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Opis: Abstract. The complex refractive index (CRI; n−ik) and the single scattering albedo (SSA) are key parameters driving the aerosol direct radiative effect. Their spatial, temporal, and spectral variabilities in anthropogenic–biogenic mixed environments are poorly understood. In this study, we retrieve the spectral CRI and SSA (370–950 nm wavelength range) from in situ surface optical measurements and the number size distribution of submicron aerosols at three sites in the greater Paris area, representative of the urban city, as well as its peri-urban and forested rural environments. Measurements were taken as part of the ACROSS (Atmospheric Chemistry of the Suburban Forest) campaign in June–July 2022 under diversified conditions: (1) two heatwaves leading to high aerosol levels, (2) an intermediate period with low aerosol concentrations, and (3) an episode of long-range-transported fire emissions. The retrieved CRI and SSA exhibit an urban-to-rural gradient, whose intensity is modulated by the weather conditions. A full campaign average CRI of 1.41−0.037i (urban), 1.52−0.038i (peri-urban), and 1.50−0.025i (rural) is retrieved. The imaginary part of the CRI (k) increases and the SSA decreases at the peri-urban and forest sites when exposed to the influence of the Paris urban plume. Values of k > 0.1 and SSA < 0.6 at 520 nm are related to a black carbon mass fraction larger than 10 %. Organic aerosols are found to contribute to more than 50 % of the aerosol mass and up to 10 % (urban), 17 % (peri-urban), and 22 % (forest) of the aerosol absorption coefficient at 370 nm. A k value of 0.022 (370 nm) was measured at the urban site for the long-range-transported fire episode.
Ključne besede: aerosol optical properties, aerosol refractive index, absorption, air pollution
Objavljeno v RUNG: 17.03.2025; Ogledov: 436; Prenosov: 3
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Ključne besede: aerosol absorption coefficient, black carbon, source apportionment, climate change
Objavljeno v RUNG: 26.02.2025; Ogledov: 616; Prenosov: 0
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Opis: Novinarska konferenca Univerze v Novi Gorici, na kateri so predstavili rezultate raziskave o onesnaženju zraka v občini Kanal ob Soči in na kateri je sodeloval tudi župan občine Kanal ob Soči Miha Stegel.
Ključne besede: onesnaženost zraka, izpostavljenost, viri, Kanal ob Soči
Objavljeno v RUNG: 24.01.2025; Ogledov: 651; Prenosov: 4
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Opis: Recent studies show that combining data with different time resolutions results in more detailed and likely more accurate source apportionment (SA) (Hopke et al., 2020; Manousakas et al., 2022; Via et al., 2023). Despite the advantages, SA studies, combining 24-hour filters and highly time-resolved analyses, are limited. This research aims to compare on- and off-line SA results in a pre-Alpine valley with a variety of sources. A comprehensive SA study of the local and regional PM sources and their size-segregated elemental fraction will be presented. PM10 was sampled daily on quartz filters from November 2020 to November 2021 and analyzed for a large array of chemical species. Equivalent black carbon (eBC) measurements were taken with the Aethalometer AE33. Hourly elemental PM10 and PM2.5 composition was measured in parallel with two Xact 625i from February until May 2021. Positive Matrix Factorization (PMF) was used to determine the sources of PM10 (off-line PMF) with 24-hour time resolution, and of the elemental fraction of PM (on-line PMF) with 1-hour time resolution for the overlapping time period. For off-line PMF, chemical species together with the source-specific eBC (Sandradewi et al., 2008) were used. For on-line PMF, two analyses were performed on the elemental composition: using PM10, and using a combination of PM2.5 and PMcoarse (PM10-PM2.5). The final off-line PM10 PMF results were compared to on-line elemental PM PMF and assessed accordingly. A combination of the different PMF models with various instrument data resulted in improved SA in terms of the number of identified sources and their uncertainties. The off-line PMF resolved ten PM10 sources (Fig. 1, left), while the on-line elemental PM10 and the combined elemental PM2.5+coarse PMF recognized 6 and 7 factors, respectively (Fig. 1, right). Due to large number of samples, we were able to separate between the sources with strong seasonality and sources featuring stability throughout the year. The study disclosed two rarely encountered factors, i.e., chloride-rich (chlorine-rich in case of on-line PMF) and cement dust. Introduction of source-specific eBC in the off-line PMF model resulted in more stable factor solutions.The high-resolution on-line PMF enabled us to distinguish between regional and local sources (see mineral dust factors). Furthermore, the size-segregated on-line PMF provided more speciated sources (traffic separation into heavy-duty and light-duty vehicles). A very good regression (R2 > 0.7, slopes = 0.05–0.35, p < 0.001) between the compared off-line PM10 and on-line elemental PM10 (daily averages) factors’ concentrations confirmed the adequacy of the SAs. Further work involves a direct comparison of fractions of the elements in the sources’ chemical profiles. The study clearly shows the advantages and limitations of the different PMF models. A combined use of various SA approaches appears to be a promising way towards a comprehensive analysis of the PM sources in complex environments.
Ključne besede: positive matrix factorization, PM10 composition, metals, Xact, HVS digitel
Objavljeno v RUNG: 24.01.2025; Ogledov: 754; Prenosov: 7
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Opis: Carbonaceous aerosols (CA), composed of black carbon (BC) and organic matter (OM), significantly impact the climate. Light absorption properties of CA, particularly of BC and brown carbon (BrC), are crucial due to their contribution to global and regional warming. We present the absorption properties of BC (bAbs,BC) and BrC (bAbs,BrC) inferred using Aethalometer data from 44 European sites covering different environments (traffic (TR), urban (UB), suburban (SUB), regional background (RB) and mountain (M)). Absorption coefficients showed a clear relationship with station setting decreasing as follows: TR > UB > SUB > RB > M, with exceptions. The contribution of bAbs,BrC to total absorption (bAbs), i.e. %AbsBrC, was lower at traffic sites (11–20 %), exceeding 30 % at some SUB and RB sites. Low AAE values were observed at TR sites, due to the dominance of internal combustion emissions, and at some remote RB/M sites, likely due to the lack of proximity to BrC sources, insufficient secondary processes generating BrC or the effect of photobleaching during transport. Higher bAbs and AAE were observed in Central/Eastern Europe compared to Western/Northern Europe, due to higher coal and biomass burning emissions in the east. Seasonal analysis showed increased bAbs, bAbs,BC, bAbs,BrC in winter, with stronger %AbsBrC, leading to higher AAE. Diel cycles of bAbs,BC peaked during morning and evening rush hours, whereas bAbs,BrC, %AbsBrC, AAE, and AAEBrC peaked at night when emissions from household activities accumulated. Decade-long trends analyses demonstrated a decrease in bAbs, due to reduction of BC emissions, while bAbs,BrC and AAE increased, suggesting a shift in CA composition, with a relative increase in BrC over BC. This study provides a unique dataset to assess the BrC effects on climate and confirms that BrC can contribute significantly to UV–VIS radiation presenting highly variable absorption properties in Europe.
Ključne besede: aerosol absorption, black carbon, brown carbon, climate change, air pollution
Objavljeno v RUNG: 10.12.2024; Ogledov: 848; Prenosov: 6
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