Determination of equivalent Black Carbon Concentrations by MABI (Multi-Wavelength Absorption Black Carbon Instrument) and of the respective mass absorption cross section (MAC): Case study for Krakow, Poland and Athens, Greece.

Equivalent black carbon (eBC) is generated from the partial combustion of fossil fuels and biomass. The scientific interest in eBC is large because its contribution to the PM_2.5 fraction is high, especially in urban areas. It should be noted that combustion-related aerosols (including eBC) have been linked to adverse health effects and are considered more harmful than other aerosol components. In addition, eBC is considered the second most important component of global warming in terms of direct forcing. Until now. there is a lack of information on eBC concentrations in Poland, mostly due to lack of relevant instrumentation. The position of Poland in the center of Europe, as well as the presence of multiple combustion sources, make this type of measurements and data very relevant to the scientific community, both for health impact assessment and climate change studies. In the present study, the MABI (Multi-Wavelength Absorption Black Carbon Instrument), a new instrument measuring light transmission of particles collected on filters, was assessed.  MABI was developed by the Australian Nuclear Science and Technology Organization (www.ansto.gov.au). The instrument consists of an optical assembly and electronic case. The instrument optics includes, among others, the multi-wavelength light source (7 LEDs), sampler holder, and photodetector. In the instrument, opaque glass is used to scatter the scattered light back through the filter to the detector. MABI offers the advantage of off-line measurements of aerosol light transmission, at seven fixed wavelengths (from 405 nm to 1050 nm). The performance of the instrument was assessed for different types of filters (Teflon and quartz fibre) collected at two distinct atmospheric environments, an urban background site in Krakow, Poland and an urban background site in Athens, Greece. Mass absorption coefficients provided by the manufacturer were used in order to calculate eBC from light transmission data (Ryś and Samek, Atmosphere, 2022). In addition, thermo-optical analysis (Lab OC-EC Aerosol Analyzer, Sunset Laboratory Inc.) was performed on the quartz fibre samples for the determination of elemental carbon (EC) concentrations. EC data were then used in order to calculate site-specific mass absorption cross section (MAC) values for the MABI. Finally, an aethalometer (AE33, Aerosol Magee Scientific) was used in parallel to PM sampling in Athens, in order to provide a reference eBC value, against which the performance of MABI was assessed.

Acknowledgments: This research project was supported by the program “Excellence initiative—research university” for the University of Science and Technology and ATMO ACCESS TNA project