In the Arctic, increasing ice-free conditions and nutrients freed from the melting ice must strongly influence the marine life. Aerosol emissions from microbiological marine processes may affect the low clouds and fogs over the summer Arctic, which in turn have effects on the melting of sea ice. The radiative properties of the high Arctic low clouds are strongly dependent on the number concentration of airborne water-soluble particles, known as cloud condensation nuclei (CCN). If the effects of CCN on cloud optical properties is to be fully understood it is important to be able to specify the source and concentrations of the Arctic aerosol particles.

Previous studies in the Arctic have indicated that organic material formed in the uppermost ocean surface is transferred to the atmosphere and plays a potentially very important role in the aerosol-fog/cloud cycle. However, many aspects of this process remain unverified and chemical characterisation of targeted groups of biomolecules is still notably fragmentary or non-existing. Investigation of biomolecules, particularly amino acids, peptides and proteins together with mono- and polysac­charides and fatty acids in the airborne aerosol, and their relative contributions to fog/cloud water, requires development of an array of “cutting edge” analytical techniques and methods.

In this thesis, electrospray ionization mass spectrometry was used for all applications and target biomolecules. The measurements in the Arctic turned out to be challenging due to the highly complex, salty matrices, combined with very low concentration and high diversity of the target biomolecules, and each step of the analytical chain needed careful consideration. To increase the detectability of the very low levels of polysaccharides and proteins in aerosols, these compounds were hydrolyzed to their subunits, monosaccharides and amino acids. Monosaccharides were separated using hydrophilic interaction chromatography, which was beneficial for their detection in electrospray ionization mass spectrometry. Amino acids were derivatized, yielding improvement in reversed-phase chromatographic separation, ionization efficiency as well as selectivity. For fatty acids in a sea surface sample, a novel fast screening method was developed, utilizing travelling-wave ion mobility separation as an orthogonal technique connected to mass spectrometry. In addition, a method for the detection of wood burning as an anthropogenic source of aerosols was developed, utilizing anhydrous monosaccharides as markers. This method can be used in the upcoming expeditions for source apportionment studies.

The results from the analyses of the aerosol and fog water samples, collected over the summer pack ice north of 80 °N, show that both total polysaccharides and total proteinaceous compounds (sum of proteins, peptides and amino acids) occurred at the pmol m^-3 to nmol m^-3 level. Interestingly, the levels were found higher between different years, suggested to be coupled to less ice coverage and thus to a higher biological activity in the ocean surface. The highest concentrations of polysaccharides, as an indication of marine polymer gels, were found during the summer over the pack ice area. In addition, a pilot source apportionment study was carried out combining the measurement of different molecular tracers, used as source markers. This study indicates the seasonality and abundance of marine polymer gels as an important feature of the Arctic Ocean connected to the melting and freezing of sea ice. It should be further studied how the abundance of these gels, which have a high potential for cloud droplet activation, affect the melting and freezing of the perennial sea ice.

Given the successful development of analytical methods for targeted groups of biomolecules, this thesis has supported the importance of biomolecules as CCN and for cloud formation in the Arctic. Less ice coverage may further increase the number of biomolecular CCN which could change the radiative balance, by the formation of more low-level clouds. Overall, more studies are required to further unravel the complex relationship of biogenic sources, atmospheric chemistry and meteorology to assess the impact of climate change on the Arctic.

Amino acids play vital roles in health, either in their native form or chemically modified. Some studies have linked certain non-proteinogenic amino acids to neurodegenerative diseases, such as in the case of β-methylaminoalanine (BMAA). Various environmental pollutants, including carcinogenic polycyclic aromatic compounds, are able to react forming adducts with blood proteins. Amino acids may also be essential in chemical ecology as constituents of flower nectar, potentially used by common feeders as butterflies to synthesize pheromones. Additionally, proteinaceous materials have been detected in aerosols with an apparent potential to influence climate, possibly having a role in cloud formation.

The determination of amino acids presents many challenges, due to the fact that they are most often constituents of complex sample matrices that contain a high level of chemical interferences. In this respect, mass spectrometry (MS) is a selective and sensitive analytical tool that can be used to measure amino acids in biological samples.

In this work, several analytical methods based on MS were developed. (i) First, derivatization with a permanently charged N-hydroxysuccinimide ester of N-butylnicotinic acid (C₄-NA-NHS) was used to increase the sensitivity and selectivity for amino acids. This strategy was applied to localize BMAA in both visceral and non-visceral parts of blue mussels. (ii) Moreover, a method was developed to separate and determine L- and D- BMAA in cycad seeds by derivatization with a chiral reagent, (+)-1-(9-fluorenyl) ethyl chloroformate (FLEC). Together with L-BMAA, appreciable amounts of D-BMAA (50.13 ± 0.05 and 4.08 ± 0.04 µg BMAA/g Cycas micronesica, wet weight, respectively) were detected for the first time after enzymatic digestion, suggesting D-BMAA may be bound to proteins or may be a conjugate and released only after hydrolysis. (iii) Derivatization with C₄-NA-NHS was applied as well for the determination of amino acids in nectar of Bunias orientalis. The presence of tryptophan and phenylalanine, purportedly used to synthesize anti-aphrodisiac pheromones by nectar feeders (adult male butterflies), could then be observed. (iv) Furthermore, the profiling of amino acids in Arctic aerosols was carried out and was used to measure the contribution of free and polyamino acids in aerosol formation. Levels detected were in the range of 0.02-2914 pmol/m³ sampled air. For the first time the measurement of polyamino acids in the Arctic atmosphere was reported. Additionally, possible anthropogenic and marine sources were suggested. The results support the hypothesis that proteinaceous materials act as cloud condensation nuclei over the Arctic. (v) Finally, a method was developed employing selective chromatography/high-resolution MS to identify histidine and lysine adducts in serum albumin of mice exposed to the carcinogen benzo(a)pyrene, as well as in human samples in vivo. Adduct isomers from diol epoxide metabolites could be detected in serum albumin from human samples at attomole/mg levels. This work shows the possibility of future exposure measurements from these compounds in different groups of the population.

This thesis presents the development of improved analytical methodologies for detecting and identifying trace levels of amino acids, to investigate their relevance in health, climate and the environment.