Sources and composition of organic aerosol on the North Slope of Alaska.


As the Arctic continues to change and warm rapidly, it is increasingly important to understand the contribution of biogenic sources to Arctic aerosol. Biogenic sources of primary and secondary aerosol in the Arctic will be impacted by climate change, including warming and earlier snow and ice melt, while local emissions and long-range transport can drive changes in anthropogenic aerosol. This dissertation focuses on identifying the contribution of biogenic aerosol to organic carbon (OC) and its seasonal trends through the analysis of aerosol chemical and isotopic composition. Aerosol samples were collected at two sites on the North Slope of Alaska (Utqiaġvik and Oliktok Point) over the summer of 2015 and from June 2016 through August 2017. Organic carbon concentrations correlated well between the sites with high contribution from contemporary sources. Backwards air mass trajectory analysis indicates that source regions are primarily marine in the summertime. Methanesulfonic acid (MSA) was utilized to confirm this marine influence. Secondary organic aerosol confirmed the contribution of terrestrial biogenic sources to organic aerosol at both sites. Strong correlations between ambient temperature and MSA and OC were found during the summer. This study provides a multiyear characterization of organic carbon, highlighting the high biogenic influence and indicating areas of interest for future research.