Insight in Antarctic aerosol particle composition regarding free amino acids

As a pristine region, the Antarctic peninsula can be a model for the preindustrial atmospheric environment and, accordingly, give insights in processes related to climate change. Most studies performed in this region focus on either aerosol sources, for example the ocean, or the chemical composition of aerosol particles. Wind and wave driven physical mechanisms for particle mobilization (e.g. bubble bursting) lead to the formation of sea-spray aerosol particles (SSA) consisting of sea salt together with primary organic aerosol (POA), which is rich in organic matter (OM). The molecular nature of this OM is not fully understood to this day. The second-largest fraction of OM are likely proteins, which consist of amino acids (AA). AA contribute massively to the global nitrogen cycle and have impact on cloud chemistry, for example by acting as cloud condensation nuclei (CCN) or ice nucleating particles (INP).

             To date, chemical analysis of AAs is often provided as sum parameter, as robust methods for their analysis in original form are lacking. Therefore, individual differences between sample sets cannot be determined and information on biotic or abiotic transfers are lacking. For that reason, we developed a hydrophilic interaction liquid chromatography electrospray ionization time-of-flight mass spectrometry (HILIC-ESI-TOF-MS) method, utilizing the potential of HILIC to separate more polar analytes, compared to standard LC methods. Advantages of the developed method are not only its broad window of analytes, but also its robustness as it can be applied to complex marine samples with a short sample preparation, as derivatization steps are not needed.

This new method was applied to Antarctic low volume size segregated aerosol samples. Due to the nature of HILIC, the polar analytes show a good retention and separation from matrix components. Through these measurements, further insights can be gained on the enrichment and chemo-selective transfer of AA from the ocean to the atmosphere and their respective degradation processes. A higher variation and concentration of FAA than in previous literature was observed, with dominating marine derived FAAs. First results, also regarding the influence of air masses to the composition of different AA and comparison with other constituents, will be shown.

Sources

Jaber et al. (2021) Biogeosciences, 18, 1067–1080.

Zeppenfeld et al. (2021), ACS Earth Space Chem. 5, 1032−1047