30 Sep 2022
 | 30 Sep 2022
Status: a revised version of this preprint is currently under review for the journal AMT.

High-resolution observation of stable carbon isotope ratios of water-soluble organic carbon in particle/gas phases at an urban site in China: Using an improved isotope ratio mass spectrometry method

Hao-Ran Yu, Yan-Lin Zhang, Fang Cao, Xiao-Ying Yang, Tian Xie, Yu-Xian Zhang, and Yongwen Xue

Abstract. A high time resolution synchronous sampling method along with determination of stable carbon isotopes of gaseous water-soluble organic carbon (WSOCg) and particulate water-soluble organic carbon (WSOCp) was realized in this research through equipment modification and method improvement. It was found that WSOCg has significant higher concentration than WSOCp and a more depleted δ13C. Both concentrations of WSOCp and WSOCg have the seasonal variation characteristics of high in winter (WSOCp = 15.7 ± 3.9 μg/m3; WSOCg = 42.4 ± 6.0 μg/m3) and low in summer (WSOCp = 5.9 ± 1.8 μg/m3; WSOCg = 25.2 ± 5.2 μg/m3), with greater increase in WSOCp (167 %) than that in WSOCg (68 %). During wintertime, WSOCp and WSOCg had similar daily variation characteristics of concentration, and opposite daily variation characteristics of δ13C. WSOCp had a bimodal distribution with obvious low value at sunrise and sunset, while δ13C-WSOCp had a unimodal distribution with low in daytime (-24.6 ± 1.1 ‰) and high in nighttime (-22.3 ± 1.7 ‰). WSOCg and δ13C-WSOCg had same distribution with high in daytime and (49.3 ± 8.8 μg/m3; -27.9 ± 1.1 ‰) low in nighttime (38.3 ± 4.6 μg/m3; -29.9 ± 0.4 ‰). Combining the δ13C variation characteristics with the synchronous observation results of meteorological conditions, gaseous precursor pollutants, gaseous oxidants, gaseous acids and fine particle components, the restriction factors of WSOC gas-particle distribution mechanism were discussed. The presence of radiation rather than its intensity decided whether generations process of WSOCp and WSOCg are divided, for δ13C-WSOC of two phases showed significant correlation only during daytime. Meteorological conditions, gaseous precursor pollutants, gaseous oxidants and gaseous acids restrict the gas particle distribution of WSOC by affecting the aging process of WSOCp and WSOCg, gas-particle conversion ratio of semi-volatile organic compounds (SVOC) and the gas phase and liquid phase generation ratio of WSOCp. At the same time, the gas-particle distribution process of WSOC is strongly related to the formation of secondary inorganic ions (nitrate, sulfate, ammonium), and the gas-particle distribution between gaseous nitrous acid and nitrite.

Hao-Ran Yu et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2022-239', Anonymous Referee #1, 31 Oct 2022
    • AC1: 'Reply on RC1', Haoran Yu, 28 Nov 2022
      • RC2: 'Reply on AC1', Anonymous Referee #1, 01 Dec 2022
        • AC2: 'Reply on RC2', Haoran Yu, 02 Dec 2022
  • RC3: 'Comment on amt-2022-239', Anonymous Referee #2, 08 Dec 2022
    • AC3: 'Reply on RC3', Haoran Yu, 10 Jan 2023

Hao-Ran Yu et al.


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Short summary
We developed a high time resolution method for determining the δ13C values of WSOCp and WSOCg by combination of wet oxidation pretreatment and IRMS. With improvement of oxidation method and determination method, δ13C value of liquid sample with a carbon content between 0.5 to 5 μg can be determined with an accuracy of 0.6 ‰. Using this method, the δ13C value of WSOCp and WSOCg in winter of 2021 at an urban site of Nanjing were determined, which were -25.9 ± 0.7 ‰ and -29.9 ± 0.9 ‰ respectively.