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Abstract

Air pollution is an inevitable problem that modern society has to face today, with particulate matter (PM) being the most dangerous part of it, threatening human health and the environment. Not all PM particles, however, are equally harmful, since the dangerous potential depends on their size and chemical composition, which can vary significantly based on its sources. Anthropogenic emissions, such as traffic, burning of biomass and fossil fuels, and industry are the most problematic sources of atmospheric PM pollution.
To limit PM pollution efficiently, the first step is to identify the most problematic PM constituents and monitor their abundance in the air, which requires accurate and precise analytical methods for their determination. Since PM is a complex mixture of various compounds, research of its whole composition is too extensive to be completed in one project. Therefore, in my dissertation, I focused on the development of two new methods for the determination of important PM constituents: trace elements and simple phenols.
In Europe, four airborne trace elements (As, Cd, Ni, Pb) are regulated (Directives 2004/107/EC and 2008/50/EC) and regularly monitored by a provided standard method (EN14902:2005). This standard method, however, has many drawbacks, mostly originating from the required microwave digestion (MW) pre-treatment. Two of the most important limitations are incomplete PM digestion and production of toxic waste. Therefore, we developed a new method using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS), which circumvents the MW digestion step. The developed method is multi-element, accurate, sensitive, fast, and green. Special attention was paid to the examination of sample homogeneity and the related LA sampling protocol, and to the calibration procedure. Apart from a 193 nm LA system used for the method development, a 213 nm LA system was also examined and proposed as a more affordable alternative that could ease the transition to waste-free analytics in air-quality monitoring laboratories. In general, LA-ICPMS was recognized to have the potential of replacing the current standard method in the future, since it is a sustainable method capable of directly analyzing PM collected on the most widely used quartz fiber filters, which is not possible with other surface-based techniques due to the filter thickness or uneven surface.
Airborne simple phenols (i.e. phenol, catechol, guaiacol, cresols) are considered toxic, but are not well investigated in PM. Moreover, they can act as precursors to even more harmful nitrophenols. Due to trace concentrations and low ionization efficiency, their determination in PM is difficult, especially without using any sample pre-concentration step, which is commonly accompanied by loss of analytes due to their semi-volatile characteristics. We show that derivatization with dansyl chloride (DnsCl) enables particulate phenols determination with liquid chromatography-tandem mass spectrometry (LC-MS/MS) without the use of a pre-concentration step. Dansylation improved ionization efficiency and the optimized method exhibits good analytical performance, low LODs, and high precision.
Application of the developed methods to ambient PM samples further revealed seasonal trends of target pollutants in Ljubljana, where both trace elements and simple phenols exhibited higher concentrations in colder months compared to the warmer part of the year. This is consistent with the combination of the prevalence of their emission sources and specific meteorological conditions in winter, as are biomass burning for heating purposes and the presence of temperature inversions.
This dissertation provides two analytical methods for trace elements and simple phenols in PM, which show good performance and are consistent with good analytical practices. The atmospheric science community will thus benefit from the alternative multi-element PM determination without concomitant burdening of the environment and by facilitating studies involving particulate phenols, which have been restricted to date.