This work is an interesting and welcome contribution to investigating the dynamics of airborne microplastics. The scientific approach and the adopted methodologies are robust and sound, both on the experimental and modelling sides. At the same time, the impact of the paper would improve adding some more information and discussion, as detailed hereafter. This, to enable the reproducibility of the research and the comparison with the multiple studies that are emerging in relation to the atmospheric transport of microplastics.

The manuscript can be considered and accepted for publication after (medium) revision.

DETAILED COMMENTS (Lx stands for the line number)

L48-49: The number of publications related to the atmospheric dispersion of microplastics is rapidly increasing, and it is indeed difficult to keep continuously updated. However, some attention should be given to more recent works that might be of interest to this investigation, while here the first and by now ‘classical’ studies are recalled only.

L81-84. Here the details of the experimental setup are kept at their minimum, then referring to two previous publications. Since an article should be as much as possible self-consistent, it would be worth adding some additional details as reported in those publications.

L110-120. A summary of the rationale, of the analytical and experimental approach behind Bagheri and Bonadonna 2016 model would be useful to better appreciate the improvement with respect to other (empirical) relationships.

L126-127. Since one of the main findings of this research is the much slower settling of glitter and fibres when compared to volume-equivalent spheres, it could be of interest for the authors to consider the results also from experimental studies treating fragments, characterised by irregular volume and shapes, for which the volume-equivalent concept may apply. In addition to the work by Preston et al. (2023) see, for instance, studies in a cylinder with water and in a wind tunnel:

http://dx.doi.org/10.1016/j.envres.2023.115783; https://doi.org/10.1016/j.hazadv.2024.100433

L135-138. It is not clear (to me) how the simulations were performed. It is specified that the particles are released each 1^st and 15^th day of each month in the year 2020 at 03:00 and 15:00 local time: for how long? One time-step as a sort of puff release, or a continuous emission starting at that time and lasting 12 hours, or? How was the emission handled: as point releases centred on the city coordinates and spread along 10 to 100 m agl? As particles distributed in a volume emission, centred in the city area and in a layer between 10 and 100 m agl?  More details are needed on the model configuration and runs, so that a reader can better understand and interpret the results of the model simulations.

L145-148. FLEXPART is a well-known and largely used model, so it can be accepted that no specific details are provided on the physics in the model. However, here the total mass deposited plays an important role, as in eq. (2), and briefly recalling how the dry and wet depositions are treated in the model would be useful.

L151-152 and 182-183. In general, and given all potential uncertainties, I wonder whether three decimals are truly significant/substantial to distinguish the measured and calculated settling velocities.

L168-169 and 196-198. A partial interpretation of the discrepancies between the model and the measurements is attributed to the imperfections in the shape and size of the glitter particles or fibres. A discussion on the possible uncertainties related to the experimental approach, leading to uncertainties also in the observed data, would be worth it. The experiments are conducted in quiet air. It would be interesting to provide some comments on the potential/expected effect of turbulence on the settling dynamics.

L239-247. Consider comparing the distances travelled by the particles and fibres in your study with findings from other studies in the literature. In this relatively recent field of study, it is important to verify similarities, convergences and differences, to evaluate whether the scientific community is following a sensible research path.

Supplementary material: please note that the citation of Bagheri and Bonadonna (2016, 2019) is repeated twice every time (a latex trap, I guess).