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
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)
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
- RC2: 'Reply on AC1', Anonymous Referee #1, 01 Dec 2022
- AC1: 'Reply on RC1', Haoran Yu, 28 Nov 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.
Hao-Ran Yu et al.
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This study developed a new method and system to determine stable carbon isotope in both the water-soluble organic carbon in the gaseous and particle phases. The novelty of this study lies in the method and its potential application. They also found the difference in WSOC mass concentration and the isotope composition between the day and night samples. Although the explanation of the influencing factors for the differences remains unresolved, I strongly recommend it for a quick publication after they can address the following specific comments.
Line 26-27: the sentence was not clear.
The authors should use the isotope expression more carefully. For examples: lower, higher, depleted or enriched. For example, to say that "one sample is enriched in 15N relative to another because of …" is proper usage. Phrases such as "a sample has an enriched d15N value" are misuses of terminology.
Line 38-40: rewording is necessary
Line 149: details are needed here,
Was the method for 13C in WSOC improved or optimized compared to the previous method. If so, the details should be given or highlighted.
The influences of the metrological condition and chemical composition should be reordered. the mechanism for the WSOCg-WSOCp distribution was not well explained and further discussion is needed.