the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Summertime fluorescence characteristics of atmospheric water-soluble organic carbon in the marine boundary layer of the western Arctic Ocean
Yuzo Miyazaki
Jin Hur
Mi Hae Jeon
Youngju Lee
Kyoung-Ho Cho
Hyun Young Chung
Kitae Kim
Jung-Ok Choi
Catherine Lalande
Joo-Hong Kim
Taejin Choi
Young Jun Yoon
Eun Jin Yang
Sung-Ho Kang
Abstract. Accelerated warming and a decline in sea ice coverage in the summertime Arctic Ocean can significantly affect the emissions of marine organic aerosols and biogenic volatile organic compounds. However, how these changes affect the characteristics of atmospheric water-soluble organic carbon (WSOC), which plays an important role in the climate system, remains unclear. Thus, to improve our understanding of WSOC characteristics, including its summertime fluorescence characteristics, in the rapidly changing Arctic Ocean, we simultaneously measured atmospheric concentrations of ionic species and WSOC, fluorescence excitation–emission matrix coupled with parallel factor (EEM–PARAFAC) analysis of WSOC, and marine biological parameters in surface seawaters of the western Arctic Ocean during the summer of 2016. WSOC was predominantly present as fine-mode aerosols (diameter < 2.5 μm) (median = 92 %) with the mean concentration being higher in the coastal water areas (462 ± 130 ngC m−3) than in the sea ice-covered areas (242 ± 88.4 ngC m−3). Moreover, the WSOC in the fine-mode aerosols was positively correlated with the methanesulfonic acid in the fine-mode aerosol samples collected over the sea ice-covered areas (r = 0.88, p < 0.01, n = 10), suggesting high sea–air gas exchange and emissions of aerosol precursor gases due to sea ice retreat and increasing available solar radiation during the Arctic summer. Two fluorescent components, humic-like C1 and protein-like C2, were identified by the PARAFAC modeling of fine-mode atmospheric WSOC. The two components varied regionally between coastal and sea ice-covered areas, with low and high fluorescence intensities observed over the coastal areas and sea ice-covered areas, respectively. Further, the humification index of WSOC was correlated with the fluorescence intensity ratio of the humic-like C1/protein-like C2 (r = 0.89, p < 0.01) and the WSOC concentration in the fine-mode aerosols (r = 0.66, p < 0.05), with the highest values observed in the coastal areas. Additionally, the WSOC concentration in the fine-mode aerosols was positively correlated with the fluorescence intensity ratio of the humic-like C1/protein-like C2 (r = 0.77, p < 0.01), but was negatively correlated to the biological index (r = −0.69, p < 0.01). Overall, these results suggested that the WSOC in the fine-mode aerosols in the coastal areas showed a higher degree of polycondensation and higher aromaticity compared that in the sea ice-covered areas, where WSOC in the fine-mode aerosols was associated with relatively new, less oxygenated, and biologically-derived secondary organic components. The findings can improve our understanding of the chemical and biological linkages of WSOC at the ocean–sea ice–atmosphere interface.
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Jinyoung Jung et al.
Status: final response (author comments only)
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RC1: 'Comment on acp-2022-665', Anonymous Referee #1, 09 Nov 2022
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AC1: 'Reply on RC1', Jinyoung Jung, 21 Feb 2023
We greatly appreciate Referee #1’s careful review and thoughtful comments. According to Referee #1’s insightful comments, we have carefully revised the manuscript and provided point-by-point responses.
Citation: https://doi.org/10.5194/acp-2022-665-AC1
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AC1: 'Reply on RC1', Jinyoung Jung, 21 Feb 2023
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RC2: 'Comment on acp-2022-665', Anonymous Referee #2, 15 Nov 2022
In this work, the fluorescent properties of water-soluble organic carbon (WSOC) present in particulate matter collected in the Western Arctic Ocean area were studied. Potential WSOC emission sources were also determined by combining parallel factor analysis (PARAFAC) and fluorescence index. On the other hand, part of the chemical composition of the collected aerosols was determined by ion chromatography.
The topic addressed in the work is relevant and current, in addition there are not many studies that use these methods to determine the sources of particulate matter, which is why it is of the utmost importance to increase knowledge of the sources that can contribute to the emission of particulate matter. WSOC in the MP.
In general terms, the work is well presented, however, the discussion of the results could be improved on some points.
Here are some recommendations in order to improve the writing:
In the Introduction section, the authors should delve into the relevance of using the EEM-PARAFAC tools in the study of particulate matter, since there are few studies on this matrix, most of which focus on the study of organic matter. dissolved in water (DOM)
In line 127 the authors could specify the type of detector of the equipment used, as well as the slit used in the measurement of both excitation and emission.
In line 133 the authors should go deeper into the objective and advantages of using fluorescence index.
Line 167. The authors should delve into how sea fog events affect the other parameters analyzed, such as TOC, among others.
Line 197. Correct resistivity units.
In section 3.2. the authors should consider changing the word “bulk” (line 232 and 236) for another that better describes the conjunction of the two fractions of the MP studied.
In section 3.4. Authors could privately benchmark their model data and compare it to a previously published dataset found in the open-access OpenFluor database located at http://openfluor.org
In section 3.4. The authors could include in the supplementary material the Split-half graphs resulting from the validation of the components of the PARAFAC models.
In the conclusions section. The authors could emphasize how their study contributes to the assignment of emission sources of the WSOC present in the PM using the EEM-PARAFAC tool.
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AC2: 'Reply on RC2', Jinyoung Jung, 21 Feb 2023
We greatly appreciate Referee #2’s careful review and thoughtful comments. According to Referee #2’s insightful comments, we have carefully revised the manuscript and provided point-by-point responses.
Citation: https://doi.org/10.5194/acp-2022-665-AC2
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AC2: 'Reply on RC2', Jinyoung Jung, 21 Feb 2023
Jinyoung Jung et al.
Jinyoung Jung et al.
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