| Abstract [eng] |
A number of health effects have been linked to exposure to airborne particles, including respiratory symptoms, cardiovascular diseases, and increased mortality. These are further complicated by the fact that people are spending more time indoors, in particular, almost 69 % we are spending in homes (EPA), where particles of indoor and outdoor origin are found. The aim of the present Master thesis was to assess the differences in physico-chemical particle characteristics inside and outside of the occupied residence and to identify the origin of major contributors to the observed levels indoors. Simultaneous, indoor and outdoor measurements were performed in naturally ventilated four-bedroom apartment in Malmö, Sweden. Scanning Mobility Particle Sizer (SMPS) and Time-of-Flight Aerosol Mass Spectrometer (AMS) were used to measure particle number and mass concentrations, and size-resolved distributions inside and outside of the apartment. Automatically switching valve alternated between indoor and outdoor lines with the time resolution of 20 and 10 minutes, respectively. Both sampling lines were mounted at the ground floor level and led to the setup where the aerosol was dried and measured by both instruments. Indoor sampling line was heated and insulated to keep the same temperature of the indoor particles and additional carrier flow was used to lower the residence time. Results have showed that indoor particle loadings, in terms of particle number and mass concentrations, substantially exceeded the outdoor values due to the contribution of indoor emission sources during occupancy period, low air exchange rate during winter season in naturally ventilated apartment, and variations of outdoor particle concentration. The main contributors to indoor loadings were identified to be various types of cooking (frying, deep frying, baking, toasting, breakfast preparation), candle burning, ironing of the clothes. Number particle size distribution of the individual indoor sources showed to be distributed in in ultra-fine particle size range (UFP, <100 nm) which made up 84% of total particle number concentration (PNC) within occupancy period, i.e. when at least one person is present indoors. This is important in relation to human health since UFP are known to have higher deposition rates in the lower respiratory tract, compared with larger particles. The period without indoor activities (non-occupancy period) showed the influence of the outdoor particles, but this period was affected by the concentration generated previously from cooking activities and particle loadings were overestimated during this time. Outdoor loadings were influenced by traffic and some local sources, such as emissions from fireplaces (used by neighbours) and from adjacent fast food restaurants. Indoor to outdoor (I/O) ratios on the basic of particle mass of chemical species have accounted: for organic matter 3.4 due to the emissions of primary PM from indoor activities, and possibly, formation of secondary organic species took place; for ammonium 0.13 and for nitrate 0.22 as semi-volatile ammonium nitrate is sensitive to the temperature and relative humidity differences, reflecting phase change upon outdoor-to-indoor transport; for sulphate 0.51 and chloride 0.25, which have showed a result of outdoor penetration assuming the absence of indoor sulphate sources. However, emissions of nitrate and chloride may have resulted from episodic sources, such as candle burning, alkali nitrate salts and zinc chloride which were possibly added as flame retardants to the candle wick. The emitted nitrate could be another precursor to the formation of secondary organic species. The present analysis of collected data from the state-of-the-art instruments reflects the real-time indoor concentrations of specific components which can be the indicators of indoor air quality. Considering substantial amount of found submicrometer-size range particulate matter of different chemical composition indoors, originated from indoor and outdoor sources, creates potential risk in relation to the human health. Further detailed data analysis will provide more information about relative contribution of different components and origin of PM and air quality management strategies will be found in order to help in achieving suitable indoor air quality. |
