TY - JOUR
T1 - An automated method for thermal-optical separation of aerosol organic/elemental carbon for 13C analysis at the sub-μgC level
T2 - A comprehensive assessment
AU - Yao, Peng
AU - Ni, Haiyan
AU - Paul, Dipayan
AU - Masalaite, Agne
AU - Huang, Ru Jin
AU - Meijer, Harro A.J.
AU - Dusek, Ulrike
N1 - Funding Information:
This work was supported by National Key Research and Development Program of China (grant no. 2017YFC0212701 ) and the program of China Scholarships Council No. 201806320346 . Special thanks are given to Henk Jansen and Marc Bleeker for their help with the system modification and tests at CIO, and to Romke Tjoelker and Katrin Zenker for developing the connection interface at CIO.
Publisher Copyright:
© 2021 Elsevier B.V.
PY - 2022/1/15
Y1 - 2022/1/15
N2 - We describe and thoroughly evaluate a method for 13C analysis in different fractions of carbonaceous aerosols, especially elemental carbon (EC). This method combines a Sunset thermal-optical analyzer and an isotope ratio mass spectrometer (IRMS) via a custom-built automated separation, purification, and injection system. Organic carbon (OC), EC, and other specific fractions from aerosol filter samples can be separated and analyzed automatically for 13C based on thermal-optical protocols (EUSAAR_2 in this study) at sub-μgC levels. The main challenges in isolating EC for 13C analysis are the possible artifacts during OC/EC separation, including the premature loss of EC and the formation of pyrolyzed OC (pOC) that is difficult to separate from EC. Since those artifacts can be accompanied with isotope fractionation, their influence on the stable isotopic composition of EC was comprehensively investigated with various test compounds. The results show that the thermal-optical method is relatively successful in OC/EC separation for 13C analysis. The method was further tested on real aerosols samples. For biomass-burning source samples, (partial) inclusion of pOC into EC has negligible influence on the 13C signature of EC. However, for ambient samples, the influence of pOC on the 13C signature of EC can be significant, if it is not well separated from EC, which is true for many current methods for measuring 13C on EC. A case study in Xi'an, China, where pOC is enriched in 13C compared to EC, shows that this can lead to an overestimate of coal and an underestimate of traffic emissions in isotope-based source apportionment.
AB - We describe and thoroughly evaluate a method for 13C analysis in different fractions of carbonaceous aerosols, especially elemental carbon (EC). This method combines a Sunset thermal-optical analyzer and an isotope ratio mass spectrometer (IRMS) via a custom-built automated separation, purification, and injection system. Organic carbon (OC), EC, and other specific fractions from aerosol filter samples can be separated and analyzed automatically for 13C based on thermal-optical protocols (EUSAAR_2 in this study) at sub-μgC levels. The main challenges in isolating EC for 13C analysis are the possible artifacts during OC/EC separation, including the premature loss of EC and the formation of pyrolyzed OC (pOC) that is difficult to separate from EC. Since those artifacts can be accompanied with isotope fractionation, their influence on the stable isotopic composition of EC was comprehensively investigated with various test compounds. The results show that the thermal-optical method is relatively successful in OC/EC separation for 13C analysis. The method was further tested on real aerosols samples. For biomass-burning source samples, (partial) inclusion of pOC into EC has negligible influence on the 13C signature of EC. However, for ambient samples, the influence of pOC on the 13C signature of EC can be significant, if it is not well separated from EC, which is true for many current methods for measuring 13C on EC. A case study in Xi'an, China, where pOC is enriched in 13C compared to EC, shows that this can lead to an overestimate of coal and an underestimate of traffic emissions in isotope-based source apportionment.
KW - C analysis
KW - Automated method
KW - Elemental carbon
KW - Isotope fractionation
KW - Pyrolysis
UR - http://www.scopus.com/inward/record.url?scp=85118740374&partnerID=8YFLogxK
U2 - 10.1016/j.scitotenv.2021.150031
DO - 10.1016/j.scitotenv.2021.150031
M3 - Article
C2 - 34509852
AN - SCOPUS:85118740374
SN - 0048-9697
VL - 804
JO - Science of the Total Environment
JF - Science of the Total Environment
M1 - 150031
ER -