Vertical leaching of paleo-saltwater in a coastal aquifer–aquitard system of the Pearl River Delta

Yu，Shengchao1,2; Jiao，Jiu Jimmy1,3,4; Luo，Xin1,3,4; Li，Hailong2; Wang，Xuejing5; Wang，Qianqian2; Yao，Meng2; Guo，Yifan2; Deng，Zhiyun2; Zuo，Jinchao1

2023-11-01

10.1016/j.jhydrol.2023.130168

Journal of Hydrology   影响因子和分区

0022-1694

1879-2707

Marine transgressive and regressive processes have promoted the formation of deltas and estuaries from the postglacial period, and the coastal aquifer-aquitard system can be identified based on the complicated sedimentary environments in the river delta. The groundwater system is usually composed of freshwater and paleo saltwater, and the vertical leaching of paleo saltwater from aquitard to fresh aquifer occurs due to density difference and gravity effect. In this study, radium quartet and radon were used as the tracers for groundwater due to their different half-lives. We constructed a radium reactive transport model considering the vertical leaching of paleo saltwater in a deltaic aquifer-aquitard system and then applied it in the Pearl River Delta (PRD). The activity ratio of Ra to Ra was used to characterize whether the groundwater system was controlled by α-recoil or sufficient Th under fully weathered condition, and results showed that the deltaic system was well weathered and the vertical leaching of paleo saltwater inhibited the α-recoil input and increased the decay of the sorbed parent nuclide in the aquifer. After incorporating the vertical leaching of saltwater in the model, the value of retardation factor in the shallow aquitard evidently increased, meaning that the leaching of salty porewater into the aquifer greatly affected the adsorption–desorption process of radium isotopes in the aquitard, and the value of retardation factor reduced to the lower limit in the basal aquifer, indicating that the desorption process was determined by the vertical leaching of saltwater here. After considering the effect of vertical leaching, the estimated water transit time in the aquifer was decreased and the groundwater discharge rate was increased, and the converse results were obtained in the aquitard. The proposed radium reactive transport model advances the understanding of the salinization process in coastal aquifers through vertical migration and facilitates the understanding of freshening process of paleo saltwater in the river delta with similar hydrogeological settings.

Aquifer-Aquitard System Leaching Effect Paleo Saltwater Radium Reactive Transport The Pearl River Delta

SCI ; EI

英语

其他

Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai)[311021004] ; National Natural Science Foundation of China["41877172","42130702"]

Engineering ; Geology ; Water Resources

Engineering, Civil ; Geosciences, Multidisciplinary ; Water Resources

WOS:001097844000001

ELSEVIER

20234114874735

Desorption ; Gems ; Groundwater resources ; Hydrogeology ; Isotopes ; Leaching ; Radium ; Rivers ; Sailing vessels

Groundwater:444.2 ; Geology:481.1 ; Gems:482.2.1 ; Radioactive Materials, General:622.1 ; Small Marine Craft:674.1 ; Chemical Operations:802.3

ENGINEERING

2-s2.0-85173630844

Scopus

1.Department of Earth Sciences,The University of Hong Kong,Hong Kong
2.School of Environmental Science and Engineering,Southern University of Science and Technology,Shenzhen,China
3.Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai),Zhuhai,China
4.The University of Hong Kong,Shenzhen Institution of Research and Innovation (SIRI),Shenzhen,China
5.Institute of Surface-Earth System Science,School of Earth System Science,Tianjin University,Tianjin,China

Yu，Shengchao,Jiao，Jiu Jimmy,Luo，Xin,等. Vertical leaching of paleo-saltwater in a coastal aquifer–aquitard system of the Pearl River Delta[J]. Journal of Hydrology,2023,626.

Yu，Shengchao.,Jiao，Jiu Jimmy.,Luo，Xin.,Li，Hailong.,Wang，Xuejing.,...&Zuo，Jinchao.(2023).Vertical leaching of paleo-saltwater in a coastal aquifer–aquitard system of the Pearl River Delta.Journal of Hydrology,626.

Yu，Shengchao,et al."Vertical leaching of paleo-saltwater in a coastal aquifer–aquitard system of the Pearl River Delta".Journal of Hydrology 626(2023).