Chemical Signatures and Salinity Evolution of Aquitard Porewater in the Haizhou Bay
Li Jing
Zhu Jiajun
Liang Xing
Liu Yan
Jiang Xinyue
Du Yongchang
Abstract：To ascertain the salinity origin and evolution of aquitard porewater in the coastal zone,this paper collected four borehole core samples in the Laizhou Bay,Lianyungang City,and porewater was then extracted by mechanical squeezing.The chemical and isotopic components of porewater were measured and a solute transport model of porewater since Holocene in a 2D typical section was established.The results show that the total dissolved solids of porewater range from 0.9 to 41.4 g/L from land to sea,and it is higher in shallower sediments and lower in deeper ones.Porewater has Cl/Br ratio of 170-533(267 in average)and 87Sr/86Sr of 0.709 3-0.711 6,together with the positive correlation between Cl‒ and δ18O,indicating that saline porewater is of marine origin and has been affected by silicate weathering and cation exchange.In the Holocene aquitard,porewater is trapped ancient seawater in 10-5 ka BP and the downward infiltration led to salinization of the underlying Pleistocene porewater.About 4 ka BP,porewater was diluted by freshwater in the regression,yet paleo-seawater has not been totally flushed.While in the area close to the coastline,the continuous evaporation led to the occurrence of much saltier porewater.Porewater simulation suggests that aquitard porewater salinity evolution is mainly controlled by transgression-regression events,and during transgression,seawater downward invaded in a"finger-like"pattern,resulting in the heterogeneous distribution of brackish and fresh groundwater.
Keywords：aquitardporewatersalinity evolutiontransportLianyungang Cityhydrochemistryenvironmental geology
Publication Date：2024-03-15
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：13( 939-951 )