Adsorption of EDCs on Reclaimed Water-Irrigated Soils: A Comparative Analysis of a Branched Nonylphenol, Nonylphenol and Bisphenol A
Round 1
Reviewer 1 Report
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Author Response
Response to comments
Reviewer 1:
Adsorption of EDCs on reclaimed water-irrigated soils: A comparative analysis of a branched nonylphenol, nonylphenol and bisphenol A by Wang et al. This study investigated the adsorption of nonylphenol (NP), a branched NP (NP7), and bisphenol-A (BPA) on reclaimed water-irrigated soils. The authors also evaluated the effect of various environmental factors (i.e., pH, temperature, and mental ions) on the adsorption of NP, NP7, and BPA as well as sorption mechanism of NP and BPA on soil. In general, the manuscript is well written. My specific comments are noted below: SPECIFIC COMMENTS:
POINT1- L76: What are concentrations of NP, NP7, and BPA in collected soils?
Response (R): Accepted and revised in L83-85. The soils were collected from the irrigation field in Daxing, which is a typical reclaimed water irrigation field in China for more than 40 years. We have conducted series of studies in this area and the background concentrations have been detected in the former study. The background concentrations of NP and BPA in collected soils were 37 μg kg-1 and below the method detection limit (MDL) respectively, which can be referred the former study Wang et al. (2018). The background concentrations of NP7 were calculated according to the ratio of the total ion chromatogram of NP. NP7 accounts for 5.41% of the total area of all isomers, which have been identified in the former study Wang et al (2013). Therefore, the background concentrations of NP7 was 2 μg kg-1. The background concentrations of NP, NP7, and BPA in collected soils can be neglected, because the initial concentration of NP and BPA in this experimental design is high (from 0.2mg/L~4mg/L), and the Cs which is the concentration of NP/BPA adsorbed on the solid phase at equilibrium is in the magnitudes of mg. kg-1 as well.
Reference:
Wang S Y.; Liu F.; Wu WY.; Hu Y Q.; Liao R K.; Chen G T.; Wang J L.; Li J L. Migration and health risks of nonylphenol and bisphenol A in soil-winter wheat systems with long-term reclaimed water irrigation. Ecotoxicology and Environmental Safety. 2018,158, 28–36.
Wang S Y., Liu F., Liu Y L., Chen L. Determination of 12 Isomers of p-Nonylphenol in Groundwater by Gas Chromatography-Mass Spectrometry.2013,41,1699-1703.
POINT2- L221: Any statistical analysis conducted in this work? Are there any statically difference among three pHs in Figure 2? – Figur.es 2, 3, and 5: I suggest changing the lines color red to the colors (red, blue, black) according to their points. - Tables 4-6: Perhaps, adding the results of statistical analysis in Tables.
R: Accepted and revised. The statically difference among three pHs were in Figure 2 L245-265. Figur.es 2, 3, and 5 have been changed the lines’ color according to their points. The difference significant analysis (p value) has been added in Tables 4-6. And the method has been supplemented in 2.4.7 part（L164-170）.
Statistical analysis results：NP for pH=3
Statistical analysis results：NP for pH=7
Statistical analysis results：NP for pH=11
Statistical analysis results：NP7 for pH=3
Statistical analysis results：NP7 for pH=7
Statistical analysis results：NP7 for pH=11
POINT3- L268: Again, statistical analysis will be help to tell if there is significant difference between the effect of temperature on NP7 and NP.
R：Accepted and revised in L290-296. Adsorption efficiency of NP7 and NP to soil was calculated at adsorption equilibrium time respectively at 5℃, 25℃ and 35℃, which is showed below.
Table1 The adsorption efficiency of NP and NP7 to soil at adsorption equilibrium time for each treatment
|
　 |
　 |
NP |
　 |
　 |
　 |
NP7 |
　 |
|
　 |
5℃ |
25℃ |
35℃ |
5℃ |
25℃ |
35℃ |
|
|
200ug/L |
81.94% |
80.87% |
67.00% |
85.95% |
83.23% |
73.25% |
|
|
500 ug/L |
78.95% |
61.94% |
68.25% |
83.38% |
80.10% |
72.49% |
|
|
1000 ug/L |
68.82% |
61.02% |
63.47% |
71.11% |
75.12% |
68.77% |
|
|
1500 ug/L |
68.74% |
63.76% |
62.44% |
73.38% |
75.12% |
69.47% |
|
|
2000 ug/L |
65.07% |
62.43% |
57.02% |
75.42% |
70.02% |
70.56% |
|
|
3000 ug/L |
67.23% |
65.14% |
65.63% |
74.26% |
68.77% |
68.21% |
|
|
4000 ug/L |
69.86% |
66.89% |
65.50% |
　 |
79.35% |
70.98% |
70.98% |
Table2 Statistical analysis of the effect of temperature on NP and NP7
|
Temperature |
　 |
Averagea |
Mean value of standard error |
t |
df |
p |
|
5℃ |
NP |
77.55% |
0.02081 |
1.9 |
12 |
0.082 |
|
NP7 |
71.52% |
0.02398 |
||||
|
25℃ |
NP |
74.76% |
0.0203 |
2.661 |
12 |
0.021 |
|
NP7 |
66.01% |
0.0259 |
||||
|
35℃ |
NP |
70.53% |
0.00708 |
4.028 |
12 |
0.002 |
|
NP7 |
64.19% |
0.01407 |
Note: a indicate the average adsorption efficiency.
From table 2, we concluded that the difference of the temperature effect on the adsorption of NP7 and NP at 5℃ was not significant(p>0.05); while the difference of the temperature effect at 25℃ was significant(p<0.05); the difference of the temperature effect at 35℃ was significant(p<0.05) as well; What’s more, the difference was more significant at 35℃ than 25℃. It indicated that with the temperature increasing, the difference between the effect of temperature on NP7 and NP was more significant.
POINT4- L273-274: Adsorption of NP decreased with increasing temperature, but not necessary for NP7 and BPA. It’s hard to tell the difference between 25 and 35°C for NP7 and the adsorption of BPA at 25°C was higher than 5°C. The sentences need to be revised.
R: The sentences “It can be seen that the adsorption of NP, NP7, and BPA on the soil all decreased with increasing temperature” in the manuscript (L295) was corrected. A mistake was made in Figure 3 by carelessness. The two lines of BPA adsorption for 25°C and 5°C were in reverse order. Actually, the adsorption of BPA at 25°C was higher than 5°C. It has been revised in Figure3 for BPA. From the figures for NP7 and BPA, it is hard to tell the difference, but from the Kd values for NP7 at different temperatures and the data of Table 5, the difference indeed exists.
POINT5- L323-328: I wonder how concentrations of the three mental ions change over the experiment.
R: Kinetic experiment was conducted in this experiment, which was similar with the former study of Wang et al (2019). Kinetic experimental results showed that the adsorption of NP first underwent a rapid stage and then followed a slow stage. More than 90% of 4-NP sorption on soils occurred during the initial rapid stage within 15 min. But the concentrations of the three mental ions change over time was not been observed. But in my point, the concentration of Na+ would have no obvious change, while the concentration of Ca2+ and As (â…¢) may decreased with time, because the multivalent ion can form cation bridges or polymeride with NP/BPA or organic substance and adsorpted on soil, which leading the concentration of the ions in solution decreased with time.
Shiyu Wang，Wenyong Wu*，Fei Liu, Xiaoou Li. Sorption and desorption behaviours of 4-nonylphenol on reclaimed water-irrigated soils. Environmental Engineering Science. (2019) 36 (9) : 1100-1111.
POINT6- L408-409: What does it mean regarding vander Waals interactions with the cavity of soil? How would it affect the adsorption of NP and BPA? What other researched found as compare to yours? what suggestions can be made based on this findings as well as the significant impacts resulting from this work.
R: According Figure 6. FTIR spectra of adsorption of NP and BPA on soil, we conjectured the sorption of NP/BPA and soil were vander Waals. Vander Waals is an electrostatic interaction, which is a physical action, leading no peaks change in the FTIR spectra.
Likewise, Jiang Lu, who are from Tsinghua University has conducted series of research about the environmental fate of NP in environment. He concluded that the sorption of NP on soil was a physical process by the calculation of Gibbs free energy. He investigated different soils and found the –ΔG为3.99~12.59KJ/moL, which is <40KJ/moL. The mechanism of NP adsorption on soil is not obvious by infrared research, because the soil is complex with many impurities. Most adsorption mechanism of NP are mainly focused on the iron mineral, such as siderite or hematite. The purpose of the FTIR spectra analysis in this study mainly provide a reference for the follow-up mechanism research in the future.
Jiang Lu. The Behavior of 17α-Ethinyl Estradiol and 4-n-Nonylphenol in Soil by Groundwater Recharge with Reclaimed Water.2012[M]. Beijing.
POINT7- L422: The entire manuscript doesn’t mention about human health risks and it as concluded that the study can provide indispensable foundations for human health risks of EDCs. How would the findings provide human health risks of EDCs? How can other researchers in the different regions benefit from your data? The authors should include a few sentences to explain these.
R: Accepted and the benefit has been mentioned in “Introduction” part in L68-72; As well in the conclusion, it has been supplemented (L436-439).
Adsorption is vital for the migration of organic pollutants into groundwater. NP can migrate to groundwater during the reclaimed water irrigation and cause risks to human for who groundwater is used as the drinking water source. This study makes the risk assessment of NP more targeted in the future. Because the estrogen activity of NP isomers was different and the harm of these isomers to human is also different. Not all the isomers have the estrogen activity. The most toxic isomer among these isomers is 4-(3-ethyl-2-methylhexan-2-yl) phenol, which is noted as NP7 (Supplementary Material 1) in this study（mentioned in manuscript L55-57）. So to study the singer isomer NP7 is more targeted for the risks of NP to environment. In the future, other researchers can assess the NP risks, not from the points of total NP, but focus on the isomer which has higher estrogen activity.
Reviewer 2 Report
The article highlights clear ideas regarding the adsorption of different endocrine disruptor chemicals in reclaimed water irrigated soils. Such detailed studies are important for the use of reclaimed water in agriculture.
However, there are some aspects to consider in the manuscript:
- The spelling and grammar of the text must be improved. Throughout the document, there are quite a few errors in terms of spaces, commas, superscripts and others.
-Line 98-99: Although all the information about the extraction process is included in the supplementary material, it is recommended to name the technique used.
-Line 148: “eV” instead “Ev”.
-Line 149: “SIM” instead “Sim”.
-Figures 4 and 5 should be improved. Specifically, the dimensions for the width of the bar chart (figure 4) are too large. It is therefore disproportionate to the rest. On the other hand, in Figure 5, the graphics are not aligned correctly.
-Line 418: adsorption instead “adoption”.
Author Response
Response to comments
Reviewer2:
The article highlights clear ideas regarding the adsorption of different endocrine disruptor chemicals in reclaimed water irrigated soils. Such detailed studies are important for the use of reclaimed water in agriculture.
However, there are some aspects to consider in the manuscript:
Point1- The spelling and grammar of the text must be improved. Throughout the document, there are quite a few errors in terms of spaces, commas, superscripts and others.
R: Accepted and revised all the manuscript. The manuscript has been checked by two colleagues who were abroad.
Point2-Line 98-99: Although all the information about the extraction process is included in the supplementary material, it is recommended to name the technique used.
R: Accepted and revised in L105. It is revised according to the USEPA 3550C, Ultrasonic Extraction which is for the organic substances’ extraction from soil and sediments. The reference has been added in the Reference Part.
USEPA. SW-846 Test Method 3550C: Ultrasonic Extraction. https://www.epa.gov/hw-sw846/sw-846-test-method-3550c-ultrasonic-extraction.
Point3-Line 148: “eV” instead “Ev”.
R: Accepted and revised in L154.
Point4-Line 149: “SIM” instead “Sim”.
R: Accepted and revised in L155.
Point5-Figures 4 and 5 should be improved. Specifically, the dimensions for the width of the bar chart (figure 4) are too large. It is therefore disproportionate to the rest. On the other hand, in Figure 5, the graphics are not aligned correctly.
R: Accepted and revised in Figure 4 and 5.
Point6-Line 418: adsorption instead “adoption”.
R: Accepted and revised all the manuscript.
Reviewer 3 Report
This paper gives useful data on the adsorptions of NP, NP7, and BPA. It is potential publishable after suitable revisions.
Line 17, Why do you use NP7 to represent a branched NP?
In the Introduction, please add some information on degradation in NP and BPA and the relationship between degradation and adsorption.
Line 62, where is the Daxing irrigation district?
Line 76, What is “Soils (<20cm)”?
Author Response
Response to comments
Reviewer3:
This paper gives useful data on the adsorptions of NP, NP7, and BPA. It is potential publishable after suitable revisions.
POINT1-Line 17, Why do you use NP7 to represent a branched NP?
R: Accepted (L53-58). NP is composed of varieties of isomers. Not all the isomers have the estrogenic activity and rise risks. According to the former researches, the most toxic isomer among these isomers is 4-(3-ethyl-2-methylhexan-2-yl) phenol, which is noted as NP7 (Supplementary Material 1) in this study.
POINT2-In the Introduction, please add some information on degradation in NP and BPA and the relationship between degradation and adsorption.
R: Accepted and revised in L58-62. Degradation is the main fate of NP and BPA in soil during the reclaimed water irrigation. NP in sewage irrigation soil completed the rapid degradation stage within 20 days, and the removal rates reached above 80%. While adsorption is the first step for NP and BPA during the degradation process, which determines the rate of migration and transformation of NP and BPA into groundwater.
POINT3-Line 62, where is the Daxing irrigation district?
R: Accepted and revised in L66-67. Daxing irrigation district, in the southeastern part of Beijing, China, was one of typical sewage irrigation districts for more than 40 years.
POINT4-Line 76, What is “Soils (<20cm)”?
R: Accepted and revised in L80. It means the soil was collected between 0~20cm.
