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Abstract: Abstract. Black carbon (BC) is a major component of submicron particulate matter (PM), with significant health and climate impacts. Many cities in emerging countries lack comprehensive knowledge about BC emissions and exposure levels. This study investigates BC concentration levels, identifies its emission sources, and characterizes the optical properties of BC at urban background sites of the two largest high-altitude Bolivian cities: La Paz (LP) (3600 m above sea level) and El Alto (EA) (4050 m a.s.l.), where atmospheric oxygen levels and intense radiation may affect BC production. The study relies on concurrent measurements of equivalent black carbon (eBC), elemental carbon (EC), and refractory black carbon (rBC) and their comparison with analogous data collected at the nearby Chacaltaya Global Atmosphere Watch Station (5240 m a.s.l). The performance of two independent source apportionment techniques was compared: a bilinear model and a least-squares multilinear regression (MLR). Maximum eBC concentrations were observed during the local dry season (LP: eBC = 1.5 ± 1.6 µg m−3; EA: 1.9±2.0 µg m−3). While eBC concentrations are lower at the mountain station, daily transport from urban areas is evident. Average mass absorption cross sections of 6.6–8.2 m2 g−1 were found in the urban area at 637 nm. Both source apportionment methods exhibited a reasonable level of agreement in the contribution of biomass burning (BB) to absorption. The MLR method allowed the estimation of the contribution and the source-specific optical properties for multiple sources, including open waste burning.
Keywords: black carbon, aerosol absorption, source apportionment, mass absorption cross-section
Published in RUNG: 29.10.2024; Views: 970; Downloads: 1
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Abstract: 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.
Keywords: equivalent black carbon, mass absorption cross-section, filter absorption photometers, elemental carbon, absorption, site specific MAC, rolling MAC
Published in RUNG: 04.03.2024; Views: 2312; Downloads: 10
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Abstract: Ultra High Energy Cosmic Ray (UHECR) detectors have been reporting on the proton-air cross section measurement beyond the capability of particle accelerators since 1984. The knowledge of this fundamental particle property is vital for our understanding of high energy particle interactions and could possibly hold the key to new physics. The data used in this work was collected over eight years using the hybrid events of Black Rock (BR) and Long Ridge (LR) fluorescence detectors as well as the Telescope Array Surface Detector (TASD). The proton-air cross section is determined at s√=73~TeV by fitting the exponential tail of the Xmax distribution of these events. The proton-air cross section is then inferred from the exponential tail fit and from the most updated high energy interaction models. σ^inel_p−air is observed to be 520.1±35.8 [Stat.] +25.3−42.9 [Sys.] mb. This is the second proton-air cross section work reported by the Telescope Array collaboration.
Keywords: Telescope Array, indirect detection, hybrid detection, ground array, fluorescence detection, ultra-high energy, cosmic rays, Xmax, proton-air cross-section, high energy particle interaction
Published in RUNG: 04.10.2023; Views: 2225; Downloads: 8
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Abstract: This article investigates the variability in the meaning of vague quantifiers across different languages, focusing on Italian’s m(any)-words molto and tanto. The aim was to replicate a previous analysis conducted on Slovenian m-words – precej and veliko – examining whether the Italian ones exhibit a similar pragmatic strengthening effect. Using a sentence-picture verification task, we tested 88 Italian monolingual participants on their evaluation of sentences of the form “Quantifier X are Y”. Our results showed that, unlike Slovenian speakers, Italian speakers do not exhibit a difference in the evaluation of molto and tanto, suggesting that the two words have the same numerical bound and are interchangeable as amount modifiers. Our analysis suggests that there are underlying semantic distinctions between molto and tanto that require further investigation. These findings contribute to our understanding of the variability in the use of quantifiers across languages and highlight the importance of examining subtle differences in meaning when studying vague quantifiers.
Keywords: cross-linguistic differences, pragmatics, quantification, semantics, vague quantifiers
Published in RUNG: 03.10.2023; Views: 2668; Downloads: 10
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Abstract: Film quality analysis is of more considerable signifcance due to its diversifed applications in various felds of technology. The present work reports the speckle interferometric analysis of the argon pressure-induced surface roughness modifcations of RF sputtered MoO3 flms. The paper suggests a new method of surface quality analysis of thin flms through a parameter δ, which is the diference between the initial and fnal inertia moment values in the study of the thermal-induced dynamic speckle pattern. The limitations of root mean square surface roughness analysis of the atomic force microscopic image of the flms is also exemplifed. The research suggests that argon pressure plays a vital role in the surface property of RF sputtered flms and also that the dynamic speckle analysis can give precise information about the quality of flms. The contour plot of particle displacement vector under thermal stress, suggests the degree of uniformity in the distribution of particles in the flm.
Keywords: speckle pattern interferometry, time history of speckle pattern, cross correlation, inertia moment
Published in RUNG: 04.07.2022; Views: 2504; Downloads: 0
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