Thesis: Investigation of Volatile Organic Compound (VOC) processes in the indoor environs of Perth, WA using a dual observational and master chemical mechanism (MCM) modeling approach.
My thesis consists of an empirical based chemical study as well as computational model construction. A number of sampling methods, including adsorption tubes, (air toxics and DNPH), bags and canisters, will be used to measure VOCs in indoor air. Analysis of these samples via thermal desorption (TD)-GC-MS, HPLC-MS and potentially PTR-MS allows for the identification and quantification of the chemical constituents of the indoor airs. Other measurements will also be made of NOx, ozone, meteorological parameters and property metadata.
The empirical data gathered from air samples taken inside and outside buildings (mainly residential dwellings) in Perth will be statistically analysed for source characterisation. The differing relationship between the indoor and outdoor environments will also be explored. This will present the first comprehensive baseline data for indoor VOCs and ozone in Perth.
The results of these studies will then be used to construct a series of tailored chemical box models using the Master Chemical Mechanism (MCM) approach. The MCM, developed by Dr Sam Saunders and colleagues, is a near explicit chemical mechanism that describes the degradation of VOCs as well as the resultant generation of ozone and secondary pollutants in the planetary boundary layer. The majority of current atmospheric models, including the MCM, do not cater specifically for what reactions may occur indoors. This research aims to address this deficit in the literature, building on previous work to adapt and extend the MCM to the indoor environment in the southern hemisphere. This geographic specificity allows differences in building design and weather to be taken into account. It also takes into account the significant differences in ambient air composition, for example the abundance and types of naturally emitted VOCs, these are factors that have not previously been explored.
Why my research is important
People spend most of their time indoors, in some cases up to 90% of their lives. The quality of indoor air therefore is immensely important from a health perspective. Despite this, very little is actually known about the chemistry of indoor air. Unlike outdoors, there is no routine monitoring of the indoor environments in Australia.
The indoor air chemistry is different to the chemistry occurring outdoors in ambient air. The degradation of volatile organic compounds (VOCs) is primarily through photochemical reactions. The nature of the light therefore will determine the type of chemistry that is occurring. In the indoor environment the intensity of light is greatly diminished and so species with a very short lifetime outside can exist for a longer time inside and the photolysis rates are different. The different conditions indoors therefore change the chemistry that occurs and ultimately the types of secondary products formed. The health effects of indoor secondary pollutant levels are not fully understood. This is perhaps due to the fact that the types and quantities of these pollutants is largely unknown because previous, exposure based, studies have not investigated the chemical reactivity of the indoor atmosphere.