| 51. |
- Isaxon, Christina, et al.
(författare)
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Contribution of indoor-generated particles to residential exposure
- 2015
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 1873-2844. ; 106, s. 458-466
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Tidskriftsartikel (refereegranskat)abstract
- The majority of airborne particles in residences, when expressed as number concentrations, are generated by the residents themselves, through combustion/thermal related activities. These particles have a considerably smaller diameter than 2.5 mu m and, due to the combination of their small size, chemical composition (e.g. soot) and intermittently very high concentrations, should be regarded as having potential to cause adverse health effects. In this study, time resolved airborne particle measurements were conducted for seven consecutive days in 22 randomly selected homes in the urban area of Lund in southern Sweden. The main purpose of the study was to analyze the influence of human activities on the concentration of particles in indoor air. Focus was on number concentrations of particles with diameters <300 nm generated by indoor activities, and how these contribute to the integrated daily residential exposure. Correlations between these particles and soot mass concentration in total dust were also investigated. It was found that candle burning and activities related to cooking (using a frying pan, oven, toaster, and their combinations) were the major particle sources. The frequency of occurrence of a given concentration indoors and outdoors was compared for ultrafine particles. Indoor data was sorted into non-occupancy and occupancy time, and the occupancy time was further divided into non-activity and activity influenced time. It was found that high levels (above 10(4) cm(-3)) indoors mainly occur during active periods of occupancy, while the concentration during non-activity influenced time differs very little from non-occupancy time. Total integrated daily residential exposure of ultrafine particles was calculated for 22 homes, the contribution from known activities was 66%, from unknown activities 20%, and from background/non-activity 14%. The collected data also allowed for estimates of particle source strengths for specific activities, and for some activities it was possible to estimate correlations between the number concentration of ultrafine particles and the mass concentration of soot in total dust in 10 homes. Particle source strengths (for 7 specific activities) ranged from 1.6.10(12) to 4.5.10(12) min(-1). The correlation between ultrafine particles and mass concentration of soot in total dust varied between 0.37 and 0.85, with an average of 0.56 (Pearson correlation coefficient). This study clearly shows that due to the importance of indoor sources, residential exposure to ultrafine particles cannot be characterized by ambient measurements alone. (C) 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).
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| 52. |
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| 53. |
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| 54. |
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| 55. |
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| 56. |
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| 57. |
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| 58. |
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| 59. |
- Isaxon, Christina, et al.
(författare)
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Realistic indoor nano-aerosols for a human exposure facility
- 2013
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 60, s. 55-66
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to achieve realistic levels of two different types of aerosols commonly abundant in indoor environments in an experimental chamber intended for human exposure studies and aerosol characterization. The aerosols chosen were particles from candle lights (in particle number dominated by inorganic water soluble particles) and from ozone-terpene reactions (organic particles). The aerosol generation and characterization system consisted of a controlled air tight stainless steel 22 m(3) chamber, to which the generation set-ups were connected. No air could enter or leave the chamber except through a conditioning system by which temperature, relative humidity and air exchange rate could be controlled. Candle smoke aerosol was generated from ten candles burning in a 1.33 m(3) glass and stainless steel chamber. The aerosol was diluted by clean air from the conditioning system before entering the chamber. Terpene vapor was generated by passing pure nitrogen through a glass bottle containing limonene oil. Ozone was generated by a spark discharge using pure O-2, and was added to the ventilation air flow downstream the inlet for terpene vapors and upstream the inlet to the chamber. Both aerosols were characterized with respect to number and mass concentrations, size distribution and chemical composition. Particle number concentration in the size range 10-650 nm could be varied from <10 cm(-3) to more than 900,000 cm(-3) (for candle smoke) or to more than 30,000 cm(-3) (for particles formed in a 160 ppb terpene/40 ppb ozone mixture). Furthermore, the set-ups were evaluated by, for each source, repeating the generation at six three-hour long events. For both aerosols repeatable generations at pre-determined concentration levels, that were stable over time, could be achieved. The results show that realistic concentrations of aerosols from real-world environments could be reproduced in a well-controlled manner and that this set-up could be used both for aerosol characterization and for human exposures. (C) 2013 Elsevier Ltd. All rights reserved.
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