Metal Transport in the Mixing Zone of an Estuarine River to the Northern Gulf of Mexico
Round 1
Reviewer 1 Report
I think that the paper needs some important additions and changes in order to become good for publications
1. More details about the area and mainly the pollution sources, as well as data from previous research in the area, concerning both the quality and quantity of pollutants and general pollution and ecological problems.
2. Better description of the area and the field work (measurements and sampling) . Have you found out any stratification between fresh and saline work ?
3. Results from previous studies in the area concerning the same pollutants
4. More details about the analytical techniques and results from the analyses of reference materials
5. Comparison of new and old measurements
6. Improvement of figures is needed because some of the are very complicated (e.g. 3,4, and 6 -p.16) . I think you must reduce the points (specially in fig. 6 ) in order to be friendly to the reader.
7. Remove table 2 and give only the very positive results.
8. Remove also table 3 and give only the most interesr data
9. Remove table 5 and give the most interest data into the discussion.
10. In the discussion and conclusion chapters make some comparisons with previous periods at this or similar systems in USA or in any other place. Also discuss the main problems of the area and give some ideas for better environmental managemet for a sustinable future of the area.
The quality of English language is good enough
Author Response
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Reviewer 2 Report
Review of the manuscript “Metal transport in the mixing zone of an estuarine river to the Northern Gulf of Mexico” by Wu et al.,
Paper describes spatial and temporal distributions om metals in the estuarine part of the river which inflows the Guld of Mexico. The aim of the paper was to explain changes in metals concentrations along the estuary influenced by river discharge and basic physico-chemical parameters like salinity, pH and dissolved oxygen. However, the analytical method used for the analysis of metals in water (ICPOES) was not adequate, as this technique is not sensitive enough for detection of most of the measured metals, so only major elements (like Ca, Mg, Al, Fe and few others) could be really measured. For measurements of metals in natural waters, which are often at ng/L or low ug/L levels, ICPMS technique, which is more sensitive, should be used. In Table 3 authors present percentage of samples in which they could detect measured elements, which is meaningless as it depends on their method, without concluding that their method is not adequate for detection of trace elements in natural waters. They did not filter water samples, so they obviously measured total metal concentrations (particulate +dissolved), but in the results and discussion they do not adequately explain what fractions of metals they measured, which is important for explanation of correlation with basic physico-chemical parameters, for example TSS. In addition, at the end of the Discussion they compare measured total concentrations of Al, Fe, B with water quality criteria which are today defined for dissolved metals, a fraction which is bioavailable to aquatic organisms, what bring them to a wrong conclusion that measured concentrations are higher that given criteria. They use term “heavy metals” for all elements they measured, which is not correct, as most of the elements they could detect with their method (Al, Si, Ca, Mg, B, Li) are not heavy metals, but major elements, and usually are also not under anthropogenic influence. For elements which concentrations are much higher in seawater than in freshwater (like Li, As, B) only graphical presentation according to salinity is usually presented, as it may show if these elements show conservative behavior or are influenced by some additional processes like anthropogenic inputs or precipitation. For all these reasons I consider this manuscript not acceptable for publication.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors have significantly improved the paper following the instructions of reviewers .
I think the paper can be accepted for publication in thjs form.
Author Response
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Reviewer 2 Report
Although there is no previous data about metals in water in the investigated area it would be useful to add into discussion some literature data about metal levels in the riverine and estuarine water from where it would be clear why for several elements about 70% of the data were not detectable by the method used in this paper. In addition it would place data from this paper into larger context of data from other water ecosystems.
Author Response
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