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Aerosols and organic source apportionment were characterized using data collected during two measurement campaigns. These campaigns were conducted during the summer and winter seasons at Măgurele, a site located southwest of Bucharest, the capital of Romania and one of the largest cities in southeastern Europe (raking seven in Europe based on population). The summer campaign was conducted between 7 June–18 July 2012, and the winter campaign from 14 January–6 February 2013. Approximately 50% of the organic fraction contribution to the total submicron particulate matter sampled by aerosol mass spectrometer was evidenced during both seasons. Submicronic organic aerosol sources were quantified using the positive matrix factorization approach. For warm (summer) and cold (winter) seasons, more than 50% from total organics was represented by oxidized factors. For the summer season, separate analyses were conducted on data influenced by urban and non-urban sources. The influence of pollution from Bucharest on the measurement site was observed in aerosol concentration and composition. The primary organic aerosols have different contribution percentage during summer, depending on their main origin. The influence of Bucharest, during summer, included cooking contribution of 13%. The periods with more regional influence were characterized by lower contribution from traffic and biomass burning in a total proportion of 28%. In winter, the influence of local non-traffic sources was dominant. For more than 99% of the measurements, the biomass burning indicator, f 60 , exceeded the background value, with residential heating being an important source in this area. Fossil fuel contribution was confirmed for one week during the winter campaign, when 14 C analysis of total and elemental carbon revealed the presence of 17% fossil contributions to total carbon. Mass spectrometry, 14 C and absorption data suggest biomass burning as the predominant primary source of organic aerosols for the winter season. [ABSTRACT FROM AUTHOR]

In this study, AERONET (Aerosol Robotic Network) and EARLINET (European Aerosol Research Lidar Network) data from 17 collocated lidar and sun photometer stations were used to characterize the optical properties of aerosol and their types for the 2008–2018 period in various regions of Europe. The analysis was done on six cluster domains defined using circulation types around each station and their common circulation features. As concluded from the lidar photometer measurements, the typical aerosol particles observed during 2008–2018 over Europe were medium-sized, medium absorbing particles with low spectral dependence. The highest mean values for the lidar ratio at 532 nm were recorded over Northeastern Europe and were associated with Smoke particles, while the lowest mean values for the Angstrom exponent were identified over the Southwest cluster and were associated with Dust and Marine particles. Smoke (37%) and Continental (25%) aerosol types were the predominant aerosol types in Europe, followed by Continental Polluted (17%), Dust (10%), and Marine/Cloud (10%) types. The seasonal variability was insignificant at the continental scale, showing a small increase in the percentage of Smoke during spring and a small increase of Dust during autumn. The aerosol optical depth (AOD) slightly decreased with time, while the Angstrom exponent oscillated between "hot and smoky" years (2011–2015) on the one hand and "dusty" years (2008–2010) and "wet" years (2017–2018) on the other hand. The high variability from year to year showed that aerosol transport in the troposphere became more and more important in the overall balance of the columnar aerosol load. [ABSTRACT FROM AUTHOR]

In this work we extract the microphysical properties of aerosols for a collection of measurement cases with low volume depolarization ratio originating from fire sources captured by the Raman lidar located at the National Institute of Optoelectronics (INOE) in Bucharest. Our algorithm was tested not only for pure smoke but also for mixed smoke and urban aerosols of variable age and growth. Applying a sensitivity analysis on initial parameter settings of our retrieval code was proved vital for producing semi-automatized retrievals with a hybrid regularization method developed at the Institute of Mathematics of Potsdam University. A direct quantitative comparison of the retrieved microphysical properties with measurements from a Compact Time of Flight Aerosol Mass Spectrometer (CToF-AMS) is used to validate our algorithm. Microphysical retrievals performed with sun photometer data are also used to explore our results. Focusing on the fine mode we observed remarkable similarities between the retrieved size distribution and the one measured by the AMS. More complicated atmospheric structures and the factor of absorption appear to depend more on particle radius being subject to variation. A good correlation was found between the aerosol effective radius and particle age, using the ratio of lidar ratios (LR: aerosol extinction to backscatter ratios) as an indicator for the latter. Finally, the dependence on relative humidity of aerosol effective radii measured on the ground and within the layers aloft show similar patterns. [ABSTRACT FROM AUTHOR]