Papers by E. Douglas Nilsson
Science of The Total Environment, 2022
Airborne and marine microplastics were sampled during a cruise over the Baltic. • The concentrati... more Airborne and marine microplastics were sampled during a cruise over the Baltic. • The concentration, shape, colour, size, and type of microplastics were recorded. • Microplastic fluxes and turnover times were calculated. • An interplay of atmospheric transport together with emissions from the sea was seen. • Microplastics deposited to the sea could be re-emitted many times.
Size-resolved dry deposition velocities of particles with diameters 0.25-0.45 μm to a tropical ra... more Size-resolved dry deposition velocities of particles with diameters 0.25-0.45 μm to a tropical rain forest
This presentation reports the discovery that substances produced by microorganisms might trigger ... more This presentation reports the discovery that substances produced by microorganisms might trigger the formation of cloud in the atmosphere, at least under certain conditions. The Cloud Condensation Nuclei (CCN) efficiency of substances produced by microorganisms (bacteria, fungi, micro-algae ") that are common at Earth 's surface and in the oceans were studied. Their Kohler curves were determined experimentally by surface tension and osmometry measurements and found to have much lower critical supersaturations than any material studied so far, including inorganic salts. The presence of these substances was evidenced in aerosols from four different origins (coastal, marine, temperate forest, and Amazonian forest) by LC/MS/MS analyses and by their unique signature on the surface tension. These substances lowered the surface tension of the aerosols below 40 mN/m, allowing them to be activated into cloud droplets before inorganic particles. Microorganisms would thus be able to control cloud formation in Earth 's atmosphere. This would explain many previous observations such as correlations between algae bloom and cloud cover. Most importantly, this work identifies a new and direct link between the biosphere, the hydrological cycle, and climate.
Aerosol physical and chemical properties and trace gas concentrations were measured during the QU... more Aerosol physical and chemical properties and trace gas concentrations were measured during the QUEST field campaign in March-April, 2003, in Hyytiälä, Finland. Our aim was to understand the role of oxidation products of VOC's such as mono-and sesquiterpenes in atmospheric nucleation events. Particle chemical compositions were ACPD 7, 7819-7841, 2007 VOC oxidation products and new particle formation A. Laaksonen et al.
Aerosol particles affect the Earth’s climate, although their impact is associated with large unc... more Aerosol particles affect the Earth’s climate, although their impact is associated with large uncertainties. Primary marine aerosol represents a significant fraction of the global aerosol budget considering the Earth’s 70-percentage coverage by oceans. They are produced when bubbles burst at the ocean surface and can consist of sea salt, organic matter and bacteria. An experimental approach was here used to investigate the primary marine aerosol production from the bubble-bursting mechanism using water from four different geographical locations. The main findings include: Similar and stable aerosol number size distributions at all locations, centered close to 0.2 μm. Largely varying aerosol organic fractions, both with size and location. Clear tendency for increased water temperature to negatively influence the aerosol production. No covariance between surface water chlorophyll α and aerosol production on a 10-minute time scale, although decreased aerosol production was observed at ...
In this study data from Hyytiala in southern Finland during late winter 2003 are used to compare ... more In this study data from Hyytiala in southern Finland during late winter 2003 are used to compare the aerosol dry deposition above and below the forest canopy at this site. Additionally, data from Varrio in northern Finland during spring this same year are used to compare the aerosol deposition in Varrio, where the canopy is relatively thin, with the deposition in Hyytiala where the canopy is more compact. Aerosol fluxes were determined by using the eddy covariance method, in Hyytiala at altitudes of 23 m and 2 m (above and below canopy) and in Varrio at an altitude of 15 m (above the canopy), using similar ultrasonic anemometers and CPCs with a cut at 10 nm diameter. In figure 1 below (Hyytiala), “canopy” represents the difference between the fluxes at 23 m and 2 m and “ground” represents 2 m flux. In this figure fluxes have been separated to emissive (upper figure) and deposition fluxes (lower figure). For the deposition cases, fluxes to the canopy are larger than the fluxes to the...
Atmospheric Chemistry and Physics Discussions, 2018
The Nordic Centre of Excellence CRAICC (CRyosphere-Atmosphere Interactions in a Changing Arctic C... more The Nordic Centre of Excellence CRAICC (CRyosphere-Atmosphere Interactions in a Changing Arctic Climate), funded by NordForsk in the years 2011-2016, was the largest joint Nordic research and innovation initiative to date, aiming to strengthen research and innovation regarding climate change issues in the Nordic Region. CRAICC gathered more than 100 scientists from all Nordic countries in a virtual Centre with the objectives to identify and quantify the major processes controlling Arctic warming and related feedback mechanisms, to outline strategies to mitigate Arctic warming and to develop Nordic Earth System modelling with a focus on the short-lived climate forcers (SLCF), including natural and anthropogenic aerosols. The outcome of CRAICC is reflected in more than 150 peer-reviewed scientific publications, most of which are in the CRAICC special-issue of the journal Atmospheric Chemistry and Physics. This manuscript presents an overview on the main scientific topics investigated in the Centre and provides the reader a state-of-the-art comprehensive summary of what has been achieved in CRAICC with links to the particular publications for further detail. Facing the vast amount of outcomes we are not claiming to cover all results from CRAICC in this manuscript but concentrate here on the main results which are related to the feedback loops in the climate change-cryosphere interaction scheme affecting the Arctic amplification. 1 Introduction Near-surface climate warming in the Arctic has proceeded at approximately twice the global average rate since 1980. This extraordinary rate of warming has been recognized since the late 1990s (Serreze et al., 2000) and has accelerated even since then (Bekryaev et al., 2010), leading to extreme events in 2016 when October-December temperatures in large parts of the Arctic were more than 5˚C above normal and daily anomalies exceeded 16˚C in many locations
In this study, we measure the submicron size distributions and cloud condensation nucleus propert... more In this study, we measure the submicron size distributions and cloud condensation nucleus properties of aerosol particles produced from a laboratory system that simulates particle formation from bubble bursting. The experimental method consists of a plunging water jet into a stainless steel tank filled with 10 L of artificial seawater, with and without added organic compounds. The tank is equipped with a water pump that can be set at variable speeds. Preliminary results from size distribution measurements agree with previous studies, in that the number concentration and size of particles produced depend on the water jet flux. Observations of cloud condensation nucleus (CCN) activity are also affected by the water pump speed. The CCN activity of artificial seawater, at a salinity of 350/00 and with no added organic compounds, is similar to that of pure sodium chloride. Addition of as much as 1 g/L of D-mannitol does not considerably alter the particle size distribution, nor does it a...
The Future of the World's Climate, 2012
Chemically active climate compounds are either primary compounds like methane (CH4), removed by o... more Chemically active climate compounds are either primary compounds like methane (CH4), removed by oxidation in the atmosphere, or secondary compounds like ozone (O-3), sulfate and organic aerosols, both formed and removed in the atmosphere. Man-induced climate-chemistry interaction is a two-way process: Emissions of pollutants change the atmospheric composition contributing to climate change through the aforementioned climate components, and climate change, through changes in temperature, dynamics, the hydrological cycle, atmospheric stability, and biosphere-atmosphere interactions, affects the atmospheric composition and oxidation processes in the troposphere. Here we present progress in our understanding of processes of importance for climate-chemistry interactions, and their contributions to changes in atmospheric composition and climate forcing. A key factor is the oxidation potential involving compounds like O-3 and the hydroxyl radical (OH). Reported studies represent both current and future changes. Reported results include new estimates of radiative forcing based on extensive model studies of chemically active climate compounds like O-3, and of particles inducing both direct and indirect effects. Through EU projects like ACCENT, QUANTIFY, and the AeroCom project, extensive studies on regional and sector-wise differences in the impact on atmospheric distribution are performed. Studies have shown that land-based emissions have a different effect on climate than ship and aircraft emissions, and different measures are needed to reduce the climate impact. Several areas where climate change can affect the tropospheric oxidation process and the chemical composition are identified. This can take place through enhanced stratospheric-tropospheric exchange of ozone, more frequent periods with stable conditions favoring pollution build up over industrial areas, enhanced temperature induced biogenic emissions, methane releases from permafrost thawing, and enhanced concentration through reduced biospheric uptake. During the last 5-10 years, new observational data have been made available and used for model validation and the study of atmospheric processes. Although there are significant uncertainties in the modeling of composition changes, access to new observational data has improved modeling capability. Emission scenarios for the coming decades have a large uncertainty range, in particular with respect to regional trends, leading to a significant uncertainty range in estimated regional composition changes and climate impact.
Journal of Aerosol Science, 2000
Journal of Aerosol Science, 1998
Atmospheric Environment, 2009
Ecosystems and the atmosphere: This review describes the state of understanding the processes inv... more Ecosystems and the atmosphere: This review describes the state of understanding the processes involved in the exchange of trace gases and aerosols between the earth's surface and the atmosphere. The gases covered include NO, NO 2 , HONO, HNO 3 , NH 3 , SO 2 , DMS, Biogenic VOC, O 3 , CH 4 , N 2 O and particles in the size range 1 nm-10 mm including organic and inorganic chemical species. The main focus of the review is on the exchange between terrestrial ecosystems, both managed and natural and the atmosphere, although some new developments in ocean-atmosphere exchange are included. The material presented is biased towards the last decade, but includes earlier work, where more recent developments are limited or absent. New methodologies and instrumentation have enabled, if not driven technical advances in measurement. These developments have advanced the process understanding and upscaling of fluxes, especially for particles, VOC and NH 3. Examples of these applications include mass spectrometric methods, such as Aerosol Mass Spectrometry (AMS) adapted for field measurement of atmosphere-surface fluxes using micrometeorological methods for chemically resolved aerosols. Also briefly described are some advances in theory and techniques in micrometeorology. For some of the compounds there have been paradigm shifts in approach and application of both techniques and assessment. These include flux measurements over marine surfaces and urban areas using micrometeorological methods and the up-scaling of flux measurements using aircraft and satellite remote sensing. The application of a flux-based approach in assessment of O 3 effects on vegetation at regional scales is an important policy linked development secured through improved quantification of fluxes. The coupling of monitoring, modelling and intensive flux measurement at a continental scale within the NitroEurope network represents a quantum development in the application of research teams to address the underpinning science of reactive nitrogen in the cycling between ecosystems and the atmosphere in Europe. Some important developments of the science have been applied to assist in addressing policy questions, which have been the main driver of the research agenda, while other developments in understanding have not been applied to their wider field especially in chemistry-transport models through deficiencies in obtaining appropriate data to enable application or inertia within the modelling community. The paper identifies applications, gaps and research questions that have remained intractable at least since 2000 within the specialized sections of the paper, and where possible these have been focussed on research questions for the coming decade.
Atmospheric Chemistry and Physics, 2008
Aerosol physical and chemical properties and trace gas concentrations were measured during the QU... more Aerosol physical and chemical properties and trace gas concentrations were measured during the QUEST field campaign in March-April 2003, in Hyytiälä, Finland. Our aim was to understand the role of oxidation products of VOC's such as mono-and sesquiterpenes in atmospheric nucleation events. Particle chemical compositions were measured using the Aerodyne Aerosol Mass Spectrometer, and chemical compositions of aerosol samples collected with low-pressure impactors and a high volume sampler were analysed using a number of techniques. The results indicate that during and after new particle formation, all parti
Environmental Science & Technology, 2012
Sea spray particles ejected as a result of bubbles bursting from artificial seawater containing s... more Sea spray particles ejected as a result of bubbles bursting from artificial seawater containing salt and organic matter in a stainless steel tank were sampled for size distribution, morphology, and cloud condensation nucleus (CCN) activity. Bubbles were generated either by aeration through a diffuser or by water jet impingement on the seawater surface. Three objectives were addressed in this study. First, CCN activities of NaCl and two types of artificial sea salt containing only inorganic components were measured to establish a baseline for further measurements of mixed organic−inorganic particles. Second, the effect of varying bubble residence time in the bulk seawater solution on particle size and CCN activity was investigated and was found to be insignificant for the organic compounds studied. Finally, CCN activities of particles produced from jet impingement were compared with those produced from diffuser aeration. Analyses indicate a considerable amount of organic enrichment in the jet-produced particles relative to the bulk seawater composition when sodium laurate, an organic surfactant, is present in the seawater. In this case, the production of a thick foam layer during impingement may explain the difference in activation and supports hypotheses that particle production from the two methods of generating bubbles is not equal.
Journal of Aerosol Science
Science
The concerns of the young protesters are justified A statement by Scientists for Future concernin... more The concerns of the young protesters are justified A statement by Scientists for Future concerning the protests for more climate protection In March 2019, German-speaking scientists and scholars calling themselves Scientists for Future, published a statement in support of the youth protesters in Germany, Austria, and Switzerland (Fridays for Future, Klimastreik/Climate Strike), verifying the scientific evidence that the youth protestors refer to. In this article, they provide the full text of the statement, including the list of supporting facts (in both English and German) as well as an analysis of the results and impacts of the statement. Furthermore, they reflect on the challenges for scientists and scholars who feel a dual responsibility: on the one hand, to remain independent and politically neutral, and, on the other hand, to inform and warn societies of the dangers that lie ahead.
Uploads
Papers by E. Douglas Nilsson