An optimised organic carbon ∕ elemental carbon (OC ∕ EC) fraction separation method for radiocarbon source apportionment applied to low-loaded Arctic aerosol filters

• Published in: Atmospheric Measurement Techniques
• Main Authors: M. Rauber, G. Salazar, K. E. Yttri, S. Szidat
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2023
• Subjects: Environmental engineering; TA170-171; Earthwork. Foundations; TA715-787; Arctic; Svalbard
• Online Access: https://doi.org/10.5194/amt-16-825-2023; https://doaj.org/article/269908e6e515408180485e3ddee6cfcd

Radiocarbon ( 14 C) 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 14 C analysis of EC. Previous work has shown that water extraction reduces charring. Here, we apply a new combination of a WSOC extraction and 14 C analysis method with an optimised <math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">OC</mi><mo>/</mo><mi mathvariant="normal">EC</mi></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="40pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="580ada1a61f0f73a9255ab81c518e127"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-16-825-2023-ie00006.svg" width="40pt" height="14pt" src="amt-16-825-2023-ie00006.png"/></svg:svg> 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 CO 2 before direct 14 C 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 14 C source ...