Environmental chamber study on the formation of indoor secondary organic aerosols from household emissions

Abstract

Biogenic volatile organic compounds (BVOCs) are commonly used as solvents or odorants in household cleaning products and air fresheners that are utilized regularly for hygiene purposes in indoor environments. However, these BVOCs are unsaturated and very reactive, which can react rapidly with indoor oxidants such as ozone (O₃) to produce secondary organic aerosols (SOAs) and secondary gaseous pollutants. These generated secondary pollutants can impose adverse effects on human health. Furthermore, the formation of indoor secondary pollutants from indoor gas-phase reactions can be influenced by environmental parameters including air exchange rate (ACH), relative humidity (RH) and temperature (T), and the co-existence of other indoor gaseous pollutants such as ammonia (NH₃). Hence, in order to scientifically assess indoor air quality (IAQ) problems caused by secondary pollutants, it is important to characterize the BVOCs components in cleaning products and air fresheners popularly used in Hong Kong, and to investigate the effect such parameters have on the indoor secondary pollutants formation. Solid-phase microextraction (SPME) coupling with gas chromatography/mass spectrometry (GC/MS) method was optimized for the determination of BVOCs in indoor environment. Parameters influencing the extraction processes, including sampling time, temperature and relative humidity were also investigated. Comparison studies were carried out on a set of floor cleaner extracts using the SPME method and traditional liquid injection method. Good agreement of the target BVOCs was obtained by the two methods. The optimized SPME-GC/MS method was then applied for the determination of BVOCs compositions in three categories of cleaning products including floor cleaners (FC), kitchen cleaners (KC) and dishwashing detergent (DD), and air fresheners (AF). The analysis results showed that the chemical compositions and concentrations of individual BVOC varied broadly with household products in the view of their different functions and scents. The effects of ACH, T, and RH on the formation of indoor SOAs through ozonolysis of BVOCs emitted from FC samples were investigated. Oxidation-generated secondary carbonyl compounds were also quantified. Acetone was the most abundant carbonyl compound. The formation mechanisms of formaldehyde and acetone were tentatively proposed in this study. The effect of NH₃on secondary pollutants formation from ozonolysis of BVOCs emitted from cleaning products including FC, KC and DD were investigated in a large environmental chamber. Our results demonstrated that the presence of NH₃can significantly enhance SOAs formation regarding all the three categories of cleaning products. The percent yields (%) of secondary carbonyl compounds generated from ozonolysis of BVOCs emitted from the cleaning products were assesed in the presence and absence of NH₃. Results obtained in this study will not only improve our understanding of the factors that influence the formation of ozone-derived SOAs but also assist home residents in improving IAQ through selecting appropriate cleaning products and air fresheners.