Impact of long-range transport on black carbon source contribution and optical aerosol properties in two urban environments.

Urban areas, as major sources of aerosol black carbon emissions, contribute to increased pollution levels in surrounding regions by air mass long-range transport, which should be taken into account in implementation of emission-reduction strategies. Properties of light-absorbing aerosol particles and a novel approach to assess the impact of long-range transport on black carbon (BC) pollution in two under-investigated urban environments: Warsaw (Poland, Central Europe) and Vilnius (Lithuania, North-Eastern Europe) are presented. During the warm season of May-August 2022, BC mass concentration and aerosol optical properties: the scattering Ångström exponent (SAE), absorption Ångström exponent (AAE), and single scattering albedo (SSA) were investigated. Generally, the mean BC mass concentration was higher at the more polluted site in Warsaw (1.07 µg/m3) than in Vilnius (0.77 µg/m3). The BC source apportionment to biomass burning (BCBB) and fossil fuel combustion (BCFF) showed similar contributions for both sites with BCBB (13-19%) being significantly lower than BCFF (81-87%). A uniform flow of air masses transporting aerosol particles over long distances to both sites was observed for 42% of the days. It affected BC mass concentration as follows: BC decrease was found similar at both sites (42% in Warsaw, 50% in Vilnius) but increase was twice higher in Vilnius (64%) than in Warsaw (30%). Despite variations in BC mass concentration, both sites exhibited a comparable abundance (90%) of submicron (SAE<1.3), BC-dominated (AAE<1.5) particles. The mean SSA was very low (0.69 ± 0.1 in Warsaw, 0.72 ± 0.1 in Vilnius), which indicates a very strong contribution of light-absorbing aerosol particles in both environments. The local episodes of biomass burning due to celebrations of May Days on 1st - 3rd May in Warsaw and Midsummer on 24th June in Vilnius showed similar aerosol properties in both cities (1.5

Evaluation of Work-Related Personal Exposure to Aerosol Particles.

The effects of air pollution on the general public received much attention recently. Personal exposure and deposition fraction of aerosol particles were studied in Vilnius, Lithuania, focusing on individuals working in an office and driving to work. Aerosol monitoring in the urban background was found to give an indication of the minimum concentrations of particulate matter (PM) expected at urban roads, as these correspond to the lowest PM concentrations measured there. In March 2021, PM2.5 concentrations at the urban background monitoring station reached values above the annual limit of 5 µg/m3 the World Health Organization in 50% of cases. Our study shows significant differences in exposure to air pollution in a car cabin and in a modern office. According to the multiple-path particle dosimetry model, the exposure of the person in the office is about 14 times lower than driving a car, where the minute deposition dose for PM1 is 0.072 µg/min for the period when the PM2.5 concentration in the urban background reaches 10 µg/m³. Compared to the PM2.5 mass concentration at the urban background station, the mean PM2.5 concentration in the vehicle reaches values that are 2-3 times higher. During the working day, when driving takes less than 10% of the time considered (commuting plus working), PM exposure during driving accounts for about 80% of the PM exposure caused by PM concentration in the office.

Evaluation of the anthropogenic black carbon emissions and deposition on Norway spruce and silver birch foliage in the Baltic region.

This study investigates potential influence of urban trees on black carbon (BC) removal by Norway spruce and silver birch along with the BC formation, mass concentration in air, and source apportionment. The main sources of BC in urban areas are transport, household and industry. BC concentrations monitored in urban background station in Vilnius (Lithuania) showed that biomass burning was a significant contributor to BC emissions even during warm period of the year. Therefore, BC emission levels were determined for the most common biomass fuels (mixed wood pellets, oak, ash, birch and spruce firewood) and two types of agro-biomass (triticale and rapeseed straw pellets) burned in modern and old heating systems. The highest emissions were obtained for biomass fuels especially birch firewood. BC aerosol particles produced by the condensation mechanism during the combustion processes were found in all samples taken from the leaf surface. The short-term effect of BC exposure on photosynthetic pigments (chlorophyll a and b; and carotenoids) in the foliage of one-year-old Norway spruce and silver birch seedlings was evaluated by the experiment carried out in the phytotron greenhouse. The seedlings showed different short-term responses to BC exposure. All treatments applied in the phytotron greenhouse resulted in lower chlorophyll content in spruce foliage compared to natural conditions but not differed for birch seedlings. However, the exposure of BC particles on the spruce and birch seedlings in the phytotron increased the content of photosynthetic pigments compared to the control seedlings in the phytotron. Overall, urban trees can help improve air quality by reducing BC levels through dry deposition on tree foliage, and needle-like trees are more efficient than broad-leaved trees in capturing BC. Nevertheless, a further study could assess the longer-term effects of BC particles on tree biochemical and chemical reactions.

TemperatureDependent Luminescence of RedEmitting Ba2Y5B5O17: Eu3+ Phosphors with Efficiencies Close to Unity for NearUV LEDs.

Solid state white light sources based on a nearUV LED chip are gaining more and more attention. This is due to the increasing efficiency of nearUVemitting LED chips and wider phosphors selection if compared to devices based on blue LED chips. Here, a brief overview is given of the concepts of generating white light employing nearUV LED and some optical properties of the available phosphors are discussed. Finally, the synthesis and optical properties of very efficient redemitting Ba2Y5B5O17:Eu3+ phosphor powder and ceramics is reported and discussed in terms of possible application as a red component in nearUV LEDbased white light sources.

Optical Properties of Red-Emitting Rb2Bi(PO4)(MoO4):Eu3+ Powders and Ceramics with High Quantum Efficiency for White LEDs.

There are several key requirements that a very good LED phosphor should meet, i.e., strong absorption, high quantum efficiency, high colour purity, and high luminescence quenching temperature. The reported Rb2Bi(PO4)(MoO4):Eu3+ phosphors have all these properties. The Rb2Bi(PO4)(MoO4):Eu3+ phosphors emit bright red light if excited with near-UV radiation. The calculated colour coordinates show good stability in the 77-500 K temperature range. Moreover, sample doped with 50% Eu3+ possesses quantum efficiency close to unity. Besides the powder samples, ceramic disks of Rb2Eu(PO4)(MoO4) specimen were also prepared, and the red light sources from these disks in combination with near-UV emitting LED were fabricated. The obtained results indicated that ceramic disks efficiently absorb the emission of 375 and 400 nm LED and could be applied as a red component in phosphor-converted white LEDs.