Sheng Chong, Jiao Jiu Jimmy, Zhang Jinpeng, Yao Yantao, Luo Xin, Yu Shengchao, Ni Yugen, Wang Shidong, Mao Rong, Yang Tao, Zhan Linsen
Department of Earth Sciences, The University of Hong Kong, Hong Kong, China.
Shenzhen Institution of Research and Innovation, The University of Hong Kong, Shenzhen, China.
Sci Adv. 2024 Apr 12;10(15):eadn3924. doi: 10.1126/sciadv.adn3924. Epub 2024 Apr 10.
Our extensive field studies demonstrate that saline groundwater inland and freshened groundwater offshore coexist in the same aquifer system in the Pearl River delta and its adjacent shelf. This counterintuitive phenomenon challenges the commonly held assumption that onshore groundwater is typically fresh, while offshore groundwater is saline. To address this knowledge gap, we conduct a series of sophisticated paleo-hydrogeological models to explore the formation mechanism and evolution process of the groundwater system in the inland-shelf systems. Our findings indicate that shelf freshened groundwater has formed during the lowstands since late Pleistocene, while onshore saline groundwater is generated by paleo-seawater intrusion during the Holocene transgression. This reveals that terrestrial and offshore groundwater systems have undergone alternating changes on a geological timescale. The groundwater system exhibits hysteresis responding to paleoclimate changes, with a lag of 7 to 8 thousand years, suggesting that paleoclimatic forcings exert a significantly residual influence on the present-day groundwater system.
我们广泛的野外研究表明，珠江三角洲及其邻近陆架的同一含水层系统中，内陆咸水地下水和近海淡水地下水共存。这一与直觉相悖的现象挑战了普遍持有的观念，即陆上地下水通常是淡水，而近海地下水是咸水。为填补这一知识空白，我们开展了一系列复杂的古水文地质模型，以探索内陆-陆架系统中地下水系统的形成机制和演化过程。我们的研究结果表明，陆架淡水地下水自晚更新世以来的海平面低水位期形成，而陆上咸水地下水是在全新世海侵期间由古海水入侵产生的。这表明陆地和近海地下水系统在地质时间尺度上经历了交替变化。地下水系统对古气候变化表现出滞后响应，滞后时间为7至8千年，这表明古气候强迫对现今地下水系统产生了显著的残余影响。
