## 5 Discussion  
The object of this study is the reduction and remediation of dredged sediment. Reduction refers to the dewatering and drying of the sediment to reduce its moisture content while making it smaller in volume and occupying less space when placed in a yard. Remediation refers to reducing the contaminant content of the contaminated sediment so that it no longer poses a continuing environmental hazard when placed in a yard. The conclusions of this study demonstrate the possibility to carry out reduction and remediation simultaneously, but there are still some issues that deserve to be discussed. First, the occurrence of blockage during vacuum electro-osmosis treatment may affect the transfer of vacuum pressure inside the soil samples [8]. Due to the limitation of the test conditions, the vacuum degree is not measured in this study. Changes in vacuum degree may affect the treatment of vacuum electro-osmosis, and an analysis of the vacuum degree can also evaluate the reduction effect. Moreover, the composition of the blockage substances varies with the composition of the contaminants. The conclusions obtained in this study are only applicable to Cu-contaminated dredged sediment. On the other hand, pH is also one of the main causes of precipitation, and the real-time change in pH can also predict the electrochemical reaction inside the soil, and the simultaneous reduction and remediation will inevitably affect the distribution of pH. Since this study focuses on the interaction between the two, the real time change of pH of the soil is not analyzed, but this does not mean that pH has no effect on vacuum electro-osmosis [25]. In addition, this study focuses only on the copper content of the soil before and after treatment and, thus, the copper content of the soil after the test is measured to obtain the copper removal rate. However, most of the removed copper is left in the discharged water. In this research, the contaminant content in the discharge water was not measured, and no further treatment was done. Copper ions in water samples can also cause secondary pollution to the environment if they are not treated properly [26]. How the contaminants are further treated after discharge from the soil can still be further refined. Lastly, the presence of copper ions greatly improves the electrical conductivity of the soil, while the presence of other contaminants does not necessarily do so. The electrochemical reactions occurring within the soil are also different, and the integration of reduction and remediation under other pollutant conditions is still to be explored. Due to the limitation of cost, microscopic tests on the soil were not conducted in this study. Because of the electrochemical reactions occurring inside the soil, more changes may occur in the microstructure of the soil, and the analysis of the reduction and remediation from the microscopic level is also a worthy direction for future research. Conceptualization, W.Q. and Y.S. ; methodology, W.Q. and S.L. ; formal analysis, W.Q. ; investigation, S.L. and K.C. ; resources, Y.S. ; data curation, W.Q. and S.L. All authors have read and agreed to the published version of the manuscript. This research was supported by the 111 Project of Ministry of Education of the People's Republic of China (grant no. B13024) and provided by the National Natural Science Foundation of China (no. 52278343). Not applicable. The data presented in this study are available upon request from the corresponding author. The data are not publicly available due to privacy. The authors acknowledge the funding provided by the National Natural Science Foundation of China (no. 52278343). This work was also supported by the 111 Project of Ministry of Education of the People's Republic of China (grant no. B13024). The authors thank the reviewers and the editor for their excellent comments and suggestions, which improved the quality of this article. The authors declare no conflict of interest. The following abbreviations are used in this manuscript:  
Vac.