and oxidation rates may be strongly influenced by internally mixed inorganic metal compounds (ash). Here, we describe the detailed microstructure of ash internally mixed with soot from four marine engines and one aviation engine. The engines were operated on different fuels and lubrication oils; the fuels included four residual fuels and five distillate fuels such as diesel, natural gas, and Jet A-1. Using annular-dark-field scanning transmission electron microscopy (ADF-STEM), we observed that ash may occur either as distinct nodules on the soot particle (decorated) or as continuous streaks (painted). Both structures may exist within a single particle. Decorated soot was observed for both distillate and residual fuels and contained elements associated with either the fuel (V, Ni, Fe, S) or with the lubrication oil (Zn, Ca, P). Painted soot was observed only for residual-fuel soot, and only contained elements associated with the fuel. Additional composition measurements by inductively coupled plasma mass spectrometry (ICP-MS) of filter samples indicated that the internal mixing trends of ash with soot were consistent with the overall ash-to-carbon ratio of the sampled combustion aerosols. Painted soot may form when molten ash coagulates with or condenses onto soot within engines.
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http://dx.doi.org/10.1021/acs.est.0c07130DOI Listing
May 2021

Comprehensive analysis of the air quality impacts of switching a marine vessel from diesel fuel to natural gas.

Environ Pollut 2020 Nov 15;266(Pt 3):115404. Epub 2020 Aug 15.

Department of Chemical and Environmental Engineering, Bourns College of Engineering, University of California, Riverside, CA, 92507, United States; University of California, Bourns College of Engineering, Center for Environmental Research and Technology (CE-CERT), 1084 Columbia Avenue, Riverside, CA, 92507, United States. Electronic address:

New environmental regulations are mandating cleaner fuels and lower emissions from all maritime operations. Natural gas (NG) is a fuel that enables mariners to meet regulations; however, emissions data from maritime operations with natural gas is limited. We measured emissions of criteria, toxic and greenhouse pollutants from a dual-fuel marine engine running either on diesel fuel or NG as well as engine activity and analyzed the impacts on pollutants, health, and climate change. Results showed that particulate matter (PM), black carbon (BC), nitric oxides (NO), and carbon dioxide (CO) were reduced by about 93%, 97%, 92%, and 18%, respectively when switching from diesel to NG. Reductions of this magnitude provide a valuable tool for the many port communities struggling with meeting air quality standards. While these pollutants were reduced, formaldehyde (HCHO), carbon monoxide (CO) and methane (CH) increased several-fold. A health risk assessment of exhaust plume focused on when the vessel was stationary, and at-berth showed the diesel plume increased long-term health risk and the NG plume increased short-term health risk. An analysis of greenhouse gases (GHGs) and BC was performed and revealed that, on a hundred year basis, the whole fuel cycle global warming potential (GWP) per kWh including well-to-tank and exhaust was 50% to few times higher than that of diesel at lower engine loads, but that it was similar at 75% load and lower at higher loads. Mitigation strategies for further reducing pollutants from NG exhaust are discussed and showed potential for reducing short-term health risks and climate impacts.
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http://dx.doi.org/10.1016/j.envpol.2020.115404DOI Listing
November 2020

Characterization and Reduction of In-Use CH Emissions from a Dual Fuel Marine Engine Using Wavelength Modulation Spectroscopy.

Environ Sci Technol 2019 03 13;53(5):2892-2899. Epub 2019 Feb 13.

Department of Mechanical Engineering , University of British Columbia , 2054-6250 Applied Science Lane , Vancouver , British Columbia V6T 1Z4 , Canada.

In-use exhaust stream CH emissions from two dual fuel marine engines were characterized and strategies for CH reduction were identified and evaluated. For this, a low-cost, portable, wavelength modulation spectroscopy (WMS) system was developed. The performance of the developed WMS sensor was assessed using gas standards and demonstrated on a heavy-duty, diesel pilot ignited, direct-injection natural gas research engine through comparison to a flame ionization detector. The WMS sensor was subsequently used to measure the exhaust-stream CH concentration from two diesel pilot-ignited, port-injected natural gas engines on a coastal vessel while under normal operation. Using cylinder deactivation to reduce the excess air ratio, λ, and vessel operation changes to minimize operation at lower loads, the total CH emission were reduced by up to 33%. The measured, load specific CH emissions were subsequently used to identify an improved vessel operation strategy, with an estimated 56-60% reduction in CH emissions. These results demonstrate the importance of considering the real-world engine operation profile for accurate estimates of the global warming potential, as well as the utility of a WMS sensor for characterizing and mitigating in-use CH emissions.
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http://dx.doi.org/10.1021/acs.est.8b04244DOI Listing
March 2019

Relatedness of wildlife and livestock avian isolates of the nosocomial pathogen Acinetobacter baumannii to lineages spread in hospitals worldwide.

Environ Microbiol 2017 10 9;19(10):4349-4364. Epub 2017 Oct 9.

Faculty of Biological Sciences, University of Zielona Góra, Prof. Z. Szafrana Street 1, 65-561 Zielona Góra, Poland.

The natural habitats and potential reservoirs of the nosocomial pathogen Acinetobacter baumannii are poorly defined. Here, we put forth and tested the hypothesis of avian reservoirs of A. baumannii. We screened tracheal and rectal swab samples from livestock (chicken, geese) and wild birds (white stork nestlings) and isolated A. baumannii from 3% of sampled chicken (n = 220), 8% of geese (n = 40) and 25% of white stork nestlings (n = 661). Virulence of selected avian A. baumannii isolates was comparable to that of clinical isolates in the Galleria mellonella infection model. Whole genome sequencing revealed the close relationship of an antibiotic-susceptible chicken isolate from Germany with a multidrug-resistant human clinical isolate from China and additional linkages between livestock isolates and human clinical isolates related to international clonal lineages. Moreover, we identified stork isolates related to human clinical isolates from the United States. Multilocus sequence typing disclosed further kinship between avian and human isolates. Avian isolates do not form a distinct clade within the phylogeny of A. baumannii, instead they diverge into different lineages. Further, we provide evidence that A. baumannii is constantly present in the habitats occupied by storks. Collectively, our study suggests A. baumannii could be a zoonotic organism that may disseminate into livestock.
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http://dx.doi.org/10.1111/1462-2920.13931DOI Listing
October 2017

A  TIR effector mediates immune evasion by targeting UBAP1 and TLR adaptors.

EMBO J 2017 07 8;36(13):1869-1887. Epub 2017 May 8.

Laboratory of Molecular Microbiology and Structural Biochemistry, Centre National de la Recherche Scientifique, University of Lyon, Lyon, France

Bacterial pathogens often subvert the innate immune system to establish a successful infection. The direct inhibition of downstream components of innate immune pathways is particularly well documented but how bacteria interfere with receptor proximal events is far less well understood. Here, we describe a Toll/interleukin 1 receptor (TIR) domain-containing protein (PumA) of the multi-drug resistant PA7 strain. We found that PumA is essential for virulence and inhibits NF-κB, a property transferable to non-PumA strain PA14, suggesting no additional factors are needed for PumA function. The TIR domain is able to interact with the Toll-like receptor (TLR) adaptors TIRAP and MyD88, as well as the ubiquitin-associated protein 1 (UBAP1), a component of the endosomal-sorting complex required for transport I (ESCRT-I). These interactions are not spatially exclusive as we show UBAP1 can associate with MyD88, enhancing its plasma membrane localization. Combined targeting of UBAP1 and TLR adaptors by PumA impedes both cytokine and TLR receptor signalling, highlighting a novel strategy for innate immune evasion.
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http://dx.doi.org/10.15252/embj.201695343DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5494471PMC
July 2017

Differential Role of the T6SS in Acinetobacter baumannii Virulence.

PLoS One 2015 24;10(9):e0138265. Epub 2015 Sep 24.

Bases Moléculaires et Structurales des Systèmes Infectieux, CNRS UMR 5086, Université Lyon 1, Institut de Biologie et Chimie des Protéines, Lyon, France.

Gram-negative bacteria, such as Acinetobacter baumannii, are an increasing burden in hospitals worldwide with an alarming spread of multi-drug resistant (MDR) strains. Herein, we compared a type strain (ATCC17978), a non-clinical isolate (DSM30011) and MDR strains of A. baumannii implicated in hospital outbreaks (Ab242, Ab244 and Ab825), revealing distinct patterns of type VI secretion system (T6SS) functionality. The T6SS genomic locus is present and was actively transcribed in all of the above strains. However, only the A. baumannii DSM30011 strain was capable of killing Escherichia coli in a T6SS-dependent manner, unlike the clinical isolates, which failed to display an active T6SS in vitro. In addition, DSM30011 was able to outcompete ATCC17978 as well as Pseudomonas aeruginosa and Klebsiella pneumoniae, bacterial pathogens relevant in mixed nosocomial infections. Finally, we found that the T6SS of DSM30011 is required for host colonization of the model organism Galleria mellonella suggesting that this system could play an important role in A. baumannii virulence in a strain-specific manner.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0138265PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4581634PMC
June 2016

Role of sulphuric acid, ammonia and galactic cosmic rays in atmospheric aerosol nucleation.

Nature 2011 Aug 24;476(7361):429-33. Epub 2011 Aug 24.

CERN, CH-1211 Geneva, Switzerland.

Atmospheric aerosols exert an important influence on climate through their effects on stratiform cloud albedo and lifetime and the invigoration of convective storms. Model calculations suggest that almost half of the global cloud condensation nuclei in the atmospheric boundary layer may originate from the nucleation of aerosols from trace condensable vapours, although the sensitivity of the number of cloud condensation nuclei to changes of nucleation rate may be small. Despite extensive research, fundamental questions remain about the nucleation rate of sulphuric acid particles and the mechanisms responsible, including the roles of galactic cosmic rays and other chemical species such as ammonia. Here we present the first results from the CLOUD experiment at CERN. We find that atmospherically relevant ammonia mixing ratios of 100 parts per trillion by volume, or less, increase the nucleation rate of sulphuric acid particles more than 100-1,000-fold. Time-resolved molecular measurements reveal that nucleation proceeds by a base-stabilization mechanism involving the stepwise accretion of ammonia molecules. Ions increase the nucleation rate by an additional factor of between two and more than ten at ground-level galactic-cosmic-ray intensities, provided that the nucleation rate lies below the limiting ion-pair production rate. We find that ion-induced binary nucleation of H(2)SO(4)-H(2)O can occur in the mid-troposphere but is negligible in the boundary layer. However, even with the large enhancements in rate due to ammonia and ions, atmospheric concentrations of ammonia and sulphuric acid are insufficient to account for observed boundary-layer nucleation.
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http://dx.doi.org/10.1038/nature10343DOI Listing
August 2011