Optical Properties of the Urban Aerosol Particles Obtained from Ground Based Measurements and Satellite-Based Modelling Studies

Applications of satellite remote sensing data combined with ground measurements and model simulation were applied to study aerosol optical properties as well as aerosol long-range transport under the impact of large scale circulation in the urban environment in Lithuania (Vilnius). Measurements included the light scattering coefficients at 3 wavelengths (450, 550, and 700 nm) measured with an integrating nephelometer and aerosol particle size distribution (0.5–12 μm) and number concentration (Dpa > 0.5 μm) registered by aerodynamic particle sizer. Particle number concentration and mean light scattering coefficient varied from relatively low values of 6.0 cm−3 and 12.8 Mm−1 associated with air masses passed over Atlantic Ocean to relatively high value of 119 cm−3 and 276 Mm−1 associated with South-Western air masses. Analysis shows such increase in the aerosol light scattering coefficient (276 Mm−1) during the 3rd of July 2012 was attributed to a major Sahara dust storm. Aerosol size distribution with pronounced coarse particles dominance was attributed to the presence of dust particles, while resuspended dust within the urban environment was not observed

Spatial and Temporal Analysis of Organic and Black Carbon Mass Concentrations in Lithuania

Both organic carbon (OC) and black carbon (BC) mass concentrations were measured in Lithuania at coastal/marine (Preila), rural (Rūgšteliškis), and urban background (Vilnius) environments have been analyzed to infer the spatial and temporal distributions of the OC/BC ratios from May 2013 to October 2014. OC/BC ratios reflected the location of the different sites, as well as possible different sources influencing air quality. The results from an industrialized and populated urban background area indicated that biomass combustion for heating contributed to BC and OC mass concentration. Typically, BC mean concentrations (±st.deviation) were higher in urban areas (1.72(±1.22 μg·m−3)) than in rural (0.40(±0.35 μg·m−3)) and coastal/marine (0.53(±0.43 μg·m−3)) during warm and cold (2.34(±2.15); 0.77(±0.52) and 0.84(±0.50) μg·m−3, respectively) periods, while OC concentrations were higher in urban backgrounds (5.91(±1.99 μg·m−3)) and rural areas (4.56(±3.98 μg·m−3)) during warm periods. The air mass backward trajectory analysis indicated influence of local sources in urban environment and strong influence of long-range transport in rural environment. A clear seasonal dependence of OC/BC ratios was observed at rural and urban environments. The highest OC/BC ratios were calculated in coastal/marine (6.3) and rural (9.5) environments in summer

Biogenic Organic Aerosol as an indicator of the forest abiotic stress

Volatile organic compounds (VOCs) have a substantial impact on the oxidant balance of the lower layers of the atmosphere. As result, they affect tree growth and ecosystem performance. Also, VOCs play significant role in new particle formation process and they change physicochemical properties of the existing particles. Wherein, such ecosystem like forest are the main source of the biogenic VOCs and in the global scale their emissions higher than anthropogenic VOCs. Thus, we investigated the changes of the physicochemical properties of the aerosol particles in forest environment. The measurements were performed applying a Scanning Mobility Particle Sizer, an Aerodynamic Particle Spectrometer and an Aerosol Chemical Speciation Monitor. During measurement campaign, it was observed new particle formation phenomena. Fresh nucleated particles were characterized by low oxidation level and high particle number concentration of the nucleation mode. Wherein, the polydisperse coagulation process was much higher than the condensation growth of the nucleated particles. Also, we determined that the nucleation process of the aerosol particle was related with the trees abiotic stress, which was observed by temperature increase. The analyse of the aerosol mass spectra showed that the methanol (CH3OH, m/z 33), acetone (C3H6O2, m/z 59), methyl-ethyle-ketone (C4H8O, m/z 73) and salicyl-aldehyde (C7H8O2, m/z 123) emissions were identified as heat related. Meanwhile, methanol, acetone and methyl emissions showed great dependency of heat and light. They showed high correlation (>0.9) with one another. However, the salicyl-aldehyde could be assigned to heat stress marker. Thus, we can conclude that biogenic organic aerosol particles can be an indicator of the abiotic stress of the forest and that could to expand understanding of the forest ecosystem. The study is based on the results from national project supported by Lithuanian Council of Research "FOREstRESS"(SIT - 3/2015)Fizinių ir technologijos mokslų centrasVytauto Didžiojo universitetasŽemės ūkio akademij

Numerical Study of Powder Flow Nozzle for Laser-Assisted Metal Deposition

Metal additive manufacturing has received much attention in the past few decades, and it offers a variety of technologies for three-dimensional object production. One of such technologies, allowing large-sized object production, is laser-assisted metal deposition, the limits of which are determined by the capabilities of the positioning system. The already-existing nozzles have either a relatively low build rate or a poor resolution. The goal of this work is to develop a new nozzle with a centered particle beam at high velocity for the laser-assisted metal additive manufacturing technologies. Scientific challenges are addressed with regards to the fluid dynamics, the particle-substrate contact, and tracking of the thermodynamic state during contact. In this paper, two nozzles based on the de Laval geometry with Witoszynski and Bicubic curves of convergence zone were designed; the results showed that the average flow velocity in a Bicubic outlet curve nozzle is around 615 m/s and in Witoszynski this is 435 m/s. Investigation of particle beam formation for the Bicubic curve geometry revealed that small particles have the highest velocity and the lowest total force at the nozzle outlet. Fine particles have a shorter response time, and therefore, a smaller dispersion area. The elasto-plastic particle-surface contact showed that particles of diameter limited up to 3 μm are able to reach experimentally obtained critical velocity without additional heating. For particle sizes above 10 μm, additional heating is needed for deposition. The maximum coefficient of restitution (COR) is achieved with a particle size of 30 μm; smaller particles are characterized by the values of COR, which are lower due to a relatively high velocity. Particles larger than 30 μm are scalable, characterized by a small change in velocity and a rise in temperature as their mass increases

Impact of changing meteorology and air pollution on forest ecosystems in Lithuania -strategies for adaptation to and mitigation of the main threats of global change

Global change in Lithuania is predicted to promote increasing air temperature across seasons, a decrease in snow cover and an increase in heavy rain events. Changes in atmospheric circulation reduce seasonal climatic amplitudes, but enhance air pollution presumably tropospheric ozone, acidification and biogenic volatile organic compounds (BVOC) which will impact on tree growth and ecosystem performance. To mitigate main threats of global change the objective of the recently established comprehensive survey in Lithuanian forests is to develop strategies for silvicultural management in order to prepare forest systems ensuring ecosystem services. Intensive investigations at selected forest sites combine growth and injury analysis with ecophysiological assessments of tree water consumption, stomatal regulation and stomatal uptake of ozone, and tree bound BVOC emissions. Combining such investigations with long-term monitoring on environmental pollution and regional peculiarities in Lithuania insight is gathered on tree growth in dependence of environmental stress. The combination of knowledge on tree growth, ecophysiolocal performance and methods of BSOA formation will provide a diagnostic tool for differential stress diagnosis and treatment measures under the specific requirements of LithuaniaFizinių ir technologijos mokslų centrasVytauto Didžiojo universitetasŽemės ūkio akademij

Ecophysiological reactions of prevailing in Lithuania tree species to meteorology and air pollution

Fizinių ir technologijos mokslų centrasVytauto Didžiojo universitetasŽemės ūkio akademij