The emissions caused by combustion of fuels for energy production, are a major cause of air pollution, and at the same time, due to their optical properties, also affect the climate change. Ambient air quality has a significant impact on human health, as it poses a risk that is difficult to avoid. In Europe, 90 percent of the urban population is exposed to excessive concentrations of particulate matter (PM), nitrogen oxides and ozone or benzene in the ambient air. Conservative estimates show that the number of premature deaths due to ambient air pollution per year in Europe is 790,000 and 7 million worldwide, and that the air pollution reduces the live expectancy in Europe by about 2.2 years, with an annual attributable mortality rate of 133/100,000. Data for Slovenia, obtained from the National Institute of Public Health of the Republic of Slovenia, show that 1500 people die every year due to air pollution. By reducing the level of PM in the air in excessively polluted areas, the life expectancy in Slovenia would increase by half to one year, which gives particular importance to the field of air pollution monitoring and management. With respect to particulates in ambient air, the restrictions usually apply to PM10 (particles with an aerodynamic diameter of less than 10 µm). EU directive 2008/50/EC establishes two limits related to PM10: the average daily concentration should not exceed 50 µg/m3 more than 35 times per year, and the average annual concentration should not exceed 40 µg/m3. However, since the toxicity of particles, which is not fully understood, is largely influenced by their chemical composition and size (the smallest particles penetrate the deepest into the lung, enter the blood stream), it is also necessary to measure the composition, mass and number densities of smaller PM2.5 and PM1 (aerodynamic diameter of less than 2.5 and 1 μm). Namely, the particle size distribution is log-normal, meaning that the number of particles smaller than 1 μm exceeds the number of particles larger than 1 μm but contributes very little to the total mass of PM10. Carbonaceous aerosols are a significant or largest fraction of PM2.5. Among carbonaceous aerosols, the most significant absorber of light is black carbon (BC) that was recognized by the latest Intergovernmental Panel on Climate Change report as the second most important contributor to global warming (immediately after CO2) with contributions ranging from 20% to 40%. Since aerosols also affect the global radiation balance by scattering of light, where their size and shape play a key role, we are not yet fully understanding the underlying processes. Many possibilities for high-impact research are open, in particular through developing novel methods for measuring the optical properties of aerosols that are directly related to the morphology and composition of particles and important for better understanding of climate change and of the impact on human health. The objective of the proposed research project is to develop new, innovative methods for measuring the optical properties of aerosols such as absorption and scattering coefficient, scattering phase function, and refractive index in real-time. A more detailed and complete information on the optical properties of aerosols will enable better classification of particles by composition, size and structure and at the same time enable better understanding of their impact on the human health and biological processes. Furthermore, knowledge of the optical properties of aerosols will also lead to a better understanding of the impact that aerosols have on the climate and its changes. By bringing together the two research groups with extensive experience and knowledge in design of state-of-the-art measurement systems for monitoring carbonaceous aerosols on one hand and utilization of light propagation modeling for estimation of optical properties on the other hand, the project creates a perfect environment for high impact research.
