An Investigation of Carboxylic Acid Chemistry in Indoor and Outdoor Environments

Anna Ziola, ANYL 3rd year,
Ziemann group

"Carboxylic acids are prominent organic molecules in indoor and outdoor environments and also have chemical properties that make them useful probes for investigating the chemistry of indoor and outdoor air. Even though the average person spends nearly 90% of their lifetime indoors, we know very little about the processes that impact volatile organic compounds (VOCs) in indoor environments, where there are a variety of surfaces that VOCs can interact with. To understand the role of wood surfaces, we have used an iodide chemical ionization mass spectrometer (I-CIMS) and an attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectrometer along with a model to quantify and better understand how carboxylic acids interact with a variety of wood species and varnishes. These experiments have provided parameters for use in models and shown that the behavior of carboxylic acid VOCs indoors relies more on the identity of the varnish and less on the identity of the wood species. We have also taken advantage of the chemical properties of carboxylic acids to study the oxidation of alkenes in low NOx environments. According to data from CalNex in 2010 and LAAQS in 2020, the concentration of mid-day NO, a prominent component in VOC oxidation mechanisms, has decreased by about 75% in Los Angeles in the past decade. There have been many studies on the oxidation of VOCs in high NOx environments, but far fewer in the absence of NOx. To gather more knowledge about low NOx chemistry, we reacted 6-heptenoic acid, a C7 1-alkene with a terminal carboxylic acid group, with OH radicals in an environmental chamber while using an I-CIMS to identify and quantify gas-phase products. We also collected aerosol particles on filters, derivatized the carboxylic acid groups, and identified and quantified the products using high performance liquid chromatography (HPLC) in tandem with an electrospray ionization mass spectrometer (ESI-MS). Therefore, by taking advantage of carboxylic acid properties, we have been able to better understand their interactions with indoor surfaces and gain insights into the oxidation of alkenes under low NOx conditions."