The fundamental insufficiency of scientific knowledge on the sources, formation and properties of aerosols, especially the organic aerosol fraction, hampers our knowledge of the climate system of the Earth. Aerosols are of particular concern in the vulnerable and quickly changing Arctic environment, and there is an urgent need to obtain more detailed knowledge of chemical and physical processes affecting aerosol formation and climate effects. At the present level of scientific understanding we do not have the tools and knowledge to predict, how air pollution and feedback mechanisms affect aerosol-ageing processes and thus chemical composition and climate properties of organic aerosols.
Aerosols during Arctic haze periods are often very acidic, and can undergo surface reactions affecting both composition and physical-chemical properties. One important and not well-understood example is the formation of organosulfates, since this group of compounds has recently been observed at considerable levels during Arctic haze. In a series of carefully designed laboratory experiments, we will investigate whether the organosulfate formation process actually occurs on the surface of a highly acidic aerosol or in the bulk phase, as well as follow the associated changes in climate-relevant properties such as volatility and viscosity. The ultra-high sensitivity and nanometer sizing resolutions of the unique single-particle mass spectrometer SPLAT II at EMSL allows us to follow coating and evaporation kinetics of individual size-selected particles by quantifying the evolution in terms of particle size, density, shape, morphology, and composition as a function of time. We will also study how changes in aerosol viscosity induced by changes in relative humidity, as well as aerosol-ageing processes, affect the coating and reactivity of seed particles. In addition the volatility and viscosity of pure organosulfate aerosols will be investigated using authentic standards.
Comprehensive chemical composition of specific Arctic aerosols will be investigated in selected atmospheric aerosol samples collected in the high-Arctic during periods representing different environmental conditions e.g. summer vs. winter. A Linear Ion Trap Quadrupole (LTQ) Orbitrap MS equipped with a nanospray desorption/electrospray ionization (nano-DESI) source will provide ultra-high resolution mass spectrometric data. The mass information and accuracy of the instrument will provide new knowledge on chemistry and organic chemical composition of high-Arctic aerosols. Data will be analyzed with particular focus on presence of organosulfates in the ambient samples and effects of aerosol ageing processes on the chemical composition.
The project will provide important new information on processes affecting composition of organic aerosols and their climate relevant effects through a unique combination of techniques and knowledge from different disciplines. The outcome will be of importance to our understanding of aerosol processes and biogenic-anthropogenic interactions in general and in the Arctic in particular. The necessary level of sensitivity, accuracy and detailed information for these investigations to be successful can only be achieved through access to the outstanding facilities at EMSL.