Prudhoe Bay Oilfield Influences on Atmospheric Particles on the North Slope of Alaska

Unprecedented summertime Arctic sea ice loss is opening the region to increased oil and gas extraction activities and ship traffic. Arctic aerosol emissions are expected to increase with increasing anthropogenic activities and production of sea spray aerosol. Given the complexity and evolving nature of atmospheric particles, as well as the challenges associated with Arctic measurements, significant uncertainties remain in our understanding of particle sources, evolution, and impacts in the Arctic. Long-term trends in aerosol size distributions at Utqiaġvik, Alaska show the significant influence of the Prudhoe Bay Oilfields on aerosol growth events, which are important for growing particles to sizes relevant to serve as cloud droplet nuclei. The chemical composition of fresh and aged combustion particles from the Prudhoe Bay Oilfields was examined through individual particle measurements during August-September 2015 and 2016 at Utqiaġvik and Oliktok Point, Alaska, respectively. An aerosol time-of-flight mass spectrometer (ATOFMS) and computer-controlled scanning electron microscopy with energy dispersive X-ray analysis were utilized to measure the size and chemical composition of individual particles associated with Prudhoe Bay air masses for the first time. Additionally, organic carbon, elemental carbon, black carbon, and inorganic ion concentrations, as well as size-resolved particle number concentrations, were measured to provide a comprehensive characterization of atmospheric aerosol chemical composition. During Utqiaġvik measurements, aerosol particle mixing states were observed to vary between Arctic Ocean and Prudhoe Bay influence, with significant secondary processing observed for the particles with air masses traveling from Prudhoe Bay, now the third largest oilfield in North America. The Oliktok Point field site is located within the Prudhoe Bay oilfields, and thus, elevated particle concentrations associated with soot particles were observed under direct combustion plume influence, with regional conditions associated with a mixture of aged sea spray, secondary organic aerosol, and combustion particles.