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In this study, we discuss for the first time the relationships between the diversity of the bacterial population and of the metals and metalloids concentrations in the sediments of the Red River Delta, Vietnam. The analysis of the 16S rRNA by the Illumina technology revealed a diversified population and a potential of bioremediation by the microorganisms, notably by the Bacilli relatively abundant in the Bach Dang estuary, where high metals and metalloids concentrations were highlighted. This work offers new information on the environmental context of the delta and highlights the potential impact that metals and metalloids may have on the bacterial population. Further investigations on the role of the bacteria in the biogeochemistry of this ecosystem will be of interest for the development of bioremediation processes., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Chifflet, Chu Van, Bui Van, Pham The, Mari and Pradel.)

A mesophilic, anaerobic, endospore-forming, fermentative bacterium designated strain 8C15b T was isolated from bank sediment of the Bach Dang Estuary, Haiphong, Vietnam. The Bach Dang Estuary, where Haiphong harbour is located, is subject to strong anthropogenic influence, resulting in high concentrations of black carbon and heavy metals. Strain 8C15b T grew optimally at 30 °C, pH 7.5 and with 2.5 % (w/v) NaCl. The main cellular fatty acids consisted of iso-C 15 : 0 (51 %), iso-C 15:1 ω7 c (32 %) and iso-C 13 : 0 (5 %). Genomic considerations of strain 8C15b T and comparisons with the phylogenetically closest strains of the genus Tepidibacter provide evidence that Tepidibacter thalassicus SC562 T (=DSM 15285 T ), Tepidibacter formicigenes DV1184 T (=DSM 15518 T ), Tepidibacter mesophilus B1 T (=JCM 16806 T ) and strain 8C15b T could be differentiated at the species level. We propose the name Tepidibacter aestuarii sp. nov. for the type strain 8C15b T (=JCM 35983 T =KCTC 25692 T ). Finally, the nickel-tolerance properties of strain 8C15b T are highlighted in this study.

We report the complete genome sequence of Tepidibacter sp. strain 8C15b, isolated from bank sediments of Haiphong Bay, Vietnam. The genome includes a 3,628,320-bp circular chromosome and a plasmid of 38,213 bp.

Emissions from ships at berth are small compared to the total ship emissions; however, they are one of the main contributors to pollutants in the air of densely-populated areas, consequently heavily affecting public health. This is due to auxiliary marine engines being used to generate electric power and steam for heating and providing services. The present study has been conducted on an engine representative of a marine auxiliary, which was a heavy duty, six-cylinder, turbocharged and after-cooled engine with a high pressure common rail injection system. Engine performance and emission characterisations during cold start are the focus of this paper, since cold start is significantly influential. Three tested fuels were used, including the reference diesel and two IMO (International Maritime Organization) compliant spiked fuels. The research engine was operated at a constant speed and 25% load condition after 12 h cooled soak. Results show that during cold start, significant heat generated from combustion is used to heat the engine block, coolant and lubricant. During the first minute, compared to the second minute, emissions of particle number (PN), carbon monoxide (CO), particulate matter (PM), and nitrogen oxides (NO x ) were approximately 10, 4, 2 and 1.5 times higher, respectively. The engine control unit (ECU) plays a vital role in reducing engine emissions by changing the engine injection strategy based on the engine coolant temperature. IMO-compliant fuels, which were higher viscosity fuels associated with high sulphur content, resulted in an engine emission increase during cold start. It should be taken into account that auxiliary marine diesel engines, working at partial load conditions during cold start, contribute considerably to emissions in coastal areas. It demonstrates a need to implement practical measures, such as engine pre-heating, to obtain both environmental and public health advantages in coastal areas., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The combustion of fossil fuels and biomass produces pyrogenic organic matter usually known as 'black carbon' (BC), which are transported across the atmosphere as particulate aerosol, eventually deposited on land and oceans. Soil studies have investigated the potential microbial colonization and remineralization of BC particles, but this process has been seldom studied in marine waters. BC provides a significant input of organic carbon to the oceans, yet its fate and role in biogeochemical cycling remains unknown. Here we explored the microbial colonization of BC particles in coastal seawater samples collected in Halong Bay (northern Vietnam). Using high-resolution mass spectrometry and microscopy methods, we observed an increasing colonization of BC particles by marine microbes in the presence of amino acids. Our results suggest that natural organic matter (NOM) present in seawater may promote the microbial colonization and eventual remineralization of BC particles. Future experiments should explore the potential microbial remineralization of BC particles to unveil the role of this massive source of carbon to marine ecosystems., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Particle emission characteristics and engine performance were investigated from an auxiliary, heavy duty, six-cylinder, turbocharged and after-cooled diesel engine with a common rail injection system using spiked fuels with different combinations of sulphur (S) and vanadium (V) spiking. The effect of fuel S content on both particle number (PN) and mass (PM) was clearly observed in this study. Higher PN and PM were observed for fuels with higher S contents at all engine load conditions. This study also found a correlation between fuel S content and nucleation mode particle number concentration which have more harmful impact on human health than larger particles. The highest PN and PM were observed at partial load conditions. In addition, S in fuel resulted in higher viscosity of spiked fuels, which led to lower engine blow-by. Fuel V content was observed in this study, evidencing that it had no clear effect on engine performance and emissions. Increased engine load also resulted in higher engine blow-by. The lower peak of in-cylinder pressure observed at both pre-mixed and diffusion combustion phases with the spiked fuels may be associated with the lower energy content in the fuel blends compared to diesel fuel., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

This study investigated particle and gaseous emission factors from a large cargo vessel for her whole voyage including at berth, manoeuvring and cruising. Quantification of these factors assists in minimising the uncertainty in the current methods of exhaust gas emission factor estimation. Engine performance and emissions from the main marine engine were measured on-board while the ship was manoeuvring and cruising at sea. Emissions of an auxiliary engine working at 55% of maximum continuous rating (MCR) were measured when the ship was at actual harbour stopovers. Gaseous and particle emission factors in this study are presented in g kWh -1 or # kWh -1 , and compared with previous studies. Results showed that the SO 2 emission factor is higher than that of previous studies due to the high sulphur content of the fuel used. The particle number size distributions showed only one mode for different operating conditions of the ship, with a peak at around 40-50 nm, which was dominated by ultrafine particles. Emission factors of CO, HC, PM and PN observed during ship manoeuvring were much higher than that of those recorded at cruising condition. These findings highlight the importance of quantification and monitoring ship emissions in close proximity to port areas, as they can have the highest impact on population exposure., (Copyright © 2017 Elsevier Ltd. All rights reserved.)