Periodic Reporting for period 4 - SURFACE (The unexplored world of aerosol surfaces and their impacts.)
Período documentado: 2021-09-01 hasta 2023-02-28
We are changing the composition of Earth’s atmosphere, with profound consequences for the environment and our wellbeing. Tiny aerosol particles are globally responsible for much of the health effects and mortality related to air pollution, now dwarfing many other major risk factors. Atmospheric particles also play several key roles in regulating Earth’s climate via their critical influence on the global radiation balance and cloud formation in the atmosphere. Every single cloud droplet has formed from water nucleating on the surface of an aerosol particle. Aerosols and droplets provide the media for condensed-phase chemistry and other multiphase processes in the atmosphere, but large gaps remain in our understanding of their formation, transformations, and climate interactions. Our key idea is that surface properties play crucial roles in these processes, but currently next to nothing is known about the surfaces of atmospheric aerosols and cloud droplets and their impacts are therefore laregly unconstrained. We have recently demonstrated that such surfaces are significantly different from the surrounding gas, liquid, and solid material and their unique properties have the potential to impact aerosol processes all the way to the global scale. However, atmospheric chemistry and global climate models have only considered surface-specific properties of aerosols in a few cases. This project aims to establish the role of surfaces in closing the knowledge gaps surrounding atmospheric aerosols and provide a new framework for describing aerosol effects in a wide range of contexts. The potential implications for our understanding of air pollution, human health effects, and climate change are profound.
A highly multidisciplinary project team has been formed of researchers with background in atmospheric and aerosol sciences, surface science and spectroscopic methods, chemical engineering and quantum chemistry. We have performed a large number of experiments to characterize surfaces for a suite of aerosol model systems and real atmospheric samples, using mainly novel synchrotron radiation spectroscopy and imaging methods. Other state-of-the-art molecular-level techniques were also successfully applied. We have carried out quantum chemistry simulations to support the interpretation of surface sensitive experiments and shed further light on the underlying molecular mechanisms.
Many experiments involve first applications of these methods for atmospherically relevant aerosol systems, or for aerosol research in general, and have involved modification and further development of setups, experimental procedures, and data analysis, as well as interpretation of first-of-a-kind experimental data. We have worked closely with facility staff, developers and leading experts in each technique. Access to synchrotron facilities have been applied worldwide in open competition and campaigns carried out in Sweden, Germany, France, United Kingdom, and Japan. In particular, we have performed some of the first experiments as commissioning experts and expert users at newly opened beamlines of the MAX IV synchrotron facility in Lund, Sweden. The globally unique properties of the MAX IV light source has already led to new discoveries which to our knowledge could not have been made anywhere else.
Specific and often surprising surface properties have been successfully identified and quantified for many of the systems studied. In particular, we demonstrated significant surface-specific shifts in acid-base equilibria of atmospheric surface active organics towards the neutral species in the surface. This has profound implications for atmospheric chemistry and cloud processing, where chemical reactions in cloud droplets and aqueous aerosols are strongly dependent on acidity.
We have begun tracing the fingerprints of surfaces in aerosol processes of atmospheric relevance through different scales. To this end, we developed a new surface model based on the insights from surface sensitive experiments. The monolayer model was validated experimentally in collaboration with University of Bristol using a globally unique setup for studying levitated single droplets. These experiments provide the first demonstration of size-dependent droplet surface tension and how surface tension is modulated by the changing surface area and composition. Surface tension is a key parameter determining the growth and cloud formation of droplets in the atmosphere and verification of this long-speculated phenomenon has large potential impacts of predictions of aerosol climate effects.
We furthermore successfully implemented the monolayer surface model into larger models describing the growth and cloud formation of both single droplets and a large ensembles, such as a cloud. These models have in turn been used to explicitly describe the evolution of droplet surfaces and demonstrate their impact in aerosol processes which are critical to the chemistry and climate effects in the atmosphere. Some of these predictions have been successfully validated in aerosol experiments at various conditions, with more currently in planning.
The project team has given keynote presentations in international conferences of both atmospheric, aerosol and synchrotron science. We have also taken part in various public outreach initiatives, including the making of the comic book “Little Things” about the project and speaking in connection with the Air Guitar World Championship and Polar Bear Pitching events, as well as the upcoming TEDxOulu event Arctic Matters.
Many experiments involve first applications of these methods for atmospherically relevant aerosol systems, or for aerosol research in general, and have involved modification and further development of setups, experimental procedures, and data analysis, as well as interpretation of first-of-a-kind experimental data. We have worked closely with facility staff, developers and leading experts in each technique. Access to synchrotron facilities have been applied worldwide in open competition and campaigns carried out in Sweden, Germany, France, United Kingdom, and Japan. In particular, we have performed some of the first experiments as commissioning experts and expert users at newly opened beamlines of the MAX IV synchrotron facility in Lund, Sweden. The globally unique properties of the MAX IV light source has already led to new discoveries which to our knowledge could not have been made anywhere else.
Specific and often surprising surface properties have been successfully identified and quantified for many of the systems studied. In particular, we demonstrated significant surface-specific shifts in acid-base equilibria of atmospheric surface active organics towards the neutral species in the surface. This has profound implications for atmospheric chemistry and cloud processing, where chemical reactions in cloud droplets and aqueous aerosols are strongly dependent on acidity.
We have begun tracing the fingerprints of surfaces in aerosol processes of atmospheric relevance through different scales. To this end, we developed a new surface model based on the insights from surface sensitive experiments. The monolayer model was validated experimentally in collaboration with University of Bristol using a globally unique setup for studying levitated single droplets. These experiments provide the first demonstration of size-dependent droplet surface tension and how surface tension is modulated by the changing surface area and composition. Surface tension is a key parameter determining the growth and cloud formation of droplets in the atmosphere and verification of this long-speculated phenomenon has large potential impacts of predictions of aerosol climate effects.
We furthermore successfully implemented the monolayer surface model into larger models describing the growth and cloud formation of both single droplets and a large ensembles, such as a cloud. These models have in turn been used to explicitly describe the evolution of droplet surfaces and demonstrate their impact in aerosol processes which are critical to the chemistry and climate effects in the atmosphere. Some of these predictions have been successfully validated in aerosol experiments at various conditions, with more currently in planning.
The project team has given keynote presentations in international conferences of both atmospheric, aerosol and synchrotron science. We have also taken part in various public outreach initiatives, including the making of the comic book “Little Things” about the project and speaking in connection with the Air Guitar World Championship and Polar Bear Pitching events, as well as the upcoming TEDxOulu event Arctic Matters.
We have successfully demonstrated how novel developments in cutting-edge experimental methods, in particular spectroscopy and imaging methods using fourth generation synchrotron radiation, enables direct molecular-level characterizations of atmospheric surfaces. In a series of experiments, we made the first direct surface specific characterizations of such surfaces in various conditions and discovered unique properties, which could profoundly change atmospheric predictions, when taken into account. We developed the theoretical platform to enable tracing the fingerprints of specific surface properties in experimental and modeled aerosol processes and atmospheric effects on increasing scale, from the molecular to the global. Successful demonstrations of unique aerosol surface fingerprints will constitute truly novel insights into a currently uncharted area of the atmospheric system and establish an entirely new frontier in aerosol research and atmospheric science.