PONE-D-21-01035

A Roman provincial city and its contamination legacy from artisanal and daily-life activities

PLOS ONE

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Reviewers' comments:

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Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: Yes

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

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3. Have the authors made all data underlying the findings in their manuscript fully available?

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Reviewer #1: Yes

Reviewer #2: Yes

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Overall: This is a well prepared manuscript which has explored the social-technological-environmental relationships in the ancient city of Jerash. The data presented are interesting but there are questions in the way the results are interpreted. A major concern is with the sources of metals to account for the large-scale contamination of Gerasa/Jerash and its hinterlands. The level of heavy metal loading into the environment is clearly out of balance with what would be expected from “small-scale but common Roman urban, artisanal and everyday site activities”. The authors claim that the main uses of metals in the city included artisanal metalworking activity, production of copper coinage and making of pigments. The environmental footprints of such activities in all likelihood were highly localized within the residential areas. The total number of people involved in such activities was probably small considering that Jerash was a famous trading center and was not particularly known for its meta-working prowess. The question of where did all the metal pollution come from was not answered satisfactorily in the paper. The authors should consider the possibility that there was a lost lead/gold or lead/silver mine in or near the city which had released enough metalliferous wastes and fumes to contaminate the entire city and its neighborhood.

Comment 1 (Lines 119-123): The documentation of the source-sink relationships between the concentrations of metals in urban soils and Wadi Suf sediments is weak. The following statements (lines 119-123) support this concern: “Evidence of fluvial sedimentation from the 2nd-3rd centuries BC to the 7th century CE remained elusive, suggesting effective management of the water and soil resources at this time. From the beginning of the 6th century, the wadi begins to in-fill, and in the absence of additional chronological data may imply a decline in land and water management with associated erosion of soils to the wadi”. It should be noted that the graphs (of Cu and Pb concentrations at the specific locations) in Figure 3 do not include the time information for the samples. The peaks in the graph should be interpreted with caution unless the samples are not of the same age.

Comment 2: The role of local climate conditions has not been adequately addressed. There are reports suggesting that the late Roman Empire period was marked by major climatic changes in the Middle East which could have had some influence in the supply and accumulation of sediments in the river basin. A major floor can easily mediate the amount and type of sediments deposited at any location in the Wadi Sufa basin. Interpreting the sedimentary record solely on the basis of human activities (without consideration of the geophysical and geochemical processes) is an over-simplification.

Comment 3 (Figure 2): What is the error range in the stimulated results?

Comment 4: The following statement (lines 138-141) cannot be justified: “We then measure and compare heavy metal concentrations in two sets of chronologically controlled stratigraphies, from within the city and from the Wadi Suf hinterland (13-15). The spatial and temporal relationships between these stratigraphic units enable assessment of local pathways, from sources to sinks”. It would be an impossible task (almost) to reliably infer the transfer pathways for the metals in the particular environment based on their concentrations in such divergent locations. In the first instance, lead is immobile in soils and the mechanism for its transfer from within the city to the Wadi Suf hinterland needs to be explained.

Comment 5 (Figures 5, S6 and S7): It is difficult to infer any historical relationships in these figures without showing any time lines. These figures probably should be redone.

Comment 6 (lines 221-222): What is the evidence that the weathering of metal-based materials and artefacts represents “significant secondary sources” of environmental metal contamination in the city? Even if so, the impacts would be very highly localized.

Comment 7 (lines 244-248): The statement that elevated silver concentrations of Jerash sediments came from secondary sources such as Pb-rich material since some galena ores contain significant amounts of silver (argentiferous galena) is interesting. It hints at a likelihood that lead ores might have been exploited in the area in ancient times. The lead deposits would have been exhausted by now.

Comment 8 (Figure S5): The difference in the spread of Pb and Cu concentrations in on-site versus off-site sediments needs to be explained

Comment 9 (Conclusions): The study purportedly shows that most of the lead and copper released into the environment in Jerash city are deposited locally. There is no evidence to suggest that the metal works in the city were able to release much of the metals into the atmosphere for regional and global circulation. The conclusion that “small-scale, daily-life use and reuse activities in urban settings are an important factor in understanding and explaining changes in the baseline of global pollution, not only today, but over the last millennia” is misleading.

Reviewer #2: The data, methodologies, and conclusions are all clearly presented and discussed. The findings are significant for the archaeological community and for other urban studies disciplines. I endorse publication.

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Reviewer #1: No

Reviewer #2: No

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A Roman provincial city and its contamination legacy from artisanal and daily-life activities

PONE-D-21-01035R1

Dear Dr. Kristiansen,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

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Andrea Zerboni, Ph.D.

Academic Editor

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Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: It is doubtful that the sources mentioned in the paper can account for the substantial amounts of lead contamination in Jerash and its surrounding areas. The paper is very well written and presents interesting data on paleo-pollution which should be available in the scientific literature. I recommend publication of the paper in its present form.

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Reviewer #1: Yes: Jerome Nriagu