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- Leinonen, Ville, et al.
(författare)
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Comparison of particle number size distribution trends in ground measurements and climate models
- 2022
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 22:19, s. 12873-12905
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Tidskriftsartikel (refereegranskat)abstract
- Despite a large number of studies, out of all drivers of radiative forcing, the effect of aerosols has the largest uncertainty in global climate model radiative forcing estimates. There have been studies of aerosol optical properties in climate models, but the effects of particle number size distribution need a more thorough inspection. We investigated the trends and seasonality of particle number concentrations in nucleation, Aitken, and accumulation modes at 21 measurement sites in Europe and the Arctic. For 13 of those sites, with longer measurement time series, we compared the field observations with the results from five climate models, namely EC-Earth3, ECHAM-M7, ECHAM-SALSA, NorESM1.2, and UKESM1. This is the first extensive comparison of detailed aerosol size distribution trends between in situ observations from Europe and five earth system models (ESMs). We found that the trends of particle number concentrations were mostly consistent and decreasing in both measurements and models. However, for many sites, climate models showed weaker decreasing trends than the measurements. Seasonal variability in measured number concentrations, quantified by the ratio between maximum and minimum monthly number concentration, was typically stronger at northern measurement sites compared to other locations. Models had large differences in their seasonal representation, and they can be roughly divided into two categories: for EC-Earth and NorESM, the seasonal cycle was relatively similar for all sites, and for other models the pattern of seasonality varied between northern and southern sites. In addition, the variability in concentrations across sites varied between models, some having relatively similar concentrations for all sites, whereas others showed clear differences in concentrations between remote and urban sites. To conclude, although all of the model simulations had identical input data to describe anthropogenic mass emissions, trends in differently sized particles vary among the models due to assumptions in emission sizes and differences in how models treat size-dependent aerosol processes. The inter-model variability was largest in the accumulation mode, i.e. sizes which have implications for aerosol–cloud interactions. Our analysis also indicates that between models there is a large variation in efficiency of long-range transportation of aerosols to remote locations. The differences in model results are most likely due to the more complex effect of different processes instead of one specific feature (e.g. the representation of aerosol or emission size distributions). Hence, a more detailed characterization of microphysical processes and deposition processes affecting the long-range transport is needed to understand the model variability.
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- Löndahl, Jakob, et al.
(författare)
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A set-up for field studies of respiratory tract deposition of fine and ultrafine particles in humans
- 2006
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 37:9, s. 1152-1163
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Tidskriftsartikel (refereegranskat)abstract
- Respiratory tract deposition data of ultrafine aerosol particles, hygroscopic particles and ambient particles in general are scarce. Measurements are associated with several difficulties. The objective of this work was to design a method for fast determination of highly size-resolved fine and ultrafine particle deposition, to be used on larger groups of human subjects in exposure studies and in typical ambient and indoor environments. The particle size distributions in dried samples of the inhaled and exhaled air are characterised with an electrical mobility spectrometer. A particle counter desmearing procedure reduces the spectrometer scan time. The precision and sensitivity of the method was tested for hygroscopic sodium chloride (NaCl) and hydrophobic Di-Ethyl-Hexyl-Sebacate (DEHS) aerosols in repeated identical experiments and experiments with different breathing frequencies on a single subject. The accuracy of the method was estimated by comparing results from three subjects with previous data obtained with monodisperse particles and with the well-established International Commission on Radiological Protection model (1994). Potential errors due to size shifts between the inhaled and exhaled samples and coagulation were simulated. The system has low losses in the studied particle size range (10-475 nm), typically 10% or less of the fraction deposited in the respiratory tract. Coagulation is noticeable at 10(5) cm(-3) but can be corrected for up to 5 x 10(5) cm(-3). The precision in the determined deposited fraction is 0.02-0.08. The method is sensitive enough to quantify differences between breathing patterns and differences between hygroscopic and hydrophobic aerosols. Our results for NaCl and DEHS are in agreement with the ICRP 66 model [International Commission on Radiological Protection. (1994). Human respiratory tract model for radiological protection (ICRP Publication 66). Oxford, UK: Elsevier Science], and also suggest that the relative humidity in the respiratory tract is close to 99.5%. A respiratory tract deposition measurement can be done in 15-30 min. Recommendations are given for field applications of the method. (C) 2005 Elsevier Ltd. All rights reserved.
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- Löndahl, Jakob, et al.
(författare)
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Deposition of biomass combustion aerosol particles in the human respiratory tract.
- 2008
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Ingår i: Inhalation Toxicology. - : Informa UK Limited. - 0895-8378 .- 1091-7691. ; 20:10, s. 923-933
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Tidskriftsartikel (refereegranskat)abstract
- Smoke from biomass combustion has been identified as a major environmental risk factor associated with adverse health effects globally. Deposition of the smoke particles in the lungs is a crucial factor for toxicological effects, but has not previously been studied experimentally. We investigated the size-dependent respiratory-tract deposition of aerosol particles from wood combustion in humans. Two combustion conditions were studied in a wood pellet burner: efficient ("complete") combustion and low-temperature (incomplete) combustion simulating "wood smoke." The size-dependent deposition fraction of 15-to 680-nm particles was measured for 10 healthy subjects with a novel setup. Both aerosols were extensively characterized with regard to chemical and physical particle properties. The deposition was additionally estimated with the ICRP model, modified for the determined aerosol properties, in order to validate the experiments and allow a generalization of the results. The measured total deposited fraction of particles from both efficient combustion and low-temperature combustion was 0.21-0.24 by number, surface, and mass. The deposition behavior can be explained by the size distributions of the particles and by their ability to grow by water uptake in the lungs, where the relative humidity is close to saturation. The experiments were in basic agreement with the model calculations. Our findings illustrate: (1) that particles from biomass combustion obtain a size in the respiratory tract at which the deposition probability is close to its minimum, (2) that particle water absorption has substantial impact on deposition, and (3) that deposition is markedly influenced by individual factors.
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