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Opis: A reliable determination of equivalent black carbon (eBC) mass concentrations derived from filter absorption photometers (FAPs) measurements depends on the appropriate quantification of the mass absorption cross-section (MAC) for converting the absorption coefficient (babs) to eBC. This study investigates the spatial–temporal variability of the MAC obtained from simultaneous elemental carbon (EC) and babs measurements performed at 22 sites. We compared different methodologies for retrieving eBC integrating different options for calculating MAC including: locally derived, median value calculated from 22 sites, and site-specific rolling regression MAC. The eBC concentrations that underwent correction using these methods were identified as LeBC (local MAC), MeBC (median MAC), and ReBC (Rolling MAC) respectively. Pronounced differences (up to more than 50 %) were observed between eBC as directly provided by FAPs (NeBC; Nominal instrumental MAC) and ReBC due to the differences observed between the experimental and nominal MAC values. The median MAC was 7.8 ± 3.4 m2/g from 12 aethalometers at 880 nm, and 10.6 ± 4.7 m2/g from 10 MAAPs at 637 nm. The experimental MAC showed significant site and seasonal dependencies, with heterogeneous patterns between summer and winter in different regions. In addition, long-term trend analysis revealed statistically significant (s.s.) decreasing trends in EC. Interestingly, we showed that the corresponding corrected eBC trends are not independent of the way eBC is calculated due to the variability of MAC. NeBC and EC decreasing trends were consistent at sites with no significant trend in experimental MAC. Conversely, where MAC showed s.s. trend, the NeBC and EC trends were not consistent while ReBC concentration followed the same pattern as EC. These results underscore the importance of accounting for MAC variations when deriving eBC measurements from FAPs and emphasizes the necessity of incorporating EC observations to constrain the uncertainty associated with eBC.
Ključne besede: equivalent black carbon, mass absorption cross-section, filter absorption photometers, elemental carbon, absorption, site specific MAC, rolling MAC
Objavljeno v RUNG: 04.03.2024; Ogledov: 278; Prenosov: 3
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Ključne besede: multi-time resolution, source apportionment, submicronic particulate matter, positive matrix factorisation, PMF, multilinear engine, SoFi, ME2, organic sources, metals
Objavljeno v RUNG: 24.10.2023; Ogledov: 653; Prenosov: 6
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Opis: The present invention belongs to the field of devices and methods for measurement of particle concentration, more precisely to the field of devices and methods for quantification of particles based ontheir physical characteristics, especially with the use of optical means. The invention relates to a method for determination of ambient mineral dust concentration based on optical absorption of particles concentrated by a virtual impactor as well as a device performing the said method. The method comprises the following steps: sampling air samples with particle size smaller than 1 mum (PM1) andsampling air samples with particle size up to 10 mum; concentrating the samples with particle sizes up to 10 mum with a virtual impactor; measuring optical absorption of collected samples at least onewavelength from UV to IR spectre, preferably from 370 to 950 nm, most preferably at 370 nm; subtracting the absorption of the samples with particle size smaller than 1 mum from the absorption of thesample concentrated by the virtual impactor.
Ključne besede: dust, black carbon, aerosol
Objavljeno v RUNG: 07.03.2023; Ogledov: 1267; Prenosov: 0
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Opis: Aerosols play an important yet uncertain role in modulating the radiation balance of the sensitive Arctic atmosphere. Organic aerosol is one of the most abundant, yet least understood, fractions of the Arctic aerosol mass. Here we use data from eight observatories that represent the entire Arctic to reveal the annual cycles in anthropogenic and biogenic sources of organic aerosol. We show that during winter, the organic aerosol in the Arctic is dominated by anthropogenic emissions, mainly from Eurasia, which consist of both direct combustion emissions and long-range transported, aged pollution. In summer, the decreasing anthropogenic pollution is replaced by natural emissions. These include marine secondary, biogenic secondary and primary biological emissions, which have the potential to be important to Arctic climate by modifying the cloud condensation nuclei properties and acting as ice-nucleating particles. Their source strength or atmospheric processing is sensitive to nutrient availability, solar radiation, temperature and snow cover. Our results provide a comprehensive understanding of the current pan-Arctic organic aerosol, which can be used to support modelling efforts that aim to quantify the climate impacts of emissions in this sensitive region.
Ključne besede: Arctic, Organic aerosols, Emission sources, Climate change
Objavljeno v RUNG: 01.03.2022; Ogledov: 1551; Prenosov: 0
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Opis: Implicatures like ‘Some politicians are smart’ (interpreted as ‘Some but not all politicians are smart’) are defined scalar implicatures. A heated linguistic debate has focused on how we derive those implicatures: some authors consider the computational process as linguistic in nature (Levinson, 2000), others as pragmatic in nature (Sperber & Wilson, 1995). A growing body of research, prompted by pioneering work by Bott and Noveck (2004), focused on the computational cost related with the computation of scalar implicatures. The present study addresses such topic through the use of different experimental techniques. With Experiment 1 (N = 57) we replicated the third experiment of Bott and Noveck (2004), the first study that identified a cost related to a pragmatic response. With Experiment 2 (N = 58), using a pseudo-word paradigm, we excluded the possibility that the computational cost is due to an experimental artifact, such as an increased difficulty in moving up in the conceptual hierarchy (e.g., ‘Some elephants are mammals’) than in moving down (e.g. ‘Some mammals are elephants’). In Experiment 3 (N = 54), with a Sentence Evaluation Task, we collected reading times, reaction times and eye gaze data. Results showed that the cost of the computation disappears when there is contextual support. Overall, our results seem to support the idea that scalar implicatures are not automatically computed with context playing an important role.
Ključne besede: scalar implicatures, eye-tracking, experimental pragmatics, reaction times
Objavljeno v RUNG: 22.09.2021; Ogledov: 1779; Prenosov: 7
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