An update on dissolved methane distribution in the subtropical North Atlantic Ocean

Methane (CH4) is a potent greenhouse gas and plays a significant role in recent increasing global temperatures. The oceans are a natural source of methane contributing to atmospheric methane concentrations, yet our understanding of the oceanic methane cycle is poorly constrained. Accumulating evidence indicates that a significant part of oceanic CH4 is produced in oxygenated surface waters as a by-product of phytoplanktonic activity. This study focused on the subtropical North Atlantic Ocean (26∘ N, 80′ W and 26∘ N, 18′ W) where the distribution of dissolved CH4 concentrations and associated air–sea fluxes during winter 2020 were investigated. Water samples from 64 stations were collected from the upper water column up to depths of 400 m. The upper oxic mixed layer was oversaturated in dissolved CH4 with concentrations ranging 3–7 nmol L−1, with the highest concentrations of 7–10 nmol L−1 found to the east of the transect, consistent with other subtropical regions of the world's oceans. The high anomalies of dissolved CH4 were found to be associated with phosphate-depleted waters and regions where the abundance of the ubiquitous picocyanobacteria Synechococcus and Prochlorococcus were elevated. Although other phytoplanktonic phyla cannot be excluded, this suggests that cyanobacteria contribute to the release of CH4 in this region. The calculation of air–sea fluxes further confirmed the subtropical North Atlantic Ocean as a source of CH4. This study provides evidence to corroborate the key role that picocyanobacteria play in helping to explain the oversaturation of CH4 found in surface mixed layer of the open ocean, otherwise known as the “ocean methane paradox”

Ein autonomes, meerestaugliches Raman/SERS-Messgerät zum In-situ-Nachweis von Chemikalien im Meerwasser

Die kontinuierliche Überwachung von Schadstoffen im Meerwasser in sehr geringen Konzentrationen (nM-Bereich) ist von weltweitem Interesse, um einen wirkungsvollen Umweltschutz zu gewährleisten. Zur Realisierung einer technologischen Plattform für derartige Untersuchungen wurde ein autonomes, meerestaugliches In-situ-System für den Nachweis ausgewählter Chemikalien mit Hilfe der oberflächenverstärkten Ramanspektroskopie (SERS) entwickelt und getestet. Die Selektivität und Empfindlichkeit der verwendeten Technik wurde anhand umfangreicher Laboruntersuchungen verifiziert. Dabei kamen mehr als 100 Wasser- und Sedimentproben ausgewählter Orte von 3 Kontinenten (Europa, Amerika und Asien) zum Einsatz. Unter Verwendung eines Mikrosystem-Diodenlasers mit zwei leicht gegeneinander verschobenen Anregungswellenlängen (671,0 nm und 671,6 nm) konnte so erstmalig ein weltweiter Vergleich der Proben mit einer Kombination von SERS und SERDS (shifted excitation Raman difference spectroscopy) durchgeführt werden. Als wesentliche Verschmutzungen ließen sich dabei polyzyklische aromatische Kohlenwasserstoffe (PAKs) wie beispielsweise Fluoranthen, Acenaphtylen oder Pyren sowie Biphenyl identifizieren. Diese Substanzen traten dabei häufig in einem Gemisch auf, in seltenen Fällen (< 5 %) jedoch auch als einzelne Komponenten. Aufbauend auf den Laboruntersuchungen erfolgte die Entwicklung eines portablen Raman¬systems. Weiterführende Untersuchungen an Bord eines Forschungsschiffes in der Arktis konnten die Einsatzfähigkeit des Systems unter rauen Umgebungsbedingungen verifizieren. Dabei wurden zahlreiche SERS-Oberflächen erfolgreich hinsichtlich ihrer Eignung zum Schadstoffnachweis sowie ihrer Stabilität analysiert. Die Stabilitätstests auf kurzen (Stunden) und langen (Tage) Zeitskalen erfolgten mit Hilfe von Oberflächenwasser, das über eine Rohrleitung kontinuierlich an Bord gepumpt wurde. Die Substrate zeigten bei einer Lagerung in Frischwasser mit einem Intensitätsabfall von nur 5 % nach 7 Tagen die besten Resultate. In Kontakt mit Meerwasser ergab sich eine Reduktion der Intensität von lediglich 2 % innerhalb der ersten 10 Stunden sowie von 20 % nach 7 Tagen. Die Zugabe ausgewählter PAKs in das Meerwasser in verschiedenen Konzentrationen ergab im Vergleich zu den Laboruntersuchungen verbesserte Nachweisgrenzen von 0,3 nM für Anthracen (Labor: 1 nM) und 1 nM für Fluoranthen (Labor: 1,2 nM). Abschließend wurde erstmals ein autonomes, meerestaugliches Messgerät konstruiert, das den SERS-Sensor mit integriertem Mikrosystem-Diodenlaser, kompakte Lasertreiber, ein speziell entwickeltes Miniaturspektrometer, alle erforderlichen elektronischen Bauteile, einen Mikrocomputer sowie einen wiederaufladbaren Akku enthält. Alle Komponenten des Systems befinden sich in einem druckfesten Gehäuse, das für den Unterwasser-Einsatz bis zu einer Tiefe von 100 m konzipiert ist. Das Messgerät wurde erfolgreich im Mittelmeer bei der IFREMER in La Syene-Sur-Mer im dortigen Hafen sowie bei Einsätzen auf See getestet, wobei sich charakteristische Ramansignale von Fluoranthen und Biphenyl nachweisen ließen. Auch ohne die Anwendung der SERS-Substrate konnten bei Integrationszeiten von 5–10 s Ramansignale von Salzionen (SO42-) im Meerwasser detektiert werden. Die durchgeführten Untersuchungen verdeutlichen die Einsetzbarkeit innovativer Raman-, SERDS- und SERS/SERDS-Sensoren zum In-situ-Nachweis gefährlicher Umweltschadstoffe im Meerwasser im nM-Bereich an beliebigen Untersuchungsorten.The continuous monitoring of dangerous pollutants at very low concentrations (nM range) in the sea is of global importance to ensure environmental protection. To realize a technological basis for this purpose, an autonomous in situ sea going instrument for SERS (surface enhanced Raman spectroscopy) detection of selected chemicals was developed and tested. The selectivity and sensitivity of the applied technique was verified by extensive laboratory investigations, with more than 100 water and sediment samples collected at chosen locations from three continents: Europe, America, and Asia. For the first time, such a worldwide comparison of specimens was carried out applying a combination of SERS with SERDS (shifted excitation Raman difference spectroscopy), by means of a microsystem diode laser with two slightly shifted emission wavelengths (671.0 nm and 671.6 nm). Here, polycyclic aromatic hydrocarbons (PAHs) as fluoranthene, acenaphtylene, and pyrene as well as biphenyl could be identified as main pollutants – usually as a mixture of several chemicals, very rarely (< 5 %) as a single component. Based on the laboratory experiments, portable Raman equipment was developed. Further studies were carried out in the Arctic area onboard a research vessel, in order to prove the ability of the system to work under harsh field conditions. Various SERS surfaces were successfully tested for its suitability for pollutant detection and stability during short (hours) and long term (days) measurements in surface seawater, which was continuously pumped on board through a pipe. The highest stability of the substrates could be achieved when immersed in fresh water, with an overall intensity decrease of only 5 % after 7 days of exposure. In contact with seawater, the overall intensity is reduced by 2 % within the first 10 h and by 20 % after 7 days. Spiking tests with selected PAHs dissolved in seawater showed lower in situ measured limits of detection compared to the calculated values for the laboratory experiments, e.g. 0.3 nM for anthracene (laboratory: 1 nM) and 1 nM for fluoranthene (laboratory: 1.2 nM). Finally, for the first time an autonomous sea going instrument was constructed, including the SERS sensor with integrated microsystem diode laser, compact laser drivers, a specially developed miniature spectrometer, all required electronic components, a microcomputer and a rechargeable battery. All parts of the system are contained in a pressure-resistant housing, enabling underwater experiments down to a depth of 100 m. The instrument was successfully tested in the Mediterranean Sea at IFREMER La Syene-Sur-Mer in the local harbor and during sea trials, detecting characteristic signals of fluoranthene and biphenyl. Even without SERS enhancement, Raman signals from the salt ions (SO42-) in seawater could be detected with integrations times of 10 s. The conducted experiments clearly demonstrate the applicability of innovative Raman, SERDS, and SERS/SERDS sensors for the in situ detection of hazardous environmental pollutions, in the nM-range, in seawater at any area of interest

GNSS applications: personal safety concerns

The current study discusses the results of a survey on the topic of “GNSS applications: user preferences”. The aim is to understand user preferences of GNSS applications in order to develop competitive research projects, new GNSS products / services and further increases in global GNSS market shares. The questionnaire was conducted during September – October 2015. The results of the questionnaire highlighted strong concerns about security and personal safety-related topics, while LBS were chosen as “least important” applications by almost half of the users.acceptedVersionPeer reviewe

Increased Temperature and Turbulence Alter the Effects of Leachates from Tire Particles on Fathead Minnow (Pimephales promelas)

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Environmental Science & Technology, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.est.9b05994Tire particles are of concern as a stressor due to the combination of their chemical constituents, high emission rates, and global distribution. Once in the environment, they will interact with physical parameters (e.g., UV, temperature). The interaction of chemical pollution with changing physical environmental parameters is often underestimated in ecotoxicology. Here, we investigate the role of temperature, mechanical stress (i.e., turbulence), UV, and CO2 on the effects of tire leachates on fish. Two samples of tire particles were exposed to four different levels of each physical stressor. A toxicological assessment was performed with fathead minnow embryos assessing five end points (hatching success, time to hatch, length, deformities, and heart rate). Results showed that variations of temperature and mechanical stress affect the toxicological impact of tire leachates. Zn and/or polycyclic aromatic hydrocarbons (pyrene, phenanthrene, chrysene, benzo[a]pyrene, anthracene, naphthalene, fluoranthene, and benzo[ghi]perylene) were identified in the leachate and tire samples by Raman/surface-enhanced Raman spectroscopy and gas chromatography with mass spectroscopy, respectively.The current study was funded by a Strategic Grant from the Natural Science and Engineering Research Council for Canada. The authors would like to acknowledge Anne-Marie Dowgiallo from Ocean Optics for the preparation of CNP-Au substrates