the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 30 Oct 2024
African dust transported to Barbados in the Wintertime Lacks Indicators of Chemical Aging
Abstract. The chemical processing (“aging”) of mineral dust is thought to increase dust light scattering efficiency, cloud droplet activation, and nutrient solubility. However, the extent of African dust aging during long-range transport to the western Atlantic is poorly understood. Here, we explore African dust aging in wintertime samples collected from Barbados when dust is transported at lower altitudes. Ion chromatography (IC) analysis of bulk nitrate, sulfate, and oxalate increase when African dust reaches Barbados, indicating dust aging. However, aerosol mixing state analysis from computer-controlled scanning electron microscopy with energy dispersive x-ray spectroscopy (CCSEM/EDX) indicates that approximately 67 % of dust particles are internally mixed with sea salt, while only about 26 % of dust particles contain no internally mixed components. SEM/EDX elemental mapping and time-of-flight secondary ion mass spectrometry (TOF-SIMS) reveals that within internally mixed dust and sea salt particles, only sea salt components contain signs of aging.
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RC1: 'Comment on egusphere-2024-3288', Mingjin Tang, 31 Oct 2024
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Royer et al. used bulk and single particle analysis to investigate African dust particles transported to Barbados. Although bulk analysis seems to imply significant aging of dust particles after long range transport, single particle analysis suggested that most dust particles were not aged after arrival at Barbados. This work provides novel insights into the mixing state of dust particles after long range transport, and has important implications for their climatic and biogeochemical impacts. The manuscript, which I found very interesting, can be accepted after some minor revision.
Comments:
Line 38: It can be great to add 1-2 sentences at the end of the abstract to discuss the broad implications of the results this work reported.
Line 63: Tang et al. (2016) reviewed the effects of chemical aging on CCN activities of mineral dust, and the authors may also cite this paper.
Line 86: I would suggest using long range transported instead of “LRT” in the manuscript, as “LRT” really reduces the readability.
Line 179: Please add a reference for this equation.
Line 311: Our work (Zhang et al., 2023) found that similar Al contents in fine and coarse particles for Asian dust, supporting what this work found for African dust.
Line 324-373: Could the authors estimate the thresholds (mass fraction in %) when nitrate and sulfate became undetectable? Such information will provide a rough idea about the upper limit of nitrate and sulfate contents when they were not detected.
Line 491-498: We found that during Asian dust events, aerosol Fe solubility at Qingdao (a coastal city of Northwest Pacific) was not elevated compared to that at desert regions (Chen et al., 2024). This suggested that Fe solubility was not significantly increased when Asian dust aerosol was transported to Qingdao, be consistent with what the authors suggested.
References:
Chen, Y. Z., Wang, Z. Y., Fang, Z. Y., Huang, C. P., Xu, H., Zhang, H. H., Zhang, T. Y., Wang, F., Luo, L., Shi, G. L., Wang, X. M., and Tang, M. J.: Dominant Contribution of Non-dust Primary Emissions and Secondary Processes to Dissolved Aerosol Iron, Environ. Sci. Technol., 58, 17355-17363, 2024.
Tang, M. J., Cziczo, D. J., and Grassian, V. H.: Interactions of Water with Mineral Dust Aerosol: Water Adsorption, Hygroscopicity, Cloud Condensation and Ice Nucleation, Chem. Rev., 116, 4205–4259, 2016.
Zhang, H. H., Li, R., Huang, C. P., Li, X. F., Dong, S. W., Wang, F., Li, T. T., Chen, Y. Z., Zhang, G. H., Ren, Y., Chen, Q. C., Huang, R. J., Chen, S. Y., Xue, T., Wang, X. M., and Tang, M. J.: Seasonal variation of aerosol iron solubility in coarse and fine particles at an inland city in northwestern China, Atmos. Chem. Phys., 23, 3543-3559, 2023.
Citation: https://doi.org/10.5194/egusphere-2024-3288-RC1
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