Loading [MathJax]/jax/output/HTML-CSS/fonts/TeX/fontdata.js
Preprints
https://doi.org/10.5194/egusphere-2022-625
https://doi.org/10.5194/egusphere-2022-625
26 Aug 2022
 | 26 Aug 2022

An Optimised OC/EC Fraction Separation Method for Radiocarbon Source Apportionment Applied to Low-Loaded Arctic Aerosol Filters

Martin Rauber, Gary Salazar, Karl Espen Yttri, and Sönke Szidat

Abstract. Radiocarbon (14C) analysis of carbonaceous aerosols is used for source apportionment, separating the carbon content into fossil vs. non-fossil origin, and is particularly useful when applied to subfractions of total carbon (TC), i.e., elemental carbon (EC), organic carbon (OC), water-soluble OC (WSOC), and water-insoluble OC (WINSOC). However, this requires an unbiased physical separation of these fractions, which is difficult to achieve. Separation of EC from OC using thermal-optical analysis (TOA) can cause EC loss during the OC removal step and form artificial EC from pyrolysis of OC (i.e., so-called charring), both distorting the 14C analysis of EC. Previous work showed that water extraction reduces charring. Here, we apply a new combination of a WSOC extraction and 14C analysis method with an optimised OC/EC separation that is coupled with a novel approach of thermal-desorption modelling for compensation of EC losses. As water-soluble components promote the formation of pyrolytic carbon, water extraction was used to minimise the charring artefact of EC, and the eluate subjected to chemical wet oxidation to CO2 before direct 14C analysis in a gas-accepting accelerator mass spectrometer (AMS). This approach was applied to 13 aerosol filter samples collected at the Arctic Zeppelin Observatory (Svalbard) in 2017 and 2018, covering all seasons, which bear challenges for a simplified 14C source apportionment due to their low loading and the large portion of pyrolysable species. Our approach provided a mean EC yield of 0.87 ± 0.07 and reduced the charring to 6.5 % of the recovered EC amounts. The mean Fraction Modern (F14C) over all seasons was 0.85 ± 0.17 for TC, 0.61 ± 0.17 and 0.66 ± 0.16 for EC before and after correction with the thermal-desorption model, respectively, and 0.81 ± 0.20 for WSOC.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Share

Journal article(s) based on this preprint

14 Feb 2023
An optimised organic carbon ∕ elemental carbon (OC ∕ EC) fraction separation method for radiocarbon source apportionment applied to low-loaded Arctic aerosol filters
Martin Rauber, Gary Salazar, Karl Espen Yttri, and Sönke Szidat
Atmos. Meas. Tech., 16, 825–844, https://doi.org/10.5194/amt-16-825-2023,https://doi.org/10.5194/amt-16-825-2023, 2023
Short summary
Download

The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

Short summary
Carbon-containing aerosols from ambient air are analysed for the radioactive isotope radiocarbon...
Share