Abstract
Section I: Laboratory studies: Chemical and sorption properties of indoor floor dust in FLEC:
Ozone reacts with C-C double bonds in common indoor VOCs and SVOCs contained in indoor dust and may be catalytically degraded on dust surfaces. The reaction between floor dust and ozone was investigated in the Field and Laboratory Emission Cell (FLEC) at different ozone concentrations and relative humidities (0, 25, and 50 % RH). One gram of dust was spread on a clean stainless steel plate which was placed in the FLEC. Steady state reaction rate (kDust) at 2.2 ppm ozone was determined for four different floor dust samples collected in Danish homes and offices. This high
concentration was necessary in order to measure and determine the consumption of ozone in the outlet air from the FLEC. Measurements were corrected for FLEC wall effects by subtraction of the steady state reaction rate between ozone and a FLEC on a stainless steel plate without dust (kFLEC). The composition of organic compounds in the dust was analyzed by pressurized liquid extraction and thermal desorption GC-MS before and after ozone exposure.
KFLEC was independent of the ozone concentration and the reaction was treated as first order. The same was indicated for KDust since it remained unchanged at 2.2 and 1.6 ppm ozone for one dust sample. However, the measured KDust in the FLEC should be considered an average rate constant due to the FLEC geometry. KDust was trice higher at 25% RH than at 50% RH and 6 times higher than at 0 % RH.
The major identified compounds before and after ozone exposure included aldehydes, saturated and unsaturated linear alkanoic acids, benzoic acid and their methyl esters, dimethyl esters, phthalates and traces of α-pinene and limonene. Substantial increase of C7-C9 aldehydes was observed after ozone exposure.
Section IIa: Field study
Field measurements were carried out inside and outside of five Danish homes throughout a year, with four measurement campaigns in each home, representing four seasons: Spring, Summer, Fall, and winter. Ozone, NO2 and aldehydes were measured outdoor for comparison with indoor measurements. Seasonal variation of indoor ozone, NO2, aldehydes, particles (0.75-15 μm), ultrafine particles (<1 μm) was investigated. The parameters measured as part of this thesis was compared, to search for correlations. Temperature, relative humidity and air exchange rates,
obtained in other parts of the CISBO-project, were also investigated with regard to seasonal variation and correlation with the parameters found as a part of this thesis. Volatile organic compounds were analyzed qualitatively.
Correlations were found between indoor and outdoor absolute humidity; opening of windows and air exchange rate; indoor aldehydes and outdoor ozone; and, indoor aldehyde and air exchange rate. A total of 85 VOCs was identified from sampling on Tenax TA in the five homes during the fall season.
Section IIb: Direct Low Temperature Plasma ionization-MS analysis of air sampling filters
The quantitative properties of a new ionization technique for mass spectrometry (Low Temperature Plasma ionization – LTP) were investigated for analysis of Teflon air sampling filters. Standards of free fatty acids (lauric, myristic , palmitic , oleic and stearic acid), phthalates (dimethyl, diethyl, dibutyl, benzylbutyl and bis(2-ethylhexyl) phthalate) and PAHs (including naphthalene, fluorene, anthracene, and pyrene) were used for the quantification and linear calibration curves were obtained within a limited concentration range. Free fatty acids and phthalates were determined on Teflon air sampling filters obtained in the field study. The results were compared to a direct thermal desorption (TD) GC-MS method of sampled filters. Advantages
and disadvantages as well as possible improvements of the LTP-MS method are discussed together with principal component analysis (PCA) of the sampled filters.
Ozone reacts with C-C double bonds in common indoor VOCs and SVOCs contained in indoor dust and may be catalytically degraded on dust surfaces. The reaction between floor dust and ozone was investigated in the Field and Laboratory Emission Cell (FLEC) at different ozone concentrations and relative humidities (0, 25, and 50 % RH). One gram of dust was spread on a clean stainless steel plate which was placed in the FLEC. Steady state reaction rate (kDust) at 2.2 ppm ozone was determined for four different floor dust samples collected in Danish homes and offices. This high
concentration was necessary in order to measure and determine the consumption of ozone in the outlet air from the FLEC. Measurements were corrected for FLEC wall effects by subtraction of the steady state reaction rate between ozone and a FLEC on a stainless steel plate without dust (kFLEC). The composition of organic compounds in the dust was analyzed by pressurized liquid extraction and thermal desorption GC-MS before and after ozone exposure.
KFLEC was independent of the ozone concentration and the reaction was treated as first order. The same was indicated for KDust since it remained unchanged at 2.2 and 1.6 ppm ozone for one dust sample. However, the measured KDust in the FLEC should be considered an average rate constant due to the FLEC geometry. KDust was trice higher at 25% RH than at 50% RH and 6 times higher than at 0 % RH.
The major identified compounds before and after ozone exposure included aldehydes, saturated and unsaturated linear alkanoic acids, benzoic acid and their methyl esters, dimethyl esters, phthalates and traces of α-pinene and limonene. Substantial increase of C7-C9 aldehydes was observed after ozone exposure.
Section IIa: Field study
Field measurements were carried out inside and outside of five Danish homes throughout a year, with four measurement campaigns in each home, representing four seasons: Spring, Summer, Fall, and winter. Ozone, NO2 and aldehydes were measured outdoor for comparison with indoor measurements. Seasonal variation of indoor ozone, NO2, aldehydes, particles (0.75-15 μm), ultrafine particles (<1 μm) was investigated. The parameters measured as part of this thesis was compared, to search for correlations. Temperature, relative humidity and air exchange rates,
obtained in other parts of the CISBO-project, were also investigated with regard to seasonal variation and correlation with the parameters found as a part of this thesis. Volatile organic compounds were analyzed qualitatively.
Correlations were found between indoor and outdoor absolute humidity; opening of windows and air exchange rate; indoor aldehydes and outdoor ozone; and, indoor aldehyde and air exchange rate. A total of 85 VOCs was identified from sampling on Tenax TA in the five homes during the fall season.
Section IIb: Direct Low Temperature Plasma ionization-MS analysis of air sampling filters
The quantitative properties of a new ionization technique for mass spectrometry (Low Temperature Plasma ionization – LTP) were investigated for analysis of Teflon air sampling filters. Standards of free fatty acids (lauric, myristic , palmitic , oleic and stearic acid), phthalates (dimethyl, diethyl, dibutyl, benzylbutyl and bis(2-ethylhexyl) phthalate) and PAHs (including naphthalene, fluorene, anthracene, and pyrene) were used for the quantification and linear calibration curves were obtained within a limited concentration range. Free fatty acids and phthalates were determined on Teflon air sampling filters obtained in the field study. The results were compared to a direct thermal desorption (TD) GC-MS method of sampled filters. Advantages
and disadvantages as well as possible improvements of the LTP-MS method are discussed together with principal component analysis (PCA) of the sampled filters.
| Original language | English |
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| Publisher | Department of Chemistry, Faculty of Science, University of Copenhagen |
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| Number of pages | 180 |
| Publication status | Published - 2013 |