Distribution of Geochemical Species of P, Fe and Mn in Surface Sediments in the Eutrophic Estuary, Northern Taiwan
Round 1
Reviewer 1 Report
Dear authors,
The research topic that you presented in this paper focusing on the SEDEX extraction method to determine the different speciation of P, Fe and Mn in the estuary sediments is very interesting.
Paper is well written and structured, and I believe that it is suitable for publishing after some revision. The main shortcoming of the paper is lack of proper discussion and disregard of flow regime variability in the analysis. Please find below detailed suggestions that need to be addressed before publishing.
General remarks
Please add the distinction between upper and lower estuary on the figures so it can be related to the text.
The paper is missing clearly defined objective. Please add one paragraph at the end of the introduction describing the paper objective and scientific contribution.
Please provide a water regime of the Danshuei River overview (min, max and avg flow rate, seasonal variation, etc.) to complement already described tidal, flow depth and sediment yield data.
Please discuss the fact that DIN and DTP values show steady trend of low values for Hsintien station and high values for Tanhan station. What is the cause of this, since they are located relatively close to one another? Please add short paragraph introducing the important differences between these sites.
Authors state that sediment sampling results suggests that the DRE is an estuary with a fully hydrodynamic area. “Fully hydrodynamic” is vague and not a commonly used in the literature. Please describe “hydrodynamics” of the river through representative parameters – flow oscillations, morphologic changes, sinuosity of the river, etc.
The data you have presented are limited to your sampling, without accounting for the flow regime that can influence the results. I suggest that you complement your data with flow rate data for the 4 sampling occasions and reflect on their potential influence on the results through sediment yield and subsequent change in sediment gradation (or non-context correlation if such exists).
In the discussion you reflect on the fact that sediment size is commonly inversely correlated with the chemical constituents concentration in marine sediment. Since your results for the sediment grain size are shown to be scattered (both in time and space) please add a small paragraph describing how can this influences your measurements and results. From the Figure 4 it is evident that after each confluence (locations 1-2 and 7-8) sediment grain distribution downstream alters significantly.
Similarly to the previous comment, from the Figure 5 it can be seen that there is an abrupt change in P concentration at the locations where WWTP outflow exists (locations 3-4 and 7-8), especially for the measurement in April 2018. Authors have reflected on the PSORB change in the previous studies, but haven’t addressed other constituents. Please add a paragraph explaining the influence of wastewater on the change in P concentration in the river visible from your results.
The conclusion is rather descriptive, and doesn’t reflect the contribution of your paper. Please formulate the conclusion in a way that reflects results of your analysis, rather than being repetitive result readout.
Specific remarks
Authors use different abbreviation for SEDEX sedimentary P fractions throughout the manuscript (the ones from literature and their own). Please use uniform abbreviations in the text. Additionally, authors introduce also F1 -F5 numbering, which is in my opinion redundant and confusing since already established naming standard is compact enough. I suggest that you use PSORB, PCDB, PDET, PCFA and PORG.
Please use full expression for the Total Organic Carbon in the abstract
Please use full expression for Dissolved Inorganic Nitrogen when it appears in the text for the first time.
The Danshuei River Estuary acronym is introduced several times throughout the text.
Please use full expression for Suspended Particulate Matter when it appears in the text for the first time.
Acronym for the sewage treatment plant (STP) is not suitable due to collision with Sedimentary Total Phosphorous acronym. I suggest to use wastewater treatment plant instead (WWTP).
Figure 4 caption should also contain the text about salinity since it is also part of the graphics.
Caption of the Table 5. contains non-formatted reference (Ruttenberg, 1992)
Caption for several figures contains “northern Taiwan” for the location, which I feel is redundant since case study location has already been established.
There are numerous typos in the manuscript, please have somebody proofread it.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Fang et all paper's studied the potential mobilization of sedimentary P in the Danshuei River Estuary, northern Taiwan during the burial processes, this study employed the SEDEX method to quantify sedimentary P speciation in the Danshuei River Estuary and established such a knowledge in the eutrophic estuary. In addition, this study examined also the sedimentary Fe and Mn fractions since are playing the crucial roles in altering the sedimentary P geochemistry in the marine environment.
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Here attached the document with some comments
Comments for author File: 
Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Dear Authors,
Thank you for addressing all my suggestions and revising the manuscript accordingly.
I feel that the manuscript has been sufficiently updated to be published in current version.
