Vidmantas Ulevicius

The Use of Trajectory Cluster Analysis to Evaluate the Long-Range Transport of Black Carbon Aerosol in the South-Eastern Baltic Region

Trajectory cluster analysis and source-receptor models (the potential source contribution function (PSCF), concentration weighted trajectories (CWT), and trajectory source apportionment (TSA)) were applied to investigate the source-receptor relationship for the aerosol black carbon (BC) measured at the coastal site (Preila, 55.55°N, 21.04°E) during 2013. The main sources and paths of advection to the south-eastern Baltic region and its relation to black carbon concentration were identified. The 72u2009h backward trajectories of air masses arriving at Preila from January to December 2013 were determined and were categorized by clustering them into six clusters. Subsequently, BC levels at Preila associated with each air mass cluster during this period were analyzed. The PSCF and CWT analysis shows that, on high BC concentration days, the air masses commonly originated and passed over southern regions of Europe before arriving at Preila in winter, while a strong impact of wildfires was observed in spring.

Identification and Characterization of Black Carbon Aerosol Sources in the East Baltic Region

One-year continuous measurements of aerosol black carbon (BC) at the background site Preila (55°55′N, 21°00′E, 5u2009m a.s.l., Lithuania) were performed. Temporal and spatial evolution and transport of biomass burning (BB) and volcanic aerosols observed within this period were explained by the air mass backward trajectory analysis in conjunction with the fire detection data produced by the MODIS Rapid Response System and AERONET database. The surface measurements and analysis of the Angstrom exponent of the absorption coefficient done separately for shorter and longer wavelengths (i.e., u2009nm and u2009nm) showed that high levels of aerosol BC were related to the transport of air masses rich in BB products from Ukraine caused by active grass burning. During the events the highest mean values of the Angstrom exponent of the absorption coefficients and u2009nm were observed ( and , resp.). The ash plume of the Grimsvotn eruption on May 21, 2011 offered an exceptional opportunity to characterize the volcanic aerosols. The largest ash plume (in terms of aerosol optical thickness) over Lithuania was observed at May 24/25, 2011. The highest values of the Angstrom exponent of the absorption coefficients and u2009nm were reached ( and , resp.).

Oxygen isotope analysis of levoglucosan, a tracer of wood burning, in experimental and ambient aerosol samples

RATIONALEnLevoglucosan is formed from cellulose during biomass burning. It is therefore often used as a specific tracer to quantify the contribution of wood burning to the aerosol loading. The stable oxygen isotope composition (δ18 O value) of biomass is determined by the water cycle and varies regionally, and hence the δ18 O value of levoglucosan could help to identify source regions of organic aerosols.nnnMETHODSnAfter solvent extraction of the organic fraction and concentration steps, a recently developed methylation derivatisation technique was applied on experimental (i.e. controlled wood-burning experiments) and on ambient aerosol samples from Switzerland and Lithuania. The method achieves sufficient compound separation for isotope analysis in atmospheric particulate matter, enabling δ18 O analysis of levoglucosan by gas chromatography/pyrolysis-isotope ratio mass spectrometry (GC/Pyr-IRMS), with a precision better than 1.0u2009‰ and an accuracy of 0.3u2009‰.nnnRESULTSnThe δ18 O value of the levoglucosan released during controlled wood-burning experiments was not significantly different from the cellulose δ18 O values, which implies very little or no isotope fractionation during wood burning under the given conditions. While the δ18 O values of levoglucosan in Swiss samples were as expected for the source region, those in Lithuania were 1-4u2009‰ lower than expected. This may be due to differences in vegetation (grass vs wood) or burning conditions (high vs low temperatures).nnnCONCLUSIONSnLow oxygen isotope fractionation between cellulose and levoglucosan and clear differences in levoglucosan δ18 O values between the Swiss and Lithuanian ambient samples demonstrate that our new method is useful for source appointment studies on wood-burning-derived aerosols.