Characterization of summertime carbonaceous aerosol on the North Slope of Alaska (Toolik and Utqiaġvik), 2022–2023

Rapid warming is likely increasing primary production and wildfire occurrence in the Arctic. Projected changes in the abundance and composition of carbonaceous aerosols during the summer are likely to impact atmospheric chemistry and climate, but our understanding of these processes is limited by sparse observations. Here, we characterize carbonaceous aerosol at two field sites, Toolik Field Station in the Interior and the Atmospheric Radiation Measurement facility at Utqiaġvik on the Arctic coast of Alaska, USA, through the summers of 2022 and 2023. We estimated particulate matter ≤2.5 micrometers (PM2.5) and particulate matter ≤10 micrometers (PM10) using laser light scattering (PurpleAir sensors) and examined total carbon (TC) and its organic carbon (OC) and elemental carbon (EC) fractions in total suspended particles (TSP). We also investigated the dominant sources of carbonaceous aerosol using air mass backward-trajectories from the National Oceanic and Atmospheric Administration (NOAA) Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model and radiocarbon source apportionment of TC. We found TC concentrations were about twice as high in the Interior than on the coast and that modern sources were the dominant sources of carbonaceous aerosol at both Toolik (95–99%) and Utqiaġvik (86–89%), with minor contributions from fossil sources. Periods of significantly elevated PM, TC, OC, and EC concentrations coincided with major boreal forest fire activity in North America that brought smoke to the region. The radiocarbon signature of EC measured at Toolik during these wildfire smoke events indicated that over 90% of the EC originated from modern sources. Our measurements demonstrate changing aerosol concentrations in the Arctic during the summer, and emphasize the need for continuous atmospheric monitoring to evaluate and advance our understanding of this rapidly changing atmospheric environment. (Manuscript in prep)

北极快速升温或正加剧初级生产与野火发生频次。夏季碳质气溶胶的丰度与组成预计将发生变化，进而对大气化学与气候产生影响，但当前我们对这些过程的认知受限于观测数据匮乏。本研究于2022年与2023年夏季，在美国阿拉斯加北极海岸的乌特恰维克（Utqiaġvik）大气辐射测量设施，以及内陆的图利克野外站（Toolik Field Station）两个野外站点开展碳质气溶胶特征表征工作。我们借助激光光散射技术（PurpleAir传感器）估算了细颗粒物≤2.5微米（PM2.5）与细颗粒物≤10微米（PM10）的浓度，并对总悬浮颗粒物（TSP）中的总碳（TC）及其有机碳（OC）、元素碳（EC）组分进行了检测分析。此外，我们通过美国国家海洋和大气管理局（NOAA）的混合单粒子拉格朗日综合轨迹（HYSPLIT）模型得到的气团后向轨迹，以及总碳的放射性碳源解析技术，探究了碳质气溶胶的主要来源。研究发现，内陆站点的总碳浓度约为海岸站点的两倍；且图利克（95%~99%）与乌特恰维克（86%~89%）两个站点的碳质气溶胶均以现代源为主要贡献，化石源贡献占比极低。PM2.5、PM10、总碳、有机碳与元素碳浓度显著升高的时段，与北美地区的北方森林大型野火活动相重合，这些野火产生的烟雾输送至北极区域。在这些野火烟雾事件期间，图利克站点测得的元素碳放射性碳特征显示，超过90%的元素碳源自现代源。本研究的观测结果表明，北极夏季气溶胶浓度正发生变化，同时强调需要开展持续的大气监测，以评估并深化我们对这一快速变化的大气环境的认知。（稿件待撰写中）