The remote central Arctic during summertime has a pristine atmosphere with very low aerosol particle concentrations. As the region becomes increasingly ice-free during summer, enhanced ocean-atmosphere fluxes of aerosol particles and precursor gases may therefore have impacts on the climate. However, large knowledge gaps remain regarding the sources and physicochemical properties of aerosols in this region. Here, we present insights into the molecular composition of semi-volatile aerosol components collected in September 2018 during the MOCCHA (Microbiology-Ocean-Cloud-Coupling in the High Arctic) campaign as part of the Arctic Ocean 2018 expedition with the Swedish Icebreaker Oden. Analysis was performed offline in the laboratory using an iodide High Resolution Time-of-Flight Chemical Ionization Mass Spectrometer with a Filter Inlet for Gases and AEROsols (FIGAERO-HRToF-CIMS). Our analysis revealed significant signal from organic and sulfur-containing compounds, indicative of marine aerosol sources, with a wide range of carbon numbers and O : C ratios. Several of the sulfur-containing compounds are oxidation products of dimethyl sulfide (DMS), a gas released by phytoplankton and ice algae. Comparison of the time series of particulate and gas-phase DMS oxidation products did not reveal a significant correlation, indicative of the different lifetimes of precursor and oxidation products in the different phases. This is the first time the FIGAERO-HRToF-CIMS was used to investigate the composition of aerosols in the central Arctic. The detailed information on the molecular composition of Arctic aerosols presented here can be used for the assessment of aerosol solubility and volatility, which is relevant for understanding aerosol–cloud interactions.
Evolution of Turbulent Swirling Flow in a Small‑Scale Cyclone with Increasing Flow Rate: A LES Study
The flow field, vortex behaviour and pressure losses in a small-scale cyclone have been studied at a wide range of flow rate 0.23–39.7 NLPM (measured at 1 atm and 20 ◦C ) using the LES simulations that have been validated based on experimental measurements of the cyclone pressure drop. The following flow characteristics such as (1) the radial distribution of the tangential velocity; (2) the maximum tangential velocity and axial downward flow rate; (3) natural vortex length and rotation frequency of the vortex end; and (4) pressure losses in the cyclone have been analysed as a function of Reynolds number. The radial distribution of the tangential velocity inside the cyclone has been described by a proposed equation for adapted Burger’s vortex. The position of the lower end of the vortex (natural vortex length) as well as its rotational frequency have been investigated with the pressure sensing method. A unique vortex behaviour such as “vortex end jump” was revealed at some Reynolds numbers. Additionally, a deep analysis of the pressure losses in the cyclone has been performed which showed that the main pressure losses (up to 48%) occur in the vortex finder. Four flow regimes were revealed and a one-term power series model has been proposed to describe the effects of the Reynolds number on the Euler number (dimensionless pressure losses).
Estimating environmental hazard and risks from exposure to per-and polyfluoroalkyl substances (PFAS): Outcome of a SETAC focused topic meeting
The anhydrosugars, levoglucosan, mannosan and galactosan, are regarded as suitable molecular indicators of natural biomass combustion. Here, we evaluate summed anhydrosugars (SAS) as a paleofire indicator in a 6000 year-long fossil core from Agios Floros fen, Peloponnese, Greece, by analyzing charcoal fragments in parallel, throughout the sediment sequence. Modern surface soil samples from the same region were analysed for the presence of SAS, confirming the biomarker as an indicator of recent fire activity. The highest SAS concentrations in the fossil core were found in sections representing periods of wet conditions, both on local and regional scales and regionally widespread arboreal vegetation. Low amounts, or the absence, of SAS in the fossil core were associated with periods of dryness, regional dominance of non-arboreal vegetation and the presence of a fen rather than a lake ecosystem at the site. Micro-charcoal fragments were generally more abundant under these conditions. This suggests that SAS yield and deposition may vary with fuel availability and fire behavior, which in turn is affected by climate, local moisture and vegetation type. Forest fires result in more SAS compared to grass fires. SAS yield is also favored by low-temperature fires sustained under wet climate conditions. Preservation of SAS is likely to be compromised in the only seasonally wet fen ecosystem under the dry and warm Mediterranean climate conditions. The moist and shallow conditions in the wetland during hot summer months probably promote oxidation and biodegradation of the labile SAS molecules, compared to the more robust charcoal fragments. Thus, a multiproxy approach - using several proxies, both for fire, hydroclimate and vegetation change - is preferred when aiming to reconstruct past biomass burning from wetland ecosystems in a Mediterranean environment. The micro-charcoal record from Agios Floros reveals significant fire activity between 4400 and 2800 cal yr BP. This partly overlaps the Bronze Age period, associated with intense human environmental interaction and climate change in this area of Peloponnese, Greece.
Baltic Sea Spray Emissions: In Situ Eddy Covariance Fluxes vs. Simulated Tank Sea Spray
We present the first ever evaluation of sea spray aerosol eddy covariance (EC) fluxes at near coastal conditions and with limited fetch, and the first over water with brackish water (on aver-age 7 ppt). The measurements were made on the island of Garpen in the Baltic Sea (56°23’ N, 16°06’ E) in September 2005. We found that wind speed is a major factor that is driving an expo-nential increase in sea spray sea salt emissions, comparable to previous studies over waters with higher salinity. We were able to show that the inclusion of a thermodenuder in the EC system al-lowed for the parallel measurements of the dry unheated aerosol flux (representing both organic and sea salt sea spray emissions) and the heated (300 ˚C) non-volatile sea salt emissions. This study’s experimental approach also included measurements of the artificial sea spray formed in a tank in locally sampled water at the same location as the EC fluxes. We attempted to use the EC aerosol flux measurements to scale the tank measurements to aerosol emissions in order to derive a complete size distribution for the sea spray emission fluxes below the size range (0.3–2 µm dry diameter) of the optical particle counters (OPCs) in the EC system, covering in total 0.01 µm to 2 µm diameter. In the wind directions with long fetches (corresponding to conditions similar to open sea), we were able to distinguish between the aerosol emission fluxes of dry aerosol and heated non-volatile (sea salt only) in the smallest size bins of the OPC, and could therefore indi-rectly estimate the organic sea spray fraction. In agreement with several previous ambient and tank experiments deriving the size resolved chemical mass concentration of sea salt and wa-ter-insoluble organic sea spray, our EC fluxes showed that sea sprays were dominated by sea salt at sizes ≥1 µm diameter, and by organics at the smallest OPC sizes. Since we used direct measures of the sea spray emission fluxes, we confirmed previous suggestions that this size distribution of sea salt and organics is a signature of sea spray aerosols. We were able to show that two sea salt source parameterizations (Mårtensson et al. (2003) and Salter et al. (2015)) agreed fairly well with our observed heated EC aerosol emission fluxes, as long as their predicted emissions were modi-fied for the actual salinity by shifting the particle diameters proportionally to the cubic rote of the salinity. If, in addition, we added organics to the parameterized sea spray following the mono-layer model by Ellison et al. (1999), the combined sea spray parameterizations for sea salt and organics fell reasonably close to the observed fluxes for diameters > 0.15 µm, while one of them overpredicted the sea spray emissions below this size. The organic mono-layer model by El-lison et al. appeared to be able to explain most of the differences we observed between the aerosol emission fluxes with and without the thermodenuder.
Mechanisms of Arctic amplification and Arctic climate change are difficult to pinpoint, and current climate models do not represent the complex local processes and feedbacks at play, in particular for aerosol–climate interactions. This Perspective highlights the role of aerosols in contemporary Arctic climate change and stresses that the Arctic natural aerosol baseline is changing fast and its regional characteristics are very diverse. We argue that to improve understanding of present day and future Arctic, more detailed knowledge is needed on natural Arctic aerosol emissions, their evolution and transport, and the effects on cloud microphysics. In particular, observation and modelling work should focus on the sensitivity of aerosol–climate interactions to the rapidly evolving base state of the Arctic.
Regulating and Cultural Ecosystem Services of Urban Green Infrastructure in the Nordic Countries: A Systematic Review
| Int J Environ Res Public Health
In the Nordic countries (Denmark, Finland, Iceland, Norway and Sweden), the Urban Green Infrastructure (UGI) has been traditionally targeted at reducing flood risk. However, other Ecosystem Services (ES) became increasingly relevant in response to the challenges of urbanization and climate change. In total, 90 scientific articles addressing ES considered crucial contributions to the quality of life in cities are reviewed. These are classified as (1) regulating ES that minimize hazards such as heat, floods, air pollution and noise, and (2) cultural ES that promote well-being and health. We conclude that the planning and design of UGI should balance both the provision of ES and their side effects and disservices, aspects that seem to have been only marginally investigated. Climatesensitive planning practices are critical to guarantee that seasonal climate variability is accounted for at high-latitude regions. Nevertheless, diverging and seemingly inconsistent findings, together with gaps in the understanding of long-term effects, create obstacles for practitioners. Additionally, the limited involvement of end users points to a need of better engagement and communication, which in overall call for more collaborative research. Close relationships and interactions among different ES provided by urban greenery were found, yet few studies attempted an integrated evaluation. We argue that promoting interdisciplinary studies is fundamental to attain a holistic understanding of how plant traits affect the resulting ES; of the synergies between biophysical, physiological and psychological processes; and of the potential disservices of UGI, specifically in Nordic cities.
Microbial degradation of hydrophobic emerging contaminants from marine sediment slurries (Capbreton Canyon) to pure bacterial strain
Azaroff A; Mathilde M; Miossec C; Gassie C; Guyneaud R
| J. Hazard. Mater.
Sorption of PFOS in 114 Well-characterized Tropical and Temperate Soils: Application of Multivariate and Artificial Neural Network Analyses