Tracking Trash: Understanding Patterns of Debris Pollution in Knoxville’s Urban Streams
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsTracking Trash: Understanding Patterns of Debris Pollution in Knoxville’s Urban Streams – reviewer comments
This paper reports on litter debris collected from 3 urban streams, with a view to identifying meteorological drivers which may assist in framing management strategies to improve the generally poor condition of these water courses. The source of debris is known to be discarded items within the urban area, transported to the streams through hard surface runoff from the urban area, as well as periodic overflows of combined sewage systems. Such pollution, especially by plastic items and E. coli bacteria, results in these urban streams being unusable for public recreation as well as ecologically and visually untenable.
The authors’ approach to analysis of the extensive data available is to apply a regression model to identify potential factors controlling rates of litter accumulation. Aggregation of the data was required, such that only a general, overall picture was possible. Results indicate a positive effect for Rainfall – clearly related to surface runoff – and, surprisingly, negative effects for Windspeed and Flow Rate. Explanations for these effects are discussed, including possible interception of debris along creek margins at high water levels and reduced efficiency of trapping of debris by the sampling booms in use for data collection. This reveals a limitation of the study, that only the surface layer of floating debris is trapped whereas mid-stream and bed-load transport is not included in the sample.
There is no discussion of specific routes of transport of debris into the 3 creeks from their urban sources, which might provide insight into alternative remediation by better prevention at source. Also, identifying the main source of E coli is not addressed – whether from direct defaecation or from overspill of sewage outfalls. Further work may be required to cover this, but potential benefits could ensue from targeted management.
Sustainable Urban Drainage Systems (SUDS) may offer an alternative approach to trapping debris before it enters urban streams, as well as ameliorating flash floods arising from extreme rainfall events. This would involve constructed wetlands and interception ponds, which could also increase local biodiversity.
Overall, the study makes a valuable contribution to the debate on the management of polluted urban waters – a pressing issue for local authorities, amenity groups and local residents.
Some specific points related to the text:
L46: Escherichia Coli (E-Coli) – lower case for species name, coli. Italicize scientific names. Also in Table 2
Table 2 is rather repetitive - could be summarized
L112: Sampling boom method traps only surface moving debris. This point appears in Discussion (L335-336), but it should be mentioned in Methods
L124: What was mesh size of recovery net? This may have a selective effect on the items recovered from the water above the boom
L148, 151, 152, 159, 160 – should metric measures be included for an international journal?
L222-224 – as discussed, this effect may indicate reduced trapping efficiency of the boom at high flows due to escape of debris beneath – should the depth of the net below the boom be increased?
L247 – a river’s
L264-6 – suggests the need for interception of overflows - SUDS/CWs – as mentioned above
L267 - to positively relate; avoid split infinitive – to relate positively
L268 - to negatively relate - to relate negatively
L281 – It is not clear why “increases in turbidity” would affecting boom function. High turbidity, meaning low clarity of the water column, may result from high flow rate. Perhaps increased turbulence is what is intended.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThis study tries to model the relationship between some variables and debris pollution in three urban creeks. It is of great help to urban water environment protection. However, the methods used in this study are not reasonable. For example, how much data is used to construct the regression model in this study? Why does the model delete the creek level, not the creek flow? The most important is that, as the author mentioned in Section 4.1, only three variables are considered in this study. More variables are necessary to confirm the reasonability of the method.
Comments on the Quality of English LanguageThe quality of the English language is good.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe concept of the article is quite interesting and concerns a contemporary important issue.
Nevertheless, to strengthen the scientific side of the article, I recommend:
1. clearly emphasizing the purpose of the article and research
2. since significant limitations of the study were indicated, the article should expand the literature review and refer to other local initiatives and projects in the field of environmental cleaning (not only rivers)
3. the literature review is quite modest, it should be expanded to at least 75 items.
After expanding the article, I leave the decision to the editor - whether the article should be sent for another review. In my opinion, introducing the changes proposed above will be sufficient for the article to be accepted for publication.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors have made significant improvements to the m/s, taking note of reviewers' comments. The study makes a valuable contribution to the debate on the management of polluted urban waters – a pressing issue for local authorities, amenity groups and local residents. This study should be published.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe author responded positively to my comments, and I recommended that the journal consider accepting the revised manuscript.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe changes introduced improved the scientific quality of the study. I recommend publishing the article without additional changes.
