Deposition and Mobilization of Microplastics in a Low-Energy Fluvial Environment from a Geomorphological Perspective
Round 1
Reviewer 1 Report
This paper evaluated the geomorphological influencing factors on microplastic deposition in fluvial sediments of the Tisza River. The paper is well organized and well written. My major concern is that, as this study focused on the deposition and mobilization of microplastics in the river sediment, and if deposition is one of the main points, should not the authors consider the vertical tranport of micriplastics? Yet, as described in the text, upper sediment (0-1cm) was collected. Also, the authors described that the samples collected in 2019 were much more polluted than those collected in 2020, would it becase some of the microplastics were deposited in deeper sediment, like 2-3 cm, or 2-5cm sediment?
Author Response
Response to Reviewer 1.
Thank you for your useful comments. We believe, they improved the quality of the text. The new, inserted parts are indicated by red fonts.
All suggestions were considered; the text was corrected accordingly.
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Reviewers note |
Response |
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My major concern is that, as this study focused on the deposition and mobilization of microplastics in the river sediment, and if deposition is one of the main points, should not the authors consider the vertical transport of microplastics? |
Thank you for your note/suggestion. EXplanation (not added to the text): The vertical transport (rate, morphological and density type) of microplastics in the water column is a very interesting, but still unclear field of MP studies. We will just start our first measurements. However in a river like the Tisza with great depth (mean bankfull depth: 10 m) it is a great challenge to sample the transported sediment and MPs in the entire cross-section. |
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Yet, as described in the text, upper sediment (0-1cm) was collected. Also, the authors described that the samples collected in 2019 were much more polluted than those collected in 2020, would it becase some of the microplastics were deposited in deeper sediment, like 2-3 cm, or 2-5cm sediment? |
Added: “Based on our former field experiences it was expected that during falling or low water stages only a thin sediment-layer is deposited. As we aimed to sample the freshly deposited sediments, therefore only the upper (0–1 cm) layer was sampled. At a given site sediments were collected at several points using an iron spatula, and the collected ca. 1 kg material was homogenised.” “ |
Reviewer 2 Report
Thank you for the opportunity to review a manuscript entitled: "Deposition and mobilization of microplastics in a low-energy fluvial environment from a geomorphological perspective"
Although it is focused on a local issue, the problem of river contamination is increasing worldwide, and the manuscript is definitely of interest, especially from the geomorphological perspective.
1. Abstract and throughout the manuscript - I've noticed in 2020-2022 papers that microplastics are more often abbreviated to MP/MPs than MiP (especially in biological studies on its toxicity and medicine). I agree with both choices, but perhaps it would be beneficial to add both versions (for example, in the introduction section) for search purposes and international readers.
2. The language needs some improvements. For the most part, it is properly written, but some grammatical errors make the manuscript a bit difficult to follow. Example in the abstract lines 17-18: Between the two surveys (in 2019 and 2020), small flood-waves were rearranged the MiP pollution, as in the sediments of the Tisza it decreased by 30%, and in the tributaries by 48%
Introduction: line 40 - wastewater is one word (please change it throughout the manuscript). The most prominent source of microplastic in agricultural land is the application of biosolids and dehydrated sewage sludge on such fields. The introduction is too long and sometimes reads as a discussion part. It is a minor remark, but please shorten the introduction part if possible.
Materials and methods are correctly detailed and well written.
Conclusions. The conclusion part is too long. The first paragraph is a very lovely introduction and perhaps should be moved to the introduction part. Conclusions should be instead based on the authors' findings.
Author Response
Thank you for your useful comments. We believe, they improved the quality of the text. The new, inserted parts are indicated by red fonts.
All suggestions were considered; the text was corrected accordingly.
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Reviewers note |
Response |
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1. Abstract and throughout the manuscript - I've noticed in 2020-2022 papers that microplastics are more often abbreviated to MP/MPs than MiP (especially in biological studies on its toxicity and medicine). I agree with both choices, but perhaps it would be beneficial to add both versions (for example, in the introduction section) for search purposes and international readers. |
We considered to use MP instead of MiP, and MP will be used throughout the text. However, we think it is an incorrect practice, as there are macroplastics and microplastics in rivers, and the best would be to use MaP and MiP, instead of the misleading MP. At the first appearance, the sentence was corrected as: L. 12: “Though microplastic (MP/MiP) pollution…” L. 39: “Microplastics (MP/MiP) entering rivers” |
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2. The language needs some improvements. For the most part, it is properly written, but some grammatical errors make the manuscript a bit difficult to follow. |
The text was checked and corrected by a native speaker. |
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Introduction: line 40 - wastewater is one word (please change it throughout the manuscript). |
Corrected all of them. |
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Introduction: The most prominent source of microplastic in agricultural land is the application of biosolids and dehydrated sewage sludge on such fields. |
L. 43 Corrected as: “…agricultural areas, especially if they were treated by biosolids and dehydrated sewage sludge…” |
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The introduction is too long and sometimes reads as a discussion part. It is a minor remark, but please shorten the introduction part if possible. |
It was shortened, some data on case studies were deleted. |
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Conclusions. The conclusion part is too long. The first paragraph is a very lovely introduction and perhaps should be moved to the introduction part. Conclusions should be instead based on the authors' findings. |
The first paragraph remained here, as it was connected to the literature review. It does not fit to the beginning of the Introduction. |
Reviewer 3 Report
The paper is very interesting. The comments are in the manuscript, in the experimental part you need to better explain some of the analyzes.
Comments for author File: 
Comments.pdf
Author Response
Thank you for your useful comments. We believe, they improved the quality of the text. The new, inserted parts are indicated by red fonts.
All suggestions were considered; the text was corrected accordingly.
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Reviewers note |
Response |
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line 159, 202, 214: italic |
All symbols were written by italic, for example: “…formed of blocks and gravel (?50=10-20 cm).” |
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line 242: Please describe how did You sampled the sediment? Put in the text |
Added: “Based on our former field experiences it was expected that during falling or low water stages only a thin sediment-layer is deposited. As we aimed to sample the freshly deposited sediments, therefore only the upper (0–1 cm) layer was sampled. At a given site, sediments were collected at several points using an iron spatula, and the collected ca. 1 kg material was homogenised.” |
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line 268-269: How did You conducted this? Please describe it, did You conducted this after separation with zinc chloride or before, which mass of MP and which volume od H202 was homogenized? |
Corrected as: “The samples were dried (65 °C) and sieved; thus, only the grain-size fraction smaller than 2 mm was processed during the separation. The separation procedure was performed on 50 g samples. If during the sieving, larger MPs (2-5 mm) or mesoplastic (≥5 mm) was found, it was counted and noted. Based on our previous experience, the silt and clay content of the samples makes it difficult to separate the MPs during the zinc chloride treatment; therefore, the fine-grained particles were removed by wet sieving (90 μm). Then the inorganic sediment fraction was separated using 50 ml zinc chloride solution (1.8 g/cm3) following Atwood et al. [44] and Kiss et al. [29]. In the next step the organic material was decomposed in 30 ml hydrogen peroxide (30%) for 24 h. The MP samples were finally washed into Petri dishes.” |
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line 282: dry matter or wet |
Corrected as: “The MP content of the dry sediment was expressed in item/dry kg.” |
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line 288, 292: in above text n is not in italic, please put everywhere n in italic |
Corrected as: “…where the ?1 is a preceding MP concentration data (e.g. of an upstream section, or a 2019 data, or of coarse-grained sediments), and ?2 is a subsequent.” |
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line 308-309: please indicate thorough whole text kg per dry or wet mass |
Corrected thorough the text, for example: “…Over the entire length of the Tisza in 2020, the MP content of the sediments ranged from 237 to 6707 item/dry kg (average: 1770±1329 item/dry kg),..” |
