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Carbonaceous aerosols exhibit seasonal variations due to a complex interplay of emission sources, meteorological conditions, and chemical processes. This study presents the first year-round dual‑carbon isotopic analysis of carbonaceous aerosols in Northeastern Europe (Lithuania). The emphasis was placed on the processes affecting carbonaceous submicron particle (PM 1 ) concentrations and their isotopic composition (δ 13 C TC , f c ) during different seasons. Aerosol particles were collected in the two distinct sites: at an urban background site (Vilnius) and a coastal site (Preila). The concentrations of total carbon (TC) and black carbon (BC) varied both spatially and temporally. The annual average concentrations were 4 μg/m 3 for TC and 2.3 μg/m 3 for BC at the urban background site. They were considerably lower at the coastal site with 2.9 μg/m 3 for TC and 0.74 μg/m 3 for BC. The peak concentrations of TC and BC that occur during the cold season indicate a significant impact from residential heating. The δ 13 C in aerosols exhibited a distinct seasonal cycle with depleted δ 13 C TC values during the warm season (April-October). Through the integration of isotopic composition, contemporary carbon (f c ), and BC source apportionment, we achieved precise predictions of isotopic parameter changes, encompassing pollution sources and the influence of meteorological parameters. To better understand the respective contributions of local and regional sources, air mass trajectories, wind patterns (speed and direction), and the polar conditional probability function (CPF) were studied in parallel. The study indicates that the isotopic composition of PM 1 at both sites is primarily controlled by emission sources (local and regional), while meteorological conditions (temperature and mixing layer height) have less influence. These variations have important implications for regional air quality, climate dynamics, and public health, which are persistently subject to continuous research and monitoring., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

We report on importance of conducting comprehensive studies of atmospheric aerosol particles, which cannot be done if information from various complementary sensors is unavailable. We present an example for such application and recommend on the types of sensors that should be used in view of the ACTRIS and RI-URBANS new strategies for monitoring at supersites. Although active and passive remote sensing data was not available in continuous mode, we show that synergic use of them with in-situ observations allows for comprehensive study of temporal and height-resolved distribution of aerosol in the lower troposphere and it can be successfully combined to assess biomass burning impact on air quality and optical properties. The analysed period was divided into three episodes based on the measured black carbon (BC) concentration and the prevailing wind direction. The dominant 72-h backward trajectories were ending in western Europe, mid-Atlantic and western Russia, respectively, The in-situ measured mass concentrations of BCtotal and BC apportioned to biomass burning as well as particulate matter (PM) concentrations in accumulation mode were twice higher during the first and last episodes compared to the second episode, representing long-range transport from different source regions. The obtained complementary surface, column-integrated, and layer-derived size distributions and other parameters demonstrate the added value of multisensor analyses., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

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, PM 2.5 concentrations at the urban background monitoring station reached values above the annual limit of 5 μg/m 3 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 PM 1 is 0.072 µg/min for the period when the PM 2.5 concentration in the urban background reaches 10 µg/m³. Compared to the PM 2.5 mass concentration at the urban background station, the mean PM 2.5 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.

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., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Background: The growing public health concern caused by non-communicable diseases in urban surroundings cannot be solved by health care alone; therefore a multidisciplinary approach is mandatory. This study aimed to evaluate the airborne aerosol pollution level in primary schools as possible factor influencing origin and course of the diseases in children., Methods: Seasonal aerosol particle number concentration (PNC) and mass concentration (PMC) were studied in the randomly selected eleven primary schools in the Lithuanian capital, Vilnius, as model of a middle-size Eastern European city. Total PNC in the size range from 0.01 to >1.0 μm in diameter was measured using a condensation particle counter. Using an optical particle sizer, PNC was measured and PMC estimated for particles from 0.3 to 10.0 μm. A descriptive statistics was used to estimate the aerosol pollution levels., Results: During all seasons, local cafeterias in the absence of ventilation were the main sources of the elevated levels of indoor PMC and PNC (up to 97,500 particles/cm). The other sources of airborne particulates were the children's activity during the lesson breaks with PMC up to 586 μg/m. Soft furniture, carpets in the classrooms and corridors were responsible for PMC up to 200 μg/m. Outdoor aerosol pollution (up to 18,170 particles/cm) was higher for schools in city center. Elevated air pollution in classrooms also resulted from intermittent sources, such as construction work during classes (200-1000 μg/m) and petrol-powered lawn trimmers (up to 66,400 particles/cm)., Conclusion: The results of our survey show that even in a relatively low polluted region of Eastern Europe there are big differences in aerosol pollution within middle-sized city. Additional efforts are needed to improve air quality in schools: more frequent wet cleaning, monitoring the operation of ventilation systems, a ban on construction works during school year, on a use of sandblasting mechanisms in the neighborhood of schools.

Aerosol particle number (PNC) and mass concentrations (PMC) were studied in 11 primary schools during the 2017-2018 school years (from September to May) in Vilnius, Lithuania, with the aim to evaluate the main aerosol pollution sources and its levels. Expeditious information on the total aerosol particle concentration over the full range of sizes (from 0.01 to > 1 μm) was estimated using a condensation particle counter (CPC). Particle number and mass concentrations in the size range of 0.3-10 μm were measured and estimated using an optical particle sizer (OPS). The use of aerosol particle size spectra (OPS) in school lodgements facilitated the identification of the main sources of indoor air pollution. The main sources responsible for the elevated levels of indoor PN and PM aerosol concentrations were determined: local canteens in the absence of ventilation (particle concentrations up to 97,500 part/cm 3 (CPC)), the school-grader activity during the lesson breaks (275-586 μg/m 3 ), soft furniture and carpets in the classrooms and corridors (~ 200 μg/m 3 ), and in some cases (city center) elevated outdoor aerosol pollution levels (16800-18,170 part/cm 3 ). Elevated aerosol pollution levels were also due to the occasional sources: construction works during lessons (200-1000 μg/m 3 ), scraping the exterior walls of buildings near schools (up to 1600 μg/m 3 ), and the use of petrol-powered trimmers during cutting of green plantings (22500-66,400 part/cm 3 (CPC)).