Poplar-Assisted Bioremediation for Recovering a PCB and Heavy-Metal-Contaminated Area

Round 1

Reviewer 1 Report

Poplar-assisted bioremediation for recovering a PCB and heavy 2 metal-contaminated area #1263512

 

This study analyzes the ability of poplar (Monviso clone) to remove PCBs and heavy metals from contaminated soil in southern Italy 900 days after planting.

The manuscript is generally well written, clear, and easy to read. The structure follows the standards of the journal, and the tables and figures are appropriate and of the expected quality.

However, there are several weaknesses and a lack of important information that must be provided before proceeding with the publication process, especially related to the experimental design and the statistical analysis used.

First of all, it should be noted that it is an observational study (not manipulative), and therefore there is no replication and randomization of the treatments required to obtain robust results on this topic. In this regard, the samples taken are a clear example of pseudo-replication.

However, the lack of data on the ability of poplar as a green filter means that the data and analyzes carried out in this work continue to be of great interest and may have repercussions for the scientific community. In this regard, it is especially relevant to note that numerous representative samples were taken from the contaminated area prior to planting that could serve as a clear control treatment (as indicated by Ancona et al. (2017) N. Biotech. 38: A preliminary sampling of the experimental site (more than 30 points in about 3,400 m2) was performed for a characterization of the soil quality in terms of pH, main nutrients (N, P), organic carbon content and contaminant occurrence (PCB and heavy metals)). The authors should place special emphasis on comparing the results obtained at 900 days with this initial control (not with respect to the unplanted control that does not appear to be replicated or randomized).

Another key aspect that is not specified is the number of samples taken per treatment. In Ancona et al (2017) the design of the sampling unit is specified (Fig. 1, pp. 67), but how many 1 x 1 m samples around the poplars were taken for each treatment?

Statistical results are scarce and not clearly developed. Do the data meet the assumptions of normality and homoscedasticity? The statistical results of multiple comparisons are not shown, especially with respect to the control (LSD, Tukey test, etc.) to visualize the differences between treatment levels (soil depth, distance to the trunk,…) and the control.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The present deals with long-term experimental study on effectiveness of a poplar-based bioremediation technology applied at a historically PCB and heavy metal polluted soil in Southern Italy.  In addition, the soil microbial community have been analyzed in the selected poplar-planted experimental plots. The study is very well established, the problem treated is relevant and contributes to the general knowledge concerning the extraction of PCB and heavy metals from polluted soils.

Author Response

Please see the attachment.

Author Response File: Author Response.docx