High resolution unattended particle-bound total carbon measurements and source identification at the Jungfraujoch global GAW station

Abstract

Total aerosol carbonaceous mass (TC) is a major constituent of atmospheric fine aerosol not yet continuously monitored with adequate time resolution. Adding a TC measurement to existing measurement programs is crucial for comprehensive interpretation of the impact of aerosols. To fill this gap, we developed the “fast thermal carbon totalizator” (FATCAT) for long-term unsupervised monitoring of TC. FATCAT has been deployed since 2019 at diverse sites including the Jungfraujoch global GAW station (JFJ). FATCAT collects particles on a metallic filter, and subsequently heats it to 800°C under an oxidizing atmosphere. The limit of detection is LoD=0.2 µg of carbon (µg-C). At the reduced atmospheric pressure of the JFJ, which limits the sampling flow, this corresponds to TC=0.3 µg-C/m3 using a time resolution of two hours. We discuss our experience during the first two year of continuous TC measurements and the possibility of using our instrument to distinguish carbonaceous aerosol from different source using fast, 50 seconds, thermograms. This unique feature allows us to identify source specific fingerprints. Several high TC episodes during September 2020 at JFJ show the typical pattern for biomass combustion. Back trajectories attribute them to long-range transported emissions from Californian wildfires. Graphitic carbon from, e.g., local fossil fuel combustion evolves at higher temperatures. The data collected at the JFJ is already the longest produced TC dataset for this site without instrument related interruptions. The dataset generated by our instrument and post-analysis data products represent an improvement to the available measurement inventory. It can serve as quality control for other measurement systems. Prominently, measurements of eBC via MAAP or Aethalometer and organic mass using ToF-ACSM. TC data can be used in parallel to these devices as a quality check, and to warrant carbon mass closure and reduce systematic biases.