Quantitative examination of microstructural transformations of clay-rich sediments in river-dominated deltas under the influence of polluted pore water

• Published in: Environmental Pollution
• Main Authors: Ma, Xiong-Ying, Liu, Zhan, Xia, Zhao, Su, Chen-Xi, Cheng, Yin, Yu, Hao, Kang, Xin
• Other Authors: Energy Resources and Petroleum Engineering Program, Physical Science and Engineering (PSE) Division, Earth Science and Engineering Program, College of Civil Engineering, Hunan University, Changsha, China., CCFEB Civil Engineering Co., Ltd., Changsha, 410004, China., Engineering Technology and Materials Research Center, China Academy of Transportation Sciences, Beijing, China.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier BV 2023
• Subjects: Sediment; Anisotropy; DELTA; Clay; Coastal Protection; Ocean acidification
• Online Access: http://hdl.handle.net/10754/693001; https://doi.org/10.1016/j.envpol.2023.122177

Coastal water pollution has a significant impact on sedimentary environments, altering the microstructure of clay-rich sediments and further destabilizing river-dominated delta strata. However, the understanding of the microstructure of clay sediment, influenced by burial depth and pore water chemistry, remains limited due to challenges in quantitatively analyzing clay texture at varying depths. The perturbable of clay microstructures, and the cost of deep sampling have hindered such efforts. To address this issue, this study aims to quantitatively analyze the clay anisotropy at different depths and pore water chemistry through laboratory-simulated sediment samples by using centrifugal modeling and 2DXRD technology. The results suggest that 1DXRD (Orientation index) is prone to generating incorrect conclusions, whereas 2DXRD (pole density) yields more precise and reliable results. Specifically, the results indicated that the introduction of salt ions promoted clay precipitation and stabilized the oriented microstructure at shallower depths. In acidic solutions, clay sediment still contained a certain proportion of edge to face (EF) microstructure at depths less than 6 m, suggesting higher soil thixotropy and lower strength than that of clay sediments in other types of solutions. Overall, our findings provide valuable insights into the relationship between water pollution, delta disappearance, and ocean acidification, highlighting the urgent need for effective environmental management strategies to prevent further damage to fragile coastal ecosystems. This study was supported by the National Natural Science Foundation of China (No. 51809129) and Basic Scientific Research Business Foundation of Central Public Welfare Scientifc Research Institutes (No. 20227501).