Assessing the Contribution of Black Carbon in Aged Biomass Burning Plumes and Asian Long-Range Transport Events at the Mt. Bachelor Observatory

 The location of the Mount Bachelor Observatory (MBO; 2764 meters asl), is an ideal site for the frequent sampling of long range transported biomass burning (BB) and pollution events. During the summer aged BB plumes are frequently observed at MBO, and Asian long-range transport (ALRT) pollution events are observed in the spring. Black carbon (BC) aerosols are short-lived but are strongly absorbing and have a significant aerosol radiative forcing globally. Additionally according to the IPCC 2013 report, the global radiative forcing of BC aerosols has the largest uncertainty of any component. Understanding the lifetime of BC in long-range transported pollution plumes and the physical and optical properties of well-aged BC is critical to constraining these uncertainties. A Single-Particle Soot Photometer (SP2; Droplet Measurement Technologies) was deployed at MBO during the summer of 2016 and in the spring of 2017 with the goal of obtaining measurements of refractory black carbon (rBC) mass concentration and size distribution in BB plumes and ALRT events. The SP2 complemented the core measurement suite at MBO that includes CO, CO₂, O₃, aerosol three wavelength scattering (σ_scat) and absorption (σ_ab), PM mass, and aerosol size distribution. Our goal is to determine the ΔrBC/ΔCO enhancement ratios and rBC mass fraction (ΔrBC/ΔPM) of the BB and ALRT events. Comparison of the ΔrBC/ΔCO and rBC mass fraction of ALRT events with other measurements of Asian continental outflows will provide an estimate of BC lifetime in long-range transported events. We will investigate the effect of wet removal on rBC in ALRT events, estimated by accumulated precipitation along the backward trajectory (APT). These analyses will be discussed with the goal of better understanding the role of BC in aged BB plumes and the impact of the trans-Pacific transport of BC.